Relations of behavior élasto-visco-plastic D [] · comprise is a kinematic variable...

Code_Aster VersiondefaultTitre : Relations de comportement élasto-visco-plastique d[...] Date : 25/09/2013 Page : 1/26Responsable : HABOUSSA David Clé : R5.03.04 Révision :

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Relations of behavior élasto-visco-plastic of Chaboche

Summary:

This document describes the integration of the model of behavior élasto-visco-plastic of Chaboche withnonlinear and isotropic kinematic work hardening, with taking into possible account of viscosity. The establishedmodel has one or two variable kinematics, and takes into account all the variations of the coefficients with thetemperature, and has an effect of work hardening on the tensorial variables of recall. This version also makes itpossible to model (in an optional way) the viscous character of the material (viscosity of Norton). It is integratedby the solution of only one scalar equation nonlinear. This model is available in 3D, plane deformation,axisymetry. Modeling in plane constraint uses a method of condensation static (of Borst). One gives alsoelements to identify the coefficients of the relation of behavior.

Warning : The translation process used on this website is a "Machine Translation". It may be imprecise and inaccurate in whole or in part and isprovided as a convenience.Copyright 2019 EDF R&D - Licensed under the terms of the GNU FDL (http://www.gnu.org/copyleft/fdl.html)


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Contents1 Models élasto-visco-plastics of Chaboche available in Code_Aster .................................................... 32 Description of the models ..................................................................................................................... 4

2.1 Description of the models .............................................................................................................. 42.2 Addition of the effect of memory .................................................................................................... 72.3 Insertion of the effect of nonproportionality of the loading ............................................................. 7

3 Integration of the relations of behavior ................................................................................................. 83.1 Integration of the terms taking of account it not radiality ............................................................. 113.2 Integration of the effect of memory .............................................................................................. 133.3 Calculation of tangent rigidity ...................................................................................................... 163.4 Significance of the internal variables ........................................................................................... 17

4 Principle of the identification of the parameters of the model. ........................................................... 195 Elements of validation. ....................................................................................................................... 206 Bibliography ........................................................................................................................................ 217 Description of the versions of the document ...................................................................................... 21Annexe 1 Tangent matrix of behavior .................................................................................................... 23Annexe 2 Resolution of the equation F ( p) = 0 .................................................................................. 26



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1 Models élasto-visco-plastics of Chaboche available inCode_AsterFor the structural analysis subjected to cyclic loadings, work hardenings isotropic (linear or not) andlinear kinematics classics [R5.03.02] and [R5.03.16] are not sufficient any more. In particular, onecannot correctly describe the stabilized cycles obtained in experiments on a tensile specimensubjected to an alternated imposed deformation or a traction and compression.

If one seeks to precisely describe the effects of a cyclic loading, it is desirable to adopt modelingsmore sophisticated (but easy to use) such as the model of Saïd Taheri, for example, cf [R5.03.05], or ifthe number of cycles is limited the model of Jean-Louis Chaboche who is introduced here.

Actually, the model of Chaboche can be more or less sophisticated. Models developed in Code_Astercomprise is a kinematic variable (VMIS_CIN1_CHAB and VISC_CIN1_CHAB) that is to say two(VISC_CIN2_CHAB and VMIS_CIN2_CHAB), and of isotropic work hardening. The choice to use two variable kinematics complicates certainly the model, but makes it possible tocorrectly identify the uniaxial tests in a broader range of deformations [bib2], [bib7]. A certain numberof identifications of the parameters of this model were carried out mainly for the stainless steels A316and A304 ([bib7], [bib8]).

The models comprise 8 parameters (only one kinematic variable) or 10 (two variable kinematics),introduced into the order DEFI_MATERIAU :CIN1_CHAB (CIN1_CHAB_FO) = _F (

♦ R_0 = R_0,◊ R_I = R_I, (useless if B=0)◊ B = B , (defect: 0.)♦ C_I = C_I, ◊ K = K , (defect: 1.)◊ W = W , (defect: 0.)♦ G_0 = G_0, ◊ A_I = A_I, (defect: 0.)

)CIN2_CHAB (CIN2_CHAB_FO) = _F (

♦ R_0 = R_0,◊ R_I = R_I,

useless if B=0 or if effect of memory)◊ B = B , (defect: 0.)♦ C1_I = C1_I, ♦ C2_I = C2_I, ◊ K = K , (defect: 1.)◊ W = W , (defect: 0.)♦ G1_0 = G1_0,♦ G2_0 = G2_0,◊ A_I = A_I, (defect: 0.)

)The 8 or 10 parameters are real constants. All these parameters can depend on the temperature(keywords CIN1_CHAB_FO or CIN2_CHAB_FO) and the expected values are of type function.

If one wants to introduce besides viscosity (models VISC_CIN1_CHAB and VISC_CIN2_CHAB), it isalso necessary to provide in the order DEFI_MATERIAU, under the keyword LEMAITRE (orLEMAITRE_FO) parameters NR and UN_SUR_K, which can depend on the temperature.



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LEMAITRE (LEMAITRE_FO) = _F (♦ NR = N,♦ UN_SUR_K = 1/K

The parameter UN_SUR_M keyword LEMAITRE (respectively LEMAITRE_FO) must obligatorily be putat zero (respectively with the identically worthless function).

