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00-11/12stran 717

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© Strojni{ki vestnik 46(2000)11/12,717Mese~nikISSN 0039-2480

© Journal of Mechanical Engineering 46(2000)11/12,717Published monthly

ISSN 0039-2480

Strojni{ki vestnik - Journal of Mechanical Engineeringletnik - volume 46, (2000), {tevilka - number 11/12

RazpraveBatista, M., Kosel, F.: Analiza obèutljivosti toplotne

obdelave jekelLegat, J., Gubeljak, N., Predan, J.: Razvoj in

presku�anje odbojnikov �elezni�kih vozil zelastomernim vzmetnim paketom

Sekavènik, M.: Analiza vibracij gonilnikaturbopuhala

Puèko, B.: Vpliv vibriranja med varjenjem in po njemna mehanske lastnosti zvarov, zavarjenih vza�èiti moèno ioniziranega veèkomponentnegaplina

Hren, G., Jezernik, A., Luk�iè, S.: Izku�nje priuvajanju raèunalni�ko podprtega konstruiranjain smeri razvoja v ADRIA Mobil d.o.o.

Ptièar, M., Dolin�ek, S., Kosel, F.: Prednosti inomejitve pri uporabi materialov z oblikovnimspominom za praktiène uporabe

Strokovna literatura

Osebne vesti

Navodila avtorjem

718

732

750

762

770

780

789

792

797

PapersBatista, M., Kosel, F.: A Sensitivity Analysis of

Heat Treatment of SteelLegat, J., Gubeljak, N., Predan, J.: The Develop-

ment and Testing of Rail-Vehicle Buffers Filledwith Elastomer Spring Packages

Sekavènik, M.: An Analysis of Turbocharger Im-peller Vibrations

Puèko, B.: The Effect of Vibrational TreatmentDuring and After Welding on the MechanicalProperties of a Transferred Ionized MoltenEnergy Weld

Hren, G., Jezernik, A., Luk�iè, S.: Experiences ofCAD Implementation and Trends in Develop-ment at ADRIA Mobil Ltd.

Ptièar, M., Dolin�ek, S., Kosel, F.: The Advantagesand Problems of Using Shape-Memory Mate-rials inPractical Applications

Professional Literature

Personal Events

Instructions for Authors

00-11/12stran 718

M. Batista - F. Kosel: Analiza ob~utljivosti - A Sensitivity Analysis

Prispevek obravnava matematièni model toplotne obdelave podeutektoidnih ogljikovih jekel. Priizraèunu zaostalih napetosti, ki so posledica faznih premen in temperaturnih sprememb, sta v modeluupo�tevana tako kinetika faznih prehodov kakor termoelasto-plastiène konstitutivne enaèbe. Izdelaniraèunalni�ki progam je bil preverjen na �e objavljenih rezultatih. Z uporabo analize obèutljivosti je ocenjenanapaka v izraèunanih zaostalih napetostih na temelju ocenjenih napak podatkov o lastnostih materiala.© 2000 Strojni�ki vestnik. Vse pravice pridr�ane.(Kljuène besede: obdelave jekel, obdelave toplotne, analize obèutljivosti, modeli matematièni)

This paper presents a mathematical model of the heat treatment of hypoeutectoid carbon steel. Inthe model, the kinetics of phase changes and a thermo-elasto-plastic constitutive relation have been appliedto calculate the residual stresses resulting from phase changes and temperature variations. The computercode has been verified for internal consistency with previously published results. The sensitivity analysis hasbeen applied to predict errors in the residual stresses from the estimated errors in the material data.© 2000 Journal of Mechanical Engineering. All rights reserved.(Keywords: steel treatment, heat treatment, sensitivity analysis, mathematical models)

A Sensitivity Analysis of the Heat Treatment of Steel

Milan Batista - Franc Kosel

© Strojni{ki vestnik 46(2000)11/12,718-731ISSN 0039-2480UDK 669.14:621.785:519.86Izvirni znanstveni ~lanek (1.01)

© Journal of Mechanical Engineering 46(2000)11/12,718-731 ISSN 0039-2480

UDC 669.14:621.785:519.86Original scientific paper (1.01)

Analiza ob~utljivosti toplotne obdelave jekel

0 UVOD

Matematièno modeliranje toplotne obdelavejekel je bilo predmet �tevilnih raziskav v zadnjihdesetletjih [10]. Te raziskave so pokazale, da se datoplotna obdelava analizirati z mehaniko kontinuovin naslednjimi predpostavkami:- reolo�ki model kontinua je termoelastoplastièni

material;- model mora vkljuèevati deformacije zaradi

strukturnih sprememb in preoblikovalnoplastiènost;

- enaèba prevoda toplote mora vsebovati èlen, kipopisuje toploto fazne premene;

- za popis difuzijskih faznih premen se uporabljaAvramijeva enaèba;

- za obravnavo austenitno-martenzitnetransformacije se uporablja Koistinen-Marburgerjeva enaèba;

- vse lastnosti materiala so linearne funkcijeprostorninskih dele�ev posameznih faz.

S temi predpostavkami je proces toplotneobdelave doloèen kot deterministièni mehanskimodel kontinua. S tem modelom se da obpredpostavki, da so znani podatki o mehanskih

0 INTRODUCTION

Mathematical modeling of the heat treatmentof steel was intensively investigated over the last twodecades [10]. It was shown that the problem of heattreatment can be analyzed by using the theory of con-tinuum mechanics with the following assumptions:- a continuum rheologic model is thermo-elasto-plastic;- in the mechanical model the structural phase de-

formation and transformation plasticity have tobe included;

- the equation of heat transfer is added to the partwhich represents the heat of the phase transfor-mation;

- the Avrami equation is used for treating the ki-netics of the diffusion-controlled transformationof phases;

- Koistinen-Marburger�s equation is used for treat-ing the austenite-martensite transformation;

- all the properties of the continuum are linear func-tions of the volume fractions of the phases.

With these assumptions, the heat-treatingprocess is defined by a deterministic mechanicalmodel of continuum. Using this model, and providedthat the data of the mechanical properties and bound-

00-11/12stran 719


lastnostih in ob znanih robnih pogojih izraèunatizaostale napetosti.

Poglavitni namen tega prispevka je ocenitinapako izraèunanih zaostalih napetosti na podlagiocene napak vhodnih podatkov o materialu. V tanamen je bil izdelan matematièni model toplotneobdelave. Na temelju modela je bil izdelan raèunalni�kiprogram, ki izraèuna razvoj temperature, strukturnihsprememb in zaostalih napetosti pri ohlajanjuneskonènega valja, izdelanega iz podeutektoidnegaogljikovega jekla. Raèunalni�ki program je bilprimerjalno testiran z rezultati objavljenimi v literaturi.V nadaljevanju so bili izraèunani koeficientiobèutljivosti za valje premera 10 mm, 30 mm in 50 mmizdelanih, iz izbranega materiala. Na podlagikoeficientov obèutljivosti smo ocenili vplivnostvhodnih podatkov in nadalje, na podlagi ocenjenihnapak vhodnih podatkov smo ocenili �e napako vizraèunu zaostalih napetosti.

1 MATEMATIÈNI MODEL

Matematièni model toplotne obdelave moravkljuèevati izraèun temperature, strukture innapetosti. V tem poglavju podajamo pregled osnovnihenaèb, ki so vkljuèene v model.

1.1 Opis materiala

Jeklo, ki je izpostavljeno toplotni obdelavi,obravnavamo kot zmes N sestavin. Te so: austenit,ferit, perlit, bainit in martenzit. Èe je kx prostorninskidele� k-te sestavine, potem velja:

Èe je kw masni dele� k-te sestavine, potem veljapodobno:

Vsaka sestavina zmesi ima gostoto rk. Èe je

r gostota zmesi, potem sta prostorninski in masnidele� k-te sestavine povezana na naslednji naèin:

Pri jeklu so razlike med gostotamiposameznih sestavin majhne, zato velja ocena

k kw x» . Iz (1) do (3) se da izpeljati naslednji zvezi, kiju bomo uporabili v nadaljevanju:

ary conditions are known, the residual stresses in atreated element can be calculated.

The main aim of this paper was to estimatethe error in the calculated residual stresses from theestimated error in the inputed material data. In order todo this a mathematical model of the heat treatment wasdeveloped. This model was converted to a computerprogram which performed the calculation of the ther-mal and structural evaluations and the residual stressesduring the cooling of an infinitely long cylinder madeof hypoeutectoid carbon steel. The computer codewas verified for internal consistency with previouslypublished results. Next, the sensitivity coefficients ofthe selected material data were calculated for cylin-ders of 10 mm, 30 mm and 50 mm diameter. On the basisof the sensitivity coefficients we estimated the impor-tance of the input data and, in addition, using the esti-mated errors of the material data we determined theerror in the calculated residual stresses.

1 MATHEMATICAL MODEL

A consistent mathematical model of heattreatment must include thermal, structural and stresscalculations. In this section we shall review the es-sential equations which were used in the model.

1.1 Material description

The steel used in the heat-treatment pro-cess is considered to be a mixture of N constituents:austenite, ferrite, pearlite, bainite and martensite. If

kx is the volume fraction of the kth constituent then:

(1).

Similarly, if kw is the mass fraction of the kth con-stituent then:

(2).

Each constituent of the mixture has a density rk. If r

is the mixture density, then the volume fraction andthe mass of the kth constituent are connected by:

(3).

In the case of steel, the differences between thedensities of the constituents are small, so in this case wehave k kw x» . On the basis of (1) to (3), the followingrelations, which will be used later, can be derived:

(4)

(5).

1

1N

kk

x=

=å

1

1N

kk

w=

=å

kk kw

rx

r=

1

N

k kk

r r x=

= å

1

1 Nk

k k

w

r r=

= å

00-11/12stran 720


1.2 Elastiènost

Èe predpostavimo, da je material izotropen,potem so elastiène deformacije e

ije podane z:

Pri tem so sij napetostni tenzor, E, n in a

Youngov modul, Poissonovo razmerje in koeficienttermiènega raztezanja, g

k pa dilatacijski koeficient k-

te sestavine. Nadalje predpostavimo, da so n in gk

konstante, E in a pa linearni funkciji prostorninskihdele�ev:

pri èemer je E(J) temperaturno odvisni Youngovmodul k-te sestavine in a

k njen razteznostni

koeficient, za katerega predpostavimo, da jenespremenljiv.

Dilatacijski koeficient gk lahko izraèunamo

takole: èe so deformacije majhne, potem po zakonuohranitve mase in (4) dobimo:

pri èemer je ev prostorninska deformacija in r

0 gostota

zmesi v referenènem stanju. S primerjavo te enaèbe in(6) dobimo za s

ij = 0 in J = 0:

1.3 Plastiènost

Prirastek plastiènih deformacij pijde

izraèunamo z uporabo klasiène teorije plastiènosti inMissesovega kriterija teèenja:

pri èemer je sij deviatorièni napetostni tenzor, definiran

kot:

in sf napetost teèenja. Pogoj F < 0 pomeni, da ni

plastiènega teèenja, pogoj F = 0 pa, da je. Èe zdru�imo(11) in (12), dobimo:

pri èemer je pde dejanski prirastek plastiènihdeformacij, podan z:

1.2 Elasticity

If we assume that a material is isotropic, thenthe elastic strain e

ije is given by:

(6).

Here sij is the stress tensor, E, n and a are

theYoung�s modulus, Poisson�s ratio and thermal ex-pansion coefficient, respectively, and g

k is the dilata-

tion coefficient of the kth constituent. We assumethat n and g

k are constants. E and a are taken as linear

functions of the volume fractions of the constituents:

(7)

(8),

where E(J) is the temperature-dependent Young�smodulus of the kth constituent and a

k is its thermal

expansion coefficient, which is assumed to be constant.We shall now describe a method for calcu-

lating the dilatation coefficients gk. If deformations in

the material are small, then from the conservation ofmass and equation (4) we obtain:

(9),

where ev is the volume deformation and r

0 is the mixture

density in a reference state. By comparing this equationwith equation (6) at s

ij = 0 and J = 0 we obtain:

(10).

1.3 Plasticity

The plastic strain increment pijde is calculated

using the classical theory of plasticity with the Missesyield criterion and the associated flow rule. Thus:

(11)

(12),

where sij are the components of the deviatoriv stress

tensor given by:

(13)

and sf is the flow stress. The condition F < 0 means that

there is no plastic flow and F = 0 means that plastic flowtakes place. Combining of (11) and (12) gives:

(14)

where pde is the effective plastic strain incrementgiven by:

( )1

11

Neij ij mm ij ij k k ij

kEe n s ns d aJd g x d

=

æ öé ù= + - + + ç ÷ë û

è øå

( )1

N

k kk

E E J x=

= å

1

N

k kk

a a x=

= å

0

10 0

1N

kv k

k

r rre x

r r=

-= - = å

0

0

1

3k

k

r rg

r

-=

22

3ij ij fF s s s= -

p pij ijd d se = L

1

3ij ij mm ijs s s d= -

3

2

pp

f

dd

e

sL =

00-11/12stran 721


(15).

We assume that the flow stress is given bythe linear hardening rule:

(16),

where sY is the yield stress and H is the strain-harden-

ing coefficient. In addition, we assume that the yieldstress and the strain-hardening coefficient are linearfunctions of the volume fractions of constituents:

(17)

(18).

Here, sY,k

and Hk correspond to the yield stress and

the strain-hardening coefficient of the kth constitu-ent, respectively.

1.4 Transformation Plasticity

For the calculation of the transformationplasticity strain increment tp

ijde we applied the modelproposed in [11] and [15]:

(19),

where

(20)

and Kk are constants which must be determined ex-

perimentally.

1.5 Heat Conduction

The temperature field is calculated by solv-ing the basic equation of heat conduction:

(21),

where t is time, J is the temperature, c is the heatcapacity, l is the coefficient of thermal conductivityand l

k are the enthalpies of transformation.

Both c and l are temperature dependent andare taken as linear functions of the volume fractionsof the constituents:

(22)

(23),

and ck(J) and l

k(J) the heat capacity and the thermal

conductivity for phase k. Equation (21) is solved to-gether with convection, boundary condition:

(24),

2

3p p p

ij ijd d de e e=

Predpostavimo, da je napetost teèenjapodana z linearnim zakonom utrjevanja:

pri èemer je sY napetost teèenja in H koeficient

utrjevanja. Nadalje predpostavimo, da sta napetostteèenja in koeficient utrjevanja linearni funkcijiprostorninskih dele�ev posameznih sestavin:

Pri tem sta sY,k

in Hk napetost teèenja in koeficient

utrjevanja k-te sestavine.

1.4 Preoblikovalna plastiènost

Za izraèun prirastka preoblikovalneplastiènosti tp

ijde uporabimo model, ki so ga predlagaliv [11] in [15]:

pri èemer je:

in Kk konstante, ki jih je treba doloèiti s preskusi.

1.5 Prevod toplote

Temperaturno polje dobimo z re�itvijoenaèbe prevoda toplote:

pri èemer so t èas, J temperatura, c specifièna toplota,l koeficient prevoda toplote in l

k latentne toplote

premen.Temperaturno odvisna c in l vzamemo kot

linearni funkciji prostorninskih dele�ev sestavin:

pri èemer sta ck(J) in l

k(J) specifièna toplota in

toplotna prevodnost sestavine k. Enaèbo (21)re�ujemo skupaj s konvekcijskim robnim pogojem:

pf Y Hs s e= +

( ),1

N

Y Y kkk

s s J x=

= å

( )1

N

k kk

H H J x=

= å

tp tpij ijd d se = L

( )2

3 1N

tpk k k

k

d K dx x=

L = -å

2

N

k kki i

c lt x x

¶J ¶ ¶Jl x

¶ ¶ ¶ =

æ ö= +ç ÷

è øå

( )1

N

k kk

c c J x=

= å

( )1

N

k kk

l l J x=

= å

( )ehn

¶Jl J J

¶- = -

00-11/12stran 722


pri èemer je h konvekcijski koeficient, ki je lahkotemperaturno odvisen in J

e temperatura okolice.

1.6 Fazne premene

Opazujmo fazni prehod faze m v fazo n. V tanamen prepi�imo (1) v obliko:

in uvedimo novo spremenljivko z, definirano kot:

ki jo bomo uporabili za opis napredovanja premene.Pri izotermnih pogojih se da heterogena premenaopisati z Avramijevo enaèbo ([5],[6] in [16]):

pri èemer je

K0 in Q sta konstanti, n je Avramijev

eksponent, ki je odvisen od geometrijske oblikerastoèih kristalnih zrn in je temperaturno neodvisen[6], T je absolutna temperatura, J

E pa ravnote�na

temperatura premene. Za neizotermne pogoje se daAvramijeva enaèba zapisati v obliki:

ki jo dobimo, èe iz (27) izloèimo èas t.Ko je n konstanta, se da K

0 in Q dobiti iz

diagramov TTT takole: èas t0, ki je potreben za

premeno z0 pri dani temperaturi T, je iz (27):

Èe sta (tm,J

m) koordinati ekstrema na krivulji

TTT, potem je v tej toèki dt/dJ = 0. Iz tega pogoja in(30) izhaja:

Ko poznamo Q,lahko iz (30) izraèunamo K0:

Martenzitna premena je odvisna le od tem-perature, zato ima v tem primeru kinetièni zakon oblikoz = f(J). Iz te enaèbe je prirastek premene dz = f�(J)dJ.

where h is the convection heat-transfer coefficient,which may be temperature dependent and J

e is the

environmental temperature.

1.6 Phase Transformations

We can consider the phase transformationfrom, say, phase m to phase n. For this purpose wewrite equation (1) as:

(25)

and then introduce a new variable z defined by:

(26),

which will be used to describe the extent of the trans-formation. Under isothermal conditions a heteroge-neous solid-state transformation can be describedby the Avrami equation ([5],[6] and [16]):

(27),

where

(28).

K0and Q are constants, n is the Avrami ex-

ponent, which is dependent on grain growth geom-etry and can be taken as temperature independent[6], T is the absolute temperature, and J

E is the equi-

librium temperature of the transformation. Fornonisothermal conditions the Avrami equation canbe written in the form:

(29),

which is obtained by eliminating t from (27).When n is constant, K

0 and Q can be deter-

mined from TTT diagrams in the following way. Thetime t

0 for a fixed amount of transformation z

0 at a

given temperature T is, from (27):

(30).

If (tm,J

m) are coordinates of the nose in the

TTT curve then dt/dJ = 0 at this point. From theseconditions and (30) it follows that:

(31).

By knowing Q we can calculate K0:

(32).

A martensitic transformation depends only on tem-perature, therefore the kinetic law is, in this case,given by z = f(J). From this equation the increment of

,

1m n kk m n

x x x¹

+ = - å

,

1n

kk m n

xz

x¹

=- å

( )1 expn

tz bé ù= - -ë û

( ) ( )0 expn

E

QK

Tb J J J

é ù= - -ê úë û

( ) ( ) ( )1

1 ln 1n

nd

ndt

zb J z z

-

= - - -é ùë û

( )( )

( )1

00 0 0ln 1

Q

Tn

n

E

K et t J z

J J= = - -é ùë û

-

2m

E m

nTQ

J J=

-

( ) ( )1

0 0ln 1m

Qn T n

m E mK t eJ J z-

= - -é ùë û

00-11/12stran 723


Iz osnovnega kinetiènega zakona lahko izrazimo Jkot funkcijo z , zato je dz = g(z)dJ. Ko je premenakonèana, tj. ko je z = 1, mora biti g(z) = 0.Najpreprostej�a funkcija, ki ustreza temu pogoju, jelinearna, torej:

Z integracijo dobimo:

pri èemer je Ms temperatura, pri kateri se zaène

martenzitna premena. Enaèba (34) je identiènaKoinstinen-Marburger empirièni enaèbi [10]. Zaveèino jekel ima konstanta k

M vrednost 0,011.

2 LASTNOSTI MATERIALA

V tej raziskavi smo za material izbralipodeutektoidno ogljikovo jeklo, ker je za ta material vliteraturi dostopnih dovolj podatkov, s katerimi lahkozgradimo analitièni model materiala. V nadaljevanjubomo uporabili oznake A,B,M,P in W za austenit,bainit, martenzit, perlit in cementit. Simbole C, Si inMn bomo uporabili za masne dele�e ogljika, silicija inmangana v jeklu.

2.1 Youngov modul in Poissonovo �tevilo

Za ogljikova jekla se da Youngov modulperlita izraèunati po naslednjem obrazcu:

Ta obrazec je dobljen na podlagiregresijske analize podatkov, ki jih je podal [7].Predpostavljamo, da ta obrazec velja prav tako zabainit in martenzit. Obrazec, ki podaja Youngovmodulu austenita, smo dobili iz podatkov, ki jihnavaja [22] in ima obliko:

Predpostavljamo, da ima Poissonovo�tevilo vrednost 0,3 za vse sestavine.

2.2 Razteznostni koeficient

V literaturi ni zaslediti enotnih podatkov zavrednost razteznostnih koeficientov, zato smo vzelinaslednje vrednosti [10]:

transformation is dz = f�(J)dJ. From the kinetic law wecan express J as a function of z , hence dz = g(z)dJ.When the transformation is completed i.e. when z =1, we must have g(z) = 0. The simplest equation com-patible with this requirement is linear, namely:

(33).

By integrating this equation we obtain:

(34),

where Ms is the martensitic starting temperature. Equa-

tion (34) is identical with the Koinstinen-Marburgerempirical formula [10]. The constant k

M is equal to

0.011 in most steels.

2 MATERIAL PROPERTIES

As a target material in this investigation we chosehypoeutectoid carbon steel because there were enoughdata available in the literature to construct a material modelas well as the analytical formulas. In the following we usethe indices A,B,M,P and W for austenite, bainite, marten-site, pearlite and cementite, respectively. We will also usethe symbols C, Si and Mn to denote the weight percent ofcarbon, silicon and manganese in the steel.

2.1 Young�s Modulus and Poisson�s Ratio

For carbon steel the Young�s modulus ofpearlite is calculated by:

(35).

This formula was obtained on the basis of aregression analysis from the data [7]. We assumethat the same formula holds for bainite and marten-site. The formula for the Young�s modulus of austen-ite was obtained from data reported by [22] and hasthe form:

(36).

The Poisson�s number is assumed to be con-stant and is equal to 0.3 for all constituents.

2.2 Coefficient of Expansion

There is no single value in the literature for theexpansion coefficient of the different phases so in thepresent model we adopted the following values [10]:

(37).

( )1Md k dz z J= -

( )1 exp M sk Mz J= - - -é ùë û

209,3 0,076 1,62 GPaPE J= - ±

200,2 0,08 0,32 GPaAE J= - ±

6 1

6 1

6 1

6 1

22 10 K

13 10 K

12 10 K

14 10 K

A

B

M

P

a

a

a

a

-

-

-

-

= ×

= ×

= ×

= ×

00-11/12stran 724


Iz podatkov v literaturi ocenjujemo, da sopodane vrednosti znotraj obmoèja 6 11 10 K- -± × .

2.3 Preoblikovalna deformacija

Veèina znanih del uporablja za dilatacijskekoeficiente eksperimentalne vrednosti iz [10]. V temdelu bomo dilatacijske koeficiente izraèunali natemelju kristalografskih podatkov iz preglednice 1 in(10). Iz kristalografskih podatkov izraèunamolinearizirane gostote sestavin jekla:

From the data published in the literature weconclude that all the above values are within the range

6 11 10 K- -± × .

2.3 Transformation Strain

Most previous studies used experimentalvalues for the dilatation coefficients [10]. We havechosen to calculate these values on the basis of thecrystallographic data in table 1 and equation (10).From crystallographic data the following lineariseddensities of the steel constituents are obtained:

(38).

3

3

3

3

8156 216 kg m

7897 kg m

7676 kg m

7897 248 kg m

A

B

M

F

C

C

r

r

r

r

= -

=

=

= -

Faza Phase

Tip Type

Fe C Lattice parameters [Å]

Vir Source

Austenit Austenite

fcc 4 - a = 3,5735 + 0,0316C [19]

Cementit Cementite

ort 12 3 a = 4,5234 b = 5,0883 c = 6,7426

[4]

Ferit Ferrite

bcc 2 0 a = 2,8664 [4]

Martenzit Martensite

bct 2 - a = 2,8664 � 0,013C c = 2,8664 + 0,116C

[4]

Preglednica 1. Kristalografski podatkiTable 1. Crystallographic data

Iz (4) je gostota perlita:

iz katere dobimo, èe vstavimo vrednosti iz (38):

Podobno dobimo gostoto zmesi ferita in perlita:

Èe vzamemo za referenèno strukturo jeklazmes ferita in perlita, dobimo na podlagi (10):

Prav tako predpostavimo, da je gB = 0.

From (4) we have for the pearlite density:

(39),

which gives, by substituting values from (38), thefollowing value:

(40).

For the ferrite-pearlite mixture we then obtain, by asimilar procedure, the result:

(41).

If we take the mixture of ferite-perlite as asteel reference structure then from (10) we obtain:

(42).

We also assume that gB = 0.

1 0,12 0,88

P W Fr r r= +

37861 kg mPr =

37897 45 kg mP F Cr + = -

0,0109 0,0072

0,0086A

M

C

C

g

g

= - +

=

00-11/12stran 725


2.4 Meja teèenja in koeficient utrjevanja

Iz podatkov, ki sta jih objavila [12] in [10],dobimo naslednje obrazce za mejo plastiènega teèenja:

in koeficient plastiènega utrjevanja:

2.5 Koeficienti preoblikovalne plastiènosti

Na temelju poskusov, opisanih v [18], smovzeli naslednje vrednosti konstant K

k:

2.6 Specifièna toplota

Podatki za regresijsko analizo specifiènetoplote so vzeti iz [9]. Iz teh podatkov je specifiènatoplota perlita:

Predpostavimo, da ta obrazec velja tudi zabainit in martenzit. Za specifièno toploto austenitasmo uporabili obrazec:

dobili smo ga iz podatkov v [22].

2.7 Toplotna prevodnost

Regresijsko formulo za toplotno prevodnostperlita smo dobili iz podatkov, objavljenih v [3] in [8]:

Predpostavimo, da ta obrazec velja tudi zabainit. Za martenzit smo vzeli vrednost

30 5 W mKMl = ± , kakor jo predlaga [10]. Izpodatkov, objavljenih v [22], smo dobili naslednjiobrazec za izraèun toplotne prevodnosti austenita:

2.4 Yield Strength and Strain-Hardening Coefficient

From the data published by [12] and [10] wederive the following formulas for the yield stresses:

(43)

and the coefficient of strain hardening:

(44).

2.5 Transformation Plasticity Coefficient

From the experimental work of [18] the follow-ing values for the constant K

k were adopted:

(45).

2.6 Specific Heat Capacity

The data for the regression analysis of thespecific heat capacity were taken from [9]. From thiswe obtain the following formula:

(46).

We take this formula to be valid also forbainite and martensite. For the austenite heat capac-ity we use the formula:

(47),

which was obtained from data published in [22].

2.7 Thermal Conductivity

The regression formula for thermal conduc-tivity was obtained from published data in [3] and [8]:

(48).

We assume that the above formula is alsovalid for bainite. For martensite we take the thermalconductivity to be 30 5 W mKMl = ± , as suggestedby [10]. From the data of [22] we obtain the followingformula for the thermal conductivity of austenite:

(49).

,

,

,

,

123 0,1 0,01 1,3 MPa

434 0,64 0,77 34, 4 MPa

491 757 1,02 26,1 MPa

445 1375 30, 4 MPa

Y A

Y P

Y B

Y M

C

C

C C

C

s J J

s J J

s J

s

= - - ±

= - + ±

= + - ±

= + ±

2

2

2

2

45,3 0,04 0,63 10 MPa

5,88 226,2 19,7 10 MPa

29,5 0,33 41,7 10 MPa

179 1,3 29,9 10 MPa

A

B

F

M

H

H C

H C

H C

J

J

J

J

= - ± ´

= + ± ´

= + ± ´

= + ± ´

5 1

5 1

5 1

4,18 10 MPa

5,08 10 MPa

4,18 10 MPa

B

M

P

K

K

K

- -

- -

- -

= ×

= ×

= ×

6 2 33,76 0,3 6,210 0,15 MJ m KPpc C J-= + + ±

4 34,152 8,410 MJ m KApc J-= +

66,2 37,9 0,049 1,74 W mKP Cl J= - - ±

15 0,01 W mKAl J= +

00-11/12stran 726


2.8 Fazne temperature

Za izraèun ravnote�nih temperatur, ki seuporabljajo v (28), smo uporabili naslednje empirièneobrazce:

Obrazce za A1, A

3 in M

s je podal [1],

temperaturo zaèetka tvorjenja bainita Bs pa [21].

3 POSTOPEK RE�EVANJA

Opisani model je bil uveden vraèunalni�ki program, ki omogoèa izraèun tem-perature, strukture in zaostalih napetosti prihlajenju neskonènega valja, izdelanega izpodeutektoidnega jekla. Temperaturno polje seraèuna na temelju implicitne metode konènihrazlik, napetosti pa z metodo zaporednihpribli�kov, ki jo podaja [17].Vhodni podatki so:- premer valja- kemièna sestava jekla- zaèetna in konèna temperatura procesa ohlajanja- konvekcijski koeficient- koordinate ekstremnih toèk na diagramu TTTIzhodni podatki so:- porazdelitev zaostalih napetosti in struktur- temperaturni in napetostni potek v osi in na povr�ini

valja

4 PRESKUS MODELA

Kot prvi primer smo obravnavali valj spremerom 60 mm, izdelan iz 0,43% ogljikovega jekla,ga�enega v vodi s temperature 870oC. Ta primer jeteoretièno in eksperimentalno obdelan v [13] in [14]in prav tako teoretièno v [20].

Iz objavljenih podatkov smo ocenili, damora biti koeficient prestopa toplote blizu 25 kW/m2K. Omenimo, da tudi s tako visokimkonvekcijskim koeficientom nismo dobili takehitrosti ohlajanja osi valja, kakor jo navaja [13].Kljub temu pa so izraèunane zaostale napetosti vskladu z eksperimentalnimi vrednostmi, kakor sevidi s slike 1.

Kot drug primer so obravnavali valje spremeri 10 mm, 30 mm, 50 mm in 100 mm izdelane iz0,44% ogljikovega jekla. Porazdelitev zaostalihnapetosti za take valje eksperimentalno obravnava[2], teoretièno pa [23]. Vsi valji so ga�eni v vodi na20 oC s temperaturo 850 oC. Vrednosti konvekcij-skega koeficienta smo vzeli med 3200 W/m2K in

2.8 Transformation temperatures

For the calculation of the equilibrium tem-peratures which are used in (28) we chose the follow-ing empirical formulae:

(50).

The formulae for A1, A

3 and M

s were given

by [1], and for bainite the start temperature Bs was

given by [21]

3 SOLUTION METHOD

The described model was converted into a com-puter program which performed the calculation of ther-mal and structural evaluations and the internal stressesduring cooling of an infinitely long cylinder made fromhypoeutectoid carbon steel. The temperature field wascalculated using the implicit finite-difference method andthe stress evaluation wasbased on the successive ap-proximation method described by [17].The input data for the program are:- cylinder diameter,- chemical composition of the steel,- process start and end temperature,- heat convection coefficient,- coordinates of the extreme point of the TTT curves.The output of the program is:- residual stress and structure distribution,- temperature-time and axial stress-time evaluation

on the surface and centere of the cylinder.

4 MODEL VERIFICATION

For the first example we took a 60-mm-diam-eter cylinder of 0.43% carbon steel quenched from870oC into water. This example was analyzed theo-retically and experimentally by [13] and [14] and alsotheoretically by [20].

From the published data we estimated thevalue of the coefficient of heat transfer to be near 25kW/m2K. It should be mentioned that even with such ahigh value for the coefficient of convection heat trans-fer we could not obtain the cooling speed at the centreof the cylinder which was reported by [13]. Neverthe-less, the calculated residual stresses were in good agree-ment with experimental values, as can be seen from Fig.1.

As a second example we considered cylindersof diameters 10 mm, 30 mm, 50 mm and 100 mm made from0.44% carbon steel. The axial residual stress distributionfor these cylinders was investigated experimentally by[2] and theoretically by [23]. All the cylinders werequenched into water at 20 oC from a temperature of 850oC. For the coefficient of convective heat transfer we

01

02

0

0

723 10,7 29,1 10 C

910 203 44,7 10 C

830 270 90 25 C

539 423 30,4 25 Cs

s

A Mn Si

A C Si

B C Mn

M C Mn

= - + ±

= - + ±

= - - ±

= - - ±

00-11/12stran 727


5700 W/m2K. Prav tako smo izvedli izraèun skonvekcijskim koeficientom, ki je temperaturnoodvisen in katerega odvisnost je iz podatkov [12].

Na slikah 2 do 5 so poleg izraèunanihosnih napetosti podane tudi eksperimentalnevrednosti, ki so jih podali [2] in [23]. Kakor se vidiiz teh slik, se izraèunane vrednosti za valje s premeri30 mm, 50 mm in 100 mm dobro ujemajo zeksperimentalnimi vrednostmi. Za valj premera 10mm so vrednosti zaostalih napetosti, ki jih podaja[2] negativne, tiste, ki jih podaja [23], pa sopozitivne, zato se nismo mogli odloèiti, ali soizraèunane vrednosti prave.

5 ANALIZA OBÈUTLJIVOSTI

Z namenom, da doloèimo zanesljivostmodela, smo izvedli analizo obèutljivosti. Kot izhodniparameter modela smo vzeli osne zaostale napetostina osi in robu valja. Za nadzor smo vzeli 36materialnih parametrov. Èe z a

k oznaèimo parameter,

potem je njegov relativni koeficient obèutljivostidefiniran z:

Izraèun koeficientov obèutljivosti smoizvedli za valje s premerom 10 mm, 30 mm in 50 mm.Parcialne odvode v (52) smo izraèunali numerièno.Podatki in rezultati izraèuna so podani v preglednici2.

took values for the constants between 3200 W/m2K and5700 W/m2K. We also performed calculations with thetemperature-dependent coefficient of convective heattransfer, which was calculated from the experimental datagiven by [12]

(51).

In figures 2 to 5 the calculated residual axialstresses are shown together with the experimentalvalues given by [2] and [23]. As can be seen fromthese figures the calculated residual stresses for thecylinders of diameter 30 mm, 50 mm and 100 mm are invery good agreement with the experimental values.For the 10 mm-diameter cylinder the value of the re-sidual stress given by [2] is negative and that givenby [23] is positive, so we could not conclude that thecalculated values are correct.

5 SENSITIVITY ANALYSIS

In order to estimate the accuracy of themodel we performed a sensitivity analysis. As anoutput parameter from the model we took the axialresidual stress on the axis of the cylinder and on itsboundary. For the control parameters we took 36 ma-terial parameters. If we denote these parameters as a

k

then the relative sensitivity coefficient is defined by:

(52).

We carried out the calculation of the sensi-tivity coefficients for cylinders of diameter 10 mm, 30mm and 50 mm. The partial derivatives in (52) wereperformed by numerical differentiation The data andthe results of the calculation are shown in Table 2.

0 5 10 15 20 25 30 -1200

-1000

-800

-600

-400

-200

0

200

400

600

800

1000

s z

s j

s r

Experimental s z (Ref 13)

Experimental s z (Ref 14)

radius[mm]

Sl 1. Zaostale napetosti v ga�enem valju premera 60 mmFig. 1. Residual stress distribution in a 60 mm-diameter quenched cylinder

2 4 3 21029 63 0,14 0,7510 W m Kh J J J-= + - +

k zk

z k

as

a

¶s

s ¶=

Preskus / Experimental

Preskus / Experimental

polmer / radiusmm

MPa

00-11/12stran 728


Sl. 2. Osne zaostale napetosti v ga�enem valjupremera 10 mm

Fig. 2. Axial residual stress distribution in aquenched 10 mm diameter cylinder







Iz preglednice 2 vidimo, da so v skoraj vsehprimerih najvplivnej�i parametri model temperaturnirazteznostni koeficient austenita a

A, dilatacija

austenita gA in martenzita g

M, ekstremna toèka na

krivulji TTT za perlit (tP,P

m) in bainit (t

B,B

m) in nazadnje

temperaturi A3 in B

s. Prav tako je model nekoliko

obèutljiv za konvekcijski koeficient h in masni dele�ogljika C.

Iz povedanega sklepamo, da je model zeloobèutljiv za kinetiko prehoda austenita v perlit inbainit. V primeru valja s premerom 10 mm, ko se skorajceloten valj spremeni v martenzit, je model tudi zeloobèutljiv za parametre kinetiène enaèbe (34). Po drugistrani pa je model razmeroma neobèutljiv za mejoplastiènega teèenja in druge mehanske in fizikalnelastnosti.

Na temelju koeficientov obèutljivosti smoocenili relativno napako izraèunanih zaostalihnapetosti po obrazcu:

From table 2 we can see that the most impor-tant parameters in the model are, in almost all cases: thethermal expansion of austenite a

A; the dilatation of aus-

tenite gA and martensite g

M; the extreme points on the

TTT curve for prearlite (tP,P

m) and bainite (t

B,B

m);and

finally, the temperatures A3 and B

s. Also, the model is

only moderately sensitive to the coefficient of convec-tive heat transfer (h) and the weight percent of carbon.

From the above we can conclude that themodel is very sensitive to the kinetics of phase changefrom austenite to pearlite and bainite. In the case ofthe 10-mm-diameter cylinder, where almost all the cyl-inder is transformed to martensite, the model is alsovery sensitive to parameters in the martensite kineticequation (34). On the other hand, the model is rela-tively insensitive to yield stresses and other mechani-cal and physical data.