It is possible also to take into account an effect of memory of largest deformation plastic using themodels ( VISC_CIN2_ MEMO and VMIS_CIN2_MEMO ) . The keywords to be informed are:

MEMO_ECRO (MEMO_ECRO_FO) = _F (♦ Q_M = Qm,♦ Q_0 = Q0,♦ DRIVEN = driven, ♦ ETA = eta, (defect: 0.5)

In the event of loading nonproportional, it is necessary to enrich the model, by the data of twoadditional parameters:

CIN2_NRAD = _F (◊ DELTA1= 1 (défaut= 1.E+0), ◊ DELTA2= 2 (défaut= 1.E+0),

with 0≤1≤1 , 0≤2≤1

The laws of behavior are accessible in all the orders using the keyword BEHAVIOR with the followingrelations : VISC_CIN1_CHAB, VISC_CIN2_CHAB, VISC_CIN2_MEMO, VISC_CIN2_NRAD, VISC_MEMO_NRAD, VMIS_CIN1_CHAB, VMIS_CIN2_CHAB, VMIS_CIN2_MEMO, VMIS_CIN2_NRAD, VMIS_MEMO_NRAD.

Notice : the model VISCOCHAB [R5.03.14] also allows to represent the effects described in thisdocument. It comprises moreover of the terms of additional restoration and work hardening. But itsuse in structural analyses is more expensive in time calculation (because one must solve either by themethod of Runge-Kutta or by the method of Newton a system of 27 equations to 27 unknown factors).Moreover, it poses problems of robustness when the step of time is large, because the method ofNewton can fail. That involves many subdivisions of the step of time.

The models described in this document are optimized, insofar as they result in solving only one scalarresolution, and the method of very robust resolution used (method of Brent or secant, cf [R5.03.14]); itis thus a model able to integrate quickly great steps of time.

In the continuation of this document, one describes the characteristics of the various models. Onepresents then the detail of their digital integration in link with the construction of the coherent tangentmatrix. Lastly, one also gives some elements for the identification of the characteristics of material.

2 Description of the models 2.1 Description of the models

At any moment, the state of material is described by the deformation , the temperature T , plasticdeformation p , cumulated plastic deformation p and the tensor of recall X . The equations ofstate then define according to these variables of state the constraint =H Id (broken up intoparts hydrostatic and deviatoric), the isotropic share of work hardening R and the kinematic shareX :



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H=13 tr

=K tr −th with th= T-T ref Id éq 2.1-1

=− H Id=2 − p éq 2.1-2

R=R p éq 2.1-3

X=X p , p=X 1 p , p X 2 p , p éq 2.1-4where K , , and coefficients of X p and R p are characteristics of material which candepend on the temperature. More precisely, they are respectively the modules of compressibility andshearing, the thermal dilation coefficient, the functions of isotropic and kinematic work hardening. Asfor T réf , it is the temperature of reference, for which one regards the thermal deformation as beingworthless.

Note:

For the model VISC_CIN1_CHAB only the only tensorial variable is considered X 1 p thusX 2 p =0 . This remains valid for all the continuation: one will describe the two models formally

in the same way, the model VISC_CIN1_CHAB resulting from VISC_CIN2_CHAB while supposingX 2 p =0 .

The evolution of the plastic deformation is controlled by a normal law of flow to a criterion of plasticityof von Mises:

F , R , X = −X 1−X 2eq−R p with Aeq= 32 A : A éq 2.1-5̇ p=̇ ∂ F

∂= 3

2̇−X 1−X 2

−X 1− X 2eqéq 2.1-6

ṗ=̇= 23 ̇ p : ̇ p éq 2.1-7As for the plastic multiplier ̇ , it is obtained by the condition of coherence:

{si F0 ou ˙F0 ̇=0si F=0 et ˙F=0 ̇≥0 éq 2.1-8Note:

Evolution of the variables X1 and X2 is given by:

X 1=23 C1 p 1

X 2=23C 2 p 2

̇1=̇p−1 p 1 ṗ

̇2=̇p− 2 p 2 ṗ

éq 2.1-9

Functions C p , p and R p are defined, in accordance with [bib2] by:



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R p =R∞ R0−R∞ e−bp

C1 p =C1∞ 1 k−1 e−wp

C2 p =C 2∞ 1k−1 e−wp

1 p =10 a∞1−a∞ e−bp

2 p =20 a∞1−a∞ e−bp

The evolution of these coefficients makes it possible to represent work hardening in several ways:classical isotropic work hardening (monotonous or cyclic) by R( p) , “work hardening” of thecoefficients relating to the kinematics terms by C ( p) and p . (cf [feeding-bottle11]). Theexpressions into exponential are similar to the definition of nonlinear kinematic work hardening (eq.2,1.9), and (in their principle) represent a variation of the coefficients since the subscripted value by 0(for p=0 ) up to the subscripted value by ∞ when p becomes large. This implies that the coefficients b and w are supposed to be positive. In the contrary case, amessage of alarm is transmitted, because the solution calculated risk to be not physics.

The presence of viscosity can model in a simple way [bib2] by replacing the condition of coherence[éq 2.1-8] by:

ṗ= 〈F 〉K N

éq 2.1-10

〈F 〉 positive part of F (hooks of Macauley), K , N characteristics of viscosity (Norton) ofmaterial. Unchanged all the other equations of the model are left. It will be seen that such anintroduction of viscosity involves only minor modifications of the implicit algorithm of integration of thelaw of behavior.