On the basis of sensitivity coefficients wecan estimate the relative error of the residual stresswith the formula:

(53),( )2

1

1 M

i ii

sMse e

=

= å

0 1 2 3 4 5-300

-200

-100

0

100

200

300

Izraèun z h=5700 [W/m2K]

Izraèun z h=h(J)

Izmerjeno [2]

Izmerjeno [23]

Calculated with h=5700 [W/m2K]

Calculated with h=h(J)

Measured [2]

Measured [23]

sz [M

Pa

]

Radius [mm]

0 2 4 6 8 10 12 14-1000

-800

-600

-400

-200

0

200

400

600



Calculated with h=h(J)

Measured [2]

Measured [23]



Izraèun z h=h(J)

Izmerjeno [2]

Izmerjeno [23]

sz [M

Pa

]

Radius [mm]

0 5 10 15 20 25-1000

-800

-600

-400

-200

0

200

400

600

800



Calculated with h=h(j)

Measured [23]



Izraèun z h=h(j)

Izmerjeno [23]

sz [M

Pa

]

Radius [mm]

0 10 20 30 40 50-800

-600

-400

-200

0

200

400

600

800



Izmerjeno [2]



Measured [2]

sz [

MP

a]

Radius [mm]

MPa

mm

polmer / radius

MPa

polmer / radius

mm

mmpolmer / radius

polmer / radiusmm

MPaMPa

00-11/12stran 729


d 10 mm 30 mm 50 mm

par. enota unit

vrednost value

obmoèje ± range ±

sredi�èe center

povr�ina surface

sredi�èe center

povr�ina surface

sredi�èe center

povr�ina surface

Pc MJ/m3K 3,76 0,15 -0,379 0,133 0,980 0,053 -0,271 -0,110

Ac MJ/m3K 4,15 0,2 -0,844 -0,857 -0,607 -0,577 0,144 -0,455

Pl W/mK 66,20 1,74 -0,126 -0,030 -4,280 -2,127 -0,198 -0,833

Al W/mK 15 0,573 -0,021 0,678 0,573 -0,424 -0,448 -0,348

Ml W/mK 25 1,74 -0,279 -0,644 0,011 -0,082 0,007 -0,003

PAl MJ/m3 630 30 -0,065 -0,074 0,420 0,042 0,063 -0,242

MAl MJ/m3 660 30 -0,257 -0,090 -0,013 -0,013 -0,002 -0,002

PE GPa 209 1,26 0,646 1,680 1,654 1,227 1,034 0,129

AE GPa 200 0,32 -0,188 0,313 -0,188 -0,063 -0,188 0

n - 0,30 0,01 0,171 0,894 0,711 0,501 0,402 0,033

Aa 10-4 K-1 22 1 -3,971 -5,223 8,452 0,363 10,86 0,147

Ba 10-4 K-1 13 1 -0,138 -0,099 -1,017 0,049 -0,052 -0,044

Pa 10-4 K-1 14 1 -0,206 -0,218 -0,678 1,740 -4,572 0,078

Ma 10-4 K-1 12 1 0,714 1,188 -0,132 -0,634 0 0,002

Mg 10-3 8,50 0,22 4,165 4,857 0,042 0,742 -0,008 0

Ag 10-3 10,7 0,7 5,397 6,385 -6,629 0,214 -7,453 -0,113

MK 10-5 MPa-1 4,18 0,1 -0,021 0,004 -0,217 -0,059 -0,385 0,008

KB 10-5 MPa-1 5,08 0,1 -1,483 -0,320 -0,218 -0,742 0,005 0,005

sYP MPa 434 34 -0,006 -0,049 0,005 0 0,794 0,128

sYB MPa 491 34 -0,003 -0,023 0 0 0,143 0,459

sYA MPa 123 2 -0,062 -0,597 0,068 0,012 0,062 -0,012

sYM MPa 445 30 0 0 0 0 0,013 0,323

J s oC 850 20 0,315 0,196 -1,441 -2,809 1,687 -2,265

J f oC 20 5 -0,228 -0,145 -0,112 -0,246 -0,093 -0,153

h W/m2K 5700 700 2,017 1,228 0,812 2,018 0,571 1,523

k M - 0,011 0,0005 3,793 3,181 0,110 0,539 0,002 0,086

Bm oC 460 20 3,190 2,082 -0,435 4,791 -0,520 2,272

Pm oC 560 20 4,819 3,693 5,547 2,918 2,111 4,460

t B s 1,3 0,1 1,080 0,849 0,260 0,922 -0,030 0,524

t P s 1 0,1 1,330 1,126 -0,816 0,110 0,054 0,779

A3 oC 910 10 -5,260 -4,186 4,150 -1,338 4,359 -3,749

Bs oC 830 25 -3,552 -2,590 0,445 -3,801 -0,601 -1,829

M s oC 539 25 -0,388 -1,150 0,296 1,156 0,024 0,559

C - 0,44 0,02 1,340 1,547 1,816 0,537 2,080 1,155

Mn - 0,66 0,1 0,391 0,349 -0,145 0,237 -0,052 0,177

Si - 0,22 0,07 -0,057 -0,046 0,045 -0,014 0,047 -0,041

Preglednica 2. Podatki o materialu in izraèunani koeficienti obèutljivosti za valje premera 10, 30 in 50 mmTable 2. Material data and calculated sensitivity coefficients for cylinders with diameter 10, 30 and 50 mm

00-11/12stran 730


where ei is the relative error of ith parameter. By us-

ing data from Table 2 the estimated relative error inthe residual stresses are calculated. The results areshown in Table 3.

pri èemer je ei relativna napaka i tega parametra. Z

uporabo podatkov iz preglednice 2 smo izraèunalioceno relativne napake izraèunanih zaostalihnapetosti. Rezultati so podani v preglednici 3.

6 SKLEP

Izdelan je bil matematièni model toplotneobdelave in zbrani vsi potrebni podatki. Model smouspe�no preskusili na dveh primerih izraèunazaostalih napetosti, za katere so znanieksperimentalni rezultati. Nadalje smo izvedli analizoobèutljivosti modela, s katero smo dobili kolikostnooceno vplivnosti posameznih podatkov v materialu.Prav tako je bila ocenjena relativna napaka vizraèunu zaostalih napetosti.

Na podlagi tega so glavne ugotovitve:1. model toplotne obdelave je izredno obèutljiv za

podatke, ki so vkljuèeni v kinetiènih enaèbah;2. model je prav tako pomembno obèutljiv za

temperaturni razteznostni koeficient austenita indilatacijski koeficient prehoda med austenitom inmartenzitom;

3. relativna napaka pri izraèunu zaostalih napetostije ocenjena na 13%.

6 CONCLUSIONS

We have developed a mathematical modelfor heat treatment and collected the necessary dataneeded for practical calculations. We successfullytested the model in two examples for which the ex-perimental data were available. We then performed asensitivity analysis of the model which resulted in aquantitative determination of the relative importanceof the various material data. The relative error in thecalculated residual stresses was also estimated.

The main conclusions are as follows:1. the model of heat treatment is very sensitive to

the data which are used in the kinetic equations;2. the model is also very sensitive to the austenite

thermal expansion coefficient and the dilatationof austenite and martensite;

3. the calculated relative error for the residualstresses, using data published in the literature,are within 13%.

Preglednica 3. Ocenjene relativne napake osnih napetostiTable 3. Estimated relative errors of the axial residual stresses

d [ ]mm Sredi�èe Center

Povr�ina Surface

10 0,11 0,11

30 0,11 0,07

50 0,13 0,05

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[22] Yu, H.J., Wolfstieg, U., E.Macherauch (1978) Calculation of residual stresses with special finite elementprogram. Arch. Eisenhüttenwes., 49, 499-503.

[23] Yu, H.J., Wolfstieg, U., E.Macherauch (1980) On the influence of the diameter on the residual stresses in oiland water quenched steel cylinders. Arch. Eisenhüttenwes., 51, 195-200.

Naslova avtorjev: Dr. Milan BatistaFakulteta za pomorstvoin prometUniverze v LjubljaniPot pomor�èakov 46320 Portoro�

Prof.dr. Franc KoselFakulteta za strojni�tvoUniverza v LjubljaniA�kerèeva 61000 Ljubljana

Authors� Addresses: Dr. Milan BatistaFaculty of Maritime Studiesand TransportUniversity of LjubljanaPot pomor�èakov 46320 Portoro�, Slovenia

Prof.Dr. Franc KoselFaculty of Mechanical Eng.University of LjubljanaA�kerèeva 61000 Ljubljana, Slovenia

Prejeto: 10.10.2000

Sprejeto: 20.12.2000Received: Accepted:

00-11/12stran 732

J. Legat - N. Gubeljak - J. Predan: Razvoj in presku{anje - The Development and Testing

V skladu z zahtevami po posodobitvi odbojnih in vleènih naprav na tirnih vozilih Slovenskih �eleznicso bili razviti vzmetni paketi z vzmetnimi elementi na podlagi vezave elastomer kovina. Pomemben delraziskav pri presku�anju vzmetnih paketov, po vgradnji v odbojne naprave �elezni�kih vozil, je naletnopresku�anje vagonov. Z naletom obte�enega vozila na mirujoèe natovorjeno vozilo se ocenjuje zmo�nostodbojne naprave in vzmetnega paketa, da obdr�i pojemek mirujoèega vozila v dopustnih mejah. V prispevkuje predstavljen potek izvajanja preskusov z razliènimi hitrostmi naleta in naèin doloèevanja koeficienta trkaza razviti vzmetni paket. Rezultati opravljenih meritev ka�ejo, da najveèji pojemek med trkom obeh vozil tudipri najveèjih hitrostih ne prese�e dovoljene vrednosti po mednarodnih �elezni�kih predpisih. Prav tako sonaletni preskusi pokazali, da razviti vzmetni paket poleg du�enja omogoèa tudi poèasno vraèanje povratnegadela.© 2000 Strojni�ki vestnik. Vse pravice pridr�ane.(Kljuène besede: vozila �elezni�ka, odbojniki, razvoj, presku�anje)

The decision of the Slovenian Railway Company to modernise the shock absorbing and tractionequipment of its existing rolling stock initiated the development of novel spring packages consisting ofelastomer-metal-based elements. The crash testing of rail vehicles represents an important part of the testingof spring packages after their installation into buffers. The collision of a loaded rail vehicle with anotherloaded rail vehicle at a standstill is used to evaluate the capacity of buffers to retain the deceleration of thevehicle at standstill within the permissible limits. The results of tests at different collision velocities and theway of determining the collision coefficient for the developed spring package is described in this paper. Theresults of measurements show that the maximum deceleration during the collision of two rail vehicles doesnot exceed the permissible values defined in international railway regulations even at the highest velocities.Crash tests have also revealed that in addition to damping, the developed spring package enables slowreaction work.© 2000 Journal of Mechanical Engineering. All rights reserved.(Keywords: rail vehicles, buffers, development, testing)

The Development and Testing of Rail-Vehicle Buffers Filled withElastomer Spring Packages

Janko Legat - Nenad Gubeljak - Jo`ef Predan

© Strojni{ki vestnik 46(2000)11/12,732-749ISSN 0039-2480UDK 629.4.01:629.4.028:656.2Izvirni znanstveni ~lanek (1.01)


UDC 629.4.01:629.4.028:656.2Original scientific paper (1.01)

Razvoj in presku{anje odbojnikov `elezni{kihvozil z elastomernim vzmetnim paketom

0 INTRODUCTION

In the mid-1990s the Slovenian Railway Com-pany decided to modernise the operating characteris-tics of its existing rolling stock. Buffers, which directlyaffect the comfort of passengers during stopping,mostly consisted of spring systems made of metal ringsprings (Fig. 1). The characteristic curve of such springsystems is composed of the gradual and the steep partof the slope. The characteristic curve of the existingspring sytems was in agreement with the UIC (UnionInternationale des Chemins de Fer) regulations ([1]and [2]), but the rupture of the curve at the point oftransition from the gradual to the steep part of theslope caused a shock which spread over the frame-work to the braking system during stopping.

0 UVOD

Pri Slovenskih �eleznicah (S�) so se vzaèetku devetdesetih let lotili posodobitve voznihznaèilnosti sedanjih tirnih vozil. Odbojne naprave,ki neposredno vplivajo na udobje pri ustavljanjuvozila, so bile v veèini primerov izdelane z vzmetnimipaketi s kovinskimi obroèastimi vzmetmi (sl. 1). Pritovrstnih paketih je karakteristika sestavljena izpolo�nega in strmega dela. Potek karakteristike jebil v skladu s predpisi Mednarodnega zdru�enja za�eleznice (UIC) ([1] in [2]), vendar v toèki prehoda izpolo�nega na strmi del ima karakteristika nalom,zaradi èesar je pri ustavljanju vozila prihajalo dosunka, ki se je prena�al èez ogrodje vozila na zavornenaprave.

00-11/12stran 733


0

200

400

600

800

1000

0 20 40 60 80 100 120

F

W a

s

400 kN

1000 kN

100 kN

400 kN

130 kN

30 kN 50 kN 10 kN

mm

kN

The problems of the broken characteristiccurve and unreliable supply of spare parts were themain reasons to begin the development of elastomerspring packages.

In order to lower the costs of modernisationthe Slovenian Railway Company demanded that thedeveloped spring package should be built into the ex-isting buffers, thus limiting the length and the diameterof the spring package. In addition, it was required thatthe characteristics of the spring package be in accor-dance with UIC standards ([1] and [2]). These stan-dards define the static and the dynamic conditions thata spring package should fulfil. As a consequence, thetesting of the spring characteristics is also divided into

Sl. 1a. Prerez odbojne naprave z vzmetnimi obroèiFig. 1a. Section of the buffer with steel ring springs

Sl. 1b. Statièna karakteristika vzmetnega paketa z vzmetnimi obroèiFig. 1b. Static characteristic of the spring system with steel ring springs

Problem naloma karakteristike pa tudiovirana oskrba z rezervnimi deli sta bila poglavitnarazloga, zaradi katerih so se lotili razvojaelastomernega vzmetnega paketa.

Zaradi ni�jih stro�kov posodobitve soSlovenske �eleznice kot naroènik zahtevale, da jetreba razviti vzmetni paket vgraditi v sedanjeodbojne naprave, s èimer so omejile dol�ino inpremer vzmetnega paketa. Prav tako mora bitikarakteristika vzmetnega paketa v skladu s standardiUIC ([1] in [2]). Oba standarda UIC predpisujetastatiène in dinamiène pogoje, ki jih mora vzmetnipaket izpolniti. Tako je tudi presku�anje vzmetnekarakteristike razdeljeno na statièno in dinamièno.

00-11/12stran 734


the static and the dynamic part. The static tests consistof compression loading of the spring system at a con-stant axial displacement velocity, where the change inforce is recorded as a function of the path. The dynamictesting is performed in the form of crash tests of railvehicles with spring packages installed in buffers, wherethe work of the spring package and the maximum decel-eration during the collision are measured.

The key condition that a spring packagemust fulfil in static testing is defined by the amountof work (strain energy) the buffer must absorb for acertain path (deformation). The choice of the elas-tomer to be used in the spring package depends onthis condition. To be able to predict the deformationit is necessary to define the rheological parameters.These can only be determined on the basis of theexperimental behaviour of the specimen made fromthe chosen elastomer.

1 DEFINING THE RHEOLOGICAL PARAMETERS

In the case of highly elastic materials [3] thematerial is not expressed in terms of constants but bya three-parametric function with three invariants inthe direction of the principal coordinate axes:

(1),

for the invariants Ik in the principal coordinate axes in

the Cauchy-Green deformation tensor [4]. The com-ponent of Cauchy�s stress component (t

k) in the direc-

tion of the principal coordinate axis is expressed by:

(2),

where lk2 is the square of strain in the direction of

principal coordinate axes (the values of tensor bG);G=-1, 0, 1.

The constitutive law for an incompressiblematerial can be written as:

(3),

where p is the hydrostatic stress, while bG=bG(I1,I

2,I

3);

G=-1,1 are two response functions. Beatty andStalnaker [3] have shown that Bell�s constraint for-mulation for different deformation in simple tensionis given by:

(4),

which is also valid for isotropic material. For smalldeformations, the deforming material may be consid-ered incompressible, where the deformation can begiven in trivial deformation state l

1 = l

2 = l

3 = 1.

The connection between the engineeringstrains (e

k) and the strain (l

k) in the direction of the

principal coordinate axis is given by expression (5):

Pri statiènih preskusih poteka stiskanje vzmetnegapaketa z nespremenljivo hitrostjo osnega pomika,pri èemer se bele�i sprememba sile v odvisnosti odpoti. Dinamièni preskusi se izvajajo z naletnimipreskusi tirnih vozil z vgrajenimi odbojniminapravami, pri èemer se merita delo vzmetnega paketain najveèji pojemek med trkom.

Kljuèni pogoj, ki ga mora vgrajen vzmetnipaket pri statiènih preskusih izpolniti, je predpisanz vi�ino dela deformacijske energije, ki jo moraodbojnik za doloèeno pot - deformacijo prevzeti.Od tega pogoja je odvisno, kateri elastomer je trebauporabiti za izdelavo vzmetnega elementa oz.vzmetnega paketa. Za napoved deformacijskegadela je treba definirati reolo�ke parametre, ki selahko doloèijo le na podlagi eksperimentalnegaobna�anja vzorca, ki je izdelan iz naèrtovanegaelastomera.

1 DEFINIRANJE REOLO�KIH PARAMETROV

V primeru visoko - elastiènih materialov [3],material ni opisan s konstantami, temveè s tri-parametrièno funkcijo s tremi invariantami v smeriglavnih koordinatnih osi:

za invariante Ik v smeri glavnih koordinatnih osi v

Cauchy-Greenovem deformacijskem tenzorju [4].Komponenta Cauchyeve komponente napetosti t

k v

smeri glavnih koordinatnih osi je doloèena z izrazom:

kjer je lk

2 kvadrat defomacije v smeri glavnihkoordinatnih osi (vrednosti tenzorja B); G=-1, 0, 1.

Za nestisljiv material se lahko konstitutivnizakon zapi�e:

kjer so p hidrostatièna napetost, bG=bG(I1,I

2,I

3);

G=-1,1 pa dve odzivni funkciji. Beatty and Stalnaker[3] sta pokazala, da omejitev, ki jo je uporabil Bell zarazliène deformacije v primeru enoosnegaobremenjevanja, podana z izrazom:

velja tudi za stisljiv in izotropen material. Dejansko setudi stisljiv material v podroèju malih deformacijobna�a enako kot nestisljiv. To ustreza trivialnemuprimeru, ko so deformacije l

1 = l

2 = l

3 = 1.

Povezava med in�enirskimi deformacijami ek

in deformacijo lk v smeri glavne koordinatne osi je

podana z izrazom:

1 2 3( , , )I I Ib bG G=

2 20 1 1k k kt b b l b l -

-= + × + × k = 1, 2, 3

2 21 1k k kt p b l b l -

-= - + × + × k = 1, 2, 3

1/ 21 2 3 3tr l l l= + + =B

00-11/12stran 735


(5).

If an incompressible isotropic hyperelasticmaterial is treated as a function of the strain energyW = W(J

1,J

2,J

3) per volume unit we can say that it

corresponds to equation (2) by depending only on J3

or bG = bG(J3). Individual parameters can be expressed

by the invariants I1,I

2,I

3:

(6a,b,c).

In their discussion of hyperelastic materi-als, Truesdell and Noll [7] derived the following val-ues for the parameters of equation (2):

(7)

(8)

(9),

It has been found, by considering the as-sumed functional relationships, [4], that the relationspresented in equations (6 a,b,c) are valid only in thecase when the partial derivations in equations (8)and (9) are equal to the constant value:

(10).

After introducing the constants a and binto expressions ((7) to (9)) the following is obtainedfor the Cauchy-Green deformation tensors:

(11a,b,c).

It has been shown that J3=1 is valid for an

incompressible elastomer, and that the difference be-tween the coefficients b1(1)-b-1(1)=a+b=m0 corre-sponds to the shear modulus of the material�s natu-ral state [5]. The constants a and b are also related tothe constant f whose value is between 0<f£1. Thusit is possible to introduce the expressions a=mo f andb=mo(1-f). The general expression for the constitu-tive equation for a hyperelastic material is obtainedby inserting Equations (11a,b,c) into Equation (2):

(12).

The deformation work for an isotropichyperelastic material depending on the modified straininvariants was calculated according to Yeoh�s model[6]:

(13),

where C10

, C20

, C30

are the material constants deter-mined from the experimentally measured stress-strainrelation. Yeoh�s model yields acceptable results in

Èe obravnavamo nestisljiv izotropenhiperelastièen material kot funkcijo deformacijskeenergije W = W(J

1,J

2,J

3) na enoto prostornine, lahko

zapi�emo, da ustreza enaèbi (2) v odvisnosti le od J3

oz. bG = bG(J3). Posamezni parametri se lahko izrazijo z

invariantami I1, I

2, I

3:

Za hiperelastiène materiale sta Truesdell inNoll [7] izpeljala naslednje vrednosti za parametreenaèbe (2):

Z upo�tevanjem predpostavljene funkcij-ske odvisnosti je ugotovljeno [4], da podanarazmerja v enaèbah (6 a,b,c) veljajo takrat in le takrat,èe sta parcialna odvoda v enaèbah (8) in (9) enakanespremenljivi vrednosti, in sicer:

Z vpeljavo konstant a,b v izraze ((7) do(9)) za Cauchy-Greenove deformacijske tenzorjedobimo:

Za nestisljiv elastomer velja J3=1 in razlika

med koeficientoma b1(1)-b-1(1)=a+b=m0 ustrezastri�nemu modulu v naravnem stanju materiala [5].Konstanti a,b sta povezani tudi s konstanto f, ki imavrednost med 0<f£1. To omogoèa uvedbo izrazova=mo f in b=mo(1-f). Z vstavitvijo enaèb (11a,b,c) venaèbo (2) dobimo splo�ni izraz za konstitutivnoenaèbo hiperelastiènega materiala:

Za izotropen hiperelastièen material vodvisnosti od prirejenih deformacijskih invariant jebilo deformacijsko delo izraèunano po Yeohovemmodelu [6]:

1 1,2,3k k ke l= - =

33

( )o

WJ

Jb

¶=

¶

1 33 1

2( )

WJ

J Jb

¶=

¶

1 2

2 2W W

J Ja b

¶ ¶= =

¶ ¶

0 1 13 3

WJ J

a bb b b-

-= = =

10 0(1 )W f fm m -= × + × × - -T I B B

( ) ( ) ( )2 2 2

10 1 20 2 30 33 3 3W C I C I C I= - + - + -

-1 1/ 221 1 2 3 3

3

detI

J I tr J tr J II

º = º = º =B B B

1 33 2

2( )

WJ

J Jb-

- ¶=

¶

kjer so C10

, C20

, C30

konstante materiala, ki se doloèajoiz eksperimentalno izmerjene odvisnosti napetost-deformacija. Yeohov model daje primerne rezultate v

00-11/12stran 736


0

1

2

3

4

5

6

7

8

0 1 2 3 4 5 6

s

F

obremenjevanje

loading

1. krog

1. cycle

5. krog

5. cycle

W e =10,1 J

W a /W e =71,5%

kN

mm

the case when the material constants are obtained byuniaxial compression or tensile tests. The parametersof Yeoh�s model C

10, C

20, C

30 are linearly volume de-

pendent, which means that it is possible to determinethe cumulative work of the assembled spring pack-age from the tested specimen for the same range ofdeformation.

1.1 Experimental determination of the relation s-e

The specimen was made in the R&D Instituteof the Sava company in Kranj, Slovenia. The materialused was an elastomer/rubber mixture containing sootand some additives. The hardness of the vulcanisedspecimen is 68°Sh. The basic assumption is that theelastomer is incompressible, which means that its vol-ume remains constant, only the shape of the specimenchanges due to the action of external loading. A stan-dard cylindrical specimen with a diameter of 29 mm, aheight of 12 mm and a volume (V) of 7926 mm3 was usedin the compression-loading test. During the test theradial and the axial strains were recorded as the forcewas varied. Static loading at a constant displacementvelocity (v=20 mm/min) was continuously repeated untilthe reproducibility of the force-axial displacement char-acteristic was reached during the fifth loading cycle.The characteristics of the first and the fifth cycles areshown in Fig. 2. It is evident from Fig. 2 that the ratio ofthe cumulative work (the surface under the loading curve)to damping work (the surface between the loading andthe decompression curve) is favourable (Wa /We=71,5%).Further analysis will therefore be focussed only on thedetermination of the cumulative work of deformationWe.

The change in shape during the compres-sion test is shown in Fig. 3. Due to the friction be-tween the specimen surface and the steel base sur-

primeru, ko se konstante materiala doloèajo zenoosnim tlaènim ali nateznim preskusom. Prav takoso parametri Yeohovega modela C

10, C

20, in C

30

linearno odvisni od prostornine, kar pomeni, da jemogoèe na podlagi presku�enega vzorca ugotoviticelotno delo sestavljenega paketa za enako obmoèjedeformacije.

1.1 Eksperimentalna doloèitev odvisnosti s-e

Vzorec je izdelal Razvojno tehnolo�kiin�titut podjetja Sava Kranj. Vzorec je bil izdelan izme�anice elastomera in naravnega kavèuka z dodatkisaj in aditivov. Trdota vulkaniziranega vzorca jezna�ala 68° Sh. Izhodi�èna predpostavka je, da jeelastomer nestisljiv, kar pomeni, da ohranjanespremenljivo prostornino, le oblika vzorca sespreminja zaradi delovanja zunanje obremenitve. Zatlaèni preskus je bil uporabljen standardni valjnivzorec s premerom 29 mm in vi�ino 12 mm(prostornina V=7926mm3). Med preskusom so bilespremljane spremembe preène in vzdol�nedeformacije v odvisnosti od sile. Statiènoobremenjevanje s stalno hitrostjo pomika (v=20 mm/min) je bilo zvezno ponavljano do dosegaponavljajoèe se karakteristike sila - osni pomik po 5.krogu obremenitve. Karakteristika 1. in 5. kroga jepodana na sliki 2. S slike 2 je razvidno, da je razmerjemed celotnim delom (povr�ina pod obremenilnokrivuljo) in du�enim delom (povr�ina medobremenilno in razobremenilno krivuljo) ugodno(Wa

/We=71,5%). Zaradi tega je nadaljnja analizanamenjena le doloèitvi celotnega deformacijskegadela We.

Sprememba oblike med tlaènim preskusomje prikazana na sliki 3. Zaradi trenja med podlago inrazporeditve napetosti med tlaènim preskusom so

Sl. 2. Statièno (tlaèno) obremenjevanje valjnega vzorcaFig. 2. Static (compression) loading of cylindrical specimen

00-11/12stran 737


face, and also due to the compressive stress distri-bution, the smallest strains were measured on thecontact surface between the specimen and the base(diameter r

1), and the largest strains in the middle

part of the specimen (diameter r2).

The relations between the strains e1,e2, e3 andthe compressive stress s

z were determined from the

change in shape and the loading, as shown in Fig. 4.

The strain invariants I1, I

2 and I

3 that are

normed by the volume of the specimen are determinedon the basis of principal strains e1,e2 and e3 accordingto equations (5) to (7) in individual points. On the basisof the known values for work W

e,i in individual strain

points and the corresponding values of strain invari-ants, and by solving the system of linear equations, wecan determine the values of the coefficients C

10=-4.9×10-4,

C20

=3.53×10-4, C30

=1.72×10-4 in Yeoh�s model in therange of 10 to 43% of strain per volume unit.

The calculated coefficients of Yoeh�s modelwere used to compare the experimentally determined

najmanj�e deformacije izmerjene v stiènem delu medvzorcem in podlago (premer r

1), medtem ko so najveèje

deformacije dose�ene v srednjem delu vzorca (premerr

2).

Na podlagi spremembe oblike in vi�ineobremenitve so doloèene odvisnosti meddeformacijami e1,e2, e3 in tlaèno napetostjo s

z, kakor

je prikazano na sliki 4.

Deformacijske invariante I1, I

2 in I

3, ki so

normirane s prostornino vzorca, so doloèene napodlagi deformacij v posameznih smereh e1,e2, e3 poenaèbah (5) do (7) po posameznih toèkah. Iz znanihvrednosti za delo W

e,i v posamezni toèki deformacije

in pripadajoèih vrednosti deformacijskih invariant inre�itve sistema linearnih enaèb so doloèene vrednostikoeficientov C

10=-4,9×10-4, C

20=3,53×10-4, C

30=1,72×10-4

v Yeohovem modelu v obmoèju od 10 do 43 %deformacije na enoto prostornine.

Z izraèunanimi koeficienti Yoehovegamodela je bila opravljena primerjava med

Sl. 3. Sprememba oblike vzorca med tlaènim preskusomFig. 3. Changes in specimen shape during compression loading

0

5

10

15

20

-25 -15 -5 5 15 25

x,y

z

r 1

r 2 Oblika èepa v prednapetem stanju 10%

Shape of specimen at 10% of strain

14% 18%

27% 35%

43%

52%

mm

mm

0

1

2

3

4

5

6

7

8

9

10

-0,55 -0,45 -0,35 -0,25 -0,15 -0,05 0,05 0,15 0,25 0,35 0,45 0,55

s z

MPa deformacija na stièni povr�ini strain on the contact surface r 1

deformacija v sredi�njem delu pr e izku�anca strain in the middle of specimen r 2

obremenjevanje

loading

obremenjevanje

loading

e 1 , mm/mm e 2,3 , mm/mm

Sl. 4. Sprememba deformacij e1,e2, e3 v smeri glavnih osi pod vplivom tlaène napetosti sz

Fig. 4. Relationship between principal strains e1,e2, e3 and compressive stress sz

00-11/12stran 738


strain energy with the strain energy calculated by themodel depending on the principal strain e

1. The experi-

mental values for the strain energy Weksp,i

were calcu-lated as an integral under the load curve F-z (Fig. 2) forindividual strain rates e

1=z/h

o, where z stands for the

displacement in the direction of the axis and ho repre-

sents the initial height of the specimen. The strainenergy values calculated according to the model W

mod,i

were obtained by taking into account the correspond-ing values for the invariants I

1, I

2 and I

3 for the corre-

sponding principal strains e1,e2, e3 according to equa-tion (13). The comparison of both strain energies showsa good agreement between the experimentally mea-sured and the calculated values, as shown in Fig. 5.

On the basis of the model constants in equa-tion (13), it is possible to calculate the strain energy ofthe same elastomer in the available buffer volume. Asthe elastomer should never come in contact with thebody of the buffer, not even at maximum compression,the deforming of the buffer must be guided in the radialand axial directions. This is achieved by vulcanising theelastomer on a steel plate, which produces the elementshown in Fig. 6. Sliding plates, equal to those used forspring elements, were installed between the individualspring elements of the whole package in order to assureequal radial deformation of all the elements. The springelements and sliding plates assembled in the springpackage [6] are shown in Fig. 7. A borehole (20 mm) inthe sliding plates and in the spring elements is made forthe guiding rod which serves to set the prestressingforce and the length of the spring package before instal-lation into the buffer body, as shown in Fig. 8a. Toachieve optimal use (efficiency) of the available buffervolume, i.e. full filling of the space with the elastomerwhen the spring package is contracted, the shape of theedge had to be defined, which was achieved by observ-ing the sliding of the elastomer�s edge over the sliding

deformacijsko energijo, doloèeno s preskusom, in zmodelom izraèunano deformacijsko energijo vodvisnosti od osne deformacije e

1. Eksperimentalne

vrednosti za deformacijsko energijo Weksp,i

soizraèunane kot integral pod obremenilno krivuljo F-z(sl. 2), za posamezno stopnjo deformacije e

1=z/h

o

(kjer je z pomik v smeri osi in ho zaèetna vi�ina vzorca).

Z upo�tevanjem pripadajoèih vrednosti invariant I1,

I2 in I

3 pri pripadajoèih deformacijah e1,e2, e3 v smeri

glavnih osi po enaèbi (13) so izraèunane vrednostideformacijske energije po modelu W

mod,i. Primerjava

med obema deformacijskima energijama ka�e dobroujemanje med eksperimentalno izmerjeno in zmodelom izraèunano vrednostjo.

Tako je na podlagi konstant modela v enaèbi(13) mogoèe izraèunati deformacijsko energijo istegaelastomera v razpolo�ljivi prostornini odbojnenaprave. Ker elastomer pri najveèjem stisku ne smepriti v stik z ogrodjem odbojnika, mora biti deformiranjeelastomera vodeno v preèni in vzdol�ni smeri. To jedose�eno z vulkanizacijo elastomera na jekleno plo�èo,s èimer je dobljen vzmetni element, ki je prikazan nasliki 6. Za zagotovitev enakomerne radialnedeformacije vseh elementov v paketu so med vzmetneelemente vstavljene drsne plo�èe, ki so enake jeklenimplo�èam za vzmetne elemente. Sestavljen vzmetnipaket [6] iz vzmetnih elementov in drsnih plo�è jeprikazan na sliki 7. Izvrtina 20mm na drsnih plo�èah invzmetnih elementih je prirejena za vodilni drog, kiomogoèa nastavitev sile prednapetja in dol�inevzmetnega paketa pred vgradnjo v odbojno napravo,kakor je prikazano na sliki 8a. Za optimalnoizkori�èenost razpolo�ljive prostornine v odbojniku,kar pomeni polno popolnitev prostora z elastomerompri stisnjenem paketu, smo obliko boènice doloèalitako, da smo opazovali potek drsenja boèniceelastomera po drsni plo�èi med razbremenjevanjem.

Sl. 5. Primerjava med eksperimentalno izmerjeno deformacijsko energijo in deformacijsko energijo,izraèunano po modelu

Fig. 5. Comparison between the experimentally determined and modelled strain energy vs. principal strain e1

0

2

4

6

8

10

0 10 20 30 40 50

e 1 %

W

J W mod

W eksp/exp

00-11/12stran 739


plate during restitution. The static characteristic of thedeveloped spring package is smoothly continuous andfulfils the requirements of the UIC standards ([1] and[2]) (Fig. 8b). This means that the loading curve mustrun between the prescribed minimum and maximum val-ues (e.g. the force must be between 100 and 400 kN at adisplacement of 60 mm) and that the cumulative work ofthe spring package must be higher than 20 kJ at the ratioWa /Wc>50%.

It is possible to evaluate the cumulativework-strain energy of the whole spring package con-sisting of 14 spring elements for the planned elas-tomer volume (V=25.135 l) by taking into account thecalculated constants of Yeoh�s model. The compari-son between the anticipated and the experimentally mea-sured work of the whole package is given in Fig. 9. Asubstantial deviation in the range between 25 to 35% ofstrain is a consequence of one missing free surface of thespring element in contrast to the specimen where bothsurfaces were free. Another reason for the differencebetween the predicted and the measured work may resultfrom the difference between the composition of the elas-tomer specimen and the elastomer used for the springpackage. Although the deviations in the composition ofelastomers are within the permissible limits, the proper-ties of the series may vary by up to 10% [7]. In any case,it is evident from Fig. 9 that we can reasonably expect thespring package to exceed 20 kJ at the pressure strain of 35to 38 %, which corresponds to the displacement of thespring package from 90 to 100 mm, and thus to fulfil thecondition stated in the UIC standards ([1] and [2]). Thepurpose of the spring package is to use the kinetic en-ergy of collision during compression loading for the workof restitution and damping. The work during packagecompression consists of the elastomer deformation work,where de-crosslinking of the elastomer takes place [8],and the work of rolling and sliding of the elastomer�s free

Vpeljan vzmetni paket ima statièno karakteristiko vceloti gladko zvezno ter hkrati izpolnjuje pogoje vskladu s standardi UIC ([1] in [2]), kakor je prikazanona sliki 8b. To pomeni, da mora obremenitvenakrivulja potekati med predpisanima najmanj�ima innajveèjima vrednostima (npr. pri 60 mm pomika morabiti sila med 100 in 400 kN) ter mora biti celotno delovzmetnega paketa veèje od 20kJ pri razmerjuWa /Wc>50%.

Za izbrano prostornino elastomera (V=25,135 l)v vzmetnem paketu iz 14 vzmetnih elementov jemogoèe z upo�tevajem izraèunanih konstantYeohovega modela oceniti deformacijsko delo -energijo celotnega vzmetnega paketa. Primerjava mednapovedanim in eksperimentalno izmerjenim delomcelotnega paketa je podana na sliki 9. Izrazitoodstopanje v obmoèju med 20 do 35% deformacijeje posledica omejitve ene proste povr�ine privzmetnem elementu, v nasprotju od vzorca, prikaterem sta bili obe povr�ini prosti. Prav tako jerazlog za odstopanje med napovedanim in spreskusom izmerjenim delom lahko v razliki medsestavo elastomera pri vzorcu in elastomerom, ki jeuporabljen za izdelavo vzmetnega paketa. Èepravso odstopanja v sestavi elastomera v dopustnihmejah, se lahko lastnosti med serijo razlikujejo tudido 10% [7]. Kakorkoli �e, na podlagi slike 9 lahkoprièakujemo, da bo vzmetni paket pri tlaènideformaciji med 35 do 38% (kar ustreza pomikuvzmetnega paketa med 90 do 100mm) presegel 20kJin s tem izpolnil pogoj po standardih UIC ([1] in[2]). Namen vzmetnega paketa je, da kinetiènoenergijo trka pri tlaènem obremenjevanju porabi zapovratno in du�eno delo. Delo pri stiskanju paketaje sestavljeno iz dela deformacije elastomera, prikaterem prihaja do razmre�enja elastomera [8] terdela kotaljenja in drsenja proste povr�ine

Sl. 6. Vzmetni elementFig. 6. Spring element

00-11/12stran 740


0

100

200

300

400

500

600

700

800

900

1000

1100

0 10 20 30 40 50 60 70 80 90 100 110

s

F

W a

130 kN

30 kN

100 kN

400 kN 400 kN

1000 kN

50 kN

10 kN

W e =25,15 kJ

W a /W p =59,7%

kN

mm

Sl. 7. Sestavljen vzmetni paketFig. 7. Assembled spring package

Sl. 8a. Prerez odbojne naprave z elastomernim vzmetnim paketomFig. 8.a. Section of the buffer with the assembled elastomer spring package

Sl. 8b. Statièna karakteristika vzmetnega paketa z elastomeromFig. 8.b. Static characteristic of the spring package with elastomer

00-11/12stran 741


0

5

10

15

20

25

30

35

5 10 15 20 25 30 35 40

e 1 %

W

W mod

W eksp/exp

kJ

surface over the sliding plate. The elastomer mixture andthe technology of binding the elastomer on the metalwere developed at the R&D Institute of the Sava com-pany in Kranj, Slovenia [7].