The effect of memory consists in replacing the evolution of isotropic work hardening by:

F , R , X = −X 1−X 2eq−R0−R p Ṙ=b Q−R ṗ Q=Q 0Qm−Q0 1−e−2 q f p , , q = 23 J 2

p− −q≤0 defining a field characterizing the maximum plastic deformations,of which q measurement the ray and the center, calculated according to a law of normality

i.e. with the law of evolution: ̇=1−

q̇ n* . The parameter (which does not exist in the initial

formulation [bib.2]), I makes it possible to partially take into account the effect of memory. If it is equalto 0.5, the initial formulation is found. If it is worth 1, q is equal to the standard of the greatest plasticdeformation reached. If it is much lower than 0.5, the effect of memory is taken into account partlyonly.

Note:

• The definition of X1 and X2 in the form [éq 2.1-9]:

• allows to keep a formulation which takes into account the variations of the parameterswith the temperature without introducing term in Ṫ as in [bib.4], in the same way that theviscoplastic model of Chaboche. These terms are necessary because their not taken intoaccount would lead to inaccurate results [bib4].

• allows to have a coherent writing with the thermodynamic expression of the plasticpotential [bib2] (p.221).



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• It is noted that the functions C1 p ,1 p ,C2 p ,2 p , R p intervening in thepreceding equations make it possible all the three to model various effects of work hardening notlinear. The introduction of work hardening, is on the level of the kinematic part, by C p , that isto say on the level of the term of recall, by the function p , the same effect on theclassification tests [bib2] does not have. The use of a model with p allows in particular toidentify more easily of strong cyclic work hardenings. Several work of identification of thecoefficients of the models of Chaboche was carried out besides on the basis of model with a workhardening represented by p ([bib5], [bib6]), in particular for the stainless steels.

2.2 Addition of the effect of memory

Implicit discretization of the problem with effect of memory led to a system of 20 equations to 20unknown factors [7]:

6 éq: = −

−2 − p

1 eq :

− 23 C11−− 23 C 22−−23 C 1 1 p −23 C 2 2 p eq=R0R− RK p t 1/N

6 eq : p=

32 p

−23 C11

−−23 C 22

−−23 C 11−

23 C 22

R0R p K p t 1/N = p n

1 eq: f p , , q =23J 2 ε p−−q=

23 32 p− : p− −q≤0

6 eq: = 1− q

n*

with R=b Q−R p Q=Q 0Qm−Q0 1−e−2μ q−Δq

q= H F 〈n:n*〉 p

i= p− i i

− p1 i p

n*=32

p−J 2 p−

n=32

−23 C11−

23 C 22

−23 C11−23 C 22 eqthe 20 unknown factors are: , p , , p , q

2.3 Insertion of the effect of nonproportionality of the loadingIn a way similar to the model VISCOCHAB, one can insert in VISC_CIN2_CHAB/MEMO equationstranslating the effect nonproportional. model obtained is here called VISC/VMIS_CIN2_NRAD, orVISC/VMIS_MEMO_NRAD (according to whether one takes into account or not the effect of memory).



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̇1=̇p−1 p 1 ṗ

̇2=̇p− 2 p 2 ṗ

becomes: ̇1=̇

p−1 p 111−11:nn ṗ̇2=̇

p−2 p 221− 2 2:nn ṗ

with n= 32 −X 1−X 2 −X 1−X 2eq thus n :n=1 and in particular ̇ p= 32 pn It is easy to check that this new expression of the evolution of the internal variables i cost with thepreceding expression if i=1 , or in the event of radial situation , where one can pose i=n . It comes then: ̇ i=̇

p− i ṗ in1− in =̇ p− i ṗ i .

3 Integration of the relations of behaviorTo numerically carry out the integration of the law of behavior, one carries out a discretization in timeand one adopts a diagram of implicit, famous Euler adapted for elastoplastic relations of behavior.Henceforth, the following notations will be employed: A- , A and A represent respectively thevalues of a quantity at the beginning and the step of time considered thus that its increment during thestep. The problem is then the following: knowing the state at time t− as well as the increments ofdeformation (resulting from the phase of prediction (cf reference material from STAT_NON_LINE[R5.03.01])) and of temperature T , to determine the state of the internal variables at time t aswell as the constraints .

One takes into account the variations of the characteristics compared to the temperature by noticingthat:

H=KK−H

−K tr − th éq 2.2-1

= −−2 − p = −2 p éq 2.2-2

with

= −−2

Within sight of the equation [éq 2.2-1], one notes that the hydrostatic behavior is purely elastic if Kis constant. Only the treatment of the deviatoric component is delicate.

In the absence of viscous term, the relation of discretized coherence is:

Elastic mode: F≤0 and p=0Plastic mode: F=0 and p≥0

On the other hand, in the presence of viscosity, the condition of coherence is replaced by the equation[éq 2.1 - 10] which, discretized, is written:

p t= 〈F 〉K

N

⇔〈F 〉=K p t 1/N

In other words, while posing:



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F=F−K p t 1/N

the viscoplastic increment of cumulated deformation is determined by:

Régime élastique : F≤0 et p=0Régime viscoplastique : F=0 et p≥0

éq 2.2-3

Finally, by adopting an implicit discretization, the only difference between the laws in plastic andviscoplastic behavior lies in the form of the function of load F : one observes a complementary termin the event of viscosity there. In fact, incremental plasticity seems the borderline case of incrementalviscoplasticity when K tends towards zero. This convergence was already described byJ.L. Chaboche and G. Cailletaud in [bib3].