2 CRASH TESTING OF BUFFERS

In dynamic crash tests, unlike static tests,the loading curve is not prescribed, just the magni-tude of the cumulative and damping work and themaximum permissible acceleration values. In addition,the force in the buffer must not exceed 1000 kN.

The UIC regulations ([1] and [2]) also definethe conditions under which measurements arerecognised to be competent. Thus two rail vehicles(m

1 and m

2) were placed on a straight horizontal track

with minimum rail defects. For the sake of safety thetesting track was 1000 m long. In this way we couldexpect the vehicles to collide in the direction of thenormal that connects the centres of gravity of bothvehicles. The dynamics of the crash test can be theo-retically described as a collision of two bodies [9]. Thevehicle with mass m

1 moves at velocity v

1 towards the

vehicle at rest (v2=0). During the collision the vehicles

are in contact for a short time interval that consists ofthe contraction and the restitution time. During thecontraction time the deformation of spring packageskeeps increasing due to the forces acting on the con-tact surfaces (buffers). During this time interval, whichlasts from the initial time (t

0) to the time t

1, the force F

in the buffer increases from the prestressing force Fp

to the maximum force Fmax

(Fig. 10).Spring packages are maximally contracted

at the time t1. The restitution time lasts from t

1 to t

2

when the spring package performs the recovery move-ment. In the time t

1 both vehicles move in the direc-

tion of the normal at the same velocity cN.

Sl. 9. Primerjava med napovedano in eksperimentalno izmerjeno deformacijsko energijo vzmetnega paketaFig. 9. Comparison between the predicted and the measured strain energy of the spring package

elastomera po drsni plo�èi. Me�anico za elastomer,kakor tudi tehnologijo vezave elastomera nakovino, je razvil Razvojno tehnolo�ki in�titut (RTI)Sava Kranj [7].

2 NALETNO PRESKU�ANJE �ELEZNI�KIHODBOJNIKOV

V nasprotju s statiènimi preskusi pri dinamiènihnaletnih preskusih ni predpisan potek obremenitvenekrivulje, temveè le vi�ina celotnega in du�enega dela ternajveèje dopustne vrednosti za pospe�ke, pri èemersila v odbojni napravi ne sme preseèi 1000 kN.

Predpisi UIC ([1] in [2]) doloèajo tudipogoje, pod katerimi so meritve odloèujoèe. Takosta bila oba vagona (m

1 in m

2) postavljena na

ravnih in ne viseèih tirih z najmanj�imi napakamina tirnicah. Zaradi varnosti je bilo naèrtovano, dabo presku�evalni ravni del proge dolg 1000 m.Tako je bilo mogoèe predpostaviti, da se bo trkvagonov opravil v smeri normale, ki povezujete�i�èa obeh vagonov. Dinamiko naletnegapreskusa je mogoèe teoretièno opisati kot trk dvehteles [9]. Vagon mase m

1 se giblje s hitrostjo v

1

proti mirujoèem vagonu (v2 = 0). V èasu trka so

vagoni v kratkem èasovnem stiku, pri èemerloèimo dva èasa: èas stiskanja in èas raztezanja. Vèasu stiskanja vzmetnih paketov se zaradi sil nadotikalnih povr�inah (odbojnikih) vzmetni paketivse bolj deformirajo. V tem èasu, ki traja od nekegazaèetnega èasa t

0 do t

1, se poveèuje sila F v

odbojniku od sile prednapetja Fp do najveèje sile

Fmaks

(sl. 10).V èasu t

1 so vzmetni paketi najbolj

stisnjeni. Èas raztezanja traja od èasa t1 do t

2, ko

vzmetni paket opravlja povratni gib. V èasu t1 se

oba vagona gibljeta z enako hitrostjo cN v smeri

normale.

00-11/12stran 742


t

F

F maks

stiskanje

contraction

reztezanje

restitution

d t

dF

F p

t 1 t 2 t 0

The parameters of the crash test (path, force,velocity and work) are time-dependent variables, sothe expression for the momentum law is given forindividual instants of the impact only. The compo-nent of the momentum law in the direction of thenormal during the contraction time is expressed forboth vehicles by the equations:

(14)

(15).

A similar situation applies to the restitution time (t1 to t

2):

(16)

(17).

Equations (14) to (17) show the change inforce F(t) due to velocity changes during the colli-sion for both vehicles.

During the collision a part of the kinetic energyis spent uncontrolled, which is ascribed to the friction inbearings and the friction between wheels and rails, andalso to the oscillations of the vehicle body and shockabsorbers. This is the reason why the rheological proper-ties of the buffer can be determined only on the buffer bydirect measurements of force and displacement as a func-tion of time. For the measurements on the buffer the gaugefor force measurements is placed between the buffer andthe vehicle body, while the displacement gauge lies be-tween the movable buffer plate and the fixed buffer body,as shown in Fig, 11. In this way it is possible to directlydefine the energy needed for a certain flexure (deflection)of the buffer. The kinetic energy loss is obtained with thehelp of reaction work measurements as the differencebetween the cumulative work and the restitution work.

Parametri naletnega preskusa, to so pot,sila, hitrost in delo, so èasovno odvisnespremenljivke, zaradi èesar se podaja izraz za zakono gibalni kolièini le v posameznem trenutku naleta.Komponenta zakona o gibalni kolièini v smerinormale je za oba vagona med stiskanjem (od t

0 do

t1) podana z enaèbami:

Podobno velja za èas raztezanja (t1 do t

2):

Sl. 10. Sprememba sile F na vzmetnem paketu v èasu stiskanja in raztezanjaFig. 10. Example of measured force F in the spring package during compression and decompression

11 1 ( )Ndc dv

m m F tdt dt

× + × =

22 2 ( )Ndc dv

m m F tdt dt

×× - = -

11 1 ( )Ndc dv

m m F tdt dt

× - =

12 2 ( )Ndc dv

m m F tdt dt

- × - × = -

Enaèbe od (14) do (17) prikazujejo spremembosile F(t) na obeh vozilih zaradi spremembe hitrostimed trkom.

Med naletom in trkom se nenadzorovanoporabi del kinetiène energije naleta zaradi trenja vle�ajih osnih dvojic ter trenja med kolesi in tiri,kakor tudi zaradi nihanj amortizerjev in ogrodjavozila. Zaradi tega je mogoèe reolo�ke lastnostiodbojnika doloèiti �ele z neposredno meritvijospremembe sile in pomika v odvisnosti od èasana samem odbojniku. Meritev na odbojniku seizvaja tako, da je sonda za silo postavljena medodbojnikom in ogrodjem vozila, medtem ko sondapomika meri pomik med odbojno plo�èo inpritrjenim ogrodjem odbojnika, kar je prikazanona sliki 11. S tem postopkom je mogoèeneposredno opredeliti energijo, ki je potrebna zadoloèen poves odbojnika, ter z meritvijopovratnega dela doloèiti dele� izgube kinetiène

00-11/12stran 743


The kinetic energy lost during buffer compression is spentfor the deformation and de-crosslinking of the elastomer,and also for the heat energy of friction between the platesand in the elastomer.

The work (We) needed for the contraction of

the spring package and the buffer is calculated bythe numerical integration of the force-displacementdiagram. The work needed for damping (W

a) is deter-

mined as the difference between the cumulative workand the restitution work, or may be defined in thesame way as W

e, only that the numerical integration

is considered in the interval from t1 to t

2. The buffer

gives out the restitution work (Wp) in the form of

kinetic energy, which is expressed as a change in therelative velocity of the rail vehicle after collision:

(18).

The ratio of the relative velocity after colli-sion 12 uuu -=D to the relative initial velocity

21 vvv -=D is presented by the coefficient of colli-sion (k):

(19).

The value of the collision coefficient for aplastic collision is k=0, and k=1 for an elastic colli-sion.

Crash testing of rail vehicles was performedby the ZRMK (Materials and Structure Testing Insti-tute) under the supervision of the chief investigator ofthe Faculty of Mechanical Engineering in Maribor onthe railway line between the towns Ptuj and Mo�kanjci.

Both railway vehicles, equipped with thedeveloped spring packages, were loaded by a cargoof nominal weight 40 t (m

1=40230 kg, m

2=40125

kg). The speed of the moving vehicle (v1) before

collision was measured by two photocells at a refer-ence distance. Forces, displacements and accelera-tions were measured by gauges. The force was mea-sured by a Hotinger Baldwin Messtechnik 200C6A-type gauge, with a measuring range of up to 2MNand an accuracy of ±0.5%. The displacement wasmeasured by a WA 100-type gauge, with a measur-ing range up to 100 mm and an accuracy of ±1%.Data acquisition of the amplified signals from thegauges was performed via an A/D converter (Fig.11).

The recorded characteristics of the time de-pendency of force and displacement on one bufferduring the collision are given in Figs. 12 to 15 forindividual velocities.

It is typical of all the recorded characteris-tics shown in Figs. 12 to 15 that the contraction time(the time to reach the highest force during the colli-sion) is substantially shorter than the time of restitu-tion. As a rule, the contraction time decreases withincreasing initial velocity, while the total collision time

energije kot razliko med celotnim in povratnimdelom. Izgubljena kinetièna energija pri stiskanjuodbojnika je porabljena za deformacijo inrazmre�enje elastomera ter toplotno energijo trenjamed plo�èami in v samem elastomeru.

Potrebno delo (We) za stiskanje vzmetnega

paketa in s tem odbojnika se izraèunava znumerièno integracijo krivulje sila - pomik. Delodu�enja W

a se lahko doloèi kot razlika med

celotnim in povratnim delom, oziroma se lahkodoloèa enako kakor W

e, le da se upo�teva

numerièna integracija v razponu od t1 do t

2.

Odbojnik odda povratno delo Wp v obliki kinetiène

energije, ki je izra�ena kot sprememba relativnehitrosti vozila po trku:

Razmerje med relativno hitrostjo po trku

12 uuu -=D in relativno naletno hitrostjo 21 vvv -=Dpomeni koeficient trka k:

Vrednost koeficienta trka je za popolnomaplastièen trk k=0, oziroma za popolnoma elastièentrk k=1.

Naletno presku�anje �elezni�kih vagonov jeizvajal Zavod za raziskavo materialov in konstrukcij -ZRMK pod nadzorom nosilca razvojne naloge -Fakultete za strojni�tvo Maribor, na delu proge medPtujem in Mo�kanjci.

Obe �elezni�ki vozili sta bili natovorjeni zbremenom nominalne mase 40 t (m

1 = 40230 kg, m

2

= 40125 kg) in opremljeni z razvitimi vzmetnimi paketi.Hitrost gibajoèega se vagona (v

1) pred trkom je bila

merjena z dvema fotocelicama na referenèni razdalji.Sile, pomiki in pospe�ki so se merili z ustreznimizaznavali. Sila je bila merjena s sondo HotingerBaldwin Messtechnik-HBM 200C6A, z merilnimobmoèjem do 2 MN in z natanènostjo ±0,5%. Pomikje bil merjen s sondo WA 100 z merilnim obmoèjem do100mm in natanènostjo ±1%. Ojaèani signali(ojaèevalnik HBM KWS 6A-5) iz zaznaval so se prekanalogno-digitalnega pretvornika DAP 2400/6 zbiraliz raèunalnikom. Povezovalna shema je prikazana nasliki 11.

Posnete karakteristike odvisnosti sile inpomika od èasa na enem odbojniku med naletom soza posamezne hitrosti naleta prikazane na slikah 12do 15.

2 11

2 pWu u u

m- = D =

2 1

1 2

u u uk

v v v

D -= =

D -

Za vse posnete karakteristike na slikah 12do 15 je znaèilno, da je èas stiskanja (èas doseganjanajvi�je sile med trkom) bistveno kraj�i od dol�inetrajanja raztezanja povratnega giba, in sicer pravilomatako, da se z veèanjem naletne hitrosti èas stiskanjazni�uje ob hkrati dalj�em trajanju celotnega trka, kar

00-11/12stran 744


0

100

200

300

400

500

600

700

800

0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45 0,5

t

F

0

10

20

30

40

50

60

70

s

F

s

v=8 km/h kN mm

s

Sl. 11. Shematski prikaz razporeditve merilne opreme med izvajanjem naletnega preskusaFig. 11. Schematic presentation of the measuring equipment during the crash test

Sl. 12. Posneta karakteristika pri hitrosti naleta v = 8 km/hFig. 12. The recorded characteristic for initial velocity v=8 km/h

0

100

200

300

400

500

600

700

800

0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45 0,5

t

F

0

10

20

30

40

50

60

70

s

F

s

v=10,3 km/h

s

mm kN

Sl. 13. Posneta karakteristika pri hitrosti naleta v = 10,3 km/hFig. 13. The recorded characteristic for initial velocity v=10,3 km/h

v1=v

m1=40 t

v2=0 m2=40 t

Sonda za silo Sonda za pomik

Load cell Displacement gauge

Merilnik pospe�ka

Acceleration gauge

A/D Vozilo z elastomernima vzmetnima paketoma Vehicle with elastomer

spring packages Raèunalnik za zajemanje podatkov

Recording of data by PC

Foto celice za meritev hitrosti

Photo cell for speed masuring

00-11/12stran 745


0

100

200

300

400

500

600

700

800

0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45 0,5

t

F

0

10

20

30

40

50

60

70

s

F

s

v=12,5 km/h kN mm

s

increases, as shown in Fig. 16. The consequence ofthis fact is that acceleration increases with increas-ing initial velocity.

As the recorded force and displacement sig-nals are given in the same time t, we can see from thecharacteristics that the highest force value is alwaysreached slightly sooner than the highest displacementof the buffer. This is a consequence of high strains inthe elastomer which weaken the crosslinking bonds.

Another typical feature of the recorded char-acteristics is the fact that the curves showing the forcedepending on time are smoother than the curves show-ing the displacements depending on time. The chat-tering of displacement curves is ascribed to the vibra-tions recorded by the gauge. During the collision, vi-brations travel over the framework of the rail vehicle tothe buffers of the next vehicle, and vice versa.

Sl. 14. Posneta karakteristika pri hitrosti naleta v = 12,5 km/hFig. 14. The recorded characteristic for initial velocity v=12,5 km/h

Sl. 15. Posneta potek sile in pomika v odvisnosti od èasa pri hitrosti naleta v = 15,1 km/hFig. 15. The recorded force and displacement depending on time at initial velocity v=15,1 km/h

je prikazano na sliki 16. Omenjena znaèilnost ima zaposledico, da se pospe�ek z veèanjem hitrosti naletatudi zvi�uje.

Ker sta zajeta signala sile in pomika podanav istem èasu t, je iz posnetih karakteristk opazno, daje najveèja vrednost sile vedno dose�ena nekaj èasapred najveèjim pomikom odbojnika. To je posledicavelikih deformacij elastomera, pri katerih mre�ne vezipostanejo �ibke.

Prav tako je ena od glavnih znaèilnostiposnetih karakteristik tudi dejstvo, da so krivulje, kika�ejo potek sile v odvisnosti od èasa, bolj gladke odkrivulj, ki prikazujejo èasovni potek pomika.Narebrièenost krivulj pomikov je posledica vibracij,ki jih merilnik pomika zaznamuje. Vibracije se medtrkom prena�ajo prek ogrodja vozila na drugi odbojnikin nasprotno.

0

100

200

300

400

500

600

700

800

0 0,1 0,2 0,3 0,4 0,5

t

F

0

10

20

30

40

50

60

70

s

F

s

v=15,1 km/h kN

s

mm

00-11/12stran 746


0,025

0,05

0,075

0,2

0,3

0,4

0,5

8 km/h 10,3 km/h 12,5 km/h 15,1 km/h

t 1 -t

0

èas stiskanja

time of contraction

celotni èas naleta

cumulative time of crash test

t 2 -t

0

s s

In order to determine the cumulative work of the bufferduring the collision, the measured characteristics ofthe spring package have to be expressed by the forceF as function of the displacement s. The force/dis-placement relationship for individual velocities isshown in Figs. 17 to 20.

Displacement variations occurring duringthe collision result in distinctive oscillations of thedynamic loading curve in the horizontal direction,which is the reason why the determination of work asan integral under the F-s curve may result in an error.

Consequently, the recorded displacementcurve was approximated. The values for cumulativework were calculated by the integration of the ap-proximated curve (Table 1).

The value of the restitution work of the springpackage was used to calculate the relative velocity of

Sl. 16. Èas trajanja stiskanja (t1-t

0) in celotnega trka (t

2-t

0) pri razliènih hitrostih naleta

Fig. 16. The duration of contraction (t1 - t

0) for different initial velocities

Za doloèitev celotnega dela odbojnikamed trkom, je treba izmerjene karakteristikevzmetnega paketa prikazati kot potek sile F vodvisnosti od pomika s. Odvisnost sila - pomikje za vsako hitrost posebej prikazana na slikah17 do 20.

Nihanja pomika med trkom imajo za posledicoizrazita osciliranja krivulje dinamiènegaobremenjevanja v vodoravni smeri, zaradi èesar lahkodoloèevanje dela kot integrala pod krivuljo F-spovzroèi napako.

Zaradi tega je bila posneta krivulja za pomikpoenostavljena. Vrednosti za celotno delo soizraèunane z integracijo pribli�ne krivulje in so podanev preglednici 1.

Iz vrednosti povratnega dela vzmetnegapaketa sta doloèena relativna hitrost vozil po trku

0

100

200

300

400

500

600

700

800

0 10 20 30 40 50 60 70

s

F

Wa/Wc=42,8%

v=8 km/h

mm

kN

Sl. 17. Karakteristika sila - pomik (F-s) pri hitrosti naleta v = 8 km/hFig. 17. Force/displacement (F-s) characteristic at initial velocity v=8 km/h

00-11/12stran 747


0

100

200

300

400

500

600

700

800

0 10 20 30 40 50 60 70

s

F

Wa/Wc=57,2%

v=15,1 km/h

mm

kN

0

100

200

300

400

500

600

700

800

0 10 20 30 40 50 60 70

s

F

Wa/Wc=34,5%

v=10,3 km/h

mm

kN

Sl. 18. Karakteristika sila - pomik (F-s) pri hitrosti naleta v = 10,3 km/hFig. 18. Force/displacement (F-s) characteristic at initial velocity v=10,3 km/h



0

100

200

300

400

500

600

700

800

0 10 20 30 40 50 60 70

s

F

Wa/Wc=35,2%

v=12,5 km/h

mm

kN

00-11/12stran 748


vehicles after collision u2-u

1 and the collision coefficient

k following equation (18). The calculated values for theaverage acceleration of a vehicle at standstill (at rest) andthe collision coefficient with the remaining characteris-tics of the developed spring package are given in Table 1.

Preglednica 1. Izmerjene znaèilnosti razvitega vzmetnega paketa med naletnim prekusomTable 1. Measured characteristics of the developed spring package during collision test

V1 km/h m/s

t2-t0

s Fmaks

kN a/g Wc

kJ Wa

kJ Wa/ Wc

% u2-u1

m/s K

8 2,22 0,25 281 1,4 5,0 2,1 42,8 0,535 0,241 10,3 2,86 0,30 421 2,1 9,4 3,2 34,5 0,785 0,274 12,5 3,47 0,33 554 2,8 11,8 4,2 35,2 0,875 0,252 15,1 4,19 0,44 784 4,0 25,0 14,1 56,2 1,047 0,249

u2-u

1 in koeficient trka k po enaèbi (18). Izraèunane

vrednosti za povpreèen pospe�ek mirujoèegavozila in koeficienta trka s preostalimi znaèilnostmirazvitega vzmetnega paketa so podane vpreglednici 1.

3 SKLEP

Z uporabo cenenega standardnega vzorca izelastomera je mogoèe definirati reolo�ke parametre,potrebne za izraèun deformacijskega dela in s tem vgrobem oceniti primernost elastomera za izdelavoprototipa oz. za vgradnjo v odbojno napravo.Odstopanja med deformacijskim delom, izraèunanimpo modelu, in eksperimentalno izmerjenim delom sopredvsem posledica razlike v vezavi povr�ineelastomera med standardnim vzorcem in realnimvzmetnim elementom. Zaradi tega je treba, da so pogojipresku�anja standardnega vzorca, kolikor se le dapodobni pogojem obremenjevanja in vezave nadejanskem vzmetnem elementu. Razvit vzmetni paketizpolnjuje pogoje v skladu s standardi UIC gledepoteka statiène obremenitvene karakteristike (sila -pot) ter velikosti celotnega in du�enega dela. Pravtako vzmetni paket izpolnjuje pogoje za dinamiènanaletna presku�anja po standardih UIC.

Opravljeni naletni preskusi so pokazali, da jekoeficient trka mogoèe doloèiti le na podlagineposrednih meritev na samem odbojniku, kerdejanski trk dveh natovorjenih �elezni�kih vozilspremljajo te�je doloèljivi dinamièni in geometrijskiparametri. Iz primerjave èasa dol�ine stiskanja inraztezanja je mogoèe sklepati, da odbojnik opravljasvojo vlogo bla�ilnika tako, da hitro akumulira energijonaleta ter nato poèasi vraèa del energije v oblikipovratnega dela. Na temelju raziskave smo opazili, darazviti vzmetni paket nima vloge le vsrkati del energijenaleta, temveè tudi preostali del energije povrniti vdalj�em èasu, kar pa je dose�eno z lastnostmielastomera.

Opravljena raziskava je pokazala, da jemogoèe na temelju kombiniranja eksperimentalnihmeritev in reolo�kega modela �tevilsko ocenitiprimernost elastomera za vgradnjo v zeloobremenjene - naletne konstrukcijske sklope in stem uspe�no nadomestiti kovinske vzmetno-du�ilneelemente z elastomerom.

3 CONCLUSION

It is possible to define the rheological prop-erties needed to calculate the deformation work bythe use of a standard inexpensive elastomer speci-men, and thus to evaluate the suitability of the elas-tomer for the development of a prototype spring pack-age installed in a buffer. The deviation of the by-the-model calculated deformation work from the experi-mentally measured work is mainly a consequence ofthe difference in the binding of the elastomer surfacein the case of the standard specimen and in the realspring element. For this reason it is imperative thatthe testing conditions of the standard specimen beas similar as possible to the loading and binding con-ditions of the real spring element. The developedspring package satisfies the requirements of the UICstandards regarding the static loading characteristic(force-path) and the magnitude of the cumulative anddamping work. It also complies with the UIC dynamiccrash testing standards.

The performed crash tests have shown that itis possible to determine the collision coefficient only bydirect measurements on the buffer, which is explainedby the fact that a real collision of two loaded vehicles isaccompanied by dynamic and geometric parameters thatare harder to determine. A comparison of the durationof contraction and restitution reveals that the bufferaccumulates the crash energy quickly and then slowlyreturns a part of the energy in the form of restitutionwork. It is evident from the performed research that thedeveloped spring package not only absorbs a part ofthe collision energy, but also recovers the non-absorbedpart of the energy over a longer period of time, which isa consequence of the properties of the elastomer.

The performed research has also shown thatby combining experimental measurements and therheological model it is possible to quantitatively evalu-ate the suitability of the elastomer for installationinto highly loaded crash-subjected parts, and to effi-ciently replace metal springs with elastomer elements.

00-11/12stran 749


ZAHVALA

Prièujoèi prispevek prikazuje le del dejavnosti,ki so potekale pri raziskovalnem projektu �Razvoj,izdelava prototipa in presku�anje odbojnika za�elezni�ka vozila� (42-0909-795), v okviruraziskovalnega projekta Minstrstva za znanost intehnologijo, ki so ga sofinancirale Slovenske�eleznice, RTI Sava Kranj in Tovarna vzmeti Ptuj.Avtorji se prav tako iskreno zahvaljujejo sodelavcempri projektu mag. Andreju Jereletu in spec. JanezuPièerku za njun prispevek k uspe�nem delu priomenjeni nalogi, kakor tudi RTI Sava Kranj pri dejavnivkljuèitvi v razvoj, pripravo in izdelavo elastomera.

ACKNOWLEDGEMENT

The presented paper describes only a partof the research work performed within the researchproject �Development and Testing of Prototype Buff-ers for Railway Vehicles� (No. 42-0909-795). The au-thors wish to thank the Ministry of Science and Tech-nology of Slovenia, the Slovenian Railway Company,R&D Sava in Kranj and Tovarna vzmeti in Ptuj fortheir financial support. The authors also wish to thankMr. Andrej Jerele and Mr. Janez Pièerko for their suc-cessful cooperation on the project, and to the R&DSava company in Kranj for their activities in the de-velopment and preparation of the elastomer.

Prejeto: 5.8.1999



[1] UIC 526-1 (1981) Güterwagen � Puffer mit 100 mm Hub. Internationaler Eisenbahnverband.[2] UIC 827-2 (1981) Technische Lieferbedingungen für stählerne Pufferfederringe.[3] Beatty, M.F., D.O. Stalnaker (1986) The Poisson function of finite elasticity. Jour. Applied Mechanics,

Vol. 53, 807-813.[4] Truesdell, C., W. Noll, The nonlinear field theories of mechanics. Flügge´s Handbuch der Physik, Vol.

III/3, 139-141, 153-158 and 317-319.[5] Blatz, P.J., W.L. Ko, Application of finite elasticity theory to the deformation of rubbery materials. Transac-

tion of the Society of Rheology, Vol. 6, 223-251.[6] Legat, J., N. Gubeljak, È. Primec, J. Pièerko (1994) Razvoj, izdelava prototipa in preizku�anje odbojnika za

�elezni�ka vozila 42-0909-795. Konèno poroèilo.[7] Jerele, A. (1994) Delovno poroèilo o preizkusih v RTI Sava Kranj.[8] Gubanc, M., P. Murih, Z. �usteriè, A. �ebenik (1996) Vpliv mehèanja in zamre�evanja naravnega kavèuka

na du�enje vulkanizatov. Sava Kranj, Razvojno tehnolo�ki in�titut, Univerza v Ljubljani, FKKT.[9] Jeciæ, S. (1989) Mehanika II, Kinematika in dinamika, �kolska knjiga Zagreb.

Authors� Address: Prof.Dr. Janko LegatDoc.Dr. Nenad GubeljakJo�ef PredanFaculty of Mechanical EngineeringUniversity of MariborSmetanova 172000 Maribor, Slovenia

Naslov avtorjev: prof.dr. Janko Legatdoc.dr. Nenad GubeljakJo�ef PredanFakulteta za strojni�tvoUniverza v MariboruSmetanova 172000 Maribor

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M. Sekav~nik: Analiza vibracij gonilnika - An Analysis of Impeller Vibrations

V prispevku so predstavljeni rezultati eksperimentalnih raziskav lastnih nihanj lopatic turbopuhala.Za vzbujanje strukture gonilnika turbopuhala (sestavljeni sistem lopatice-disk) sta bili uporabljeni impulznamotnja in akustièno harmonsko vzbujanje. Odziv sistema je bil merjen z merilniki pospe�kov, prilepljenimi nalopaticah gonilnika. Za doloèitev razmernika du�enja je bila uporabljena metoda logaritemskegazmanj�evanja. Meritve so pokazale, da se lopatice na motnje odzivajo najbolj intenzivno (najveèje amplitude)z upogibnimi lastnimi nihanji, ki pripadajo prvi lastni obliki. V izmerjenih odzivih so bili ocenjeni razmernikidu�enja. Izkazalo se je, da je razmernik du�enja za prve lastne oblike pri obeh naèinih vzbujanja enak inkonstanten d = 5E 05. Razmerniki du�enja za preostale lastne oblike nihanj so za velikostni razred veèje.Analiza dinamiènih karakteristik lastnih nihanj lopatic s prvo lastno obliko naka�e mo�nosti numeriènegamodeliranja mehanizmov du�enja, ki bi omogoèilo simuliranje obratovanja v resonanci in njeni bli�ini.© 2000 Strojni�ki vestnik. Vse pravice pridr�ane.(Kljuène besede: turbopuhala, gonilniki, analize vibracij, du�enje vibracij)

The paper presents the results of experimental studies of natural vibrations of turbocharger blades.In order to excite the structure of a turbocharger impeller (composite blade-disc system), impulse distur-bance and acoustic harmonic excitation were used. The response of the system was measured using acceler-ometers attached to the impeller blades. The logarithmic decrement method was used to determine thedamping ratio. Measurements showed that the blades are most responsive (the largest amplitudes) to distur-bances with bending natural vibrations, classified as the first mode. The damping ratia were estimated fromthe measured responses. It turned out that the damping ratio for the first free form is equal and constant forboth excitation methods: d = 5E 05. The damping ratia for other free forms of the oscillations were greaterby one order of magnitude. The analysis of the dynamic characteristics of the blades� natural vibrations withthe first free form indicated possibilities for numerical modeling of damping mechanisms that would enablethe simulation of operation at, or near, resonance frequency.© 2000 Journal of Mechanical Engineering. All rights reserved.(Keywords: turbocharger, impellers, vibration analysis, vibrations damping)

An Analysis of Turbocharger Impeller Vibrations

Mihael Sekav~nik

© Strojni{ki vestnik 46(2000)11/12,750-761ISSN 0039-2480UDK 62-155:620.178.3Izvirni znanstveni ~lanek (1.01)


UDC 62-155:620.178.3Original scientific paper (1.01)

Analiza vibracij gonilnika turbopuhala

0 UVOD

Lopatice gonilnikov modernih turbinskihstrojev postajajo zaradi aerodinamiènega optimiranjaèedalje tanj�e, zaradi èesar so izpostavljene vseveèjim statiènim in �e zlasti dinamiènim, mehanskimobremenitvam. Mehanske po�kodbe zaradi utrujanjagradiva ali celo trenutni lom konstrukcije sonajpogosteje posledica dinamiènih obremenitev,povzroèenih zaradi vibracij lopatic. Te so lahkovzbujane z razliènimi mehanizmi, to so: izsrednostrotorja, neustaljene aerodinamiène sile, turbulencain akustièna resonanca [1]. Zaradi velikega vplivaznaèilnosti geometrijskih oblik turbinskega gonilnikana njegovo dinamièno obna�anje so bili v dosedanjihraziskavah razviti in uporabljeni razlièni modeli in

0 INTRODUCTION

The impeller blades used in modernturbomachinery are being produced in increasinglythinner form due to the demands of aerodynamicoptimisation. A consequence of this is that blades arebeing subjected to increasing static, and especiallydynamic, mechanical loads. Mechanical damage re-sulting from material fatigue or even the instantane-ous fracture of the structure are most frequently theresult of dynamic loads caused by the blade vibra-tions. These can be created by various mechanismssuch as rotor eccentricity, nonstationary aerodynamicforces, turbulence and acoustic resonance [1]. Due tothe large influence of the geometric characteristics ofturbine impellers on their dynamic behavior, various

00-11/12stran 751


numeriène metode za popis dinamiènih lastnostikonstrukcije ([2] do [4]).

V nasprotju z vitkimi, elastiènimi lopaticamiv aksialnih turbinskih strojih (npr. aksialni kompresorjiali nizkotlaène stopnje parnih in plinskih turbin), solopatice v turbopuhalih izpostavljene vibracijam zvisokimi frekvencami in majhnimi amplitudami, zaradièesar je vpliv samovzbujevalnih uèinkov zanemarljivomajhen [2]. Omeniti velja, da kljub majhnimamplitudam pomikov lopatic, lahko napetosti dose�ejoprecej�nje vrednosti.

Pri obravnavi vibracij so poleg vzbujevalnihsil pomembni tudi mehanizmi du�enja, zlasti vpodroèju resonance in njeni okolici. Pri turbinskihstrojih razlikujemo tri vrste du�enja:- strukturno du�enje,- sistemsko du�enje in- aerodinamièno du�enje.

Strukturno du�enje predstavlja razliènedisipacijske procese v materialu. Pri tem senapetostna in kinetièna energija vibrirajoèegasistema spreminja v toploto. Za modeliranjesestavljenih sistemov lopatice � disk je ta vrstadu�enja najpomembnej�a. Analizirano inpredlagano je bilo nekaj primernih metod za identi-fikacijo parametrov du�enja in modeliranja, kitemeljijo na poznavanju lastnih nihanj konstrukcije([3] in [4]).

Sistemsko du�enje se pojavlja na spojihposameznih elementov konstrukcije. Doloèa gadisipacija energije zaradi trenja in stri�nih uèinkov napovr�inah med posameznimi sestavnimi delikonstrukcije (npr. v korenskem spoju lopate in gredi).V primerjavi z vzdol�nimi in torzijskimi vibracijami grediturbine, je tovrstno du�enje pri vibracijah lopaticnepomembno.

Aerodinamièno du�enje se pojavlja kotposledica interakcije konstrukcije (lopatice) inobtekajoèega toka tekoèine. Ta je tem veèja, èim veèjeso amplitude deformacij vibrirajoèih lopatic. Priaksialnih kompresorjih in nizkotlaènih stopnjahplinskih in parnih turbin so deformacije lopatic zaradinjihove vitkosti razmeroma velike, zato je trebaaerodinamièno du�enje upo�tevati. Nasprotno pa solopatice na gonilniku turbopuhala kratke in zatoizpostavljene vibracijam z zelo majhnimi amplitudami.V tem primeru je vpliv aerodinamiènega du�enja pravtako zanemarljivo majhen.

Raziskava je osredotoèena naeksperimentalno doloèevanje odzivov sestavljenegasistema lopatice - disk na motnje in na ocenopripadajoèih razmernikov du�enja.

Gonilnik, ki je predmet raziskave, imapremer 130 mm in ima 11 lopatic (sl. 1). Izdelan je iztemperaturno obstojne nikel-kromove zlitineINCONEL 713 LC, ki ima naslednjo sestavo: Ni(76%), Cr (17%) in Fe (7%). Vroèi izpu�ni plinivstopajo v gonilnik skozi spiralni okrov brez lopatic

models and numerical methods for the description ofthe dynamic properties of the structure have been de-veloped and used in research ([2] to [4]).

As distinct from the thin, elastic blades inaxial turbomachinery (e.g. axial compressors or low-pressure stages of steam and gas turbines), the bladesin turbochargers are exposed to high-frequency small-amplitude vibrations, making the influence of self-excitation effects negligible [2]. It should be men-tioned that in spite of the small blade-displacementamplitudes, the stresses can be very high.

In addition to the excitation forces, damp-ing mechanisms are also important for the study ofvibrations, especially at, or near, resonance frequen-cies. Three types of damping can be distinguished inturbomachinery:- structural damping,- system damping,- aerodynamic damping.

Structural damping includes various dissi-pation processes within the material. The strain andkinetic energy of the vibrating system is convertedto heat. This type of damping is the most importantfor the modeling of composite blade-disc systems. Afew suitable methods based on the knowledge offree-structure vibrations were analysed and proposedfor the identification of damping and modeling pa-rameters ([3] and [4]).

System damping occurs at the joints be-tween individual elements of a structure. It is deter-mined by the energy dissipation due to friction andshear forces on the surfaces between individual com-ponents of the structure (e.g. at the base of the jointbetween the blade and the shaft). In contrast to lon-gitudinal and torsional vibrations in turbine shafts,such damping is insignificant for blade vibrations.

Aerodynamic damping occurs as a result ofthe interaction between the structure (blade) and thefluid flow surrounding it. It increases in proportionto the displacement amplitudes of the vibrating blades.In axial compressors and low-pressure stages of gasand steam turbines, blade deformations are relativelylarge due to their thinness, therefore aerodynamicdamping has to be taken into account. On the otherhand, the blades of turbocharger impellers are shortand are thus subjected to vibrations with very smallamplitudes. In this case, the influence of aerodynamicdamping is also negligible.

Our research focused on the experimentaldetermination of the responses of a composite blade-disc system to disturbances and the assessment ofthe corresponding damping ratios.

The impeller which is the subject of this re-search has a diameter of 130 mm and 11 blades (Fig-ure 1). It was produced from a heat-resistant nickel-chromium alloy, INCONEL 713 LC, which has the fol-lowing composition: Ni (76%), Cr (17%), Fe (7%). Hotexhaust gases enter the impeller through a spiral cas-

00-11/12stran 752


s kro�nim preènim prerezom. Glavni obratovalnipodatki so:- najveèja vstopna temperatura 1020 K,- najveèji masni tok 1 kg/s,- tlaèno razmerje 3,5,- najveèja kro�na frekvenca 60 000 min-1.

V prej�nji raziskavi [5] je bila z metodokonènih elementov izvedena numerièna analizadinamiènega obna�anja obravnavanega gonilnika. Spomoèjo modalne analize so bile izraèunane lastnefrekvence rotorja. Poudarek je bil na doloèevanju tistihlastnih oblik, pri katerih so lopatice upogibno nihale.�tevilu lopatic ustrezno je bilo izraèunanih 11 razliènihlastnih frekvenc, pri katerih so lopatice nihaleupogibno z vozlom v korenu lopatic. Ta nihanja so vnadaljevanju imenovana s skupnim pojmom 1. lastnaoblika. Lastna nihanja s 1. lastno obliko se med sebojrazlikujejo s �tevilom t.i. vozelnih èrt po premerugonilnika (imenovanih tudi vozelni premeri), kirazmejujejo lopatice, nihajoèe v protifazi.

V zgoraj omenjenem modelu du�enje ni biloupo�tevano. Pri numeriènem simuliranju resonancetak model odpove, saj se amplitude s èasom zveèujejov neskonènost. Znano pa je, da se v obratovalnemobmoèju kro�nih frekvenc radialnih turbopuhalpojavlja veè resonanc.

V literaturi [6] so predstavljeni zanimivipodatki o meritvah vibracij lopatic gonilnikaturbopuhala v celotnem obratovalnem obmoèju vdejanskih obratovalnih razmerah. Pri teh raziskavahje bila uporabljena tehnika merjenja dinamiènih sil zvisokotemperaturnimi uporovnimi listièi, prilepljenimina lopatico gonilnika. Pri tem je bil signal prenesen zrotirajoèega se rotorja z uporabo enokanalnegatelemetrijskega sistema. Pokazano je bilo, da se v

ing without blades and with a circular cross-section.The basic operating data are as follows:- max. inlet temperature: 1020 K,- max. mass flow: 1 kg/s,- pressure ratio: 3.5,- max. rotating speed: 60,000 rpm.