In the continuation of this paragraph, one will thus detail the integration of the viscoplastic law. To findthe case of the plastic behavior, it is enough to take K=0 in the equations below (one recalls thatthe user to place itself in this case must obligatorily remove the keyword LEMAITRE or LEMAITRE_FOorder DEFI_MATERIAU).

−X 1−X 2= e−

23 C11

−−23 C22

−−2 p− 23 C 11C 22

Equations of flow [éq 2.1-6] and [éq 2.1-7], once discretized, and the condition of coherence [éq 2.2-3]are written (by noticing that p= ):

p=32 p

e−23 C 11

−−23 C 22

−−2 p−23 C11−23 C 22

e−23 C11−−23 C 22−−2 p−23 C11−23 C 22eqéq 2.2-4

F≤0 p≥0 F p=0 éq 2.2-5

The treatment of the condition of coherence (preceding equation) is classical. One starts with anelastic test ( p=0 ) who is well the solution if the criterion of plasticity is not exceeded, i.e. if:

e−23 C 1 p− 1−− 23 C2 p− 2−eq−R p−0 éq 2.2-6In the contrary case, the solution is plastic ( p0 ) and the condition of coherence is reduced toF=0 . To solve it, it is shown that one can bring back oneself to a scalar problem while expressing p and 1 ,2 according to p . By gathering the equations of the problem resulting from

the implicit discretization, one obtains the system of equations:



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e− 23 C11−−23 C22−−2 p−23 C11− 23 C 22eq=R p K p t 1 /N

éq 2.2-7

p=32 p

e−23 C 11

−−23 C 2 2

−−2 p−23 C11−23 C22

R p K p t 1 /N éq 2.2-8

1= p−11 p

2= p− 22 p

éq 2.2-9

In this writing, it should well be noted that p= p− p and i=i−i and that C i , i arefunctions of p . By considering the three last equations, this linear system in p and i can besolved to express these quantities according to p . Indeed, it is equivalent to:

p R p 3 pK p t 1/N = p 32 e− C11−−C 22−− C 11−C 2 2 éq 2.2-101 11 p = p−11− p2 12 p= p−22−Dp

éq 2.2-11

While calculating C11 and C22 and by replacing them in the expression of p oneobtains an expression of p according to p only:

C11= C 111 p p−C111− p

11 p =M 1 p p−M 1 p 1 p 1−C22= C 212 p p−C 2 22

− p12 p =M 2 p p−M 2 p 2 p2−

avec M i p =C i p

1 i p p

éq 2.2-12

By deferring this expression in the expression of p one finds:

p= 1

R p 3M 1M 2 pK p t 1/N

32 p e− p C1−M 11 p 1−C 2−M 2 2 p 2−

what is simplified in:



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p= 1D p 32 p e− p M 11−M 22− éq 2.2-13

with:

D p =R p 3M 1 p M 2 p pK p t 1/N

It now only remains to replace p in the expressions of C11 and C22 to express thisterm according to p by:

C11=M 1D 32 p e− p M 11−M 22− −M 11 p1−

C22=M 2D 32 p e− p M 11−M 22− −M 22 p2−

then to substitute the expression obtained thus that p according to p in the equation F=0 ,and one obtains a scalar equation in p to solve, namely:

F p = e− 23 C11−− 23 C 22−−2 p−23 C 11− 23 C 22eq−R p −K p t 1/N

=0

what is simplified in:

F p =R p K p t

1/N

D p e−23 M 11−− 23 M 22−eq−R p −K p t 1/N

=0éq 2.2-14

This scalar equation in p is solved numerically, by a research method of zero of function (methodof secants which one briefly describes in appendix 2).

It is normalized in the following way:

F p =1− D p

e− 23 M 11−− 23 M 22−eq=0

éq 2.2-15

Once determined p , one can calculate p using the equation [éq 2.2-13] then 1 and2 using the equations [éq 2.2-11]. It any more but does not remain to calculate the tensor of the

constraints, by the equations [éq 2.2-1] and [éq 2.2-2], and to bring up to date the internal variables1 and 2 .

Note:

• an interesting borderline case (for the validation of this model) arises while posing i=0 .One finds oneself then exactly in the situation of linear kinematic work hardening (ifR p = y , [R5.03.02]) or of mixed work hardening for R p unspecified (cf

[R5.03.16]), • these models are also available in plane constraints, by a global method (static condensation

due to R. of Borst) [R5.03.03].

3.1 Integration of the terms taking of account it not radiality Warning : The translation process used on this website is a "Machine Translation". It may be imprecise and inaccurate in whole or in part and isprovided as a convenience.Copyright 2019 EDF R&D - Licensed under the terms of the GNU FDL (http://www.gnu.org/copyleft/fdl.html)


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The discretization leads to: i= p− i p [ i i- i1−i i- i:nn ]

Let us calculate

i :n= 32 p− i p i 32 ii i :n1− i 32 i1−i i :n

while having posed i- :n= 32 i . O N can thus express i :n according to p and i

i :n 1 i p = 32 p 1− i i that is to say i :n=32 p 1− i i 1 i p

One can thus express i only according to p and i= 23 i- :n and to propagatethese modifications in method of resolution used previously:

i 1i i p = p− i pi i-−i p1−i i- :nn− i p1− i i :nn

By using the expression of i :n in fonction of p and i ,

i 1i i p = p−i p i i-−i p 1− i 32 i n−i p 1−i 32 p 1−i i 1i p

n

i 1i i p = p−i p i i-−i 1−i i p

1i p p

i 1i i p = pN i p , i− i p i i- with

N i p , i=1i pi−i 1− i i

1 i p

There still, one can check that if i=1 , one finds the equations without effect ofnonradiality.

To continue to solve, it is necessary to calculate:

C i i=M i N i p−i p iM i i

- with M i=C i

1i i p

S I although the calculation of the increase in plastic deformation is similar to the classicalcase:

p= 32 pn with n= 32−

23 C1 1−

23 C 22

−23 C11−23 C 22eq.

By using the expressions calculated previously as well as the expression of the criterion:Warning : The translation process used on this website is a "Machine Translation". It may be imprecise and inaccurate in whole or in part and isprovided as a convenience.Copyright 2019 EDF R&D - Licensed under the terms of the GNU FDL (http://www.gnu.org/copyleft/fdl.html)


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e− 23 C11−−23 C22−−2 p−23 C11− 23 C 22eq=R p K p t 1/ N

it comes:

p R p 3K p t 1/N

p 3M 1N 1M 2N 2=32 p e− 23 M 1 1-− 23 M 22- thus n= 32

e−23 M 11

-−23 M 2 2

-

D with

D p; 1; 2=R p K p t 1/N

p 3M 1 N 1M 2 N 2

Notice : L with still, O N can check that if one does not take account of the nonradial effect,i=1 , which involves N=1 . One finds well the classical expression of the normal n .

In this case; there are 3 scalar unknown factors: p , 1 , 2 . In fact, it is possible toexpress 1 and 2 according to p by noticing that :

n= 32 e−

23 M 11

-−23 M 22

-

e−23 M 11-−23 M 2 2- eq. One can thus determine n according to p only,

then to calculate directly i= 23 i- :n , which becomes explicit functions then of p . Tosolve, it is enough to replace the expressions above in the criterion (what returns to to writen :n=1 ):

F p = e−23 M 11-−23 M 22- eq−D p ;1 p ;2 p =0

3.2 Integration of the effect of memoryIn the case of the effect of memory, the function R p is not known any more explicitly, but via thesystem of equations:

1 eq : f p , , q =23J 2 p− −q=

23 32 p− : p− −q≤0

6 eq: =1−η H F 〈n:n* 〉 pn*=1− q

n*

With

R=b Q−R p Q=Q 0Qm−Q0 1−e−2 q− q n*=32

p−J 2 p−



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Knowing p , one starts by calculating f p ,− , q− .

If this quantity is negative, then the solution of the system managing the effect of memory is:0,0 ξq .

In the contrary case, knowing p , it is necessary to find q and such as:

f p , , q =23 J 2 p−−− −q−− q=0

=1−η

q n*=1−

q 32 p− p−−−

32q− q

Because p=1

D p 32 p e− p M 11−M 2 2− can be calculated explicitly from p.

It remains:

1 1− q q− q = 1− q p− p−−

q− q ⇒

q− q = 1−η q p−− ⇒ = 1− q p−−

q− q

while deferring in the equation of surface threshold: f p , , q =0

23

J 2 p−−− −q−− q=0=23

J 2 p−− ∣1− 1−η q q− q ∣−q−− q=0⇔2

3J 2 p−− ∣η q− q ∣−q− q ηq− q =0 si q− q0

what makes it possible to calculate explicitly q from p :

q= 23 J 2 p−− − q−

It then remains to modify the function of isotropic work hardening while calculating:

Q=Q 0Qm−Q0 1−e−2 q−Δq then R=b Q−R p

One can thus use the resolution of the scalar equation in p (éq 2.2-14) by using the expressionsabove.

Note:

• In [bib2] one also finds the expression : dq= H f 〈n:n*〉 dp . This last equation results from the expression of speed of the multiplier. In the implicit discretizationcarried out here, it is not used for the resolution (since then the system would comprise moreequations than unknown factors). Moreover, the 3 equations given in [bib2] are redundant: indeed,knowing p should be determined a tensorial variable and a scalar variable. q Howeverwe have a tensorial equation and two scalar equations.



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This is due to the fact that the equation dq= H f 〈n:n*〉 dp is resulting from the condition ofcoherence df =0 (what is specified in [bib2]) but is not used for the implicit resolution of theproblem.

df p , , q = p−

J 2 p−d p−

p−J 2 p−

d −dq=n : n*dp−n* :n* dq−dq=n: n* dp−2dq=0

It would be useful for an explicit resolution, by expressing the derivative compared to the time of allthe sought variables.

• an interesting criterion, given in [bib2] makes it possible to adjust the parameters of the effect of memory. Indeed, by considering a simple loading of traction and compression, one must find

q=12 p

max (while choosing =12

). For a material point in uniaxial load, the fields (uniform)

have as components:

= 1 0 00 0 00 0 0 p=p 1 0 00 −12 00 0 −12

In this case, at the time of the first uniaxial load in the direction x :

−=0q−=0 q= x

p

In this case, q=12 pmax , implies that

=12

and =12 p

Moreover, in the case of a cycle of symmetrical traction compression (in plastic deformation), one

obtains, during the first symmetrical discharge (with =12

):

−=12

pmax

q−=12xxpmax

q= 23 J 2 p−q−= ∣xxpmin−−∣−12 xxpmax=12 ∣ xxpmin∣q=q− q=xx max

p =12 xx

p

=1− q p−−

q− q=−1

2 xx max

p

=0=0

what corresponds well to the expected result (cf [bib2]): field F=0 centered on the origin, and of raythe half-amplitude of plastic deformation.