In a previous study [5], the finite-elementmethod was used to perform the numerical analysisof the impeller�s dynamic behaviour. The rotor�s freefrequencies were calculated using modal analysis.Emphasis was on determining those free forms inwhich the blades oscillated by bending. In accord-ance with the number of blades, 11 different free fre-quencies were calculated in which the blades experi-enced bending vibrations with the node at the bladeroot. Later on, these oscillations were jointly namedthe �first free form�. Natural vibrations with the firstfree form differ in the number of node lines along theimpeller diameter (also called nodal diameters), whichdelimit the blades oscillating in counterphases.

Damping was not taken into account in theabove-mentioned model. Such a model fails in the nu-merical simulation of resonance, since amplitudes in-crease to infinity over time. It is known, however, thatseveral resonant frequencies occur within the operat-ing range (circular frequencies) of radial turbochargers.

The literature [6] presents interesting dataon measurements of turbocharger impeller-blade vi-brations over the entire operating range under actualoperating conditions. In this research, the techniqueof measuring dynamic forces using highly tempera-ture-resistant rods attached to the impeller blade wasused. The signal was transferred from a rotating ro-tor using a single-channel telemetry system. It wasshown that several resonances occur in the turbo-

Sl. 1. Gonilnik turbopuhala z 11 lopaticamiFig. 1. Turbocharger impeller with 11 blades

00-11/12stran 753


obratovalnem obmoèju turbopuhala pojavlja veèresonanc, ki so bile vrisane v Campbellov diagram.

Du�enje turbinskih lopatic je bilo predmeteksperimentalnih raziskav razliènih avtorjev. Velikaveèina prispevkov se zaradi njihove raz�irjenostinana�a na lopatice aksialnih turbinskih strojev. Te soizdelane posamièno in loèeno vpete v turbinsko kolo,zato eksperimentalni podatki vsebujejo informacijotako o strukturnem kakor tudi o sistemskem du�enju.V literaturi [2] so zbrani rezultati podrobnih raziskavdu�enja lopatic nizkotlaènega gonilnika aksialne,parne turbine. Predmet raziskav je bila doloèitevsoodvisnosti du�enja, amplitude vibracij,geometrijske oblike lopatic, vzdol�ne obremenitvelopatic, oblike nihanja, gradiva in tokovnega polja.Rezultati ka�ejo, da imajo na du�enje prete�ni vplivhisterezni pojavi (strukturno du�enje), medtem kotrenje na korenskih spojih lopatic, kakor tudi tokovnopolje zanemarljivo malo prispevata k celotnemudu�enju.

Glavni nameni teh raziskav so bili:- s preskusi doloèiti lastnosti strukturnega du�enja

nihanja lopatic pri lastnih nihanjih lopaticgonilnika (upogibna nihanja lopatic sistemalopatice - disk);

- doloèiti obliko lastnega nihanja, ki pripadanajmanj�emu du�enju;

- z metodo logaritemskega dekrementa ocenitivelikost razmernika du�enja, in sicer z razlièniminaèini vzbujanja lastnih nihanj.

1 DOLOÈANJE DISIPACIJE ENERGIJE ZARADIDU�ENJA

Za doloèitev velikosti strukturnega du�enjasmo opravili meritve odziva turbinskih lopatic nazaèetno motnjo. Meritve so bile opravljene nagonilniku brez okrova v atmosferskih razmerah vlaboratoriju.

Merilni sistem je bil sestavljen iz �tirihmerilnikov pospe�kov (Brüel & Kjær, frekvenènoobmoèje do 80 kHz) in pripadajoèih nabojnihpredojaèevalnikov. Izmerjeni signali so bili posnetina raèunalnik s pomoèjo 4-kanalne 16-bitne merilnekartice. Loèljivost zbiranja rezultatov je bilanastavljena na 80 kHz. Merilni sistem in sistem zazbiranje podatkov sta prikazana na sliki 2. Èasovnisignali odzivov so bili soèasno merjeni na 4 od 11lopatic. Slika 3 prikazuje namestitev merilnikovpospe�kov. Razvidno je, da sta bila uporabljena dvapara merilnikov pospe�kov � prvi z maso 0,2 g indrugi z maso 2 g. Merilno obmoèje vseh merilnikovpospe�kov je za velikostni razred veèje od izraèunanihlastnih frekvenc sestavljenega sistema lopatice - disk[5]. Mesto namestitve merilnika pospe�kov na lopaticije bilo izbrano s poprej�njo numerièno analizo lastnihnihanj, in sicer na mestu najveèjih deformacij (inpospe�kov) pri lastnih nihanjih s 1. lastno obliko. S

charger operating range, and these were drawn on aCampbell diagram.

The damping of turbine blades has beenthe subject of experimental research by various au-thors. A large majority of the contributions refer tothe blades of axial turbomachinery, because of theirwidespread use. These blades are produced individu-ally and attached to the turbine wheel separately, soexperimental data contains information on both struc-tural and system damping. The literature [2] statesthe collected results of a detailed study of dampingof the blades of low-pressure impellers in axial steamturbines. The subject of this research was the deter-mination of the interdependence of damping, vibra-tion amplitude, blade geometry, axial blade loads, typeof oscillation, material and flow field. The results in-dicate that hysteresis phenomena (structural damp-ing) have a predominant influence on damping, whilefriction at the blade-root joints and the flow field con-tribute negligibly to the total damping.

The main objectives of this study were:- to experimentally determine the properties of

structural damping of blade oscillations duringfree impeller-blade oscillations (bending oscilla-tions of the blades in a blade-disc system);

- to determine the type of free oscillation whichcorresponds to the lowest amount of damping;

- using the logarithmic decrement method, to as-sess the magnitude of the damping ratio usingvarious methods to excite natural vibrations.

1 DETERMINATION OF ENERGY DISSIPATIONDUE TO DAMPING

In order to determine the magnitude of struc-tural damping, we performed measurements on turbine-blade response to the initial disturbance. The measure-ments were performed on an impeller without a casingunder atmospheric conditions in the laboratory.

The measurement system consisted of fouraccelerometers (Brüel&Kjær, frequency range up to 80kHz) and matching signal pre-amplifiers. The measuredsignals were recorded on a computer using a 4-channel16-bit measurement card. The resolution of the dataacquisition was set to 80 kHz. The measurement systemand the data acquisition system are shown in Figure 2.The time signals of the responses were measured si-multaneously on 4 of the 11 blades. Figure 3 shows thepositions of the accelerometers. Two pairs of acceler-ometers were used � the first pair with a mass of 0.2 gand the second pair with a mass of 2 g. The measure-ment range of all the accelerometers was greater thanthe calculated free frequencies by one order of magni-tude of the composite blade-disc system [5]. The posi-tion of the accelerometer on the blade was selected withthe aid of a previous numerical analysis of the naturalvibrations, i.e. at the location of the largest strains (andaccelerations) in natural vibrations of the first free form.

00-11/12stran 754


poprej�njimi meritvami je bil preverjen vpliv mase nalastna nihanja lopatic obeh uporabljenih tipovmerilnikov pospe�kov. Rezultati ka�ejo zanemarljivomajhna odstopanja pri meritvi lastne frekvence, ki sezelo dobro ujema z izraèunanimi.

Pri meritvah odzivov sta bila uporabljenadva razlièna naèina vzbujanja:- impulzno in- harmonsko-akustièno vzbujanje.

Preliminary measurements verified the influence of masson the free blade oscillations in both types of acceler-ometer. The results show negligible deviations in themeasurement of free frequency, which compares verywell with the calculations.

Two types of excitation were used in themeasurement of responses:- impulse,- harmonic�acoustic excitation.

Sl. 2. Presku�evali�èe in merilni sistem za merjenje odziva gonilnika na impulzno motnjo: 1 � gonilnik zgredjo; 2 � prime� z vpenjalno glavo; 3 � merilnik pospe�kov (eden od �tirih); 4 � nabojni predojaèevalniki;

raèunalnik z merilno kartico in programsko opremo za zbiranje in obdelavo izmerjenih podatkovFig. 2. Test rig and the measurement system for measuring impeller response to impulse disturbances: 1 �

impeller with shaft; 2 � clamp with clamping head; 3 � accelerometer (one of four); 4 � signal pre-amplifiers;computer with measurement card and software for acquisition and processing of measured data

Sl. 3. Pritrditev pospe�komerov na lopatice gonilnikaFig. 3. Attachment of accelerometers to impeller blades

00-11/12stran 755


Ker vibracije lopatic povzroèajo rezultirajoèedinamiène sile prete�no v obodni smeri gonilnika, jetreba prepreèiti rotacijo osi z dovolj togim vpetjem vvpenjalno pripravo (prime� s podstavkom). Prav takoso bile, v izogib kakr�nimkoli vplivom interakcijedinamiènih lastnosti merilnega mesta (podstavka sprime�em) z gonilnikom kot merjenim objektom,izmerjene lastne frekvence merilnega mesta samega.Rezultati so pokazali, da so le-te za dva velikostnarazreda manj�e od analiziranih lastnih frekvencgonilnika.

2 OCENA METODE ZA DOLOÈITEVRAZMERNIKA DU�ENJA

Teoretièno ozadje temelji na lastnemharmonskem nihanju sistema z eno prostostnostopnjo [7]. Razmernik du�enja, ki je vpeljan vrazliène modele du�enja za uporabo metode konènihelementov, je doloèen kot razmerje medekvivalentnim viskoznim du�enjem sistema inkritiènim du�enjem:

Pogost primer v tehnièni praksi je, da jedu�enje sistema zelo majhno, zato se frekvence lastnih

nihanj du�enega in nedu�enega sistema le neznatno

razlikujejo. Razmernik du�enja se v tem primeru da

izpeljati iz logaritemskega dekrementa:

kjer je logaritemski dekrement D naravni logaritemrazmerja sosednjih amplitud harmoniènega delaodziva sistema:

Logaritemski dekrement je bil za izmerjenesignale izraèunano z uporabo diskretne Fourierjevetransformacije (DFT) na ekvidistantnih intervalihsignala. Kot merilo za srednjo amplitudo na intervaluje vzeta vektorska vsota koeficientov realnega inimaginarnega dela Fourierjeve vrste pri 1. lastnifrekvenci (z najveèjo vsebnostjo v signalu). Na tanaèin se logaritemski dekrement izrazi iz enaèbe:

kjer sta ai in a

i+1 srednji amplitudi dveh zaporednih

intervalov merjenega signala.

Since blade vibrations cause dynamic forcesprimarily in the tangential (circumferential) direction ofthe impeller, axis rotation needs to be prevented by asufficiently rigid attachment to the clamping device (vicewith stand). In addition, in order to avoid any influenceof the interactions between the dynamic properties ofthe measurement site (vice with stand) with the impelleras the measured object, the free frequencies of the meas-urement site itself were measured. The results showthat these were smaller by two orders of magnitudethan the analysed free frequencies of the impeller.

2 ASSESSMENT OF THE METHOD FOR DETER-MINING THE DAMPING RATIO

The theoretical background is based on freeharmonic oscillation of the system with a single de-gree of freedom [7]. The damping ratio which wasintroduced into various damping models for the useof the finite-element method was determined as a ra-tio between equivalent viscous damping of the sys-tem and critical damping:

(1).

A case frequently encountered in engineer-

ing practice is that the damping of the system is very

small, therefore the frequencies of the natural vibra-

tions of a damped and undamped system differ insig-

nificantly. In this case it is possible to derive the

damping ratio from logarithmic decrement:

(2),

where the logarithmic decrement D is the natural loga-

rithm of the ratio between adjacent amplitudes of the

harmonic part of the system�s response:

(3).

For the measured signals, the logarithmic

decrement was calculated using the discrete Fourier

transformation (DFT) on equidistant signal intervals.

As a criterion of mean amplitude on the interval we

used the vector sum of the coefficients of the real

and imaginary part of the Fourier series at the first

free frequency (with the highest content in the sig-

nal). In this way the logarithmic decrement can be

expressed by the following equation:

(4),

where ai and a

i+1 are the mean amplitudes of two

successive intervals of the measured signal.

kr

c

cd =

2ðd

D»

1

ln i

i

x

x +

æ öD = ç ÷

è ø

1

ln i

i

a

a +

æ öD = ç ÷

è ø

00-11/12stran 756


Sl. 4. Znaèilni signal odziva lopatice na impulzno motnjo (zgoraj) in pripadajoèi spektrogram (spodaj)Fig. 4. Characteristic signal of blade response to an impulse disturbance (above) and corresponding

spectrogram (below)

3 REZULTATI MERITEV

3.1 Impulzno vzbujanje

Frekvenèna razstavitev impulznega signalapoka�e �irok frekvenèni spekter, zato je ta naèinvzbujanja primeren za vzbujanje lastnih nihanj v�irokem frekvenènem pasu. Izvajan je bil z udarcikovinske palice po merjeni konstrukciji. Presku�enoje bilo veè naèinov vpetja turbinskega gonilnika vvpenjalno glavo in razlièna mesta izvajanjavzbujanja. Iz analize dobljenih rezultatov je bila zavse razlièice ugotovljena enaka frekvenènavsebnost signalov, vendar se je izkazalo, da vpetje,kakor je prikazano na sliki 3, omogoèa najbolj�erezultate.

Na sliki 4 je prikazan izmerjeni signal

odziva lopatic na impulzno motnjo in njegov

spektrogram. Impulzna motnja vzbudi lastne

3 RESULTS OF MEASUREMENTS

3.1 Impulse excitation

The frequency decomposition of an impulse

signal shows a broad spectrum of frequencies, there-

fore this method of excitation is suitable for exciting

natural vibrations over a wide frequency band. It was

performed by hitting the measured structure with a

metal bar. Several methods for clamping the turbine

impeller in the clamping head and various places at

which excitation was performed were tested. The

analysis of the obtained results showed that all the

variants had the same frequency signal content, but

it turned out that the clamping method presented in

Figure 3 afforded the best results.

Figure 4 shows the measured signal of the blade

response to an impulse disturbance and corresponding

spectrogram. Impulse disturbances excite the free fre-

00-11/12stran 757


frekvence celotne konstrukcije (gonilnika z gredjo)v �irokem frekvenènem obmoèju. Po prièakovanjihje veèina moèneje du�enih, zato se v zaèetnem deluodziva zelo hitro iznihajo (sl. 5, interval A), kar selepo vidi tudi iz spektrograma na sliki 4 spodaj. Vnadaljevanju signala prevladuje samo �e lastnafrekvenca z najmanj�im du�enjem, ki pripada 1.lastni obliki: 9,84 kHz. Lastna nihanja vi�jih redovsistema lopatice - disk imajo za velikostni razredveèje du�enje od nihanj v 1. lastni obliki, zato vresonanci amplitude teh nihanj lopatic nisokritiène. Zaèetni deli signalov, ki imajo vsebnostlastnih frekvenc vi�jih redov, so bili zatorej izloèeniiz analize.

Diagram na sliki 5 prikazuje èasovnoodvisnost soèasno merjenih amplitud lastnih nihanjs 1. lastno obliko za 4 sosednje lopatice (pr. sliko 3).Signal je zajet v èasovnem intervalu 5 s, v katerem soizmerjeni celotni odzivi na tri zaporedne impulznemotnje. V logaritemski skali ima potek amplitud(oznaka a) linearno naravo (sl. 5, interval z oznako B)z enakim nagibom za vse merjene lopatice. Zaopazovano 1. lastno obliko je razmernik du�enjakonstanten in zna�a: d = 5 E-05. Ta ugotovitev imadvojni pomen:- Du�enje vibracij sestavljenega sistema lopatice

- disk s 1. lastno obliko je ustrezno popisano zrazmernikom viskoznega trenja, kar omogoèaprimerno uporabo uveljavljenih modelovdinamiènega du�enja, temeljeèih na sistemu z enoprostostno stopnjo.

- Signali vseh �tirih merilnikov pospe�kov seujemajo (izmerjena lastna frekvenca in razmernikdu�enja), kar dokazuje, da so mase merilnikovpospe�kov samih dovolj majhne, dazanemarljivo malo vplivajo na dinamiènoobna�anje lopatic.

3.2 Harmonsko akustièno vzbujanje

Drugi naèin vzbujanja je bil izveden zakustièno metodo. V ta namen so bili za vzbujanjeuporabljeni: frekvenèni generator kot izvorelektriènega signala, ojaèevalnik in zvoènik sprimerno frekvenèno karakteristiko (sl. 6).Frekvenca in oblika (harmonska) signala sta bilinastavljeni s frekvenènim generatorjem. Zuporabo 4-kanalnega digitalnega osciloskopa sobile najprej zaznane lastne frekvence gonilnika.Odzivi nihanja merjenih lopatic se tako pofrekvenci, kakor tudi po obliki dobro ujemajo ssignalom vsiljenega nihanja (akustiènega signala).Za vsako resonanco je potekalo snemanje signalatakole:- Po ugotovitvi resonance (lokalni maksimum

amplitude merjenega odziva), se je zaèelameritev.

quencies of the entire structure (impeller and the shaft)

over a wide frequency band. As expected, most of them

are strongly damped, therefore in the initial part of the

response they dissipate very rapidly (see also Figure 5,

interval A), which can also be seen nicely from the spec-

trogram in Figure 4. Later on in the signal, only the free

frequency with the smallest damping predominates,

which belongs to the first free form: 9.84 kHz. Natural

vibrations of higher orders of the blade-disc system

have greater damping, by an order of magnitude higher

than the natural vibrations in the first free form, there-

fore at resonance frequency the amplitudes of these

blade oscillations are not critical. The initial part of the

signals, which contained free frequencies of higher or-

ders, were therefore eliminated from the analysis.

The diagram in Figure 5 shows the time de-

pendence of simultaneously measured amplitudes of

natural vibrations with the first free form for 4 adjacent

blades (cf. Figure 3). The signal occurs within a time

interval of 5 s, during which the entire responses to

three consecutive impulse disturbances were measured.

On the logarithmic scale, the course of amplitudes (a) is

linear (Figure 5, interval designated B) with the same

slope for all the measured blades. For the observed first

free form, the damping ratio is constant and amounts to

d = 5 E-05. This finding has a twofold meaning:

- The damping of vibrations of a composite blade-

disc system with the first free form is described

satisfactorily by the viscous friction ratio, which

enables the convenient use of the established

models of dynamic damping based on a system

with one degree of freedom.

- The signals of all four accelerometers agree (the

measured free frequency and the damping ra-

tio), which proves that the masses of the accel-

erometers themselves are sufficiently small so

as to have a negligible effect on the dynamic

behavior of the blades.

3.2 Harmonic acoustic excitation

The following elements were used for

acoustic excitation: a frequency generator as the

source for the electrical signal, an amplifier and a

loudspeaker with the appropriate frequency re-

sponse characteristics (Figure 6). The frequency and

the shape (harmonic) of the signal were set using

the frequency generator. By means of a 4-channel

digital oscilloscope, the impeller�s free frequencies

were first detected. The responses in the form of

oscillations of the measured blades agreed well, both

in terms of frequency and shape, with the signal of

the forced oscillation (acoustic signal). For each

resonance frequency, the signal was recorded as

follows:

- When resonance was established (local maximum

of the measured response amplitude), measure-

ments began.

00-11/12stran 758


- Med meritvijo je bil akustièni signal prekinjens stikalom na zvoèniku. Dobljeni odzivlastnega nihanja je bil uporabljen za analizosignala.

Glede na prièakovanja iz prej�njihnumeriènih analiz [5] in frekvenène razstavitveodzivov pri impulznem vzbujanju je bilo obmoèjemed 8,5 kHz in 11,5 kHz, kjer le�ijo vse lastnefrekvence, ki pripadajo 1. lastni obliki, podrobnoraziskano. Med kar nekaj resonancami v temfrekvenènem obmoèju je zanimiva tista, prifrekvenci 9,64 kHz, saj ima od drugih za velikostni

- During the measurement, the acoustic signal was

interrupted using a switch on the loudspeaker.

The obtained free oscillation response was used

for signal analysis.

Based on our expectations from previous nu-

merical analyses [5] and the frequency decomposition of

responses in impulse excitation, the frequency range be-

tween 8.5 kHz and 11.5 kHz was studied in detail, be-

cause all the free frequencies corresponding to the first

free form were located in this range. Of the many reso-

nant frequencies in this range, the most interesting one

was at 9.64 kHz, because its damping was smaller than

Sl. 5. Izmerjene vrednosti amplitud odziva �tirih sosednjih lopatic na tri zaporedne impulzne motnje terpripadajoèi razmernik du�enja

Fig. 5. Measured values of amplitudes of the response of four adjacent blades to three consecutive impulsedisturbances and the corresponding damping ratio

00-11/12stran 759


Sl. 6. Sistem za akustièno harmonsko vzbujanje: 1 � frekvenèni generator; 2 � ojaèevalnik; 3 � zvoènik; 4 �turbinski gonilnik z gredjo

Fig. 6. System for acoustic harmonic excitation: 1 � frequency generator; 2 � amplifier; 3 � loudspeaker; 4� turbine impeller with shaft

Sl. 7. Izmerjene vrednosti amplitud odziva �tirih sosednjih lopatic na harmonsko vsiljeno nihanje terpripadajoèi razmernik du�enja

Fig. 7. Measured values of response amplitudes for four adjacent blades � harmonic forced oscillation andthe corresponding damping ratio

00-11/12stran 760


razred manj�e du�enje in enako obliko, kakor priimpulznem vzbujanju. Kakor je razvidno izdiagramov na sliki 7, ki prikazujejo odzive lastneganihanja 4 sosednjih lopatic, so nagibiamplitudnega odziva sistema, prikazanega vlogaritemski lestvici enaki, kakor pri impulznemvzbujanju, zatorej je razmernik du�enja enak: d = 5E-05.

V primerjavi z omenjeno lastno frekvenco,

so preostala nihanja povezana z znatno veèjimdu�enjem. Razen tega ima du�enje teh lastnih frekvencmoèno nelinearno karakteristiko, zato ga ni mogoèepopisati z uporabljenim modelom. Zaradi velikostidu�enja je bilo vzeto, da te lastne frekvence nisokritiène pri obravnavi vibracij med obratovanjem in

so bile zato izvzete iz obravnave.

4 SKLEPI

V raziskavi so bile analizirane dinamiènelastnosti vibracij gonilnika turbopuhala, ki predstavlja

sestavljen sistem lopatice - disk.

Eksperimentalno je bil doloèen koeficientdu�enja, in sicer z dvema razliènima naèinomavzbujanja sistema: z impulzno motnjo in z akustiènimharmonskim vzbujanjem. Iz analize izmerjenih signalovje mogoèe povzeti naslednje:- lastna nihanja vi�jih redov se zaradi relativno

velikega du�enja zelo hitro iznihajo;

- v signalu po iznihanju lastnih frekvenc vi�jih

redov ostane samo �e nihanje prvega reda (1.

lastna oblika).

V obeh primerih vzbujanja se za lastnanihanja s 1. lastno obliko izka�e linearna naravadu�enja, pri èemer zna�a razmernik du�enja zaobravnavano gradivo d = 5 E05.

Eksperimentalno dobljeni podatki o du�enju

so koristna informacija za oblikovanje numeriènegamodela, katerega namen je simuliranje in analizaobratovanja gonilnika turbopuhala v resonanci innjeni okolici.

Zahvala

Predstavljeno raziskovalno delo je bilo

opravljeno v okviru raziskovalnega usposabljanja na

In�titutu za toplotne turbinske stroje Tehni�keuniverze Karlsruhe, Nemèija, s finanèno podporoSklada Alexandra von Humboldta. Obemaustanovama se za podporo pri tem delu iskrenozahvaljujem.

that of the others by an order of magnitude, and its shape

was the same as in impulse excitation. As can be seen

from the diagrams in Figure 7, which show the responses

of the free oscillation of 4 adjacent blades, the slopes of

the amplitude response of the system shown on the loga-

rithmic scale are the same as in impulse excitation, there-

fore the damping ratio is the same: d = 5 E-05.

In contrast to the above-mentioned free fre-

quency, the other oscillations are associated with a

considerably greater damping. In addition, the damp-

ing of these free frequencies has a strongly nonlinear

characteristic, therefore it cannot be described using

the above model. Due to the magnitude of the damp-

ing it is assumed that these free frequencies are not

critical in the study of vibrations during operation

and were therefore excluded from the analysis.

4 CONCLUSION

This study analyses the dynamic proper-

ties of the vibrations of a turbocharger impeller, rep-

resenting a composite blade-disc system.

The damping coefficient was determined ex-

perimentally using two different methods of exciting

the system: impulse disturbance or acoustic harmonic

excitation. The analysis of the measured signals leads

to the following conclusions:

- natural vibrations of higher orders dissipate very

quickly due to a relatively large degree of damp-

ing;

- after free frequency oscillations of higher orders

have dissipated, the signal contains only oscil-

lations of the first order (first free form).

In both methods of excitation, natural vibrations of

the first free form exhibit linear damping, whereby the

damping ratio for the studied material is d = 5 E05.

Experimentally obtained data on damping

can serve as useful information for the development

of a numerical model for the purposes of simulation

and analysis of the operation of turbocharger

impellers at or near resonance frequency.

Acknowledgement

The described research work was performed

within the framework of research training at the Insti-

tute of Thermal Turbomachinery of the Technical

University of Karlsruhe, Germany, with the financial

assistance of the Alexander von Humboldt Fundation

I gratefully acknowledge the support of both institu-

tions in my work.

00-11/12stran 761


5 LITERATURA

5 REFERENCES

[1] Baumgartner, M., Dameier, F., J. Hourmouziadis (1995) Non-engine blade vibration in a high pressure

compressor. Paper ISABE 95-7094.

[2] Rieger, N., C.M. Beck (1980) Damping tests on steam turbine blades. EPRI Project, RP-1185-1.

[3] Hillerin, C.A. (1989) Free response to an initial displacement for a s.d.o.f. system in presence of dry friction

and viscous damping. Proc. of the 7th International Modal Analyses Conference, Volume 2, p. 1123-1127.

[4] Badrakhan, F. (1985) Separation and determination of combined dampings from free vibrations. Journal ofSound and Vibration, 100(2): p 243-255.

[5] Filsinger, D., Sekavènik, M., Kreuz-Ihli, T., Schulz, A., S. Wittig (1999) Finite element analyses of the

vibration characteristics of a turbocharger impeller. Proc. of First International Conference of StructuralEngineering and Mechanics, Seoul, Korea.

[6] Ludewig, H. (1969) Schwingungsmessungen an Turbinenschaufeln von Abgasturboladern mit

Hochtemperatur-Dehnmessstreifen. Messtechnische Briefe 1.

[7] Genta, G. (1998) Vibrations of strucures and machines. Springer Verlag.

Naslov avtorja: dr. Mihael SekavènikFakulteta za strojni�tvoUniverze v LjubljaniA�kerèeva 61000 LJUBLJANA

Author�s Address: Dr. Mihael SekavènikFaculty of Mechanical EngineeringUniversity of LjubljanaA�kerèeva 61000 Ljubljana, Slovenia

Prejeto: 14.9.2000

Sprejeto: 20.12.2000

Received: Accepted:

00-11/12stran 762

B. Pu~ko: Vpliv vibriranja med varjenjem - The Effect of Vibrational Treatment During Welding

Vibriranje za odpravo napetosti (VON - VSR) je eden od naèinov odpravljanja zaostalih notranjihnapetosti v zvaru. Pri tem se lahko spremene tudi nekatere druge mehanske lastnosti zvarnega spoja.

Namen raziskave je bil primerjati lastnosti veèvarkovnih zvarnih spojev, zavarjenih in vibriranih vrazliènih razmerah. Z osnovnim stanjem smo primerjali �arjeno stanje, stanje z vibriranjem med varjenjem inpo njem ter kombinacijo vibriranja in �arjenja. Varili smo po postopku T.I.M.E. (varjenje v za�èiti moènoioniziranega veèkomponentnega plina). Z metodami verifikacije varilnega postopka in dodatnimi raziskavamilomne �ilavosti smo ocenili razlike med razliènimi stanji. Opravili smo mehanske preskuse natezne trdnosti,udarne �ilavosti, lomne �ilavosti in meritve trdot. Med seboj smo primerjali lastnosti v strjenem zvaru. Izsledkiraziskav ka�ejo izbolj�anje udarne in lomne �ilavosti, èe so zvari vibrirani med varjenjem ali po njem. Nadruge mehanske lastnosti ni bilo bistvenega vpliva. �arjenje nasprotno poslab�a omenjene lastnosti terpovzroèi zveèanje trdote v toplotno vplivanem podroèju (TVP) zvara presku�anega jekla.© 2000 Strojni�ki vestnik. Vse pravice pridr�ane.(Kljuène besede: VSR, vibriranje, odprava napetosti, postopek TIME)

The vibrational stress relief (VSR) technique has been shown to reduce the internal residual stressescaused by welding. By lowering or redistributing the stress it is possible to alter the mechanical propertiesof the weld joint.

The aim of this study was to determine the effect of vibration on the properties of multilayer weldspecimens which were welded and vibrated under various conditions. Specimens which were stress annealed,vibrated after and during welding were compared with specimen in the as-welded condition. Each specimenwas welded using the T.I.M.E. (transferred ionized molten energy) process. Using weld-procedure-specificationmethods and the fracture-toughness method we established differences in the properties of the differentspecimens. Properties were also assessed using the tensile stress test, the Charpy V-notch test, the fracturemechanics test and hardness measurements. Measurements were made primarily in the weld metal. Theresults show an effect of vibration after, and during, welding on the Charpy and fracture toughness, the othermechanical properties were not seriously affected. Stress annealing, in contrast, lowers the toughness andincreases the hardness in the heat-affected zone (HAZ) of the weld.© 2000 Journal of Mechanical Engineering. All rights reserved.(Keywords: VSR, vibrational stress relief, TIME process)

The Effect of Vibrational Treatment During and After Weldingon the Mechanical Properties of a Transferred Ionized MoltenEnergy Weld

Bogdan Pu~ko

© Strojni{ki vestnik 46(2000)11/12,762-769ISSN 0039-2480UDK 621.791.75:620.178.3Pregledni znanstveni ~lanek (1.02)


UDC 621.791.75:620.178.3Review scientific paper (1.02)

Vpliv vibriranja med varjenjem in po njem namehanske lastnosti zvarov, zavarjenih v za{~itimo~no ionoziranega ve~komponentnega plina

0 UVOD

�e v tridesetih letih dvajsetega stoletjazasledimo, da se v konstrukcijah poleg napetosti, kotposledici zunanje obremenitve, pojavljajo tudi takoimenovane notranje zaostale napetosti. V �tiridesetih inpetdesetih letih so objavili vrsto èlankov, v katerih seukvarjajo s �tudijem vira, nastanka in meritev tehnapetosti. Hkrati s tem so se razvijale tudi metode za

0 INTRODUCTION

By the 1930s researchers had discovered

that all stresses in a structure were not just the

result of loading. Residual stresses are also formed.

In 1940s and 1950s many publications refered to

the origin, development and measurement of re-

sidual stresses. During that time the reduction or

methods for elimination of stresses were devel-

00-11/12stran 763


njihovo zmanj�evanje ali odpravljanje. �ele v sredini�estdesetih let se moèno raz�irijo raziskave z mehanskimvibriranjem kot mo�nim naèinom za zmanj�evanjenapetosti. V velikem �tevilu èlankov ugotavljajougoden uèinek vibriranja na zmanj�anje notranjih mikronapetosti z meritvijo zaostalih napetosti in deformacij([1] do [9]).

Manj jasen ostaja vpliv vibriranja na mehanskelastnosti osnovnega materiala in zvara. Razlièni avtorjiugotavljajo zanemarljiv [10] ali celo negativen [2] vplivna mehanske lastnosti. Vibriranje med varjenjem lahkovpliva na zmanj�anje trdote [11]. Novej�e raziskave [12]med drugim podajajo ugoden vpliv vi�jih frekvenc (80do 400 Hz) med varjenjem na mehanske lastnostialuminija. Gnirss [13] v svojem èlanku poudarja tudivpliv na dele� vodika in njegove razporeditve. Zaradiveèje gibljivosti vodika pri vibriranju se ta ugodnejerazporedi in tudi la�e prodre od dislokacij, kar zmanj�anevarnost hladne pokljivosti. Zmanj�anje zrna podvplivom vibriranja med varjenjem bi naj bilo premosorazmerno prostorninski spremembi med strjevanjem([14] in [15]). Nasprotno Crawmer [16] dokazuje, da privarjenju ni vpliva na velikost zrna, kar lahko pojasnimoz veliko hitrostjo ohlajanja v primerjavi z litjem. Prav takoje najti trditev [11], da ni vidne spremembe velikosti zrnavarka in TVP pri vibriranju med varjenjem. Nekateri avtorjidokazujejo, da vibriranje pospe�uje uèinke toplotneobdelave [17]. S tem se poveèuje hitrost odtaljevanjadodajnega materiala za 10 odstotkov ([16] in [18]), hitrostohlajanja taline [19] in s tem globina prekalitve [20].Razlaga teh procesov je povezana z nastankom veèjega�tevila praznin v kristalni strukturi in tako poveèanjadifuzijskih koeficientov [21]. Z nastankom praznin jepoveèana gibljivost dislokacij, kar je tudi ena od razlagin je v prid zmanj�anju deformacij kristalne mre�e ([1],[6], [11] in [22]). Kot posledica poveèane hitrostiodtaljevanja je lahko tudi poveèanje hitrosti varjenja,kar je opisano v èlanku [6]. Vpliv na globino pretaljevanjaje opisan v èlankih ([11] in [23]). Èlanki ne ugotavljajobistvenega vpliva vibracije na globino uvara in nageometrijsko obliko prereza varka.

Da bi se izognili �tevilnim vplivnimdejavnikom, ki se pojavljajo pri varjenju, je veèinaraziskav izvedena na preprostih presku�ancih,obièajno na manj�ih plo�èah ali palicah. Varjenje senajveèkrat omejuje na navarjanje ali pa se simuliravnos napetosti pri varjenju, na primer z valjanjem.Rezultati, predstavljeni v tem èlanku, so rezultatimeritev na veèvarkovnih zvarnih spojih, ki po svojiobliki in velikosti ustrezajo zvarom na konstrukcijah.Izmerjene so bile mehanske lastnosti (natezna trdnost,trdota, udarna in lomna �ilavost).

1 TEORIJA

VON je v prvi vrsti namenjeno zmanj�anjuzaostalih mikro napetosti in poveèanju dimenzijskestabilnosti. Metoda se je pokazala uporabna pri vseh

oped. During the 1960s research on mechanical

vibrations as a possible method for stress reduc-

tion began. Many papers reported positive results

with regard to measurements of internal stresses

and deformation ([1] to [9]).

The effect of vibration on the base mate-

rial and the weld metal mechanical properties re-

mains unclear. Many authors found negligible [10]

or negative [2] effects on the mechanical proper-

ties. Vibration during welding was observed to

lower hardness [11] and the latest research on alu-

minum [12] has shown a positive effect on the me-

chanical properties when the aluminium is vibrated

(80 to 400 Hz) during welding. In his paper [13]

Gnirss discusses the effect of vibration on hydro-

gen distribution. Because of the higher mobility of

atoms during vibration, the hydrogen can easily

move from dislocations and therefore lower the

cold crack sensitivity. Grain refining caused by the

vibration during welding should be directly corre-

lated to the volume change during solidification

([14] and [15]), however, Crawmer [16] showed no

effect on grain refinement, which could be the re-

sult of a very short solidification time within weld-

ing in comparison to casting. No change in the

grain size has been reported also by other authors

[11]. Other reports suggest that vibration can in-

crease the effects of heat treatment [17]. The depo-

sition rate can be increased for about 10 % ([16]

and [18]), cooling time can be shortened [19] and

weld penetration can be affected [20]. The expla-

nation of these processes is connected with an

increase in the number of vacancies in the crystal

lattice and therefore an increase in the diffusion

rate [21]. With vacancy formation, dislocation

movement is increased, which is important in re-

covery mechanisms ([1], [6], [11] and [22]). A higher

deposition rate can also increase welding speed

[6]. Penetration of the weld has been discussed

([11] and [23]) and a connection between vibration

and weld geometry could not be found.

To avoid a number of the parameters which

affect the welding process, most of the research was

carried out on simple specimens, usually on small

plates or bars. Welding was often reduced to surfac-

ing or residual stresses were simulated, for example,

with rolling. Results obtained from welding multilayer

weld specimens, which, because of their shape and

dimensions, can be compared to construction welds

are presented. Mechanical properties were obtained

from tensile tests, hardness tests, Charpy toughness

and fracture toughness measurement.

1 THEORY

The VSR technique is used to reduce the

residual microstresses in a material and increase of

dimensional stability. This technique is used for rolled,

00-11/12stran 764


vrstah valjanih, litih, varjenih, kovanih in mehanskoobdelanih izdelkih. Primerna je za konstrukcijska,normalizirana, popu�èena, kaljiva in nerjavna jekla.VON ni zamenjava za toplotno obdelavo, pri kateripoleg odpravljanja makro napetosti povzroèamometalur�ke spremembe v mikrostrukturi materiala. Vliteraturi se uèinki te metode najveèkrat primerjajo zuèinki naravnega staranja.

Vsaka konstrukcija ima svojo lastno frekvenco.Resonanène vrhove doloèimo z meritvijo pred prièetkomvibriranja. S spreminjanjem frekvence od vrednosti nièdo konène vrednosti w merimo velikost toka vibratorjapri nekaj (3 do 5) resonanènih vrhovih (w

i). Na sliki 1 je

shematsko prikazan postopek vibriranja po varjenju. Povibriranju, obièajno 15 do 30 minut pri najvi�ji harmoniènifrekvenci, zmanj�ujemo hitrost rotorja na vrednost nièin medtem merimo vrednost toka vibratorja pri istihfrekvencah kakor pred vibriranjem. Razlika tokov (DI

i)

rabi kot merilo zmanj�anja napetosti. Vèasih, èe je padectoka premajhen, je treba postopek ponoviti. Pri tem selahko napetosti dodatno zmanj�ajo. Èe ne zaznamospremembe toka v primerjavi s prej�njo meritvijo,pomeni, da smo element stabilizirali. Opisan postopekvelja za vibriranje po varjenju.