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3.3 Calculation of tangent rigidityIn order to allow a resolution of the total problem (equilibrium equations) by a method of Newton[R5.03.01], it is necessary to determine the coherent tangent matrix of the incremental problem.

This matrix is composed classically of an elastic contribution and a plastic contribution:

=

e

−2

p

éq 2.3-1

with e=2 p , which gives again in particular e=−−2

One from of deduced immediately that in elastic mode (classical or pseudo-discharge), the tangentmatrix is reduced to the elastic matrix:

=

e

éq 2.3-2

For that, one once more adopts the convention of writing of the symmetrical tensors of order 2 in theform of vectors with 6 components. Thus, for a tensor a :

a=t [a xx a yy azz 2axy 2axz 2a yz ] éq 2.3-3

If moreover the hydrostatic vector is introduced 1 and stamps it deviatoric projection P :

1= t [1 1 1 0 0 0 ] éq 2.3-4

P=Id−13 1⊗1 éq 2.3-5

where ⊗ is the tensorial product

Then the matrix of coherent tangent rigidity is written for an elastic behavior:

∂e

∂ =K 1⊗12 P éq 2.3-6

On the other hand, in plastic mode, the variation of the plastic deformation is not worthless any more.

One derives compared to e , knowing that one a:

p

=

p

e.

e

=2

p

e. P éq 2.3-7

s space of the symmetrical tensorsP projector on the diverters

To calculate p

e, one uses the expression of p according to e and p :



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p= 1D p 32 p e− p M 11−M 22− what is written in the form:

p=A p eB1 p 1−B2 p 2

−

Thus:

p

e=A p Id e⊗ A p

e B1 p e

⊗1− B2 p e

⊗2−

Quantities of the type A p e

are calculated using: A p e

= A p p

p e

Finally, it any more but does not remain to calculate the variation of p : p e

One uses for that: F p , e =0

F p , e =R p K p t

1/N

D p e−23 M 11−−23 M 22−eq−R p −K p t 1/N

=0

F , p p , e p = − F , e p , e e ⇒ p

e= −

F, e

p , e F , p p , e

éq 2.3-8

The detail of calculations is given in appendix 1.

The initial tangent matrix, used by the option RIGI_MECA_TANG is obtained by adopting the behavior of the preceding step (elastic or plastic, meant by internal variable being worth 0 or 1) and while making tend p towards zero in the preceding equations.

3.4 Significance of the internal variablesInternal variables of the two models at the points of Gauss (VELGA) are:

• V1 = p : cumulated plastic deformation (positive or worthless)• V2 = : being worth n (iteration count internal) if the point of Gauss plasticized during the

increment or 0 if not.

The following internal variables are, for modeling 3D:

• For the model VMIS/VISC_CIN1_CHAB • V3 = 1 xx • V4 = 1 yy • V5 = 1 zz • V6 = 1 xy • V7 = 1 xz



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• V8 = 1 yz

• For the model VMIS/VISC_CIN2_CHAB• V3 = 1 xx • V4 = 1 yy • V5 = 1 zz • V6 = 1 xy • V7 = 1 xz • V8 = 1 yz • V9 = 2 xx • V10 = 2 yy • V11 = 2 zz • V12 = 2 xy • V13 = 2 xz • V14 = 2 yz •

For modelings C_PLAN, D_PLAN, and AXIS :

• V7 = 0• V8 = 0• V13 = 0• V14 = 0

• For the model VMIS/VISC_CIN2_MEMO• V3 = 1 xx • V4 = 1 yy • V5 = 1 zz • V6 = 1 xy • V7 = 1 xz • V8 = 1 yz • V9 = 2 xx • V10 = 2 yy • V11 = 2 zz • V12 = 2 xy • V13 = 2 xz • V14 = 2 yz

• V15 = R p • V16 = q

• V17 = xx • V18 = yy • V19 = zz • V20 = xy



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• V21 = xz • V22 = yz •• V23 =

p xx

• V24 = p yy

• V25 = p zz

• V26 = p xy

• V27 = p xz

• V28 = p yz

4 Principle of the identification of the parameters of themodel.In the simplest case (only one kinematic variable, 1=cste ,C1=cste , R p = y ) coefficients ofthe model 1 ,C1 can be identified on a simple tensile test uniaxial, or of course a cyclic curve ofwork hardening.

Indeed in the uniaxial case, the model is reduced in 1D to [bib2]:

dX 1=C1d

p−1 X 1d p ,=±1

∣−X 1∣= y

that one can integrate (in monotonous loading) in the following way:

X 1=C11 X 10−C 11 exp −1 p−0p ,=±1

= yX 1

whose asymptote of the traction diagram makes it possible to obtain C11

by:

p∞ X 1C11

thus yC11 and whose slope in the beginning provides C1 (if X 1

0=0 ) : p0 Ẋ 1C1− y1 X 1

0 X 10=C1− y1 X 1

For a model has two variable kinematics, without isotropic work hardening, a traction diagram stillallows to find these relations:

p∞ yC11C2 2 and the slope in the beginning is worth C1C2Warning : The translation process used on this website is a "Machine Translation". It may be imprecise and inaccurate in whole or in part and isprovided as a convenience.Copyright 2019 EDF R&D - Licensed under the terms of the GNU FDL (http://www.gnu.org/copyleft/fdl.html)


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But apart from these simple cases a digital identification is necessary to obtain the parameters. Onewill be able to make this identification for example on tensile tests compression to imposeddeformation. (cf. 10).

5 Elements of validation.The tests allowing the elementary validation of these behaviors are:

test title behavior (S)elementary tests of robustness

comp001f test of robustness law of behavior 3D VMIS_CIN1_CHAB VMIS_CIN1_CHABcomp001g test of robustness law of behavior 3D VMIS_CIN2_CHAB VMIS_CIN2_CHABcomp002b test of robustness law of behavior 3D VISC_CIN1_CHAB VISC_CIN1_CHABcomp002c test of robustness law of behavior 3D VISC_CIN2_CHAB VISC_CIN2_CHABcomp002h test of robustness law of behavior 3D VISC_CIN2_MEMO VISC_CIN2_MEMOcomp008g variation temperature in the behavior VMIS_CIN1_CHAB VMIS_CIN1_CHABcomp008h variation temperature in the behavior VMIS_CIN2_CHAB VMIS_CIN2_CHABcomp008j variation temperature in the behavior VISC_CIN1_CHAB VISC_CIN1_CHABcomp008k variation temperature in the behavior VISC_CIN2_CHAB VISC_CIN2_CHABcomp008i variation temperature in the behavior VMIS_CIN2_MEMO VMIS_CIN2_MEMOcomp008l variation temperature in the behavior VISC_CIN2_MEMO VISC_CIN2_MEMO

thermoplastic tests of the IPSIhsnv124c test phi2as number 1 VMIS_CIN1_CHAB VMIS_CIN2_CHABhsnv124d test phi2as number 1 VMIS_CIN1_CHAB VMIS_CIN2_CHABhsnv125c test phi2as number 2: traction, shearing, temperature variables VMIS_CIN1_CHAB VMIS_CIN2_CHABhsnv125e test phi2as number 2: traction, shearing, temperature variables VMIS_CIN2_MEMO

retimingssna109a model VISC_CIN2_CHAB with 550 degrees, prevalent viscosity VISC_CIN2_CHABssna110a model retiming VISC_CIN2_CHAB on 4 traction diagrams VISC_CIN2_CHAB

effect of memoryssnd105a tensile test with maximum memory of work hardening VMIS_CIN2_MEMOssnd105b tensile test with maximum memory of work hardening VISC_CIN2_MEMOssnd105c traction with maximum memory of work hardening axis VISC_CIN2_MEMOssnd111a validation effect of memory VISC_CIN2_MEMO VISC_CIN2_MEMO

Traction-shearingssnv101b test of traction-shearing in plane constraints (chaboche) VMIS_CIN1_CHAB VMIS_CIN2_CHABssnv101c test of traction-shearing 3D (chaboche) VMIS_CIN1_CHAB VMIS_CIN2_CHABssnv101d test of traction-shearing in plane deformations (chaboche) VMIS_CIN1_CHAB VMIS_CIN2_CHABssnv118d tensile test shearing in 3D (viscochab/ VISC_CIN2_MEMO) VISC_CIN1_CHAB VISC_CIN2_CHAB

great deformationsssnd107b multiple traction-rotations gdef_log in kinematic 3D VMIS_CIN2_CHAB VMIS_CIN2_MEMO

Effect of nonproportionalityssnd105d tensile test with maximum memory of work hardening and not radiality VMIS_CIN2_NRAD VISC_CIN2_NRADssnd115a test of traction-torsion with loading nonproportional VMIS_CIN2_NRAD

A validation compared to experimental results was carried out in (cf. 10 ), on traction-torsion andtensile tests compression. It makes it possible to highlight the effect of memory and nonproportionality.



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6 Bibliography1 P. MIALON, Elements of analysis and digital resolution of the relations of elastoplasticity. EDF -

Bulletin of the Management of the Studies and Research - Series C - N° 3 1986, p. 57 -89.

2 J.LEMAITRE, J.L.CHABOCHE, Mechanics of solid materials. Dunod 1996

3 J.L.CHABOCHE, G.CAILLETAUD, constitutive Integration methods for complex equations,Methods Computer in Applied Machanics Engineering, N°133 (1996), pp 125-155

4 J.L.CHABOCHE, Cyclic viscoplastic constitutive equations, Newspaper of Applied Mechanics,Vol.60, December 1993, pp. 813-828

5 R.FORTUNIER, Law of behavior of Chaboche: identification of the plastic parameters élasto - andélasto-visco-plastics of steel EDF-SPH between 20°C and 600°C. NoteFRAMATOME/NOVATOME, NOVTUDD90011, October 1990

6 C.MIGNE, Retiming of the parameters of the model of kinematic plasticity nonlinear of SYSTUS.Modeling of the phenomenon of progressive deformation with cyclic consolidation ofmaterial. Note FRAMATOME EE/R.DC.0286. September 1992.