Pri vibriranju med varjenjem v èasu strjevanjamateriala varjenja vibriramo s stalno frekvenco in nemerimo resonanènih vrhov. Med varjenjem se vibriranjeizvaja v podresonanènem podroèju, da ne bi dobiliprevelikih nihanj zaradi resonanènih pojavov, kar lahkoneugodno vpliva na stabilnost obloka.

V materialu se z vibriranjem pojavlja takoimenovano notranje trenje oziroma du�enje, kimehansko (vibracijsko) energijo spreminja v toploto.Pojavljajo se mikroplastiène deformacije. To se dogajaznatno pod makroskopsko mejo elastiènosti.

Po�kodbe materiala pri vibriranju z majhnimiamplitudami so v primerjavi z utrujanjem pridinamiènem presku�anju izredno majhne [24], prvièzaradi majhne energije vibriranja, drugiè zaradimajhnega �tevila obremenitvenih ponovitev.

Loèimo lahko tri osnovne modele vibriranja.Pri prvem s preobremenitvijo konstrukcije dose�emo

cast, welded, forged and machined parts. We can use

it for normalized, tempered, quenched, structure and

stainless steels. It cannot be a substitute for thermal

annealing, where the relief of macrostresses is ac-

companied by changes in the microstructure. It is

common to compare the VSR technique to natural

aging.

Every structure has its own resonant

frequency. The method of vibration is schemati-

cally presented in Figure 1. The resonant peaks

can be found before the vibration starts by

changing the frequency from zero to the final

value of w. The values of the vibrator-current

consumption at a few (3 to 5) resonant peaks wI

are recorded. After vibration, usually 15 to 30

min at the highest frequency, the rotor frequency

is reduced to zero, and the current consumption

at the same resonant peaks is recorded. The cur-

rent difference (DIi) is an indication of the stress

reduction. If the current drop is too small, the

procedure has to be repeated to obtain stress

reduction. If there is no change in the current

compared to the previous measurements, the part

or specimen is stabilized.

During welding the resonant peaks are not

measured but maximum frequency is used during the

weld solidification. In fact, the frequency has to be

adjusted to a subresonant value to avoid maximum

amplitudes which can have a negative effect on arc

stability.

According to internal friction and attenua-

tion, mechanical (vibrational) energy in the material

changes to heat. Microplastic deformations can oc-

cur, and this process takes place under the macro-

scopic yield point.

Low-amplitude vibration causes no seri-

ous material damage and is smaller than during fa-

tigue testing [24]. The energy of vibration is very

low and there is a relatively small number of duty

cycles.

We can distinguish three different basic

models to explain the vibration effects. The first model

I (A)

D I 1

D I 2

D I 3

w 2 w 3

w 1 w 3 w 2

w 1

t vibr

Sl. 1. Shematski prikaz postopka vibriranja po varjenjuFig. 1. Method of vibrational treatment after welding - shematically

00-11/12stran 765


zmanj�anje napetosti na raèun makroskopskihdeformacij. Drugi (standardni) model razlagazmanj�anje napetosti kot posledico mikroplastiènegateèenja v podroèju elastièno obremenjenekonstrukcije ([25] in [26]). Ta model je uporaben privibriranju po varjenju. Tretji model je modelstabilizacije dislokacij ([11], [21] in [27]). V odvisnostiod temperature je pod vplivom vibracij poveèanagibljivost dislokacij in s tem mo�nost za prenosmateriala in medsebojno reakcijo dislokacij alidislokacij s tujimi atomi, kar zmanj�a skupno elastiènoenergijo. Ta model lahko uporabimo pri vibriranju medvarjenjem.

2 EKSPERIMENT

Preiskave, omenjene v tem prispevku, so bileopravljene na jeklu domaèega proizvajalca S500 NL1(EN 10027) s trgovsko oznako NIOMOL 490K, nazavarjenih talonih izmer 1200x400 mm. Zagotovljenemehanske lastnosti so R

m=560 MPa ter R

p=470 MPa

za izbrano debelino ploèevine 25 mm. Za dodajnimaterial smo izbrali polno �ico G3 NiMo (EN 12534) znekoliko veèjimi vrednostmi natezne trdnosti.Kemijska sestava osnovnega (OM) in dodajnegamateriala je podana v preglednici 1.

Za postopek varjenja je bil izbran novej�i, zeloproduktiven postopek, imenovan T.I.M.E. Parametrivarjenja so izbrani tako, da je bil vnos toplote do 1,5 kJ/mm zvara, oziroma so bili èasi ohlajanja t

8/5 kraj�i od 10 s,

kar po zagotovilih proizvajalca ploèevine �e zagotavljaugodne mehanske lastnosti TVP. Oblika zvara je zaradinaèina odvzema presku�ancev simetrièni zvar K.

Izhodi�èe za primerjavo rezultatov je bilpreskusni talon, zavarjen po naèrtovani tehnologiji, brezdodatne obdelave (S1). Drugi talon v seriji je v nasprotjuod prvega vkljuèeval �arjenje za odpravo napetosti povarjenju (S2). Tretji naèin priprave preskusnega talonapomeni standarni naèin vibriranja (S3). Po konèanemvarjenju smo ohlajen varjenec vibrirali okoli 20 min.Uporabili smo napravo za vibriranje, ki deluje vfrekvenènem podroèju do 75 Hz. Podobno kakor pri�arjenju prihaja pri vibriranju po varjenju do premikaposameznih atomov in dislokacij, vendar na lokalnihpodroèjih in v isti drsni ravnini. Ne pride do plezanjadislokacij, ampak le do drsenja. Pod vplivom vibriranjapride do manj�ih premikov dislokacij ter do njihovihreakcij s tujimi atomi, kar vodi do stabilnej�e kristalnestrukture. Manj uporabljano mo�nost vibriranja pomenivibriranje med varjenjem (S4). V tem primeru izrabljamo

suggests that overloading of a structure and macro-

scopic plastic deformation are the main reason for stress

reduction. The second (classical) model explains stress

reduction as the result of microplastic flow in elastic

stress structure ([25] and [26]). This model can prop-

erly explain vibration after welding. The third model

refers to dislocation stabilization ([11], [21] and [27]).

Dislocation mobility is increased with temperature.

With vibration excitation there is a greater possibility

of material transport and the reaction of dislocations

with dislocations or impurity atoms resulting in a low-

ering of the elastic energy of the system. This model

can explain processes by vibration during welding.

2 EXPERIMENT

The material used in this study was S 500

NL1 (EN 10027) with the trade name NIOMOL 490K.

The dimensions of the welded test plate were 1200x400

mm. The minimum mechanical properties were Rm =

560 MPa, Rp = 470 MPa for 25 mm plate thickness.

The filler material used was G3 NiMo (EN 12534) solid

wire with overmatched material properties. The chemi-

cal composition of the base (BM) and filler materials

is shown in Table 1.

The welding process used was the highly

efficient T.I.M.E. process. The welding parameters

were defined so that heat input did not exceed

1.5 kJ/mm and the cooling time t8/5

was shorter than

10 s; this should, according to the steel producer,

ensure proper mechanical properties in the heat-

affected zone (HAZ). To facilitate and ensure the

cutting out of the specimens the symmetrical K

weld type of joint was used.

The (S1) specimen, without further me-

chanical or heat treatment, was used as a control

sample. The second specimen in the series (S2) was

stress annealed after welding. The third specimen

represents (S3) the classical vibration treatment af-

ter welding with vibration for about 20 min. The

vibration device can operate with frequencies up to

75 Hz. With vibration after welding we can expect

the movement of some dislocations and atoms in

the same way as with annealing, but in the local

area and in the same gliding plane. There is no climb-

ing of the dislocations. The vibrational treatment

during welding can promote dislocation movement

and hence reactions with impurity atoms, the reac-

tion results in the stabilization of the crystal struc-

Preglednica 1. Kemijska sestava osnovnega (OM) in dodajnega materialaTable 1. Chemical composition of base (BM) and filler material

element C Si Mn P S Cr Mo Ni Nb Al

OM/BM 0,07 0,54 0,56 0,008 0,002 0,67 0,35 / 0,062 / dodajni/filler mat. 0,09 0,62 1,77 0,011 0,003 0,31 0,95 / / /

00-11/12stran 766


ture (S4). In this case we use the advantage of good

atom mobility because of the high temperatures and

the internal friction at critical points in the crystal

lattice. To evaluate the correlation between vibrat-

ing and annealing, one specimen was vibrated dur-

ing welding and then stress annealed after welding

(S5). Table 2 shows the specimens� symbol desig-

nation with preparation conditions.

3 RESULTS

Before testing the welded specimens longi-

tudinal and transverse residual stresses near the cen-

ter line of the weld were measured across the weld

[28]. The basis for the mechanical testing methods

was a standard for weld-procedure specification [29]

with corresponding standards.

In Figure 2 results of the tensile test speci-

mens are shown. The tensile specimens were ma-

chined from the weld metal in the longitudinal direc-

tion. Each column represents an average value of

two specimens. The measurement of elongation and

contraction showed no significant difference.

The hardness measurements in Figure 3

were at the top of the weld, about 2 mm under the

surface, across the region BM-HAZ-weld-HAZ-BM.

dobro gibljivost atomov zaradi visokih temperatur innotranje trenje na kritiènih mestih kristalne strukture.Primerjalno smo zavarili tudi talon z vibriranjem medvarjenjem, ki smo ga po konèanem varjenju tudi od�ariliza odpravo napetosti (S5). Tako smo �eleli ocenitikombinacijo vplivov vibriranja in �arjenja. V preglednici2 so prikazane oznake za posamezna stanja, ki sepojavljajo tudi v diagramih.

3 REZULTATI

Pred presku�anjem vzorcev iz zavarjenihtalonov so bile najprej izmerjene zaostale vzdol�ne inpreène napetosti glede na zvar, merjene preèno èezzvar v sredini talona [28]. Temelj za ovrednotenjemehanskih lastnosti je standard za verifikacijo varilnihpostopkov [29] z ustreznimi spremljevalnimistandardi.

Na sliki 2 so prikazani rezultati nateznegapreskusa vzorcev, vzetih vzdol�no iz zvara. Vsakstolpec pomeni popreèje dveh meritev. Meritevraztezka in skrèka ni pokazala vpliva vibriranja.

Trdote, prikazane na sliki 3, so bile izmerjenev temenu varka, pribli�no 2 mm pod povr�ino, skozipodroèje OM-TVP-zvar-TVP-OM.

Preglednica 2. Oznaka talonov glede na stanje zavaritveTable 2. Specimen designation according to condition of preparation

oznaka/ symbol

stanje / condition

S1 osnovno stanje / as welded

S2 �arjeno / annealed

S3 vibrirano po varjenju / vibrated after welding

S4 vibrirano med varjenjem / vibrated during welding

S5 vibrirano in �arjeno / vibrated and annealed

0

100

200

300

400

500

600

700

800

900

S1 S2 S3 S4 S5

MP

a Rp

Rm

Sl. 2. Natezna trdnost in napetost teèenja zvaraFig. 2. Tensile strength and yield stress of weld metal

00-11/12stran 767


0

50

100

150

200

-60 -40 -20 0 20

temp. (°C)

�ila

vost

/tou

ghn

ess

(J)

S1

S2

S3

S4

S5

S1

S2

S3

S4

S5

0

0,2

0,4

0,6

0,8

1

1,2

1,4

S1 S2 S3 S4 S5

d (

mm

)

For each weld preparation, five series of

Charpy V-notch specimens were made. Charpy tough-

ness was measured in the range from �60°C to +20°C,

which is the range of guaranteed specified mechani-

cal properties. In Figure 4 it should be noted that all

values for the vibrated specimens are higher than for

Za vsak naèin varjenja je bilo izdelanih petserij presku�ancev za preskus udarne �ilavosti poCharpyju. Z njimi smo izmerili udarno �ilavost vtemperaturnem podroèju od �60°C do +20°C, to jepodroèje, za katero proizvajalec jekla zagotavljadoloèene mehanske lastnosti. Na sliki 4 velja opozoriti,

200

250

300

350

trdo

ta /

hard

ness

HV

1 S1 S2 S3 S4 S5

5mm

Sl. 3. Trdota v temenu zvaraFig. 3. Hardness at the top of the weld

Sl. 4. Udarna �ilavost zvarovFig. 4. Charpy toughness of welds

Sl. 5. Lomna �ilavost zvarovFig. 5. Fracture toughness of welds

00-11/12stran 768


da so vrednosti �ilavosti pri vseh vibriranih stanjihveèje kakor osnovno in �arjeno stanje.

Vrednosti lomne �ilavosti posameznih epruvetso bile doloèene na podlagi koncepta lomne mehanikeCOD (Crack Opening Displacement). Temperaturapresku�anja je bila -40 °C. Na sliki 5 vsak stolpec pomenieno izraèunano vrednost parametra lomne �ilavosti d.

4 SKLEPI

Natezna trdnost se z vibriranjem praktiènone spreminja. Vibriranje po varjenju ali med njim zamalenkost zmanj�a napetost teèenja, kar bi moralipotrditi z natanènej�imi preiskavami. Zmanj�anje je vmejah natanènosti metode. Na raztezek in skrèekvibriranje nima bistvenega vpliva. Spremembtrdnostnih lastnosti pri vibriranju po varjenju in mednjim nismo opazili.

Trdota v strjenem zvaru se z �arjenjemzmanj�a, vendar se v TVP pojavijo konice trdot, ki sonajverjetneje posledice izloèilnih pojavov. V primerjaviz osnovnim stanjem (S1) vibriranje med varjenjem (S3)ali po varjenju (S4) pri tem postopku vidno ne vplivana trdote v temenu zvara. V stanju vibrirano medvarjenjem in �arjeno (S5) pa so se trdotne konice zvibriranjem glede na samo �arjeno stanje (S2) zni�ale.

Z vibriranjem med varjenjem se �ilavost zvarapoveèa. Vibriranje po varjenju in med njim izbolj�a�ilavost v primerjavi z osnovnim stanjem.

Opaziti je nagnjenje k poveèevanju lomne�ilavosti zaradi vibriranja. Vendar glede lomne �ilavostini bistvene razlike pri vibriranju med varjenjem in ponjem. Vrednost parametra lomne mehanike d se zaradivibriranja moèno poveèa glede na osnovno stanje.

�arjenje moèno zmanj�a lomno �ilavoststrjenega zvara, tudi kadar ga kombiniramo zvibriranjem. Za obravnavano jeklo �arjenje ni primerennaèin zmanj�evanja zaostalih napetosti.

the unvibrated specimens.

Fracture toughness values are obtained

with the Crack Opening Displacement fracture

(COD) mechanics method. The testing temperature

was -40 °C. In Figure 5 each column refers to one

value of the calculated fracture mechanics para-

meter d.

4 CONCLUSIONS

There is no significant change in the tensile

strength. Vibration after, or during, welding slightly

lowers the yield stress, but we should confirm this

with additional research. It seems there is no effect

on the ductility and contraction. Vibrating after and

during welding has a similar effect on the mechanical

properties.

The weld hardness drops with annealing,

but peaks in the HAZ occur. These peaks are obvi-

ously the result of the precipitation of carbides in

the HAZ. In comparison to the as-welded condition

(S1) vibration after welding (S3) and during welding

(S4) seems to have no significant effect on the hard-

ness for this welding process. But the specimen

vibrated before annealing (S5) exibits no hardness

peaks in the HAZ compared to annealed-only con-

dition (S2).

An increase in the fracture toughness due

to vibration is apparent.

There is no difference between vibrating the

specimen after or during welding. The increase in

fracture toughness is reflected in an increase in the

parameter of fracture mechanics d.

Annealing has a significant effect on the

fracture toughness for this material. Vibration cannot

remove this effect. For this material annealing is cer-

tainly not a suitable method for lowering the residual

stresses.

5 LITERATURA

5 REFERENCES

[1] (1968) Vibratory stress relieving, Welding and Metal fabrication[2] Kalna, K. (1987) Mechanical stress-relief treatment of welded pressure vessels by warm pressure test,

Stress relieving heat treatments of welded steel constructions, Proceedings Conference, Sofia.

[3] Batyuk, V.V., A.A. Khryplivy (1987) Efficiency of application of heat- and vibro-treatment to reduce re-

sidual stresses in weldments, Stress relieving heat treatments of welded steel constructions, ProceedingsConference, Sofia, 1987

[4] Sedek, P. (1988) Vibratory stress relief of welded components, Welding International.[5] Noskova, N.I., N.F. Vil�danova (1986) Relaksacija ostatoènyh naprja�enij metallov v pole uprugih kolebanij,

Problemy proènosti.[6] N.N. (1969) A Vibration Shakedown, Welding Design & Fabrication.

[7] Döbler, von E. (1981) Abbau von Eigenspannungen durch Vibration, Werkstatt und Betrieb.[8] Ohol, R.D., Nagendra Kumar, B.V., R.A. Noras (1988) Measurement of vibration-induced stress relief in the

heavy fabrication industry, Mechanical relaxation of residual stresses, American Society for Testing andMaterials, Philadelphia.

00-11/12stran 769


[9] Bouhelier, C., P. Barbarin (1988) Vibratory stress relief of welded parts, Mechanical relaxation of residual

stresses, American Society for Testing and Materials, Philadelphia.

[10] Jesensky, M. (1987) Vibratory lowering of residual stresses in weldments, Stress relieving heat treatments

of welded steel constructions, Proceedings Conference, Sofia.

[11] Weidner, C.W. (1967) A study of the effects of low frequency mechanical vibration during welding on the

resulting residual stresses and microstructure, The Ohio State University.[12] Tewari, S.P., A. Shanker (1994) Effects of longitudinal vibration on tensile properties of weldments, Weld-

ing Journal, Vol. 73.

[13] Gnirss, G. (1986) Rütteln und Vibrationsentspannen, Werkstofftechnik, Bd.27-11.

[14] Freedman, A.H., J.F. Wallace (1957) The influence of vibration on solidifying metals, American Foundryman�sSociety Transactions, Vol. 65.

[15] Garlick, R.G., J.F. Wallace (1959) Grain refinement of solidifying metals by vibration, American Foundryman�sSociety Transactions, Vol. 67.

[16] Crawmer, G.R. (1965) The effect of sonic or ultrasonic vibration of a consumable electrode during arc

welding, Ohio State University PhD. Thesis.[17] Pogodin-Alekseev, G.I., V.S. Mirotoviskii (1966) Use of ultrasonics in metal science and heat treatment of

metals, Metal Science and Heat Treatment.[18] Szekeros, E.S. (1961) A Discussion of arc physics and metal transfer in manual arc welding and experiments

with ultrasonic vibrated electrodes, Ohio State University PhD. Thesis.[19] Nakarni, S.V (1988) Modern arc welding technology, New Delhi.

[20] Chacin, V.N., V.E. Eremin (1966) Effect of ultrasonic vibrations on the cooling capacity of the quenching

medium, Metal Science and Heat Treatment.[21] Brown, A.F. (1966) The effect of vibrational deformation on diffusion-controled reactions in metals, Ap-

plied Materials Research, Vol. 5.

[22] Rappen, A.: Vibration nach dem VSR-Verfahren zur Verminderung des Eigenspanungsverzugs

[23] Xiao, Y.H., G. den Ouden (1993) Weld pool oscillation during GTA welding of mild steel, Welding Journal.[24] Munz, D., Schwalbe, K., P. Mayr (1971) Dauerschwingverhalten metallischer Wekstoffe, Fridr. Vieweg &

Sohn GmbH, Verlag, Braunschweig.

[25] Dawson, R., D.G. Moffat (1980) Vibratory stress relief: A fundamental study of its effectiveness, Journalof Engineering Materials and Technology, Vol. 102.

[26] Wohlfahrt, H. (1973) Zum Eigenspannungsabbau bei der Schwingungsbeanspruchung von Stählen,

Härterei-technische Mitteilungen 28.

[27] Walker, C.A., A.J. Waddell (1995) Vibratory stress relief � an investigation of the underlaying processes,

Journal of Process Mechanical Engineering.

[28] Vuherer, T. (1999) Analiza zaostalih notranjih napetosti s posebnim poudarkom na ponovnem vnosutoplote in njih meritev v soèelnih zvarnih spojih, Univerza v Mariboru, magistrsko delo.

[29] SIST EN 288-3 (1996) Zahteve in priznavanje varilnih postopkov za kovinske materiale � 3. del: Presku�anjevarilnih postopkov za obloèno varjenje jekel.

Author�s Address: Mag. Bogdan PuèkoUniversity of Maribor

Faculty of Mechanical Eng.

Smetanova 17

2000 Maribor, Slovenia

Avtorjev naslov: mag. Bogdan PuèkoUniverza v Mariboru

Fakulteta za strojni�tvo

Smetanova 17

2000 Maribor

Prejeto: 30.6.2000

Sprejeto: 20.12.2000

Received: Accepted:

00-11/12stran 770

G. Hren - A. Jezernik - S. Luk{i~: Izku{nje pri uvajanju RPK - Experiences of CAD Implementation

Adria-Mobil d.o.o. je znano slovensko podjetje poèitni�kih prikolic in avtodomov, ki se je za uvajanjedvodimenzionalnega sistema raèunalni�ko podprtega konstruiranja (RPK - CAD) odloèilo �e pred leti. Vèlanku je opisan naèin uvajanja, pa tudi izku�nje, pridobljene ob uvajanju in uporabi sistema RPK. Danes jepodjetje prisiljeno v menjavo sistema RPK in se sreèuje z nekaterimi dilemami, ki so posledica hitrega razvojasistemov informacijske tehnologije (IT) pa tudi pridobljenih spoznanj. Pred nadaljnjimi investicijami vnapredne tehnologije mora biti doloèena strategija podjetja na tem podroèju.© 2000 Strojni�ki vestnik. Vse pravice pridr�ane.(Kljuène besede: uvajanje CAD, resniènost navidezna, prototipi navidezni, razvoj)

Adria-Mobil Ltd. is a well-known Slovenian caravan and motorhomes producer, which introduceda 2D CAD system some years ago. In the article, the implementation, development and experiences since aresystem�s introduction are described. The company is about to change its CAD system and is faced with certaindilemmas due to rapid IT-systems development. A company strategy is required before making any majoradvanced-technology-related investment decisions.© 2000 Journal of Mechanical Engineering. All rights reserved.(Keywords: CAD implementation, virtual reality, virtual prototyping, development)

Experiences of CAD Implementation and Trends in Developmentat ADRIA Mobil Ltd.

Gorazd Hren - Anton Jezernik - Stanislav Luk{i~

© Strojni{ki vestnik 46(2000)11/12,770-779ISSN 0039-2480UDK 658.512.2:629.334:728.76Pregledni znanstveni ~lanek (1.02)


UDC 658.512.2:629.334:728.76Review scientific paper (1.02)

Izku{nje pri uvajanju ra~unalni{ko podprtegakonstruiranja in smeri razvoja v ADRIAMobil d.o.o.

0 UVOD

ADRIA Mobil d.o.o. je znan kot edenvodilnih evropskih izdelovalcev poèitni�kih prikolicin avtodomov in ta polo�aj ima podjetje namenobdr�ati tudi v prihodnosti. �e od samih zaèetkov, kisegajo v leto 1965, sodi Adria med tradicionalnozanesljive izdelovalce prikolic. Velik tr�ni dele� nanajzahtevnej�ih in najbogatej�ih evropskih trgih jeposledica zelo kakovostnih proizvodov ter �irokorazvejane prodajne mre�e po vsej Evropi.

Podjetje izdeluje tri osnovne serije prikolic,ki se razlikujejo predvsem po dol�ini in sevedaopremljenosti, pribli�no �tirideset tlorisnihrazporeditev ter tri izvedbe avtodomov. Podjetje jeusmerjeno veèinoma v izvoz v zahodnoevropskedr�ave, pojavlja pa se tudi na tr�i�èih srednje Evropein Japonske. Vsak trg ima svoje specifiène zahteve,tako glede tehniènih predpisov kakor okusa in potrebkupcev, kar seveda �e poveèuje �tevilo izvedb. Gledena velikost proizvodnje (pribl. 6000 enot) in �tevilazaposlenih (342) spada med srednje velika podjetja vsvoji veji.

0 INTRODUCTION

ADRIA Mobil Ltd. is well known as one ofthe leading European producers of caravans andmotorhomes, and the company�s intention is to pre-serve this status. Since the beginning of caravan pro-duction in 1965, Adria has been one of the most im-portant traditional producers of caravans. A largemarket share in the most lucrative and demanding ofEuropean markets is the result of high-quality prod-ucts and a European-wide sales network.

The company produces the three basic typesof caravan, which differ mainly in terms of length, equip-ment and layout, as well as three varieties ofmotorhome. The company is mainly focused on ex-porting to Western European countries but is alsopresent in the markets of Central Europe and Japan.Every market has its own technical regulations, differ-ent customer preferences and needs; and this increasesthe number of different models which are produced.Considering the level of production (ca. 6000 units)and the number of employees (342), the company isclassed as a medium-sized enterprise in this area.

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Konkurenca na tr�i�èu je izredno huda, zatoje nujno potrebno sprotno izbolj�evanje kakovosti inosve�evanje proizvodov, tako zunanjosti kakornotranjosti, ter zmanj�evanje èasa proizvodnegakroga. Precej znaèilen je tudi proizvodni krog, saj sedokumentacija in prototipi izdelajo do predstavitvena specializiranih sejmih in nato glede na odzivespremenijo in dopolnijo. Enako pomemben je skloppoprodajnih dejavnosti, ki moèno vpliva na nadaljnjesmernice razvoja in zagotavljanje kakovosti. Letnaproizvodnja dokumentacijskih risb je okrog 6000.

1 UVAJANJE IN RAZVOJ

1.1 Opis uvajanja RPK

V èasu, tj. v osemdesetih letih, ko se je podjetjeodloèalo za uvajanje sistema RPK, je �e uporabljalostandardno zasnovan mre�ni poslovno informacijskisistem ULTRA na platformi VAX. Sistem za obvladovanjekosovnic in naèrtovanja potreb pomaterialih (NPM -MRP) je bil del poslovnega informacijskega sistema.Pred odloèitvijo o izboru programske in aparaturneopreme je bilo izvedeno izobra�evanje o temeljnih znanjihs podroèja raèunalni�tva, baz podatkov in sistemov RPK.Odloèitev o nabavi sistema za RPK je bila sprejeta potestiranjih veè programskih paketov. Izbran je bil DIAD,produkt CADCentre iz Cambridga. Odloèitvi so botrovalinaslednji dejavniki:- zaradi razmeroma preproste geometrijske oblike

prikolic je bil potreben le 2D paket (risanje), pa tudi3D paketi �e niso bili na nivoju polne industrijskeuporabe;

- delovanje na platformi VAX, kar je obljubljalosorazmerno preprosto povezljivost s poslovniminformacijskim sistemom;

- paket je sorazmerno preprost za uporabo, z zelokakovostnimi re�itvami uporabe knji�nicstandardnih elementov, pa tudi ustvarjanja lastnihknji�nic objektov;

- zelo zmogljiv makro jezik za parametrizacijo objektovin variantno konstruiranje,

- tehnièna podpora in izobra�evanje ter odprtprogramski paket, ki ga je sorazmerno preprostoprilagajati �eljam uporabnika;

- cena.

Competition in the market is very tight andso companies are forced to continuously improvethe quality of their products, very often by addingnew features or updating the interior design. Theproduction cycle is predictable, prototypes are pre-sented at the specialised fairs and feedback is usedfor improvement in the final documentation prepara-tion. Equally important are the after-sales activities,which have a great impact on quality improvementand further development guidelines. The annualnumber of drawings is approximately 6000.

1 CAD IMPLEMENTATION AND DEVELOPMENT

1.1 Description of the CAD implementation

The company invested in a CAD/CAMsystem in the early 1980s and has reached an enviableposition in the design process. At the time of theCAD/CAM installation the company was alreadyusing a classically framed information system UL-TRA, running on a VAX platform. The maintenanceof the parts lists and the MRP (Material Require-ments Planning) were performed with this system.Education with respect to computer usage, data basesand CAD systems was undertaken prior to the CADsystem�s implementation. The decision to purchasethe DIAD CAD system from the CADCentre Cam-bridge, was made after extensive testing of all theavailable major software packages. This system waschosen because of:- our requirement for only a 2D system, caravans

have a comparatively simply geometry and 3D sys-tems were still in their infancy;

- its ability to work on a common hardware platform,which promised relatively easy connection to theexisting parts lists and MRP database;

- the systems ease of use, with powerful solutionsfor using libraries of standard elements and creat-ing our own libraries of objects;

- the powerful macro language for an objectparameterisation and variant design;

- good technical support and education as well asan open, and for special requests, easily adaptedprogram system;

- price.

Sl. 1. Poèitni�ka prikolica Adrie nekoè in danesFig. 1. Adria caravans from yesterday and today

00-11/12stran 772


V zaèetni fazi uvajanja sistema je bilaoblikovana skupina konstrukterjev, ki se je aktivnospoznala s paketom in delom z njim. V tem èasu je �epotekala nabava programske in aparaturne opreme.Prilagoditev na delo s RPK z obièajnih roènih metodpomeni veliko spremembo pri obvladovanju risb.Sprememba sistema je na zaèetku vplivala na zmanj�anjeproduktivnosti, kar je neizbe�no in je znan podatek izraziskav. Trajanje zmanj�anja produktivnosti je zeloodvisno od kakovosti in kolièine usposabljanja nasistemu. Grafi na sliki 2 prikazujejo rezultate neodvisnihraziskav Richarda Sheperda o odvisnosti usposabljanjain metod usposabljanja na produktivnostkonstrukcijskih oddelkov, pa tudi razmerje medproduktivnostjo in uporabo tehnologij RPK. Raziskavaje bila narejena v podjetjih v Veliki Britaniji inpredstavljena na MCAD�95. Zaradi dobregausposabljanja in velike motivacije je bil ta èas v Adriizelo kratek (raven s RPK nepodprte produktivnostikonstrukcijskega oddelka je bila dose�ena �e v dvehmesecih). Izbira prvega projekta, ki je zelo pomembna, jebila zelo hrabra. Izbran je bil projekt konstruiranja prikoliceza novo sezono, katerega terminski naèrt je bil �e doloèen.Sprva je bilo delo zelo zamudno, saj je bilo treba hkratipripravljati �e knji�nice v podjetju standardiziranihobjektov in pripravljati nove metode konstruiranja tersistem shranjevanja dokumentacije. Kljub dodatnemudelu je bila dokumentacija pripravljena pred èasovnimrokom, naèrtovanim za obièajno konstruiranje.

Za samo uvajanje je pomembno, da sodoloèeni uspehi vidni zelo hitro, kar bistvenopripomore k motiviranosti kadra. S tem delom jekonstrukcijski oddelek podjetja uspe�no konèal tadel uvajanja in dokazal, da je bila nalo�ba upravièena.Vsi naèrti so bili izdelani na novo.

V èasu konèevanja projekta se je izvajalododatno izobra�evanje in �irjenje kroga uporabnikov.Glavni konstrukter je kot najbolj�i uporabnik nadaljevaldelo z izbolj�avo metod in uporabo knji�nic in je priizobra�evanju sodeloval le obèasno s seznanjanjemuporabnikov z najnovej�imi metodami. Po tej fazi jepodjetje raz�irilo uporabo paketa na celotenkonstrukcijski oddelek. Hkrati je zaèelo tudi sodelovatis tehnolo�kim oddelkom za èimbolj primerno uporabogeometrijskih podatkov paketa RPK v tehnologiji.Uporaba makro programiranja je zelo moèno orodje, kiomogoèa parameterizacijo objekta in sprotno doloèanjeteh parametrov. Zgradili smo splet makro programov zapopolnjevanje kosovnic na risbi, izdelavo prerezov,spreminjanje geometrijske oblike prikolic, pozicioniranjestandardnih delov v sklop, kot so okna in vrata, kuhinjskiali kopalni�ki blok ipd. Z uporabo makro programov seje produktivnost konstrukterjev izredno zveèala in kar je�e bolj pomembno, pogostost napak se je zmanj�ala.

Podobni makro programi so bili narejeni tudi zaprogramiranje �tevilsko krmiljenih strojev (�KS - CNC).Posebnosti paketa so bile uporabljene za izdelavo �tevilskokrmiljenega programa za rezkanje stene prikolice. Ti

In the initial phase of the implementationa group of designers was formed that were onactive training with the system. At that time thesoftware and hardware were purchased. Adapt-ing to 2D CAD from manual methods was a majorchange in the mechanics of working with draw-ings. As is often reported, the change to a newsystem inevitably produces an initial drop in pro-ductivity, the length of which depends on theamount and level of the training given. Figure 2shows results from a UK survey by Richard Shep-herd, a researcher, presented at MCAD�95 whichshow the impact of training and training meth-ods on design productivity as well as the pro-ductivity growth, depending on the use of CADtechnology. Because of the well-trained andhighly motivated staff the effect of the initial pro-ductivity drop at Adria was very low (the pre-implementation level of productivity was recov-ered within 2 months). Choosing the first CADproject was also a crucial decision. It was a verybrave decision to start on a project with a fixeddeadline. During the work the standard elementswere produced for libraries as well as novel pro-cedures and design methods. In spite of this theproject was successfully finished before the dead-line.

In terms of confidence in the system itwas very important that encouraging results wereachieved quickly. It should also be pointed outthat no blueprints were scanned or included inany other way, everything was designed fromscratch.

When the first project was finished thein-house training for the other designers was in-troduced. During this time the best user-designerwas pushing the development of the methods andlibraries further and occasionally providing rapidand more relevant answers at the training. The newtechnology was expanded to the whole design de-partment. Later, as all designers worked on projectswith the CAD technology the system was extendedto support the manufacturing process with the ge-ometry data. Macro programming is a very power-ful tool where human interaction with decisionsand input parameters is available. We built a set ofmacro programs to fill the parts list on drawings,to mark sections; to extend or shorten the caravanwalls, positioning the assembly of parts such aswindows, doors, cooking or shower blocks; etc.With the introduction of macro programs the pro-ductivity of the users increased significantly, andeven more importantly, common mistakes wereavoided.

Macro programs for design were used andupgraded for NC machine coding. Their ability torecognise geometry was used for a macro programthat writes the NC code for a CNC machine used for

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elementi so precej veliki, vendar geometrijsko nezahtevni(èeprav so postale doloèene krivulje bistveno bolj gladke).Makroprogrami za krmiljenje �tevilsko krmiljenega strojaso pospe�ili delo tudi do desetkrat.

milling the caravan wall. As the elements are quitelarge but geometrically not very complex (althoughsome curves become much smoother) the code wasproduced up to ten-times faster than before.

0

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meseci / months

pro

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vsi u

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nik

i

pro

du

ctivity,

all

use

rs

usposabljanje na f akulteti /

college trained

usposabljanje v podjetju /

company trained

usposabljanje pri

dobav itelju / dealer trained

Uspe�nost metode usposabljanja

Effect of training method

produktivnost "klasièno"

manual productivity

-30

-10

10

30

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190

0 3 6 9 12 15 18 21 24 27 30

meseci / months

pro

du

ktivn

ost

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obèasni uporabniki 2D /

occasional 2D users

redni uporabniki 2D / regular

2D users

redni uporabniki 3D / regular

3D users

redni uporabniki 3D+orodij za

v izualizacijo / regular

3D+v isualisation users

Primerjava rednih in obèasnih uporabnikov 2D ali 3D

Occasional vs. regular 2D or 3D users

produktivnost "klasièno

manual productivity

0

20

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v si usposabljani

uporabniki / all trained

usersv si neusposabljani

uporabniki / all untrained

users

Produktivnost usposabljanih in neusposabljanih

uporabnikov

Productivity of trained & untrained users


manual productivity

-30

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2D risanje / 2D draf ting

3D modeliranje / 3D solid

modeling

3D povr�inski modelirnik / 3D

surf ace modeling

Produktivnost pri uporabi RPK v strojni�tvu

Productivity in general mechanical CAD work


manual productivity

% %

%%

Sl. 2. Odvisnost produktivnosti od usposabljanja uporabnikov in uporabe sistemov za RPK (R. Shepherd)Fig. 2. Productivity related to user training and the CAD systems used (R. Shepherd)

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1.2 Prednosti in pomanjkljivosti sistema

Uvedba sistema za RPK je prinesla �tevilneprednosti, ki se ugodno ka�ejo na stro�kih, rokih inkakovosti. Sistem zadovoljivo pokriva potrebekonstrukcije. Dosegli smo bistveno poveèanje kakovostikonstrukcijske dokumentacije ob zmanj�anju potrebnegaèasa za njeno izdelavo. Poveèala se je produktivnostkonstrukterjev, pa tudi njihova motiviranost. Doseglismo hitrej�e in la�je uvajanje sprememb, ki so posledicanenehnih zahtev naroènikov in samih izbolj�av. Izbolj�alase je funkcionalna analiza v èasu razvoja, zaradi èesar sose zmanj�ala potrebna testiranja prototipov. Vse to jevplivalo na veèje prilagajanje �eljam in potrebam kupcev.Uvedba sistema za RPK je imela velik vpliv na poveèanjestandardiziranosti konstrukcij, kar je vplivalo nazmanj�anje porabe materialov ter na la�jo in cenej�oproizvodnjo. Posebni optimizacijski algoritmi, ki sovgrajeni v makro programe za izdelavo �tevilskokrmiljenih programov, so prispevali k zmanj�anjuizdelovalnih èasov.

Na drugi strani so oèitne tudi pomanjkljivosti.Poglavitni problem pomeni nepovezanost inneodvisnost sistemov za RPK in NPM, èeprav delujetana enaki osnovi. Informacij med razliènimi podatkovnimiskladi�èi ni mogoèe povezovati, niti jih ni mogoèe medskladi�èi prena�ati. Izdelava ustreznih vmesnikov je vveèini primerov neizvedljiva. Zmo�nosti sistema za RPKso bile dose�ene po pribli�no petih letih uporabe, ko sobile izrabljene vse mo�nosti tehnik konstruiranja inprena�anja podatkov v tehnologijo. V tem èasu se jepokazala nujnost po dograditvi ali zamenjavi sistema.Tehnologija sama ni zadovoljivo informacijsko pokrita.Izrisane risbe pomenijo zaèetek tehnolo�kega postopka,pri katerem so tehnolo�ki podatki dodani v tekstovniobliki. Te podatke je skoraj nemogoèe uporabiti v drugihprimerih. Programirani so makro programi za zbiranjeelementov iz enakega materiala, ki pa ne morejo dodajatiimen ali katalo�kih �tevilk. Podsistem za NPM je delposlovnega informacijskega sistema. V njem so podatkio materialih, standardih, zbirnikih èasov, cenah insestavnice vseh prikolic. Med sistemom za RPK insistemom za NPM oz. med geometrijskim modelomprikolice in med sestavnico prikolice ni povezave. Toje najveèja pomanjkljivost sedanjega informacijskegasistema. Vse sestavnice je treba roèno vna�ati, vprimeru sprememb na prikolicah je treba skrbeti zatakoj�nje popravljanje. Zaradi takega naèina dela jedoloèevanje porabljenega dela in izdelovalnih èasov vveliki meri roèno. Napake pri delu so pogoste.Ocenjujemo, da je porabljen èas za izdelavo sestavnictako velik kakor za samo konstruiranje, kar jenesorazmerno veliko. Z zmanj�anjem tega èasa in zodpravo napak, bi podjetje veliko pridobilo.

Druge slu�be, npr.: tr�enje, kakovost, servis,prodaja, nabava, vodstvo itn., so si zgradileinformacijske podsisteme, ki niso povezani niti ssistemom za RPK niti s poslovnim sistemom. Katalogi,

1.2 The benefits and drawbacks of the system

The introduction of the CAD systembrought a number of benefits to the engineeringdesign department that are reflected in cost savings,quality of design and time reduction. The system isable to provede the designers with what they needand significantly increase the productivity of thesedesigners. We achieved a faster and an easierincorporation of changes or re-design resulting fromdifferent customer requirements. The consistency ofthe drawings improves both prototype productionand testing. All of this allows us to adapt to customerwishes and requirements. The CAD-systemimplementation had big influence on thestandardisation of the elements used, reduced materialconsumption, and resulted in an easier and cheapermanufacturing process. The special macro programs,which included an optimisation algorithm for the NCmachines, reduced the coding time.

There are, however, some drawbacks. Themain problem was the unconnected, independentinformation systems of CAD and MRP; even thoughthey were on the same platform. As a consequencethere was a lack of information, feedback, data sharingand manual data transfer. The different systems usea different code record so interfacing is almostimpossible. The possibilities of this CAD system wereexhausted after approximately five years, after thistime nothing can be done to improve the CAD systemany further. The need for a new system was evident.The manufacturing part of the production processhad not had enough IT support. The plotted drawingswere the starting point, where some technologicaldata were added in text form. This data could not beused in other applications. Macro programs werecreated for collecting all the parts made from the samematerial, but they were not able to add part names orcatalogue numbers. The MRP system is where thedata on materials, standards, production-timecalculations, parts prices and production costs, andparts lists of all the caravans are maintained. We hadno direct connection between the CAD system andthe MRP system or between the geometry model andthe parts list of the caravan. The parts list from thedrawing was manually transferred to the MRP system.Avoiding mistakes was almost impossible, especiallywhen some changes were needed. It is a very timeconsuming job and the time to design the caravan isalmost equal to the time to rewrite the data to theMRP system. Simply by eliminating this data-transfertime and avoiding the errors in data entry the companywill benefit enormously.

Other services, such as marketing, qualitycontrol, sales management, administration, etc. builttheir own information systems that were not inte-grated with the CAD system nor with the companyinformation system. Brochures, catalogues, service

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prospekti, servisne knji�ice, razliène sheme,dokumentacija za slu�bo kakovosti, dokumentacijaza dobavitelje in poslovne partnerje ter preostaladokumentacija, nastajajo na neodvisni sistemih.

2 RPK V PRIHODNOSTI

Pomembnost tridimenzionalnega modeli-ranja dandanes v industriji ni veè vpra�ljiva. In�enirjidelajo s 3D modelirniki rutinsko pri razvoju inpreverjanju re�itev. Ob dose�eni stopnji razvoja 3Dsistemov so tudi drugi udele�enci proizvodnegaprocesa spoznali in zaèeli ceniti mo�nosti tetehnologije za povezavo in naèrtovanje.

3D modeliranje je v konstruiranju �edodobra uveljavljeno, novej�e usmeritve panakazujejo vpeljevanje raèunalni�ke podpore vzgodnje faze konstruiranja, predvsem v fazo izdelaveosnutka. To je faza konstrukcijskega procesa, vkateri je sprejetih veèina odloèitev o izdelku, kibistveno vplivajo na njegovo funkcionalnost,lastnosti in stro�ke izdelave. To je tudi faza, ki jeraèunalni�ko najmanj podprta in hkrati faza najveèjihinovativnosti pri razvoju izdelkov. Vse podatke,dobljene pri procesu konstruiranja bi bilo trebaintegrirati z naslednjimi fazami, kakor je nakazano v[1] in [2]. �e veè, uporaba najnovej�ihveèpredstavnostnih interaktivnih tehnologij zapredstavitev in pripravljanje navideznih okolijomogoèa izbolj�anje in pospe�itev procesapreverjanja in testiranja izdelka [3]. Tehnike navideznihprototipov (TNP - VP) med drugim omogoèajopredstavitev kalkulacij, simuliranj obna�anja izdelkovpri uporabi, teste ergonomiènosti, preverjanje intestiranje mo�nosti monta�e in izdelave izdelkov patudi potrditev lastnosti izdelka. TNP je pravzapravuporaba dinamiènega 3D modeliranja za natanènopredstavitev in razvoj potencialnih konstrukcijskihre�itev. Modeli TNP natanèno predstavljajogeometrijsko obliko in kinematiène lastnosti nekegaobjekta v resniènem svetu, pa jih kljub temu ni trebafizièno izdelati. Naslednja zanimiva zamisel je digitalnimodel (DM - DMU) [4], ki temelji na integraciji vsehpodatkov o izdelku v njegovi celotni dobi trajanja, odzasnove skozi prototip, izdelavo, uporabo dorecikliranja v enotnem podatkovnem skladi�èu.

Zmanj�evanje èasa in sredstev za razvojnovega izdelka sta dandanes v industriji nujna pogojaza konkurenènost in zmanj�evanje stro�kov izdelave.Prav s tem namenom se izdelujejo raèunalni�ki modeliv sistemih za RPK za predstavitev razliènih idejnihre�itev. Pred procesom izdelave je treba za vsak izdelekpreveriti, ali izpolnjuje vse podane funkcionalnezahteve in ali ga je mogoèe izdelati. To je lahko zelopreprosto ali pa terja veliko èasa in sredstev, kar jeseveda odvisno od izdelka. Kot alternativa izdelavefiziènega prototipa in testiranja na njem se vse veèuporabljajo raèunalni�ke simulacije, ki ponazarjajo

books, schemes, quality-control documentation,documentation for partners and co-operation com-panies and all other documentation is maintainedmanually or with separate systems.

2 CAD IN THE FUTURE

There is no question that 3D solid modelshave became critical to manufacturing industry.Engineers routinely rely on them to develop, verifyand communicate their designs. And as 3Dtechnology has matured, people outside of theengineering domain have begun to appreciate thevalue of the technology for communication andplanning purposes.

As 3D modelling is well established in thedesign process, the trend is now to introduce computersupport to earlier phases of the design process suchas conceptual design. In these phases, importantdecisions about the product, that have a greatinfluence on functionality, properties and the costs ofa product are taken. All the data relating to a productwhich is collected at these stages of the product lifecycle should be integrated with the downstreamapplication of the product development process as in[1] and [2]. Moreover, using the new multimediainteractive and real-time visualisation techniques,virtual environments are used for improving andspeeding-up the process of verifying and testing theproduct [3]. Virtual Prototyping (VP), among othersincorporates the visualisation of calculations,simulations of product behaviour and ergonomic tests,prediction and checking of production and assemblypossibilities and the validation of product properties.VP is the use of dynamic 3D graphic models toaccurately visualise and evaluate potential designsfor physical devices or manipulators. The VP modelsprecisely represent the geometry and kinematicsassociated with an actual physical (real-world) model,without the need to physically fabricate the item.Another interesting concept is a digital mock-up(DMU) [4], integrating all the data about a productcollected during the product life cycle, beginning fromthe early design phases, through prototyping, on toproduction, maintenance, and even recycling.

Because of competitionand cost reduction,the time and resources needed for developing a newproduct are nowadays very important in industry.For this reason, computer models of an engineer�sideas about design objects are created and outlinedin CAD systems. Before the manufacturing processa design object should be verified in two ways: first,that all construction constrains are obeyed, and se-cond, that the object is manufacturable. Whether thisis an easy or time consuming and expensive processdepends on the object. As an alternative to physicalprototyping and testing, computer techniques areincreasingly used to present and test the functionality

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funkcionalnost izdelka. Stro�ki izdelave navideznegaprototipa so v veliki veèini primerov bistveno manj�iod testiranja fiziènih prototipov.

Navidezno okolje (NO - VE) je v bistvuprojekcija resniènega sveta. NO ne obstaja, vendardeluje dovolj resnièno za in�enirsko prakso, ki jeveèinoma manj zahtevna, kakor so aplikacije v svetuzabave, kjer se ta tehnologija uporablja �e dalj èasa.Najveèja posebnost navidezna resniènost (NR - VR)je obèutek èloveka, da deluje v navideznem svetu, kije videti dovolj realistièno. NR je kompozicija 3Draèunalni�ke grafike, orodij za simuliranje intehnologije veèpredstavnosti, ki omogoèajointeraktivno v realnem èasu vodenje in delovanjeznotraj raèunalni�ko nastalega okolja.

Obogatena resniènost (OR - AR) je me�anaoblika, pri kateri so v realno okolje dodani raèunalni�kogenerirani objekti. Sliki realnega sveta so dodani znaki,navodila ali raèunalni�ko generirane slike. UporabeOR morajo imeti enake lastnosti kakor NR, prostorskoin dinamièno predstavljanje objektov in interaktivnostv realnem èasu, dodana pa je mo�nost kombiniranjarealnega in navideznega sveta [3]. Èe NR omogoèazmanj�evanje sredstev pri razvoju izdelkov inomogoèa zgodnje odkrivanje napak, omogoèa ORkombiniranje realnih in raèunalni�ko generiranihobjektov, kar je sploh velika prednost, kadar nekateriobjekti �e obstajajo.

Nobena druga tehnologija dandanes neomogoèa uporabniku bolj stvarnega pogleda intestiranja novih izdelkov pred njihovo izdelavo. Gledena sposobnosti aparaturne opreme pa je treba poiskatikompromis med kakovostjo raèunalni�kogeneriranega sveta in mo�nostjo interaktivnosti [5].

V procesu razvoja izdelkov je veèinaodloèitev o obliki, funkcionalnosti, izdelavi, monta�i,vzdr�evanju in naèinu uporabe izdeleka sprejeta vzgodnji fazi razvoja izdelka [3]. Te odloèitve sosprejete na temelju poznavanja teorije, modelov zaRPK in izku�enj, dobljenih z delom. Mnogo te�av, kise pojavijo pri izdelavi ali vzdr�evanju, je odkritih zelopozno ali celo potem, ko je izdelek �e prodan.Odpravljanje takih te�av pomeni ponavljanje inpopravljanje postopka razvoja izdelka, kar je zelodrago in dolgotrajno. Tehnike NR omogoèajo izvedbotestov funkcionalnosti in preverjanje vnaprej, èesarni mogoèe izvesti samo s sistemi za RPK.Veèpredstavnostni sistemi omogoèajo interaktivnostmed èlovekom in objekti, pa tudi med ljudmi,vpletenimi v postopek razvoja.

3 SKLEPI

Kot posledica zgodovinskega razvoja invkljuèevanja raèunalnikov v proizvodni proces so vpodjetjih nastali loèeni poslovni in tehnièni informacijskisistemi kot samostojne in nepovezane baze podatkov,kar dandanes predstavlja glavni problem pri povezovanju.

of an object. The costs involved in VP are often verymuch less than doing a similar test on real prototypes.

The Virtual Environment (VE) is actually aprojection of the real environment on a different scale.The VE does not exist, but it is fairly realistic, realenough for engineering purposes, which do not havethe demands of the entertainment world. The keyfeature of Virtual Reality (VR) is immersion (a realisticor believable outlook) and interaction. VR is a com-position of 3D graphics, simulation tools and multi-media technologies that allows the user to controland operate within a computer-generated environ-ment on an interactive basis and in real time.

Augmented Reality (AR) is a mixed form wherecomputer-generated images are superimpased on a realenvironment. The image of the real world is augmentedby signs, instructions or computer-generated images.The application in AR must have the same characteris-tic as VR: spatial and dynamic registration in 3D andreal-time interaction, but it must also have a combina-tion of real and virtual objects [3]. While VR reducescosts and conserves resources by detecting designerrors early with a fast evaluation of the design, ARoffers the possibility to mix physical and virtual objects,which is very helpful because only some objects haveto be reconstructed while others exist already.

At the moment no other technology can al-low the user to see and explore new products or con-cepts before they exist in reality in a more realisticmanner. Today�s hardware performance means a com-promise between the realism, the image quality andrate for interactivity [5].

In industrial product development, majordecisions about the design, functionality, mechani-cal construction, production and assembly planning,maintenance and user interface are taken at earlystages of the design or development [3]. These deci-sions are made on a theoretical basis, CAD systemsand experiences from earlier work. Many problemsthat emerge in production and maintenance are dis-covered at late stages of the production, practicaltests or even after the final product is sold. To fixsuch problems, feedback loops are required to a de-sign stage for modifications, which is a very timeconsuming and expensive procedure. The VR tech-niques offers the possibility of performing the func-tionality tests and verifications in advance, a proce-dure which cannot be done just from the CAD data.The multimedia techniques support the man-machineinteraction as well as dialogue among the users.

3 CONCLUSIONS AND REMARKS

Typically, the MRPs which are suppliedfrom the company information database and thetechnical information systems have their owndatabases. This represents the fundamentalproblem in industry, and is the result of historical

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Pogosto je pojavljanje veèkrat zapisanih podatkov zaisti objekt in neusklajenih podatkov. To je poglavitnirazlog, zakaj morajo podjetja izbolj�ati svoje podatkovnesisteme. Zagotovljeno mora biti naèelo, da je vsakainformacija zapisana le enkrat in da je na voljo vedno invsem, ki jo potrebujejo. Vse funkcije podjetja ali vseslu�be morajo biti ustrezno informacijsko podprte. Vsakainformacija mora biti zapisana v tak�ni obliki, da niuporabna le za avtorja, ampak za naj�ir�i kroguporabnikov. Naèelo avtomatiziranih otokov znotrajproizvodnega procesa, ki ga je vna�al osnutek RPP(CIM), se je izkazal za napaènega. Posamezniavtomatizirani otoki so se razvijali neodvisno in postalivedno bolj specializirani. Razvoj je �el tako daleè, da soposamezni otoki uporabljali razliène sisteme na razliènihnaèelih, tako da je izdelava vmesnikov skoraj nemogoèa.

Poglavitna napaka je bila v na�em primeruustavitev razvoja sistema, kar pa se je zgodilo iz veèvzrokov: dobavitelj je ustavil razvoj sistema za RPK in sepreusmeril na novo podroèje, zaradi nedefiniranostilastnika v prehodnem postopku in ustavitve investicij vpodjetju. Poglavitna investicija v RPK ni le zaèetnanabava opreme in �olanje ter seveda samo uvajanje,temveè tudi vzdr�evanje sistema, posodabljanje strojnein programske opreme, stro�ki obratovanja, dodatno�olanje kadra na posodobljeni opremi in uvajanje novosti.Zelo pogosto je spregledano dejstvo, da so stro�kivzdr�evanja veèji od stro�kov nabave in uvajanja.

Pri omenjanju usposabljanja lahko omenimo tudistrah in nenaklonjenost vodstva kakovostnem treninguzaradi mi�ljenja, da bo dober kader po usposabljanju zapustilpodjetje. Tak�no razmi�ljanje je samounièujoèe, sajnezadovoljen kader zapusti podjetje v vsakem primeru.Bistveno bolje in ceneje je primerno nagrajevanje dobregain izku�enega kadra preden se odloèi zapustiti podjetje in sseboj odnese dragoceno znanje in izku�nje. Podobnanapaka je aktiviranje pogodbenega kadra (ali drugegapodjetja), ki je veèinoma �e manj dovzeten za trening in jehkrati nemogoèe prièakovati velik prispevek zaradinepoznavanja specifiènosti podjetja in njegovihproizvodnih znaèilnosti.

Zelo znan problem je tudi sprotno �olanje insledenje vsem novostim v sistemih IT, ki jih je trebavnesti v znane tehnike in metode konstruiranja, sevedapri vsakodnevnem delu. Tudi proizvajalci programskihpaketov se tega zavedajo, saj lahko v zadnjem èasuopazimo bolj pogosto dopolnjevanje sistemov z manjspremembami, kar omogoèa la�je vkljuèevanje novosti.

Kljub razmeroma preprosti geometrijski obliki vAdrii, je uporaba 3D modelirnika nujna, zaradi uporabemodelov pri sestavljanju sklopov, upravljanje prodaje,predstavitvi modelov, administraciji, predstavitvenihizdelkih, katalogih, servisnih knji�ic, dokumentaciji zazagotavljanje kakovosti, dokumentaciji za poslovnepartnerje in kooperante. Preskok iz 2D risanja v 3Dmodeliranje pomeni enako stopnjo spremembe v mi�ljenjuin obvladovanju modelov ter organizacijski shemi dela,kakor prehod in uporaba iz roènega dela na 2D risanje.

development. The appearance of duplicated dataand unadjusted records for different applicationsis frequent. The principle of once-only registereddata should be achieved and that data should beaccessed from anywhere, and at anytime that it isneeded. The entire company should use a commondatabase and the data should be useful for a broadset of users. The principle of automated islandsfrom the time of the CIM philosophy weredefinitely wrong. That automated islandsdeveloped independently from each other andbecame more and more specialised. Thedevelopment went so far that the differentsystems used different code records so interfacingbecame almost impossible.

The problem in our case was the stoppeddevelopment for various reasons: the supplierstopped the development of the drafting system dueto, undefined ownership in the transformationprocess and investment drawback. The investmentis not the only initial system implementation. Thereis also hardware, software tools and training; andafterwards, the system support, maintenance costs,development of design methods and updating staffwith new versions and introducing them: all are morecostly. Quite frequently the fact that the later costsare larger that initial ones is overlooked.

When training is planned, companies aresometimes reluctant to train staff to the highest level,feeling that they are then more likely to lose them.This is self-defeating, as unsatisfied staff will leaveanyway. Far better to reward well-qualified and expe-rienced staff before they decide to take that vital ex-perience of your products and methods elsewhere.A compounding error is to take on increasing num-bers of contract staff who you are even more reluc-tant to train, and who are unlikely to be able to con-tribute fully to concurrent engineering andmanufacturability exercises.

A common problem is following thedevelopment of systems, where new possibilitiesshould be introduced in existing design methodssimultaneously with every day work. The softwaresuppliers are aware of this, and so it is noticeablethat new versions are more frequent with lesschanges, which makes it easier to follow thechanges.

In spite of relatively simple geometry, the3D modeller is necessary at Adria due to the use ofmodels for assembly design, marketing efforts, salesmanagement, administration, brochures, catalogues,service books, schemes, quality-controldocumentation, documentation for partners and co-operation companies. The move from 2D drafting to3D solid modelling involves an equivalent level ofchange in the way of thinking about designs and inthe management of the design model as an adaptationof 2D drafting from manual methods.

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Ob uvajanju novih tehnologij, ki tako zelovplivajo na celotno organizacijsko shemo podjetja,ni nujno treba poznati le specifiènosti lastneproizvodnje, ampak razumeti tudi posledice, ki jihuvajanje spro�i, ne samo v konstrukcijskem oddelku,temveè v celotni sestavi podjetja. Enanajpomembnej�ih stvari je zagotovo prenos podatkovmed posameznimi oddelki podjetja, kakor tudi zzunanjimi partnerji. Veèina izdelovalcev programskeopreme omogoèi prenos podatkov z vmesniki instandardnimi zapisi vhoda in izhoda, ki pa jih jeveèinoma treba prilagoditi, da omogoèajo uspe�nodelo med veè sistemi. Prav tako je pomembna mo�nostuporabe sedanjih objektov in datotek v novemsistemu. Snemanje in digitalizacija risb sta zelozamudna in nenatanèna prenosa, zato nista za�elena.Prenos prek (vpra�ljivo) standardnih vmesnikov (npr.IGES) je uporaben le za prena�anje osnovnih oblik inkot pomoè pri ustvarjanju modelov na novo.

Razvoj svetovnega spleta (WWW) jepomemben korak pri razvoju raèunalni�kih tehnologijin komunikacije, ki moèno vpliva na razvoj aplikacij.Vedno veè sistemov vsebuje orodja za komuniciranjeprek spleta. V bli�nji prihodnosti bo vsaka pomembnaraèunalni�ka aplikacija zmo�na komunicirati prekspleta kot informacijskega kanala.

Sestava projektne ekipe je zelo pomembno inte�avno dejanje, saj morajo èlani obvladati ve�èinevodenja projektov, tehniène posebnosti, ekonomskeuèinke in organizacijske zmo�nosti. Zelo pomembna jenenehna podpora in spremljanje projekta od vodstvapodjetja med celotnim trajanjem projekta. V na�emprimeru je uvajanje 2D RPK v konstrukcijski oddelekspodbujal predvsem konstrukcijski oddelek, zaradibolj�ega in bolj uspe�nega dela, dopolnjevanje pa jeprevzelo vodstvo podjetja, ki je spoznalo vse prednostipodatkov konstrukcijskega oddelka in vpliv termo�nosti uporabe teh v vseh dejavnostih podjetja.

Nove tehnologije NR so veè ali manj �evedno v fazi raziskav in presegajo sprejemljive mejeinvesticij, predvsem v majhnih in srednjih podjetjih.Vsekakor pa je treba biti pozoren na kasnej�e mo�nosti�iritve sistema za RPK in njihovo vkljuèevanje venovito podatkovno skladi�èe. Za izmenjavopodatkov morajo biti zagotovljeni raz�irjeni in dobripodatkovni vmesniki, kakr�en je na primer STEP. Nasliki 3 je predstavljen 3D model prikolice in avtodomakot startna toèka za uporabo tehnik NP in NR.

Uspe�nost podjetja je utemeljena na lastnihkonstrukcijskih izku�jah, tako dobrih kakor slabih.Osnutek hkratnega in�enirskega dela naèrtuje soèasnekonstrukterske dejavnosti in preverjanje posledic tehodloèitev na lastnosti in funkcionalnost izdelka, patudi mo�nosti izdelave in kalkulacije stro�kov.

Glede na hitrost razvoja IT je pogosto opazitineodloènost o primernem èasu vpeljave novih tehnologij.Reèi je mogoèe le: �Idealnega èasa za zaèetek ni, edinizanesljiv dejavnik je potreba po spremembi.�

It is not enough to understand theproduction process in the company, theunderstanding of the process from the new-technology point of view should be attained togetherwith all possible consequences for the organisationof production and interfaces to other processes. Dataexchange with external partners should be considered,with the responsibilities for converting and adaptingdata input and output. Most vendors publishspecified input and output formats, but these mayneed adaptation for successful working between dif-ferent systems. It is also important to re-use theexisting CAD system as much as possible, to convertexisting system files into a new system. The scanningand digitising of drawings from paper are very timeconsuming and inaccurate processes, and should beavoided. Converting existing files through(questionable) standard interfaces (e.g. IGES) isuseful only for the basic transfer of geometry data orfor assistance in the creation of new models.

The WWW is the step in the evolution ofcomputing that communication and immediately makesa big impact. Everyday more software products con-tain tools to interact with the WWW. In the very nearfuture every major application will be able to operatewith the WWW as a communication channel.

To establish the project team is a crucialand difficult task due to the need for project, techni-cal, commercial and organisational skills. The fullengagement of senior management is important andnecessary. The first implementation benefitted thedesign department, the next one was put forward bythe company management who recognised the ben-efits of data quality from the design department andthe influence and possibilities of using design data.

New VR techniques are still in the researchstage and therefore too expensive for small and me-dium-sized companies. What should be taken into con-sideration is the possibility of extending chosen CADsystem with new techniques at a later stage and incor-poration into the overall product-data management.For effective and easy data exchange, data formatsmust be widespread or at least good and reliable inter-faces like STEP should be available. In figure 3, 3DCAD models of a caravan and a motorhome are pre-sented as the starting points for VP and VR techniques.

Concurrent engineering is defined as the con-cept of running design activities and reflecting the ef-fect of design influences simultaneously. A company�ssuccess is built on its own design experience, successesand failures. Clearly, concurrent engineering requiresinteraction between the early and later stages of design,as well as manufacture feasibility and cost analyses.

It is always a question when to start with theintroduction and implementation of new IT, especiallybecause it is developing so rapidly. But the only thingto be said is: �There is no ideal start time, the onlycertain factor is the necessity for change.�

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Sl. 3. 3D RPK model prikolice in avtodomaFig. 3. 3D CAD models of caravan and motorhome

4 OKRAJ�AVE4 ABBREVIATIONS

IT - IT Information TechnologiesRPK - CAD Computer Aided DesignRPP - CIM Computer Integrated ManufacturingNR - VR Virtual RealityNP - VP Virtual PrototypeOR - AR Augmented RealityDM - DMU Digital Mock-upWWW World Wide Web

informacijske tehnologijeraèunalni�ko podprto konstruiranjeraèunalni�ko povezana proizvodnjanavidezna resniènostnavidezni prototipobogatena resniènostdigitalni modelsvetovni splet


[1] Hsu, W., I.M.Y. Woon (1998) Current research in the conceptual design of mechanical products. Computer-Aided Design, Vol. 30, No. 5, 377-389, Elsevier Science Ltd.

[2] Brunetti, G., B.Golob (accepted in January 2000) A Feature-based approach towards an integrated productmodel including conceptual design information; to be published in: Computer-Aided Design, ElsevierScience Ltd, Special Issue: Conceptual Design: Issues and Challenges.

[3] Matthias, B. (1997) Immersive user interaction within industrial virtual environments, Virtual Reality forIndustrial Applications (ed. Fan Dai), Springer-Verlag.

[4] Gomes de Sa, A. (2000) Digital mock-up und virtual prototyping in der Automobilindustrie-Einsatz, Erfahrungund Potential. Forum 2000, Velenje, Slovenia.

[5] Mahoney, D.P. (1999) Better than real. Computer Graphics World, www.cgw.com.[6] Jezernik, A., Golob, B., G.Hren (2000) Conventional CAD/CAM and virtual engineering for design and

manufacturing. DESIGN 2000-International Design Conference, Dubrovnik.

Naslova avtorjev: mag. Gorazd Hrenprof.dr. Anton JezernikFakulteta za strojni�tvoUniverze v MariboruSmetanova 172000 Maribor

mag. Stanislav Luk�ièADRIA Mobil d.o.o.Skalickega 17000 Novo mesto

Authors Address: Mag. Gorazd HrenProf.Dr. Anton JezernikFaculty of Mechanical Eng.University of MariborSmetanova 172000 Maribor, Slovenia

Mag. Stanislav Luk�ièADRIA Mobil Ltd.Skalickega 17000 Novo mesto, Slovenia

Prejeto: 16.6.2000


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M. Pti~ar - S. Dolin{ek - F. Kosel: Prednosti in omejitve - The Advantages and Problems

Novi materiali omogoèajo v strojni�tvu doseganje ciljev, ki do odkritja teh materialov niso biliuresnièljivi. Razvoj materialov se usmerja predvsem k izbolj�evanju najpogosteje zahtevanih lastnosti, nekaterimateriali pa izkazujejo doloèene posebnosti, zaradi katerih je podroèje njihove uporabe �e posebej �iroko.Med slednje spadajo tudi materiali z oblikovnim spominom, ki so pod vplivom temperaturnih spremembzmo�ni spreminjati obliko in pri tem tudi opravljati delo. V prispevku so opisane posebnosti teh materialovter njihove prednosti in pomanjkljivosti pri uporabi za praktiène primere.© 2000 Strojni�ki vestnik. Vse pravice pridr�ane.(Kljuène besede: materiali pomnilni, spomin oblikovni, superelastiènost, varovala termièna)

New materials lead to advances in mechanical engineering, advances which could not be realizedbefore these materials were discovered. In most cases, materials are developed to improve their most fre-quently used properties, but some of these materials also exhibit specific properties which make them usefulin a wide variety of applications. An example are the shape-memory materials, which, under the influence oftemperature changes, are capable of changing their shape and producing work. In this paper the specificproperties of shape-memory materials and the advantages and disadvantages of using these materials inpractical applications are discussed.© 2000 Journal of Mechanical Engineering. All rights reserved.(Keywords: shape-memory materials, superelasticity, safety valves, thermal valves)

The Advantages and Problems of Using Shape-MemoryMaterials in Practical Applications

Matja` Pti~ar - Slavko Dolin{ek - Franc Kosel

© Strojni{ki vestnik 46(2000)11/12,780-788ISSN 0039-2480UDK 539.371:620.16:681.587Pregledni znanstveni ~lanek (1.02)


UDC 539.371:620.16:681.587Review scientific paper (1.02)

Prednosti in omejitve pri uporabi materialovz oblikovnim spominom za prakti~ne uporabe

0 UVOD

Materiali z oblikovnim spominom so prisegrevanju oziroma ohlajanju prek doloèenegatemperaturnega obmoèja zmo�ni spreminjati obliko izdeformirane v prvotno in nasprotno. Èeprav so jih odkrili�e pred veè desetletji in bi lahko njihove lastnostiuporabljali v mnogih, zelo razliènih primerih, so ti materialioziroma njihove lastnosti mnogim �e vedno neznani. Vraziskovalne namene je bilo preuèenih �e mnogomo�nosti uporabe, vendar pa je le redko uporaba tehmaterialov res nujno potrebna. V veèini primerov je zaradinjihove visoke cene, ki se zaradi poveèevanja uporabeteh materialov sicer zni�uje, vsaj za zdaj �e vedno cenejeuporabiti obièajne materiale, �eleno gibanje, ki bi gadrugaèe opravljali elementi z oblikovnim spominom, paomogoèiti z uporabo elektromotorjev, pnevmatskih in

0 FORWORD

If heated or cooled through a certaintemperature range, shape-memory materials canchange their shape from deformed to original or viceversa. Even though they were discovered decadesago and their properties have been used in variousapplications, these materials are still unknown tomany people. Scientists have already found manyways to use shape-memory materials, but in only afew cases is the use of these materials reallynecessary. Shape-memory materials are expensive,however, their increasing use is leading to a reductionin these costs. In most cases it is still less expensiveto use standard materials, with the movement - whichwould otherwise come from the shape-memoryelements - provided by electromotors, hydraulic or

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hidravliènih ventilov ali kako drugaèe. Pri tem pomeninajveèjo te�avo dejstvo, da so cenovno najbolj neugodneprav TiNi zlitine, ki imajo najbolj�e mehanske in oblikovnospominske lastnosti in se zato uporabljajo v skoraj 90%uporab. Raziskovalci so sicer odkrili �e mnogo cenej�ihmaterialov z oblikovnim spominom, vendar pa so le redkiod teh primerni za uporabo v praksi. Razlogi za to sopremalo izrazita lastnost oblikovnega spomina, izgubljanjete lastnosti med uporabo ter zahtevna izdelava intermomehanska obdelava. Poleg TiNi in Cu zlitin, ki so �eprecej raziskane in se tudi najveè uporabljajo, raziskujejouèinek oblikovnega spomina predvsem �e v Fe zlitinah,ki obetajo ni�jo ceno. Cenovno gledano je torej uporabamaterialov z oblikovnim spominom ustrezna le v primeru,èe so elementi iz teh materialov dovolj majhni.

Naslednja te�ava je izdelava tak�negaelementa. Materiali z oblikovnim spominom so sicer navoljo v razliènih oblikah, v razliènih termomehanskihstanjih in z razliènimi temperaturami, pri katerih pridedo spremembe oblike, vendar ima naèrtovani elementv mnogih primerih povsem specifièno obliko in tudi�elene termomehanske lastnosti so pogosto drugaèneod lastnosti materialov, ki so na voljo. V tem primerulahko element �elene oblike in z ustreznimitermomehanskimi lastnostmi izdela kar proizvajalecmaterialov z oblikovnim spominom, vendar pa ima toza posledico �e veèje stro�ke in dalj�o èakalno dobo.

1 TEMELJI OBLIKOVNEGA SPOMINA

Osnovo oblikovnega spomina pomeninasprotna martenzitna transformacija, ki se pojavi prisegrevanju dovolj malo plastièno deformiranenizkotemperaturne faze. O martenzitni transformacijiobièajno govorimo pri kaljenju jekel, vendar pa jo lahkonajdemo tudi v materialih z oblikovnim spominom. Zmartenzitno transformacijo namreè v splo�nemoznaèujemo brezdifuzijski naèin nastajanja nove faze,pri katerem pride do stri�nega premika atomov, med katerimse atomi v posameznih kristalnih ravninah premikajoodvisno eden od drugega, ter prestanejo stri�ni premikkot celota. Slednje je tudi razlog, da martenzit ohranisestavo in razporeditev atomov avstenita, kar je eden odpogojev za pojav oblikovnega spomina. [1] Deformiranain prvotna oblika izdelka namreè ustrezata martenzituoziroma avstenitu, povezava med obema oblikama pa jena neki naèin zapisana v materialu, zato pri preoblikovanjuiz ene strukture v drugo ne sme priti do nikakr�nihnepovratnih sprememb. To je tudi razlog, da se morapopaèenje kristalnih re�etk, do katerega pride medmartenzitno transformacijo, nadomestiti z dvojèenjem inne z zdrsi. Pri zdrsih namreè pride do trganja medatomskihvezi, zato je tak�na transformacija nepovratna. Vdvojèenem martenzitu so atomske vezi nepretrgane inostanejo tak�ne tudi pri dovolj majhnih deformacijah, zatose pri segrevanju tako nedeformirana kakor tudideformirana dvojèena martenzitna struktura preoblikujetav enako avstenitno strukturo, kakor prikazuje slika 1.

pneumatic valves. It is unfortunate that TiNi alloys,which have the best mechanical and shape-memorypropeties and are therefore used in almost 90% ofthe applications, are also the most expensive. Manycheaper shape-memory materials have beendiscovered, but only a few of them are suitable forpractical applications. The reasons for this are atoo weak shape-memory effect, a fading of theeffect during use and complicated manufacturingor thermomechanical treatments. Besides TiNi andCu alloys, which have been throughly investigatedand are also the most frequently used materials,the shape-memory effect in Fe alloys is beinglooked into because of the potentially low price ofthese alloys. The use of shape-memory materialstends to be economic only if the elements madefrom this material are small.

The manufacturing of such elementsrepresents another problem. Even though shape-memory materials are available in different shapes,with different thermomechanical treatments and withdifferent characteristic temperatures, the desiredshape and thermomechanical properties often differfrom the properties of available materials. In such acase the shape-memory element can be produced bya specialized manufacturer, but this means highercosts and longer delivery times.

1 THE BASICS OF SHAPE MEMORY

A reverse martensitic transformation whichoccurs during the heating of a moderately plasticallydeformed low-temperature phase represents the ba-sics of the shape-memory effect. Martensitic transfor-mations are usually mentioned in connection with steelquenching, but can also be found in shape-memorymaterials. A martensitic transformation generally meansthe diffusionless formation of a new phase, with theatoms in particular crystallographic planes moving asa unit rather than individually. In this way martensiteretains the chemical composition and atomic arrange-ment of the austenite, which is necessary for the shape-memory effect to occur [1]. The deformed and initialshape of the product correspond to martensite or aus-tenite, while the connection between these two shapesis somehow written in the material. As a result, noirreversible changes should occur during the transfor-mation from one structure to the other. This is also thereason why lattice distortion, which occurs during themartensitic transformation, should be compensatedby twinning and not by slip. During slip the atomicbonds are broken, which makes such a transforma-tion irreversible. Twinning does not break the atomicbonds, which can remain unbroken even for smalldeformations. Therefore, the undeformed and the de-formed martensite structures are transformed into thesame austenite structure during heating, as shown inFigure 1.

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The shape-memory material which wasdeformed in the martensitic state returns to its origi-nal shape when heated to the austenite temperaturerange. This process is called the one-way shape-memory effect because it cannot be repeated withouta new deformation. Microstresses which cause theappearance of two-way shape memory can be inducedin the material with a special thermomechanicaltreatment. The shape of such material changes duringevery cooling or heating through the transformatontemperature. One- and two-way shape memory areshown in Figure 2.

deformacija

deformation

deformacija

deformation

avstenit austenite

segrevanje heating

ohlajanje

cooling

dvojèni martenzit twinning martensite

deformirani martenzit deformed martensite

razdvojèeni martenzit detwinned martensite

Sl. 1. Sprememba martenzita v avstenit in nasprotnoFig. 1. Transformation from martensite to austenite and in the opposite way

Oblika v martenzitnem stanju deformiranegaizdelka se torej pri segrevanju do avstenitnegapodroèja spremeni nazaj v tisto obliko, ki jo je imelizdelek pred deformacijo. Tega procesa ne moremoponoviti brez ponovne deformacije, zato imenujemota pojav enosmerni oblikovni spomin. S posebnimitermomehanskimi postopki pa je mogoèe v materialupovzroèiti mikronapetosti, ki omogoèajo dvosmernioblikovni spomin. Tako obdelanemu materialu seoblika spremeni pri vsakem ohlajanju ali segrevanjuprek temperature preoblikovanja. Eno- in dvosmernioblikovni spomin sta prikazana na sliki 2.

Sl. 2. Eno- in dvosmerni oblikovni spomin [2]Fig. 2. One- and two-way shape memory [2]

a) enosmerni oblikovni spomin: one-way shape memory:

b) dvosmerni oblikovni spomin: two-way shape memory:

segrevanje

heating

segrevanje

heating

segrevanje

heating

ohlajanje

cooling

ohlajanje

cooling

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Loading the material in the austenitetemperature range can result in the appearance ofthe so-called stress-induced martensite, becausethe stresses increase the stability of the martensiteat high temperatures and therefore broaden thetemperature range where martensite can be found.Martensite can appear at higher temperatures iflarger stresses are applied, but the temperaturerange of stress-induced martensite has an upperlimit, because stresses which are too big wouldcause the material to slip. The most usefulcharacteristic of the stress-induced martensite isthat during the transformation from austenite tostress-induced martensite the stress causes anequal orientation of all the crystal lattices whichresults in the maximum reversible strain. Even slightunloading can cause martensite destabilisation andthe appearance of austenite. This property is calledsuperelasticity and is used very often. Figure 3shows a stress-strain curve of a shape-memorymaterial in the temperature range of superelasticity[2].

Shape-memory materials therefore havethree specific properties by which they differ fromother materials. Which of these properties we decideto use, depends on the purpose of the product.

2 SOME EXAMPLES OF THE USE OF SHAPE-MEMORY MATERIALS

Shape-memory materials can be used inmany different ways, these uses can be roughly di-vided into four main categories:

Free recovery: The only function of prod-ucts in this category is to move with minimum forceduring the shape change. Examples of such productsare toys, whose purpose is entertainment and thepresentation of the shape-memory effect.

Constrained recovery: If, during the trans-formation of the material, the change of product�s

Nastanek martenzita lahko z zunanjiminapetostmi povzroèimo tudi v tistem temperaturnemobmoèju, v katerem je obièajno �e avstenit, takonastalemu martenzitu pa pravimo napetostnoinducirani martenzit. Zunanje napetosti namreè �irijostabilnost martenzita pri vi�jih temperaturah in torej�irijo temperaturno obmoèje, v katerem je martenzit. Privi�jih temperaturah je za nastanek martenzita potrebnaveèja napetost, vendar je temperaturno obmoèje, vkaterem lahko dobimo napetostno inducirani martenzit,navzgor omejeno, saj bi prevelike napetosti povzroèilev materialu pojavljanje zdrsov. Glavna prednostnapetostno induciranega martenzita je ta, da zunanjenapetosti povzroèijo enako usmerjenost kristalnihre�etk, zato pride pri premeni avstenita v napetostnoinducirani martenzit do velikih povraèljivih raztezkov.�e rahla razbremenitev povzroèi destabilizacijomartenzita oziroma nastanek avstenita. Ta lastnost jezelo uporabna, imenujemo pa jo superelastiènost. Nasliki 3 je prikazana napetostna krivulja materiala zoblikovnim spominom v temperaturnem obmoèjusuperelastiènosti [2].

Sl. 3. Superelastièna zanka [2]Fig. 3. Superelastic loop [2]

125

100 75 50 25

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nape

tost

st

ress

avstenit ® napetostno inducirani martenzit austenite ® stress induced martensite napetostno inducirani martenzit ® avstenit stress induced martensite ® austenite

0 2 4 6 8 10 raztezek

strain

MPa

%

Materiali z oblikovnim spominom imajo torejkar tri posebne lastnosti, po katerih se razlikujejo oddrugih materialov. Katero od teh lastnosti se odloèimoizkoristiti, pa je odvisno od namena izdelka.

2 PRIMERI PRAKTIÈNE UPORABEMATERIALOV Z OBLIKOVNIM SPOMINOM

Materiale z oblikovnim spominom lahkouporabljamo na mnogo razliènih naèinov, ki jih lahkov grobem razdelimo v �tiri glavne kategorije.

Prosta povraèljivost: Edina naloga izdelkov,ki spadajo v to kategorijo, je sprememba oblike oziromaopravljanje doloèenega giba ob minimalni sili. Semspadajo na primer igraèe, katerih namen je predvsemrazvedrilo in prikaz uèinka oblikovnega spomina.

Ovirana povraèljivost: Èe je medpreoblikovanjem materiala sprememba oblike izdelka

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shape is constrained, force is generated between thisproduct and the obstacle. The movement and workare therefore minimal. This generated force is oftenused to assemble elements.

Actuators: During the movement caused bythe change of shape, actuators act with force onnearby elements and produce work. Because theshape of the products with shape memory does notchange at a certain temperature but over a tempera-ture range, actuators can also be used to positiondifferent mechanisms in a range, the limits of whichare defined by the initial and deformed shape of theshape-memory element. In this case, the temperaturemust be very precisely controlled.

Superelastic applications: Superelasticityis often used in situations where large strains areneeded with small forces. It is also useful in thoseproducts which are frequently bent or otherwise de-formed during their use but must keep the same shapeafter the use [2].

The research work on the use of shape-memory materials has focused on replacingelectromotors or similar devices with shape-memoryelements. An example is the use of thin shape-memory wires and springs to control a small robot,as shown in figure 4. These elements can be rapidlyheated with low electric currents, while their lightweight allows quick cooling in air. The robot is ableto move quickly and its weight is much less than foron electromotor-based robot. Also, the manufac-turing of shape-memory wire and springs is wide-spread enough to make the use of these elementseconomic.

onemogoèena, nastaja med njim in oviro sila. Premikin zato tudi delo sta minimalna. Nastala sila se pogostouporablja za spajanje elementov.

Aktuatorji: Aktuatorji med gibanjem, dokaterega pride med spremembo oblike, s silo delujejona okoli�ne elemente in opravljajo delo. Ker se oblikaizdelkov z oblikovnim spominom ne spremeni pridoloèeni temperaturi, temveè v nekem temperaturnemobmoèju, lahko aktuatorje ob natanènem uravnavanjutemperature uporabimo tudi za pozicioniranje razliènihmehanizmov v nekem obmoèju, katerega meji stadefinirani s prvotno in deformirano obliko elementa zoblikovnim spominom.

Superelastiène uporabe: Superelastiènostnajveèkrat uporabljamo v tistih primerih, v katerih jepri majhnih spremembah sile potreben velik raztezek.Uporabna pa je tudi pri izdelkih, ki se med uporaboveèkrat zvijajo ali kako drugaèe deformirajo, po uporabipa mora njihova oblika ostati nespremenjena. [2]

Raziskave mo�nosti uporabe materialov zoblikovnim spominom so potekale predvsem v smerinadome�èanja elektromotorjev in podobnih naprav zelementi z oblikovnim spominom. Tak primer jeuporaba tankih �ic in vzmeti z oblikovnim spominomza krmiljenje manj�ega robota, kakor prikazuje slika 4.Te elemente je mogoèe hitro segreti z uporabo majhnihelektriènih tokov, zaradi majhne mase pa je tudiohlajanje na zraku dovolj hitro. S tem je omogoèenohitro delovanje robota, poleg tega pa je njegova te�abistveno manj�a kakor pri uporabi elektromotorjev.Izdelava �ic in vzmeti iz materialov z oblikovnimspominom je �e dovolj raz�irjena, da je uporabatak�nih elementov tudi cenovno upravièljiva.

vzmeti �ice

Sl. 4. Robot z �icami in vzmetmi z oblikovnim spominom [1]Fig. 4. Robot with shape-memory wires and springs [1]

As mentioned earlier, the costs are, in mostcases, still lower if electromotors or similar devicesare used. However, this is what makes those useswhere shape-memory elements cannot be replacedwith other devices even more interesting. One suchexample is connecting pipes or other round elements

Kakor je bilo �e omenjeno, je zaradi manj�ihstro�kov v veèini primerov �e vedno primernejeuporabiti elektromotorje oziroma podobne pogonskenaprave, zato so bolj zanimive tiste mo�nosti uporabematerialov s spominom, pri katerih elementov iz tehmaterialov ni mogoèe nadomestiti z drugimi

springs wires

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with pipe couplings, as shown in Figure 5. Afterboth ends are inserted into the pipe coupling, thetemperature increase causes the inner diameter ofthe pipe coupling to contract, which results in astrong and tight connection. The temperature atwhich the shape of the pipe coupling changes canbe below the outside temperature, allowing to makea connection without heating. This pipe-connecting method is therefore very useful insituations where welding or some other high-temperature method could damage nearby elements[1].

Medicine is a field where shape-memorymaterials are already well established. Only TiNi al-loys, which have appropriate mechanical propertiesand good biocompatibility are used in medicine.These alloys are used for medical instruments as wellas orthopedic and dental devices. Medical instru-ments and orthopedic devices are very often made ofmaterial in which the shape change occurs at bodytemperature, while in dentistry, superelastic wire isthe most common material. Medical instruments areusually in contact with body tissues for only a shorttime, however, orthopedic devices can stay insidethe body for a few months [2], which requires goodbiocompatibility.

Shape-memory alloys are also frequentlyused in safety valves for water, gas or otherinstallations, where they are designed to stop thefluid flow if the temperature gets too high. The useof shape-memory materials in gas thermic safetyvalves is very interesting, because in manycountries the use of these devices is alreadyprescribed by law. The use of shape-memorymaterials in other devices has advantages anddisadvantages, these are described in the followingsection.

3 THERMIC SAFETY VALVE WITH SHAPEMEMORY

Thermic safety gas valves are deviceswhich are inserted into gas pipelines. Their task is

napravami. Eden tak�nih primerov je spajanje cevioziroma drugih valjastih predmetov z objemkami zoblikovnim spominom, kar ka�e slika 5. Po vstavitviobeh koncev cevi v objemko povzroèi povi�anje tem-perature zmanj�anje njenega notranjega premera, sèimer dobimo moèan in tesen spoj. Temperatura, prikateri se oblika objemke spremeni, je lahko ni�ja odtemperature okolice, kar omogoèa, da izvedemo spojbrez dodatnega segrevanja. Tak�en naèin spajanjacevi je zato zelo primeren tam, kjer bi varjenje oziromakak�na druga visokotemperaturna tehnika spajanjapovzroèila po�kodbe sosednjih elementov [1].

Sl. 5. Spajanje cevi z objemko z oblikovnim spominom [1]Fig. 5. Pipe connecting with a shape-memory coupling [1]

Podroèje, na katerem so materiali z oblikovnimspominom �e sedaj dokaj dobro uveljavljeni, je medicina.Na tem podroèju se uporabljajo le TiNi zlitine, ki imajopoleg ustreznih mehanskih lastnosti tudi dobro biolo�kozdru�ljivost, namenjene pa so izdelavi medicinskihinstrumentov ter ortopedskih in zobozdravstvenihpripomoèkov. Medicinski instrumenti in ortopedskipripomoèki so obièajno izdelani iz materiala, v katerempride do spremembe oblike pri telesni temperaturi, vzobozdravstvu pa se uporablja predvsem superelastièna�ica. V nasprotju z medicinskimi instrumenti, katerih nalogeso obièajno kratkotrajne, lahko ortopedski pripomoèkizaradi dobre zdru�ljivosti TiNi zlitine s telesnimi tkivi svojonalogo v telesu opravljajo tudi po veè mesecev [2].

Materiali z oblikovnim spominom se pogostouporabljajo tudi v razliènih varovalnih ventilih vvodovodnih, plinskih ali drugih napeljavah, njihovanaloga pa je ustaviti pretok tekoèine pri èezmernempovi�anju temperature. Trenutno je predvsem zanimivauporaba materialov s spominom v termiènih varovalihza plin, saj je uporaba teh naprav v mnogih dr�avah �ezakonsko predpisana. Uporaba materialov z oblikovnimspominom v teh napravah ima glede na druge izvedbedoloèene prednosti in pa tudi doloèene pomanjkljivosti,kar je opisano v nadaljevanju.

3 TERMIÈNO VAROVALO Z OBLIKOVNIMSPOMINOM

Termièna varovala za plin so naprave, ki jihvgrajujejo pred konène porabnike plina. Njihova naloga je

segrevanje heating

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to stop the flow of a gas into the room if the tem-perature rises too much, this significantly de-creases the possibility of a gas explosion. Safetyregulations which demand the use of thermic safetyvalves in gas installations have stimulated the de-velopment of these devices, especially the searchfor a simple, cheap, but still reliable valve-closingmechanism.

The thermic safety valve mechanismshould consist of a critical-temperature sensorand an active element to close the valve. To use atemperature sensor and a pneumatic valve or asimilar device in this mechanism would, of course,be unsuitable, while the price and the size of thevalve would lead to problems. Because of thedemands for simplicity, small dimensions and lowprice, materials which change at a certaintemperature to activate the closing mechanismseem to be the best choice. Materials which workas the temperature sensor and at the same time asthe active element can be solders with anappropriate melting point or shape-memory alloys.Solders are more often used because they aremuch better known and researched than shape-memory alloys. A possible variant of the solderedthermic safety valve is shown in figure 6. Atordinary temperatures the closing element is fixedin position with a solder, this allows the gas toflow. At a critical temperature the solder meltsand allows the spring to stretch, pushing theclosing element against the outlet and stopingthe gas flow.

This type of thermic safety valve meets mostof the requirements, only the assembly of the innerelements can cause problems. The shapes of the con-nected elements make soldering quite difficult andthe time required for the solder to harden lengthensthe total assembly time.

In thermic safety valves with shape-memoryelements the working mechanism is very similar, ex-

zaustavitev dotoka plina v prostor v primeru èezmernegapovi�anja temperature, s èimer se v primeru po�ara bistvenozmanj�a mo�nost eksplozije plina. Varnostni predpisi, kizahtevajo uporabo termiènih varoval v plinskih napeljavah,so moèno pospe�ili razvoj teh naprav, ta je potekal predvsemv smeri iskanja èimbolj preprostega in poceni, a kljub temuzanesljivega mehanizma za zapiranje ventila.

Za uspe�no opravljanje svoje naloge mora torejmehanizem za zapiranje termiènega varovala vsebovatielement za zaznavanje kritiène temperature in aktiven ele-ment, ki omogoèa ali povzroèa premik zapirnega elementa.Izvedba tak�nega mehanizma z uporabo toplotnegazaznavala in pnevmatskega valja ali druge pogonskenaprave bi bila seveda povsem neprimerna, saj bi bili takocena kakor velikost tak�nih termiènih varoval neustrezni.Zaradi zahtev po enostavnosti, majhnih izmerah in nizkiceni so se kot najprimernej�i za izdelavo mehanizmov zazapiranje termiènega varovala izkazali materiali, pri katerihje mogoèe spremembo njihovih lastnosti, do katere morapriti pri ustrezni temperaturi, izkoristiti za spro�enjezapirnega mehanizma. Tak�ni materiali, ki torej delujejokot temperaturno zaznavalo in hkrati tudi kot aktivni ele-ment, so predvsem loti z ustrezno temperaturo tali�èa inpa materiali z oblikovnim spominom. Uveljavile so sepredvsem izvedbe z loti, saj so loti v splo�nem mnogobolj poznani in raziskani kakor materiali s spominom.Zgradba ene od izvedb termiènega varovala z lotom jeprikazana na sliki 6. Pri dovoljenih temperaturah je zapirnielement z lotom utrjen v legi, ki dopu�èa pretok plina. Prikritièni temperaturi se lot stali, kar omogoèa vzmeti, da seraztegne, potisne zapirni element ob izstopno odprtinotermiènega varovala in s tem zapre pretok plina.

Tak�no termièno varovalo za plin v skorajvseh pogledih ustreza zahtevam, manj�e te�ave sepojavijo le pri sestavljanju notranjih elementov. Lotanjeje namreè v tem primeru zaradi oblik spajanih elementovdokaj zahtevno, poleg tega pa je za strditev lotapotreben doloèen èas, ki podalj�a skupni èas monta�e.

V termiènih varovalih z elementi z oblikovnimspominom je naèelo delovanja obièajno zelo podobno,

Sl. 6. Primer termiènega varovala z lotomFig. 6. An example of a thermic safety valve with a solder

vzmet spring

okrov vzmeti spring housing

lot solder

dotok plina gas flow

okrov termiènega varovala thermic safety valve housing

zapirni element closing element

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le da zapirni element v osnovni legi ni utrjen z lotom,temveè s primerno oblikovanim elementom iz materialaz oblikovnim spominom. Ta element je vez medzapirnim elementom in okrovom termiènega varovalaali pa med zapirnim elementom in okrovom vzmeti.Sprememba oblike elementa z oblikovnim spominom,do katere pride pri ustrezni temperaturi, sprosti zapirnielement, ki ga vzmet potisne v drugo lego in s temonemogoèi pretok plina.

Da bi element z oblikovnim spominom ustrezalzahtevam, mora biti zaradi razmeroma visoke cenematerialov s spominom èim la�ji oziroma èim manj�i.Majhne izmere elementa so zahtevane tudi zaradiomejenega prostora v notranjosti termiènega varovala.Za doseganje konkurenène cene izdelka je najboljprimerno, èe je element izdelan iz �ice, saj so materiali zoblikovnim spominom v tej obliki najcenej�i in tudiponudba je najveèja. �ica je ustrezna tudi zaradipreprostega oblikovanja, pri èemer pa je treba paziti, dapolmeri ukrivljenosti �ice niso premajhni, ker prevelikedeformacije oziroma raztezki privedejo do poslab�anjaali celo izgube lastnosti oblikovnega spomina. Èeelementa ni mogoèe izdelati iz �ice, lahko izbiramo medpreostalimi oblikami, v skrajnem primeru pa je prinekaterih ponudnikih materialov z oblikovnim spominommogoèe naroèiti izdelavo elementov posebnih oblik.

Termièna varovala z elementom z oblikovnimspominom je mogoèe preprosteje in hitreje sestavitikakor izvedbe z lotom, katerih edina te�ava je monta�a.Uporaba materialov z oblikovnim spominom vtermiènih varovalih za plin je torej teoretièno idealna,vendar se zaradi te�av pri konstrukciji elementa zoblikovnim spominom in pri nabavi materialaizdelovalci teh naprav raje odloèajo za izvedbe z loti.Ponudniki materialov z oblikovnim spominom namreètudi kupcem ne ponujajo dovolj informacij o tistihmehanskih lastnostih, ki so potrebne pri konstruiranjudoloèenega izdelka. Presku�anje vzorcev in iskanjeustreznega materiala zahteva veliko èasa in tudidenarja, zato se mnogi potencialni kupci raje odloèijoza alternativne izvedbe svojih izdelkov.

4 SKLEP

Èeprav bi lahko posebne lastnostimaterialov z oblikovnim spominom s pridomizkoristili v marsikaterem primeru, se uporaba tehmaterialov zelo poèasi zveèuje. Razloga za to stapredvsem razmeroma visoka cena in slabopoznavanje teh materialov. Veèina proizvajalcev, kibi �elela razviti uporabo z elementi z oblikovnimspominom, bi se morala najprej podrobno seznanitiz lastnostmi teh materialov, preuèiti njihovoponudbo na trgu in s preskusi priti �e do preostalihpodatkov, potrebnih za razvoj izdelka. Celotenrazvojni proces bi bil zato dolgotrajen in drag, zatose posku�a veèina proizvajalcev temu izogniti zuporabo bolj znanih materialov in naprav.

cept that in the initial position the closing elementis not fixed with solder but with a shape-memoryelement. This element represents a bond betweenthe closing element and the thermic safety-valvehousing or between the closing element and thespring housing. The change in the shape of theshape-memory element at a particular temperaturereleases the closing element, which is pushed bythe spring into oposite position, where it stops thegas flow.

For the shape-memory element to meet therequirements, it must be as light and as small aspossible due to the high price of shape-memorymaterials. This element also has to be small be-cause of the limited space inside the thermic safetyvalve. For the product to have a competitive pricethe element should be made from wire, becausematerials in this form are the least expensive. Wireis also a good choice because it is easily shaped,providing that the bending radii are not too small:large deformations can lead to fading or even to acomplete loss of the shape-memory effect. If theelement cannot be made from wire, another shapemust be selected. In extreme situations it may benecessary to manufacture specially shaped ele-ments.

Thermic safety valves with shape-memoryelements are easier and faster to assemble thansolder-based valves. The use of shape-memory ma-terials seems to be ideal, but due to problematicshape-memory-element design and the ordering ofthe material, the manufacturers of these devicesprefer to choose the soldered options. Even to theircustomers shape-memory material suppliers do notgive enough information about the mechanicalproperties which are necessary to design a par-ticular product. Because testing samples andsearching for the right material take a lot of timeand money, many potential customers prefer tochoose products that are not loased on shape-memory materials.

4 CONCLUSION

Even though the properties of shape-memory materials could be used in manyapplications, the use of these materials is increasingvery slowly. The reasons are the relatively high priceand the lack of knowledge associated with thesematerials. Most of the manufacturers wanting todevelop a certain application with shape-memoryelements would first have to learn about the specificproperties of these materials, study the market anddo tests to obtain the data necessary for thedevelopment of this application. Because this wholeprocess would be time consuming and expensive,many manufacturers simply use standard materialsand devices.

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Dokler ti materiali ne bodo bolj raz�irjeni inpoceni, bo njihova uporaba omejena predvsem naprimere, pri katerih zaradi prostorskih omejitevuporaba elektromotorjev ali drugih pogonskih napravni mogoèa, in tam, kjer imajo elementi z oblikovnimspominom funkcijo temperaturnega zaznavala terpogonske naprave hkrati.

Kakor je bilo �e omenjeno, pomeni izdelavaelementov iz materialov z oblikovnim spominom enoveèjih te�av pri uporabi teh materialov, saj o mo�nostihnjihove obdelave ni na voljo dovolj podatkov. Zatoso v nadaljevanju raziskav uporabnosti materialov zoblikovnim spominom naèrtovani testi, s katerimi bidobili osnovne podatke o mo�nostih njihoveobdelave. Ti podatki bi olaj�ali razvoj izdelkov zelementi iz materialov z oblikovnim spominom in tudipripomogli k la�jemu odloèanju proizvajalcev zauporabo teh materialov v njihovih izdelkih.

As long as these materials are in niche mar-kets and their price remains high, their use will belimited either to those applications where space limi-tations do not allow the use of electromotors andsimilar devices or applications where shape-memoryelements function as both the temperature sensorand the drive.

As as already mentioned, the manufac-turing of shape-memory elements represents amajor problem in the use of these materials be-cause there is not enough available informationon the machining of these materials. Therefore,research which would give some basic informationon machining is required. This would make the de-velopment of new products with shape-memoryelements easier and would also help manufactur-ers of devices to use these materials in their appli-cations.


[1] Funakubo H. (1987) Shape Memory Alloys. Gordon and Breach Science Publishers, New York.[2] Duerig T. W., Melton K. N., Stoeckel D., C.M. Wayman (1990) Engineering aspects of shape memory alloys.

Butterworth-Heinemann Ltd., London.

Naslova avtorjev: Matja� PtièarLjubljanska 121241 Kamnik

doc.dr. Slavko Dolin�ekprof.dr. Franc KoselFakulteta za strojni�tvoUniverze v LjubljaniA�kerèeva 61000 Ljubljana

Authors� Addresses: Matja� PtièarLjubljanska 121241 Kamnik, Slovenia

Doc.Dr. Slavko Dolin�ekProf.Dr. Franc KoselFaculty of Mechanical Eng.University of LjubljanaA�kerèeva 61000 Ljubljana, Slovenia

Prejeto: 27.7.2000


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Strokovna literatura - Professional Literature

Strokovna literaturaProfessional Literature

© Strojni{ki vestnik 46(2000)11/12,789-791ISSN 0039-2480Strokovna literatura


Professional Literature

Ocene knjig

K. Zimmermann: Technische Mechanik -multimedial

Zal.: Fachbuchverlag Leipzig Carl Hanser VerlagMünchen, Wien 2000.

Obseg: format 16 x 23 cm, 207 strani, 72 slik,45 preglednic, CD-ROM.

Cena je 49,80 DEM.

Knjiga, ki jo avtor imenuje vadnica iz tehni�kemehanike, je razdeljena na naslednja poglavja: naloges potekom re�evanja, re�evanje nekaterih vrst nalogtehni�ke mehanike z uporabo raèunalni�kih programov,izbor izpitnih nalog na konènem izpitu iz mehanike naTehni�ki univerzi v Ilmenau, zbirke formul iz mehanike,formule iz matematike in CD - ROM za modeliranje vtehni�ki mehaniki.

V prvem delu uèbenika, ki obsega 6 poglavij,so naloge iz statike, trdnosti, kinematike, kinetike,nihanj in kritiènih vrtilnih frekvenc. Pri statiki je skupaj54 nalog, ki obravnavajo sestavljanje in ravnote�jesil, grafièno re�evanje, doloèanje te�i�è, trenje ternotranje sile in momente v nosilcih. V glavnem soobravnavani ravninski primeri, nekaj nalog pa je tudiprostorskih. Podroèje trdnosti je zajeto v 90 nalogah,ki obravnavajo podroèje napetosti in deformacij,nateg in tlak, torzijo, geometrijske znaèilnostiprerezov, upogib, strig, uklon, Castiglianov inMenabreanov princip in sestavljene napetosti. Snovkinematike je zajeta v 23 nalogah. Pri kinematiki toèkeje obravnavano gibanje v kartezijskem, naravnem inpolarnem koordinatnem sistemu, pri togem telesu paso naloge iz vrtenja telesa okoli stalne osi inravninskega gibanja telesa. Vsebine kinetike so zajetev 29 nalogah, najveè iz masne toèke in togega telesa,nekaj nalog je tudi iz sistema togih teles. V 37 nalogahje obravnavano mehansko nihanje, ki obravnavajoenomasna nihanja ( lastna nedu�ena in du�ena tervsiljena du�ena), nihanja veèmasnih sistemov, nihanjakontinuov in nelinearna nihanja. V sklepnem delupodroèja nalog je snov kritiènih vrtilnih frekvenc zajetav 4 nalogah. Kratek potek re�evanja in rezultati vsehnalog so podani v poglavju 9.

V poglavju 7 so podane nekatere naloge iztehni�ke mehanike, ki jih lahko re�ujemo zraèunalni�kimi programi in so podani na CD-ROMu.Tako je podanih po 10 nalog za raèunanje trdnostnihgeometrijskih znaèlnosti sestavljenih prerezov, prire�evanju ravninskega palièja, pri raèunanju osnihpritiskov pri razliènih delovnih vozilih, ki preva�ajorazlièno opremo in pri kinematièni analizi robotov.

Podan je primer raèunalni�ke obdelave testa razbijanjapri avtomobilu ter upogibnih in torzijskih nihanjnosilca.

V osmem poglavju so podane naloge iz 16izpitov na Tehni�ki univerzi v Ilmenau. Vsak izpitvsebuje �tiri naloge, po eno nalogo iz statike, trdnosti,kinematike in kinetike. Naloge so brez rezultatov inpoteka re�evanja. S podanimi izpitnimi nalogami lahko�tudenti domnevajo o zahtevnostni stopnji pri izpitih,na�i �tudenti in pedago�ki delavci pa vidijozahtevnost na izpitih drugje.

V desetem poglavju je avtor zbral obrazce spodroèja tehni�ke mehanike za vsebine, ki jihobravnavajo naloge v poprej�njih poglavjih tegauèbenika. Obrazce so opremljene �e s kratkimikomentarji, definicijami in pomembnimi sklepi.

Vsa tista matematièna sredstva, ki so nujnopotrebna za re�evanje podanih nalog, je avtor zbral venajstem poglavju pod naslovom matematièneosnove. Tako �tudent pri re�evanju nalog iz uèbenikane potrebuje �e drugih priroènikov, saj ima praktiènovse zbrano v njem.

V zadnjem delu je na kratko opisana uporabaCD-ROMa. Tukaj je obravnavano modeliranjein�enirskih problemov. Vemo, da je prav to podroèjeza �tudente najte�je, kako si torej pripraviti model, kiga bomo z znanjem mehanike in matematièno pomoèjonato obravnavali in re�ili. Preprièan sem, da bo taraèunalni�ka podpora marsikomu pomagala premagatiovire pri modeliranju praktiènih primerov.

Na podlagi vsega opisanega je vidnaaktualnost in sodobnost uèbenika, zato sempreprièan, da bo koristil �tudentom univerzitetnegain visoko�olskega �tudija pri pripravi na izpite izmehanike in tudi za ka�nej�e delo v praksi, zato gatoplo priporoèam.

J. Stropnik

F. Neumann: Gusseisen-Schmelztecnik,Metallurgie, Schmeltzbehandlung

Zal.: Expert Verlag, GmbH, Renningen �Malmsheim, 2. predelana in dopolnjena izdaja, 1999.

Obseg: format 15 x 21 cm, 452 strani, 300 slik,53 preglednic, 287 lit. pod.

Cena je 128 DEM.

Litje je izjemno pomembna tehnologija, skatero dose�emo konèno obliko izdelka. Celotnotehnologijo torej vkljuèujejo razlièni postopki taljenja

00-11/12stran 790

Strojni{ki vestnik - Journal of Mechanical Engineering

in litja taline dane zlitine in razlièni postopki formiranjaoziroma oblikovanja livne votline. V omenjenem deluo litem �elezu so prikazani razlièni postopkipretaljevanja vhodnega materiala, ki vkljuèujejorazliène talilni�ke sisteme in pomo�no opremo.Uvodoma avtor predstavi posamezne vrste �eleznihlitin, njihove lastnosti in njihovo uporabnost vnem�kem prostoru v zadnjih dvajsetih letih. Zaradivse ostrej�ih zahtev po zelo trdnih ulitkih sledi vseveèja uporaba nodularne litine ali legirane oziromatoplotno obdelane �elezne litine. Zelo pomembno jepoveèevanje porabe nodularne litine v avtomobilskiindustriji in s tem tudi zahteve po razvoju postopkovpridobivanja kakovostne nodularne litine in hkratipo zni�evanju cene ulitka.

Zato delo prina�a pregled razliènihtehnolo�kih postopkov in metalur�ke osnovetalilni�kih procesov. Zbrani in podani so �tevilnipodatki za posamezne talilni�ke postopke. Avtor jeob pomoèi sodelavcev opravil zelo obse�noeksperimentalno delo, ga primerno priredil za splo�nouporabo v obliki �tevilnih preglednic oziromadiagramov.V delu je predstavljena naslednja problematika:- pregled razliènih talilni�kih postopkov na podlagi

kupolk z metalur�ko tehnolo�kimi pogoji;- pregled razliènih talilni�kih postopkov na podlagi

visokofrekvenènih oziroma srednjefrekvenènihtalilni�kih peèi in prikaz tehnolo�kih razmer;

- pregled razliènih talilni�kih postopkov v bobnastihrotacijskih peèeh in prikaz metalur�kotehnolo�kihrazmer;

- postopki izbolj�anja talilni�kih postopkov zraèunalni�ko podprtim nadzorom in vodenjemprocesa;

- racionalizacija pretoka surovin;- optimiranje talilnih postopkov z vidika prihranka

energije;- skrb za èisto okolje, glede na vse ostrej�e zahteve

in predpise;- spreminjanje kadrovske sestave v livarnah in

uvajanje avtomatizacije v livarnah;- zmanj�evanje izgube materiala oziroma

zmanj�evanje stro�kov izgubljenega materiala;- izbolj�anje kakovosti ulitkov glede na njihove

trdnostne lastnosti z uporabo razliènih vrstmodifikatorjev in tehnik modificiranja razliènih talin.

Delo je izjemno obse�no in specializirano,zato je namenjeno predvsem vodilnemu tehniènemuosebju v livarnah �eleznih litin, tehnikom inin�enirjem, ki se ukvarjajo s tovrstnimitehnologijami in �tudentom livarstva. Delo jepisano zelo preprosto, jasno in pregledno, s�tevilnimi slikovnimi predstavitvami procesnihsistemov, posameznih naprav oziroma njihovihelementov. Posebno skrb so na eksperimentalniosnovi izdelani �tevilni diagrami metalur�kotehnolo�kega znaèaja, ki omogoèajo praktikom v

proizvodnji bolj�e razumevanje talilni�kegaprocesa.

J. Grum

H. Wenzl: Batterietechnik

Zal.: Expert Verlag, GmbH, Renningen �Malmsheim, 1999.

Obseg: format 15 x 21 cm, 253 strani, 73 slik,13 preglednic.

Cena je 69 DEM.

Neodvisnost, premiènost, razpolo�ljivost itn.transportnih naprav, naprav za komuniciranje, napravza zabavo itn. terjajo uporabo samostojnih, neodvisnihvirov energije. Posledica tak�nega razvoja je vse �ir�auporaba elektriènih baterij in akumulatorjev. Zaradivplivov na okolje �elijo tudi nekatere druge vire energijenadomestiti z elektriènimi, tako pospe�eno razvijajosonène celice, gorivne celice, nove tipe elektriènihakumulatorjev in podobno. Èeprav so novice o novihdose�kih na podroèju akumulatorjev pogoste, jedandanes, kot naprava za kemièno shranjevanjeelektriène energije, �e vedno v naj�ir�i uporabi svinèevakumulator, ki deluje na osnovi kemiènih procesov,znanih skoraj 150 let. Svinèevemu akumulatorju pouporabi sledi nekoliko mlaj�i nikel-kadmijev akumulator.

Kakor je razvidno iz podnaslova knjige, avtormeni, da je za vkljuèevanje akumulatorjev v uporabo innjihovo uspe�no uporabo potrebno èimbolj�epoznavanje zgradbe, lastnosti in delovanja akumulatorjev.Tako obravnava v delu kemiène procese in spremljajoèepojave v akumulatorjih, materiale za gradnjo, postopkepolnjenja in praznjenja, nadomestna vezja, vplive tem-perature, korozijo, vplive na okolje, dobo trajanjaakumulatorjev in na koncu tudi najznaèilnej�e vrsteuporabe (akumulatorji, kot shranjevalniki elektrièneenergije, kot vir energije pri transportnih napravah,pomo�ni vir energije v vezanih sistemih napajanja in kotvir energije pri zagonu motornih vozil).

V delu zbrane informacije o najpogostejeuporabljanih akumulatorjih bodo dobrodo�le vsem,ki imajo opraviti z akumulatorji, bodisi pri naèrtovanjuuporabe ali sami uporabi.

A. Hussu

R. Hürten: Function-Point Analysis

Zal.: Expert Verlag, GmbH, Renningen �Malmsheim 1999.

Obseg: format 16 x 23 cm, 1771 strani.Cena je 98 DEM.

Function-Point Analysis (FPA) je metodaanalize za merjenje nivoja funkcionalnosti, ki jo nekaprogramska oprema ponuja uporabniku. Mera nivoja

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Strokovna literatura - Professional Literature

funkcionalnosti ni odvisna niti od metodologijerazvoja niti od uporabljene tehnologije programiranja.Zato daje mera nivoja funkcionalnosti osnovnoznaèilnico, ki omogoèa dolgoroèno primerjavoproduktivnosti pri razvoju programske opreme in stem temelj za obvladovanje stro�kov razvoja.

Prièujoèa knjiga predstavlja predvsemsplo�no naèelo FPA in njenih najpomembnej�ihuporabnih znaèilnosti. Uporaba FPA v praksi in opiskljuènih predpostavk za uspe�no rabo analize stapodrobno opisana in predstavljena na primerih.Prilo�eni preglednièni izraèuni ne pomenijo zgolj vrstepouènih primerov, ampak omogoèajo, da jih prikonkretni metodi FPA lahko neposredno tudiuporabimo. Pri tem gre za niz raznovrstnih preglednic,ki se uporabljajo za izraèun merske karakteristikefunkcionalnosti vse od pred�tudij, analize problemovin za sam potek projektov. Pri tem upo�teva metodarazliène znaèilnosti, npr. kupca, naroèila, zapletenostzahtev in podatkov, vkljuèevanje �e znanih re�itev,programskega okolja in jezika, v katerem poteka razvojipd.

Knjiga je zelo primerna za:- izvajalce nadzora programske opreme, ki �ele

preglednost stro�kovne sestave izdelaveprogramske opreme;

- vodstveni kader s podroèja informacijsketehnologije, ki �eli izbolj�evati produktivnostrazvoja programske opreme;

- projektne vodje s podroèja informacijsketehnologije, ki hoèejo imeti uèinkovit nadzor nadobsegom projektov razvoja programske opreme;

- vodstveni kader podjetij, ki izdeluje programskoopremo, za podporo pri izdelavi ponudb ter

- uporabnike programske opreme, ki jih zanimaprimerjava cenovne uèinkovitosti za stro�kenjihove programske opreme.

A. Sluga

K. Felte: Verzahntechnik

Zal.: Expert Verlag, GmbH, Renningen �Malmsheim 1999.

Obseg: format 15 x 21 cm, 171 strani, 66 slik,7 pregl., 46 navedb literature.

Cena je 69 DEM.

V knjigi avtor razlaga zgodovino ozobja,osnove o geometrijski obliki posameznih vrst ozobja,postopke izdelave zobni�kih dvojic, termièno

obdelavo èelnih in sto�èastih zobnikov in postopkepreverjanja geometrijske oblike zobni�kih dvojic.

Posebej obravnava valjaste zobnike z ravnimiin po�evnimi zobmi in sto�èaste zobnike.Pri vsakempostopku izdelave zobni�kih dvojic (litje, sintranje,natanèno kovanje, stiskanje, frezanje, skobljanje itn.)so podane zahteve posebej za osnovne in toplotnoobdelane materiale. Popisuje osnove tehnologij,kinematiko obdelovalnih strojev in oblike orodij, ki sov veliki meri odvisne od �elene kakovosti ozobja.

Knjiga je namenjena predavateljem in�tudentom strojni�tva kot spremljajoèa literatura pripredavanjih in strokovnjakom, ki za pripavo inproizvodnjo zobni�kih dvojic potrebujejo natanèneinformacije.

I. Prebil

Z. Balantiè: Èlovek � delo � uèinek

Zal.: Moderna organizacija, Kranj 2000Obseg: 17 tematskih sklopov, 20 predstavljenih

uporab, 710 multimedijsko podprtih strani, 260 slik,353 avtorskih skic in 233 diagramov.

Cena je 1900 SIT.

Interaktivna elektronska publikacija jenarejena v obliki zgo�èenke, ki zdru�uje �tudijskovsebino sklopa èlovek � delo � uèinek, povezano spraktiènimi izku�njami delovne uèinkovitosti,izvedene v izbranih uspe�nih slovenskih podjetjih.Zgo�èenka je razdeljena na dva dela, teoretièni inpraktièni, ki sta medsebojno dinamièno povezana inprepletena.

Vsebina zgo�èenke: ergonomija,antropometrija, informacijski tokovi med èlovekom inokolico, biomehanika, raba energije pri èloveku, èutila,mikroklimatsko okolje, oblikovanje in znaèaj dela,stopnja razvoja delovnih sistemov, varovanje pri delu,�tudij in oblikovanje dela, delovni èas, metode intehnike izbolj�evanja dela, merjenje dela inergonomsko ocenjevanje.

Zgo�èenka je namenjena vsem, ki �elijospoznati vplivne elemente na èlovekovo delovnouèinkovitost, spoznati problematiko razmerja medèlovekom in strojem, predvsem pa spodbujainovativne dejavnosti s podroèja èlovek v delovnemprocesu.

V. Butala

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Osebne vestiPersonal Events

© Strojni{ki vestnik 46(2000)11/12,792-796ISSN 0039-2480Osebne vesti


Personal Events

V spomin prof. Stanetu Potr~u

Sredi visokega poletja, 6.avgusta 2000, je preminil moj starej�ikolega po stroki, prof. Stane Potrè,prvi uèitelj s podroèja Transportnihnaprav na Vi�ji in nato Visokitehni�ki �oli v Mariboru. Pokojniprofesor Stane Potrè se je rodil vobrtni�ki dru�ini 2. julija leta 1924oèetu Alojzu in materi Tonji.Osnovno �olo je obiskoval vMozirju in v Mariboru. Kot zelonadarjenega dijaka so ga star�iusmerili v takrat osemletno Gimnazijov Mariboru, ki jo je moral prekinitizaradi druge svetovne vojne in sezaposliti. �e leta 1942 se je, star komaj18 let, vkljuèil v delo OF ter èez dobro leto vstopil vNOV kot aktivni borec.

Gimnazijo je dokonèal �ele po vojni, poznojeseni leta 1945 z maturo na Ptuju, ter se jeseni leta1946 vpisal na Tehni�ko fakulteto, Oddelek zastrojni�tvo v Ljubljani. Vse svoje �tudijske obveznostije do absolutorija opravljal redno in zelo uspe�no. Vzadnjem semestru se je prikljuèil znani konstrukterskiskupini �tudentov in diplomantov pri prof. FranèkuKovaèecu, ki je v prvih povojnih letih postavljaltemelje nekaterim osnovnim konstrukterskimpredmetom in �e posebej predmetom s podroèjaTransportnih naprav. Jeseni leta 1949 se je za tri letazaposlil na Srednji tehnièni �oli v Ljubljani kotpredavatelj, kar je nekoliko upoèasnilo njegov �tudij.Prof. Kovaèec, ki je s konkretnimi projekti za industrijouvajal mlade strojnike v konstruktersko prakso, mu jebil mentor tudi pri diplomskem delu s podroèjaprojektiranja �erjavov. Diplomiral je marca leta 1953kot 79. diplomant strojni�tva v Ljubljani.

Prof. Stane Potrè je prièel svojo in�enirskopot v �elezarni �tore takoj po diplomi. �e julija istegaleta se mu je ponudila zaposlitev v Metalni Maribor,katere proizvodni program je bil bli�e univerzitetnodiplomiranemu strojnemu in�enirju in znotraj tematike,ki jo je podrobno spoznaval pri svojem mentorju vLjubljani. Njegova prva zadol�itev je bilo vodenjemonta�e metalni�ke opreme v �elezarni Zenica, insicer: transportne opreme za pripravo rude pri visokihpeèeh, jeklene konstrukcije pri aglomeraciji, jeklenekonstrukcije za halo valjarne ter �erjave v njej.

Po vrnitvi s �terena�, najbolj�e pripravljalniceza samostojno projektiranje, je v Metalni postalprojektant in vodja skupine v projektivnem biroju za

transportne naprave v letih 1954 do1960 s prekinitvijo v letih 1956 do1958, ko se je izpopolnjeval vNemèiji. Pod njegovim vodstvom sobili zasnovani in izvedeni mnogiveliki in manj�i objekti zajugoslovanski in izvozni trg. Najna�tejem samo nekatere: prekladalnimostovi razpetine 60 m s traènimitransporterji in elevatorjem nasamem �erjavu za TE �o�tanj,prekladalni most razpetine 50 m + 10m + 15 m s traènimi transporterji invrtljivim maèkom z grabilom zaJugoviskozo Loznica (Bosna),prekladalni most razpetine 50 m s

traènimi transporterji in dvema elevatorjema za TEKolubaro (Srbija), prekladalni most za TE Kakanj(Bosna), te�ki mostni �erjavi za �elezarno Zenica, veèdrugih industrijskih �erjavov, transporterji za rudnike,itn.

Novembra leta 1956 je prof. Stane Potrè od�elv nem�ko dru�bo Walter & Cie Aktiengesellschaft,Köln-Dellbrück, kjer je najprej deloval kot projektantna podroèju nosilnih ogrodij parnih kotlov terokrovov razliènih filtrov za odpra�evanje. Kmalu somu poverili tudi dela statika na celovitih objektih spodroèja jeklenih konstrukcij, kjer se je izkazal s svojimistrokovnimi izku�njami in �irokim pogledom nazahtevno problematiko. V Metalno se je z novimznanjem in izku�njami vrnil leta 1958.

Dve leti po njegovi vrnitvi v Metalno je bilaustanovljena Vi�ja tehni�ka �ola v Mariboru in prof.Stane Potrè je bil v prvi generaciji njenih uèiteljev. Ssvojimi bogatimi strokovnimi izku�njami je utemeljilvsebino, pripravil predavanja ter celih dvaindvajsetlet predaval naslednje aplikativne predmete:Transportne naprave na vi�je�olskem �tudiju terTransportne naprave I, Transportne naprave II inTransportne sisteme na visoko�olskem �tudiju. V tehpredmetih je zajel potrebno znanje o konstruiranju,projektiranju ter uporabi transportnih naprav vindustriji, rudarstvu, na pretovornih mestih v prometublaga in drugod. Na vi�je�olskem �tudiju je predavaltudi predmeta Mehanika I in Mehanika II.

Po zgledu svojega uèitelja in mentorja prof.F.Kovaèeca je na �oli ustanovil projektivno skupino,v kateri so se urili ter nabirali svoje prve konstrukterskein projektantske izku�nje �tudentje v okviruseminarskih in diplomskih nalog. Za zasnovo in razvoj

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novih in prenovljenih izdelkov ni dovolj samoteoretska podlaga, temveè je potrebno tudi obilonavdiha pri obvladovanju funkcionalnih zahtev teriskanju optimalnih oblikovnih re�itev, ki morajo bitikonkurenèno izvedljive. Ta pristop, ki ga dandanesna modernih univerzah gojijo kot ��tudij na primerih�,daje najbolj�e rezultate. Mladi ljudje, ki so ves èas�olanja re�evali v veliki meri le kratke, najveè enourne�olske naloge, se morajo spopasti s stvarno inzapleteno nekajmeseèno nalogo z mnogimi robnimipogoji in skopimi podatki. Prav pri vodenju takihnalog je pokojni profesor dal v znanju svojihdiplomantov svoj velik prispevek �oli in industriji.Poleg tega je projektivna skupina, ki jo je vodil, dala vsamo desetih letih njenega obstoja (leta 1970 jo je�ola ukinila) dokumentacijo za 24 veèjih in manj�ihobjektov s podroèja gradenj �erjavov, valjarni�kih indrugih �elezarni�kih naprav, ki so bili tudi izvedeni.

V �olskem letu 1966/67 je bil �e enkrat naizpopolnjevanju v tujini, tokrat pri podjetju Wartmann& Cie.A.G. (Brugg v �vici). Kot samostojen projektantje izdeloval statiène in trdnostne izraèune terpripravljal ponudbe za velike rezervoarje, tlaèneposode in tlaène cevovode. S statiènim preraèunomin kontrolnim pregledom je sodeloval tudi pri gradnjizadr�evalnega hrama JE Beznau (�vica).

Profesor Stane Potrè je bil do svojihkolegov profesorjev, svojih sodelavcev in�tudentov izjemen èlovek. Bil je ugledenstrokovnjak ter odlièen pedagog. Rad je imel glasboin bil velik ljubitelj gora, kjer si je nabiral novihmoèi za predano delo. Prav je, da se njegovemuspominu oddol�imo tudi s temi skromnimi vrsticamiv Strojni�kem vestniku.

prof.dr. Janez Kramar

Prof.dr. Viktor Prosenc - 80 letnik

12. decembra praznuje visokjubilej � 80 letnico prof. dr. ViktorProsenc, pionir varilstva na Fakultetiza strojni�tvo Univerze v Ljubljani,upo�tevan uèitelj in uspe�enznanstvenik � raziskovalec v Slovenijiin zunaj nje, mentor mlaj�im uèiteljemvarilstva na matièni fakulteti, redniprofesor Fakultete za strojni�tvo vpokoju.

Profesor Prosenc je bil rojenv Zagorju ob Savi leta 1920. Tam jekonèal osemletno osnovno �olo in senato vpisal na takratno I. dr�avnorealno gimnazijo v Ljubljani, kjer jematuriral leta 1941, ko je bil prisiljen prekiniti nadaljnje�olanje zaradi vojne. Zato se je zaposlil v rudniku vZagorju, kjer je delal kot rudar.

Po konèani vojni se je vpisal na Metalur�kiodsek Montanistiènega oddelka takratne Tehni�kefakultete v Ljubljani, kjer je diplomiral leta 1951 in jenato bil redni asistent pri Katedri za metalur�kostrojni�tvo na Fakulteti za rudarstvo in metalurgijoTehni�ke visoke �ole v Ljubljani do leta 1958.

Tedaj se je zaposlil na Zavodu za varjenjeSRS (sedaj Institut za varilstvo) v Ljubljani, kar je bilousodno za njegovo nadaljnje strokovno, pedago�koin znanstveno raziskovalno delovanje, saj se je tedajzapisal varilstvu.

Na Zavodu za varjenje SRS se je usmeril vvarilstvo s poudarkom na tehnologiji varilskihprocesov in bil tri mesece na specializaciji na Institutuza varjenje (Institut de la soudure) v Parizu.

�e v �olskem letu 1962/63 je bilizvoljen na Odseku za montanistikoFakultete za naravoslovje intehnologijo Univerze v Ljubljani zahonorarnega predavatelja za podroèjevarjenja.

Po izvolitvi za predavatelja za varilskepredmete in toplotno obdelavo naFakulteti za strojni�tvo je bil tunastavljen za predavatelja januarja 1964.Po poprej�nji habilitaciji za docenta jebil 15. julija 1966 izvoljen za docenta naFakulteti za strojni�tvo Univerze vLjubljani.

Do tedaj je �e bil od leta 1964 rednisodelavec Instituta za strojni�tvo na Fakulteti zastrojni�tvo in predstojnik njegovega Tehnolo�kegaodseka.

Doktoriral je leta 1975 na Tehni�ki univerzi vHannovru (TU Hannover) pri prof. dr. FriedrichErdmann�Jesnitzer-ju, mednarodno uveljavljenemstrokovnjaku za varilstvo.

Disertacijo je pripravljal na Fakulteti zastrojni�tvo v Ljubljani in pri imenovanem profesorju naInstitutu za kovinoznanstvo (B) Fakultete za strojni�tvoUniverze v Hannovru. Naslednje leto 1976 je bil izvoljenza izrednega in leta 1981 za rednega profesorja naFakulteti za strojni�tvo Univerze v Ljubljani.

Na matièni fakulteti je oblikoval in predavalpredmete na vi�je�olskem in visoko�olskemuniverzitetnem �tudiju strojni�tva: Tehnologija kovinII, Toplotna obdelava in za�èita, Tehnika spajanja,Fizikalno-kemijske osnove varilnih procesov in

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tehnologija varjenja, za katere je izdelal uène programe.Za splo�na predmeta Varjenje in Tehnika spajanja jespisal skripta pod naslovom Varjenje (leta 1980) ter zapredmet Fizikalno kemijske osnove varilnih procesovin tehnologija varjenja pa �e skripta pod naslovomVarilska tehnologija. Skripta je zalo�ila in izdalaFakulteta za strojni�tvo Univerze v Ljubljani.

Bil je mnoga leta tudi nosilec predmeta Varilniprocesi na podiplomskem magistrskem �tudiju zapodroèje Avtomatizacija in proizvodna kibernetika.

V zadnjih letih aktivnega dela na Fakultetiza strojni�tvo je predaval �e predmet Nauk o kovinah.�e tedaj in po upokojitvi je predaval �e na Visokitehni�ki �oli oziroma Tehni�ki fakulteti Univerze vMariboru praktièno vse varilske predmete medsobotno odsotnostjo tamkaj�njega profesorja dr.Inoslava Raka.

Predaval je tudi na podiplomskem �tudijuna drugih univerzah (Univerza v Mostarju in druge).Gostoval je na drugih Univerzah kot èlan komisije zaocene in zagovore magistrskih in doktorskih disertacij(Univerza v Zagrebu, Univerza v Sarajevu idr.). Sicerje njegov opus na podroèju izobra�evanje precejobse�nej�i.

Tak�no je tudi njegovo znanstveno �raziskovalno in strokovno delovanje. �e kot mladasistent je sodeloval pri projektiranju metalur�kihobratov (�elezarna Sisak, Tovarna ferozlitin �ibenik,Livarna STT Trbovlje). Deloval je na podroèjupreiskav materialov za Rudarski in�titut v Ljubljaniter za ladijske registre.

Na Zavodu za varjenje SRS v Ljubljani je kotvodja Tehnolo�kega oddelka re�eval in sodeloval prire�evanju razliènih tehnolo�kih varilskih problemov zznanstveno raziskovalnim pa tudi razvojnim delom v�tevilnih obratih kovinsko predelovalne industrije,energetike in v drugih industrijskih obratih po vsejnekdanji dr�avi Jugoslaviji.

Poudariti moramo tudi njegovo delo napodroèju kristalizacije kovin, s katerim je doktoriral.Problem nukleacije in kristalizacije je �tudiral pojeklarskem postopku pretaljevanja pod �lindro.

Tako delo kakor tudi publikacije so bilidele�ni precej�njega zanimanja v tujini, zato je v okvirubilateralnega znanstveno-tehniènega sodelovanja,

med komisijami nekdanje SFRJ in Zvezno republikoNemèijo nem�ka stran dala prednost nadaljevanju tehraziskav.

Na Fakulteti za strojni�tvo je v okviru PREza tehnologijo materialov ustanovil Laboratorij zavarjenje (1972), s katerim je �ele bilo omogoèenoraziskovalno in strokovno delo na podroèju varjenja,ki se je raz�irilo na raziskave in razvoj za slovenskoindustrijo.

Re�eval je probleme, ki so zanimalislovensko industrijo in neposredno proizvodnjo: toso razlièni tehnolo�ki in varivostni problemi, razvojdodajnih materialov in razvoj varilnih naprav.

Jubilant pa ni bil dejaven le na pedago�kemin raziskovalnem podroèju, paè pa tudi v �tevilnihdru�benih in strokovnih organizacijah, kjer jeopravljal pomembne funkcije.

Na Fakulteti za strojni�tvo je bil predstojnikPRE za tehnolgijo materialov (2 leti), dekan Fakulteteza strojni�tvo dve mandatni obdobji (1979 � 1983).Èlan uredni�kega odbora za strokovni èasopis Varilnatehnika (1958 � 1964), ekspert v raznih komisijahMednarodnega in�tituta za varjenje, tajnik Zvezerudarskih, metalur�kih in geolo�kih in�enirjev intehnikov SRS idr.

Za svoj mnogostranski, bogati in plodniprispevek na razliènih podroèjih je prejel veè priznanjv obliki pohvalnic, znakov, diplom in medalj: èastnièlan ZGRMIT, zaslu�ni èlan ZIT Jugoslavije,Jugoslovanski red dela idr.

V �olskem letu 1990/91 je prof. Prosenc od�elv pokoj, in sicer februarja leta 1991.

Tudi po upokojitvi se prof. Prosenc rednovraèa na Fakulteto za strojni�tvo, je vedrega duha inrad razpravlja in svetuje, strokovno recenzira rokopiseuniverzitetnih uèbenikov s podroèja varilstva, je �evedno vabljen predavatelj na teèajih za evropskein�enirje varilstva na In�titutu za varilstvo v Ljubljani.Njegovo zanimanje je �e vedno bogato invsestransko.

Ob doèakanem visokem �ivljenjskem jubilejuprof. Prosencu prisrèno èestitamo in mu iskreno�elimo, da bi bil �e naprej veliko let èil in zdrav.

prof.dr. Viljem Kralj

Doktorati, magisteriji, diplome

DOKTORATI

Na Fakulteti za strojni�tvo Univerze vLjubljani so z uspehom zagovarjali svoje doktorskedisertacije, in sicer:

dne 23. oktobra 2000: mag. DeanBesednjak, disertacijo z naslovom: �Interakcija filma

kondenzata in vla�nega zraka v kri�nem toku�;dne 14. decembra 2000: mag. Tadej Kosel,

disertacijo z naslovom: �Slepo loèevanje neodvisnihizvorov akustiène emisije�;

dne 20. decembra 2000: mag. Boris Pukl,disertacijo z naslovom: �Obratovalna trdnostmehanskih zvez delov iz jekla in aluminijevih zlitin� in

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Osebne vesti - Personal Events

dne 21. decembra 2000: mag. �eljkoWarga, disertacijo z naslovom: �Prenos toplote vkotlih za centralno ogrevanje�.

Na Fakulteti za strojni�tvo Univerze vMariboru sta z uspehom zagovarjala svoji doktorskidisertaciji, in sicer:

dne 15. novembra 2000: mag. Krsto Pand�a,disertacijo z naslovom: �Strate�ki proces akumulacijesposobnosti v proizvodnem podjetju� in

dne 15. decembra 2000: mag. MatejPo�arnik, disertacijo z naslovom: �Robno obmoènaintegralska metoda za numerièno modeliranje lebdeèihslojev�.

S tem so navedeni kandidati dosegliakademsko stopnjo doktorja tehniènih znanosti.

MAGISTERIJI

Na Fakulteti za strojni�tvo Univerze vLjubljani so z uspehom zagovarjali svoja magistrskadela, in sicer:

dne 25. oktobra 2000: Metod Èe�arek, deloz naslovom: �Eksperimentalni sistem za preverjanje�ivljenjske dobe velikih kotalnih le�ajev�;

dne 6. decembra 2000: Drago Kovaèiè, deloz naslovom: �Razvoj merilne in programske opremeza modernizacijo trgalnih strojev�;

dne 7. decembra 2000: Miroslav Haliloviè,delo z naslovom: �Analiza tehnolo�kih parametrovpri procesu kontinuirnega litja z vidika njihovegavpliva na mehanski odziv�;

dne 12. decembra 2000: Evald Kranjèeviè,delo z naslovom: �Termoenergetska analiza in nadzorrazpr�ilnega su�ilnika�;

dne 18. decembra 2000: Miha Bobiè, delo znaslovom: �Dinamika preizku�evali�èa za razvoj insimuliranje delovanja toplotne podpostaje�;

dne 19. decembra 2000: Peter Peternel,delo z naslovom: �Naèrtovanje rein�eniringa vmonta�i�;

dne 20. decembra 2000: Primo� Podr�aj,delo z naslovom: �Grobost optimalnega krmilnegasistema� in

dne 21. decembra 2000: Jo�e Lenart, deloz naslovom: �Spremljanje dobe trajanja parovodov�.

Na Fakulteti za strojni�tvo Univerze vMariboru so z uspehom zagovarjali svoja magistrskadela, in sicer:

dne 5. oktobra 2000: Andrej Poredo�, deloz naslovom: �Analiza toplotnih razmer daljinskihenergetskih sistemov�;

dne 8. novembra 2000: Danilo Rojko, deloz naslovom: �Doloèitev lomne �ilavosti na velikihpreizku�ancih in primerjava lomne �ilavosti dobljenena standardnih preizku�ancih� in

dne 15. novembra 2000: Andrej Hartman,delo z naslovom: �Uporaba umetne inteligence vokoljski vzgoji�.

S tem so navedeni kandidati dosegliakademsko stopnjo magistra tehniènih znanosti.

DIPLOMIRALI SO

Na Fakulteti za strojni�tvo Univerze vLjubljani so pridobili naziv univerzitetni diplomiraniin�enir strojni�tva:

dne 2. oktobra 2000: Metod ÈUK, Toma�JERAS, Janez KOGOV�EK, Elvis PRELAZ;

dne 27. oktobra 2000: Jurij GERBEC, MihaGREGORC, Borut HABIÈ, Ale� JEREB, Vito LOJK,Franc MAJDIÈ, Andrej MARLIN, Jaka PELHAN,Uro� PRIMO�IÈ;

dne 27. novembra 2000: Gregor JELENC,Tilen JENKO, �eljko KATU�IN, Borut MIHOLIÈ,Leon OMEJC, Miha PEKOLJ, Toma� VADNJAL;

dne 21. decembra 2000: Tilen KUHAR,Damijan MILO�EVIÈ, Rok NAGODE, Iztok �PAN;

dne 22. decembra 2000: Uro� AVSEC, Da-vid KAP�, Andreja SMRDELJ, Tadej �TRANCAR,Nebolj�a TOPIÆ, Bo�tjan ZAJC, Jernej ZORKO.

Na Fakulteti za strojni�tvo Univerze vMariboru so pridobili naziv univerzitetni diplomiraniin�enir strojni�tva:

dne 5. oktobra 2000: Andrej BENKO, Gre-gor SEDMINEK, Gorazd URLEB, Elvis VINCEK, Ale�ZOREC;

dne 26. oktobra 2000: Darko GROZDINA,Milan ZORKO;

dne 30. novembra 2000: Ante MOROVIÆ,Timotej �NAJDER, Aleksander VADNJAL, RobertVREÈKO;

dne 21. decembra 2000: Matej RO�IÈ, Si-mon SMOLAK.

*

Na Fakulteti za strojni�tvo Univerze vLjubljani so pridobili naziv diplomirani in�enirstrojni�tva:

dne 13. oktobra 2000: Bojan BIÈIÈ, VinkoCORN, Matej ERZNO�NIK, Janez GOLOB, MilanHRAST, Anton MARC, Toma� POPIT, AndrejRAJAR, Ivan �MON, Jure VIDEC, Bojan �MUC;

dne 16. oktobra 2000: Darko BERUS, An-ton GALE, Tone KOVAÈ, Andrej MEZINEC, MiranPENKO, Dejan STAMENKOVIÆ, Alojz �IMC, Toma��VAJGER, Marko WEBER, Toma� �ARKOVIÈ, Mar-ko �IBERNA;

dne 17. oktobra 2000: Anton KE�, DamijanLOZAR, Igor MARC, Matija OBOLNAR;

dne 10. novembra 2000: Ado BARBI�,

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Franc BOR�TNAR, Ale� DREMPETIÈ, VitomirStanko GORNIK, Peter HUMAR, Peter JERALA, Jo�eKASTELIC, Marko MLINAR, Iztok STARC, DejanVELIKANJE;

dne 7. decembra 2000: Bogdan JAZBEC,Tine VADNAL, Slavko VELKAVRH;

dne 8. decembra 2000: Marjan BO�IÈ,Tadej ÈERNE, Vojko FON, Andrej KAJFE�, SlavkoKAJFE�, Bo�tjan KERIN, Roman POTOÈNIK,Kristofer �TEMBERGAR, Janko ZIHERL;

dne 11. decembra 2000: Franc BANKO;dne 12. decembra 2000: Tadej DRNOV�EK.Na Fakulteti za strojni�tvo Univerze v

Mariboru so pridobili naziv diplomirani in�enirstrojni�tva:

dne 5. oktobra 2000: Matja� FLEISINGER,Dejan �LEMER;

dne 26. oktobra 2000: Peter HUDOURNIK,Bojan O�LAK, �eljko PUSTOSLEM�EK;

dne 30. novembra 2000: AndrejHRIBERNIK, Miran KERNDL, Roman KRESLIN,Slobodan MRKONJIÆ, Kristijan PAVLIN, IgorPLETER�EK, Miroslav POPLAS, Robert TURN�EK;

dne 21. decembra 2000: Zvonko KOPÈIÈ,Primo� POSINEK, Vid POVALEJ, Borut ZEMLJIÈ.

*

Na Fakulteti za strojni�tvo Univerze vLjubljani so pridobili naziv in�enir strojni�tva:

dne 7. decembra 2000: Anita PLESNIÈAR,Izidor SIR�E;

dne 8. decembra 2000: Marjan BAJUK, InaÈARIÆ, Damjan GOVEKAR, Danijel MILAVEC,Alenka OBERÈ, Rajko PETERLIN, Mitja PI�EK, SamoZIGMUND, Marko ZUPAN;

dne 11. decembra 2000: Franc GOMBAÈ,Matja� GRMEK, Mitja JUKIÈ GRM, Denis MARU�IÈ,Marko �VIGELJ, Robert TISOVEC, Luka �NIDAR�IÈ;

dne 12. decembra 2000: Marko BAJC,Bo�tjan BARTOL, Marjan GOVEKAR, RobertPOGORELC, Bo�tjan VODOPIVEC.

Na Fakulteti za strojni�tvo Univerze vMariboru so pridobili naziv in�enir strojni�tva:

dne 5. oktobra 2000: Bo�tjan DOBOV�EK,Stanko FILÈIÈ, Damir LUKE�IÈ, Bo�tjan PRESKER,Gorazd SMREÈNIK, Tone STAROVE�KI, Egon VRABIÈ;

dne 26. oktobra 2000: Andrej DROBNE,Andrej SOTEL�EK;

dne 30. novembra 2000: Mirko DOBNIK,Konrad HLADIN, Sebastjan PARADI�NIK, AntonPOTOÈNIK, Jo�e STEINER, Jo�e TITOV�EK;

dne 21. decembra 2000: Primo� CEPU�,Borut �VAJKER, Igor ZVER.

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Navodila avtorjemInstructions for Authors

© Strojni{ki vestnik 46(2000)11/12,797-798ISSN 0039-2480Navodila avtorjem


Instructions for Authors

Papers submitted for publication should comprise:- Title, Abstract, Main Body of Text and Figure Captions in

Slovene and English,- Bilingual Tables and Figures (graphs, drawings or photo-

graphs),- List of references and- Information about the authors.

Since 1992, the Journal of Mechanical Engineeringhas been published bilingually, in Slovenian and English. The twotexts must be compatible both in terms of technical content andlanguage. Papers should be as short as possible and should onaverage comprise 8 typed pages. In exceptional cases, at therequest of the authors, speciality papers may be written only inSlovene, but must include an English abstract.

The format of the paper

The paper should be written in the following format:- A Title, which adequately describes the content of the paper.- An Abstract, which should be viewed as a miniversion of the

paper and should not exceed 250 words. The Abstract shouldstate the principal objectives and the scope of the investiga-tion, the methodology employed, summarize the resultsand state the principal conclusions.

- An Introduction, which should provide a review of recentliterature and sufficient background information to allowthe results of the paper to be understood and evaluated.

- A Theory- An Experimental section, which should provide details of

the experimental set-up and the methods used for obtain-ing the results.

- A Results section, which should clearly and concisely presentthe data using figures and tables where appropriate.

- A Discussion section, which should describe the relation-ships and generalisations shown by the results and discussthe significance of the results making comparisons withpreviously published work. (Because of the nature of somestudies it may be appropriate to combine the Results andDiscussion sections into a single section to improve theclarity and make it easier for the reader.)

- Conclusions, which should present one or more conclu-sions that have been drawn from the results and subsequentdiscussion.

- References, which must be numbered consecutively in thetext using square brackets [1] and collected together in areference list at the end of the paper. Any footnotes shouldbe indicated by the use of a superscript1.

The layout of the text

Texts should be written in A4 format, with doublespacing and margins of 3 cm to provide editors with space towrite in their corrections. Microsoft Word for Windows isthe preferred format for submission. If you use another wordprocessor, please convert to normal ASCII (text) format.One hard copy, including all figures, tables and illustrationsand an identical electronic version of the manuscript must besubmitted simultaneously.

Please do not use a LaTeX text editor, since this isnot compatible with the publishing procedure of the Journal ofMechanical Engineering. Graphs, tables and equations in LaTeXmay be supplied in good quality hard-copy format, so that theycan be copied for inclusion in the Journal.

Equations should be on a separate line in the mainbody of the text and marked on the right-hand side of thepage with numbers in round brackets.

Units and abbreviations

Only standard SI symbols and abbreviations shouldbe used in the text, tables and figures. Symbols for physicalquantities in the text should be written in Italics (e.g. v, T, n,etc.). Symbols for units that consist of letters should be inplain text (e.g. ms-1, K, min, mm, etc.).

Èlanki morajo vsebovati:- naslov, povzetek, besedilo èlanka in podnaslove slik v

slovenskem in angle�kem jeziku,- dvojeziène preglednice in slike (diagrami, risbe ali

fotografije),- seznam literature in- podatke o avtorjih.

Strojni�ki vestnik izhaja od leta 1992 v dveh jezikih,tj. v sloven�èini in angle�èini, zato je obvezen prevod vangle�èino. Obe besedili morata biti strokovno in jezikovnomed seboj usklajeni. Èlanki naj bodo kratki in naj obsegajopribli�no 8 tipkanih strani. Izjemoma so strokovni èlanki, na�eljo avtorja, lahko tudi samo v sloven�èini, vsebovati pamorajo angle�ki povzetek.

Vsebina èlanka

Èlanek naj bo napisan v naslednji obliki:- Naslov, ki primerno opisuje vsebino èlanka.- Povzetek, ki naj bo skraj�ana oblika èlanka in naj ne

presega 250 besed. Povzetek mora vsebovati osnove, jedroin cilje raziskave, uporabljeno metodologijo dela,povzetekrezulatov in osnovne sklepe.

- Uvod, v katerem naj bo pregled novej�ega stanja in zadostneinformacije za razumevanje ter pregled rezultatov dela,predstavljenih v èlanku.

- Teorija.- Eksperimentalni del, ki naj vsebuje podatke o postavitvi

preskusa in metode, uporabljene pri pridobitvi rezultatov.- Rezultati, ki naj bodo jasno prikazani, po potrebi v obliki

slik in preglednic.- Razprava, v kateri naj bodo prikazane povezave in

posplo�itve, uporabljene za pridobitev rezultatov.Prikazana naj bo tudi pomembnost rezultatov inprimerjava s poprej objavljenimi deli. (Zaradi naraveposameznih raziskav so lahko rezultati in razprava, zajasnost in preprostej�e bralèevo razumevanje, zdru�eni veno poglavje.)

- Sklepi, v katerih naj bo prikazan en ali veè sklepov, kiizhajajo iz rezultatov in razprave.

- Literatura, ki mora biti v besedilu o�tevilèena zaporednoin oznaèena z oglatimi oklepaji [1] ter na koncu èlankazbrana v seznamu literature. Vse opombe naj bodooznaèene z uporabo dvignjene �tevilke1.

Oblika èlanka

Besedilo naj bo pisano na listih formata A4, zdvojnim presledkom med vrstami in s 3 cm �irokim robom,da je dovolj prostora za popravke lektorjev. Najbolje je, dapripravite besedilo v urejevalnilku Microsoft Word. Èeuporabljate kak�en drug urejevalnik besedil, prosimo, dabesedilo konvertirate v navadno ASCII (tekstovno) obliko.Hkrati dostavite odtis èlanka na papirju, vkljuèno z vsemislikami in preglednicami ter identièno kopijo v elektronskiobliki.

Prosimo, da ne uporabljate urejevalnika LaTeX, sajprogram, s katerim pripravljamo Strojni�ki vestnik, ne uporabljanjegovega formata. V urejevalniku LaTeX oblikujte grafe,preglednice in enaèbe in jih stiskajte na kakovostnem laserskemtiskalniku, da jih bomo lahko presneli.

Enaèbe naj bodo v besedilu postavljene v loèenevrstice in na desnem robu oznaèene s tekoèo �tevilko vokroglih oklepajih

Enote in okraj�ave

V besedilu, preglednicah in slikah uporabljajte lestandardne oznaèbe in okraj�ave SI. Simbole fizikalnih velièinv besedilu pi�ite po�evno (kurzivno), (npr. v, T, n itn.). Simboleenot, ki sestojijo iz èrk, pa pokonèno (npr. ms-1, K, min, mmitn.).

00-11/12stran 798


All abbreviations should be spelt out in full on firstappearance, e.g., variable time geometry (VTG).

Figures

Figures must be cited in consecutive numerical orderin the text and referred to in both the text and the caption asFig. 1, Fig. 2, etc. Figures may be saved in any commonformat, e.g. BMP, GIF, JPG. However, the use of CDR format(CorelDraw) is recommended for graphs and line drawings,since vector images can be easily reduced or enlarged duringfinal processing of the paper.

When labelling axes, physical quantities, e.g. t, v, m,etc. should be used whenever possible to minimise the need tolabel the axes in two languages. Multi-curve graphs should haveindividual curves marked with a symbol, the meaning of thesymbol should be explained in the figure caption.

All figure captions must be bilingual.Good quality black-and-white photographs or

scanned images should be supplied for illustrations. In certaincircumstances, colour figures may be considered.

Tables

Tables must be cited in consecutive numerical order inthe text and referred to in both the text and the caption as Table 1,Table 2, etc. The use of names for quantities in tables should beavoided if possible: corresponding symbols are preferred to minimisethe need to use both Slovenian and English names. In addition tothe physical quantity, e.g. t (in Italics), units (normal text), shouldbe added in new line without brackets.

All table captions must be bilingual.

The list of references

References should be collected at the end of thepaper in the following styles for journals, proceedings andbooks, respectively:[1] Tarng, Y.S., Y.S. Wang (1994) A new adaptive controler

for constant turning force. Int J Adv Manuf Technol9(1994) London, pp. 211-216.

[2] Èu�, F., J. Baliè (1996) Rationale Gestaltung derorganisatorischen Abläufe im Werkzeugwesen. Proceed-ings of International Conference on Computer Integra-tion Manufacturing, Zakopane, 14.-17. maj 1996.

[3] Oertli, P.C. (1977) Praktische Wirtschaftskybernetik.Carl Hanser Verlag, München.

Author information

The following information about the authorsshould be enclosed with the paper: names, complete postaladdresses, telephone and fax numbers and E-mail addresses.

Acceptance of papers and copyright

The Editorial Committee of the Journal ofMechanical Engineering reserves the right to decide whethera paper is acceptable for publication, obtain professionalreviews for submitted papers, and if necessary, require changesto the content, length or language.

Authors must also enclose a written statement thatthe paper is original unpublished work, and not under considerationfor publication elsewhere. On publication, copyright for the papershall pass to the Journal of Mechanical Engineering. The JMEmust be stated as a source in all later publications.

Papers will be kept in the archives of the JME.

You can obtain further information from:

Editorial Board of theJOURNAL OF MECHANICAL ENGINEERING

P.O.Box 197/IV1001 Ljubljana, Slovenia

Telephone: +386 (0)61 1771-428Fax: +386 (0)61 218-567

E-mail: [email protected]

Vse okraj�ave naj bodo, ko se prviè pojavijo,napisane v celoti, npr. èasovno spremenljiva geometrija (ÈSG).

Slike

Slike morajo biti zaporedno o�tevilèene inoznaèene, v besedilu in podnaslovu, kot sl. 1, sl. 2 itn. Posnetenaj bodo v kateremkoli od raz�irjenih formatov, npr. BMP,JPG, GIF. Za pripravo diagramov in risb priporoèamo CDRformat (CorelDraw), saj so slike v njem vektorske in jihlahko pri konèni obdelavi preprosto poveèujemo alipomanj�ujemo.

Pri oznaèevanju osi v diagramih, kadar je le mogoèe,uporabite oznaèbe velièin (npr. t, v, m itn.), da ni potrebnodvojezièno oznaèevanje. V diagramih z veè krivuljami, morabiti vsaka krivulja oznaèena. Pomen oznake mora bitipojasnjen v podnapisu slike.

Vse oznaèbe na slikah morajo biti dvojeziène.Za vse slike po fotografskih posnetkih je treba

prilo�iti izvirne fotografije ali kakovostno narejen posnetek.V izjemnih primerih so lahko slike tudi barvne.

Preglednice

Preglednice morajo biti zaporedno o�tevilèene inoznaèene, v besedilu in podnaslovu, kot preglednica 1,preglednica 2 itn. V preglednicah ne uporabljajte izpisanihimen velièin, ampak samo ustrezne simbole, da se izognemodvojezièni podvojitvi imen. K fizikalnim velièinam, npr. t(pisano po�evno), pripi�ite enote (pisano pokonèno) v novovrsto brez oklepajev.

Vsi podnaslovi preglednic morajo biti dvojezièni.

Seznam literature

Vsa literatura mora biti navedena v seznamu nakoncu èlanka v prikazani obliki po vrsti za revije, zbornike inknjige:[1] Tarng, Y.S., Y.S. Wang (1994) A new adaptive controler

for constant turning force. Int J Adv Manuf Technol9(1994) London, pp. 211-216.

[2] Èu�, F., J. Baliè (1996) Rationale Gestaltung derorganisatorischen Abläufe im Werkzeugwesen. Proceed-ings of International Conference on Computer Integra-tion Manufacturing, Zakopane, 14.-17. maj 1996.

[3] Oertli, P.C. (1977) Praktische Wirtschaftskybernetik.Carl Hanser Verlag, München.

Podatki o avtorjih

Èlanku prilo�ite tudi podatke o avtorjih: imena,nazive, popolne po�tne naslove, �tevilke telefona in faksater naslove elektronske po�te.

Sprejem èlankov in avtorske pravice

Uredni�tvo Strojni�kega vestnika si pridr�ujepravico do odloèanja o sprejemu èlanka za objavo,strokovno oceno recenzentov in morebitnem predlogu zakraj�anje ali izpopolnitev ter terminolo�ke in jezikovnekorekture.

Avtor mora predlo�iti pisno izjavo, da je besedilonjegovo izvirno delo in ni bilo v dani obliki �e nikjerobjavljeno. Z objavo preidejo avtorske pravice na Strojni�kivestnik. Pri morebitnih kasnej�ih objavah mora biti SVnaveden kot vir.

Rokopisi èlankov ostanejo v arhivu SV.

Vsa nadaljnja pojasnila daje:

Uredni�tvoSTROJNI�KEGA VESTNIKA

p.p. 197/IV1001 Ljubljana

Telefon: (061) 1771-428Telefaks: (061) 218-567

E-mail: [email protected]

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