7 J.J.ENGEL, G.ROUSSELIER, Behavior in uniaxial constraint under cyclic loading of theaustenitic stainless steel 17-12 Mo with very low carbon and nitrogenizes control.Identification of 20)C with 600°C of a model of elastoplastic behaviour to nonlinearkinematic work hardening. Note EDF/DER/EMA N°D599 MAT/T43 (1985)

8 P.GEYER, C.COUTEROT, characterization of steel 304L used at the time as of tests“deformation, progressive” on CUMULUS and identification of the parameters of themodel of Chaboche, Note EDF/DER/HT-26/93/040/A

9 R . DE BORST “the zero normal stress condition in plane stress and Shell elastoplasticity”Communications in applied numerical methods, Flight 7, 29-33 (1991)

10 J.M.PROIX “ Fascinating viscoplastic behavior of account it not proportionality of the loading”EDF R & D - CR-AMA12-284, 12/12/12

11 J.L.CHABOCHE, A review of nap plasticity and viscoplasticity constitutive theories, Inter.Newspaper of Plasticity, Vol.24, 2008, pp. 1642-1693

7 Description of the versions of the documentVersion Aster Author (S) or

contributor (S),organization

Description of the modifications

5 P.SchoenbergerEDF/R & D /MMN

Initial text, law of Chaboche

7 E.Lorentz,J.M.ProixEDF/R & D /AMA

Addition of the laws VMIS_CIN1_CHAB, VMIS_CIN2_CHAB

8 P. of Bonnières,J.M.ProixEDF/R & D /AMA

Addition of viscosity: laws VISC_CIN1_CHAB andVISC_CIN2_CHAB, and suppression of the law CHABOCHE.

9.3 J.M.ProixEDF/R & D /AMA

Addition of the law VMIS/VISC_CIN2_MEMO, fascinating ofaccount the effect of memory of maximum work hardening.

11 3 J.M.ProixEDF/R & D /AMA

Addition of the law VMIS/VISC_CIN2_NRAD, fascinating ofaccount the effect of nonproportionality of the loading.

12.1 J.M.Proix Addition of the remark on the positivity of the coefficients K and W,Warning : The translation process used on this website is a "Machine Translation". It may be imprecise and inaccurate in whole or in part and isprovided as a convenience.Copyright 2019 EDF R&D - Licensed under the terms of the GNU FDL (http://www.gnu.org/copyleft/fdl.html)


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EDF/R & D /AMA card 21019



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Annexe 1 Tangent matrix of behavior

To obtain the tangent behavior in the elastoplastic case, it is necessary to calculate d p

d e [éq 2.3-7].

One uses for that the expression of p according to e and p , which is written in the form:

p= 3 p2D p

eB1* p 1

−B2* p 2

−

with

Bi* p =− p

M i p D p

M i p =C i p

1i i p p

D p =R p 3M 1 p N 1 p ,1M 2 p N 2 p ,2 pK p t 1/N

The following definitions are pointed out:

R p =R∞ R0−R∞ e−bp

C i p =C i∞ 1 k−1 e−wp

i p = i0 a∞ 1−a∞ e−bp

thus:

p

e= 3 p

2D p Id

3 p2D p e

⊗ e B1

* p e

⊗1− B2

* p e

⊗2−

Quantities of the type A p e

are calculated using: A p e

= A p p

p e

These various terms are expressed by:

• 3 p2D p p

= 32I p

with I p = 1D p −

D' p D2 p

p

• Bi

* p p

=−M i

' p D p

p−M i p . I p =H i p

Let us detail the calculation of D ' : • In the case of the effect of memory, it is enough to modify the term R' p .

Like R=R− R=R−bQ p −R−

1b p p=R− b p

1b p QMQ0−QM e−2 q−R−

R' p = b1b p Q−R

−

1b p−2 p Q−QM

∂ q∂ p = b1b p Q−R

−

1b p−2μΔp Q0−QM

∂ q∂ p



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however q= 23 J 2 p−− −q− thus ∂ q∂ p= p−−

J 2 p−−∂ p

∂ p

and p

p= 3 p2D p p

e B1

* p p

1− B2

* p p

2−= 3

2I p eH 1* p 1−H 2* p 2−

• In the case of not proportionality ( 1≠1 or 2≠1 ), some derivative are modified:

M i' p =

C i' p

1 ii p p−

C i p 1ii p p

2 i'i pi i

D'=R' KN t p t

1N−13M 1 N 1M 2 N 2 p M 1

' N 1M 2' N 2M 1 N 1

'M 2 N 2'

with N i'=

1i' i p i−1 i i i i−1i

' −N i ii' p

1 i p

It remains to calculate: p e

One thus uses, following [éq 2.3-8]: p e

= −F

, e p , e

F , p p , e

F p , e =S eq p , e −R p −K p t 1 /N

=G p , e −R p −K p t 1/N

with S=A eB11

−B22− A=

R p K p t 1/N

D p Bi=−

23

M i p R p K p t 1/N

D p

Then, while posing Rv p =R p K p t 1/N

:

δpδ σ e

= −G , σ e p , σ

e G , p p , σ e −Rv' p

=−

32Rv p D p

SS eq

32

SS eq

: S , p−Rv' p

=−32

RvDS eq

A σ eB1α1−B2α2− 32

SS eq

: S , p−Rv' p

=−32L1 p . σ

eL21 p α1−L22 p α2

−

L3 p ¿

with



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L1 p =Rv

2 p D2 p ×S eq

=A2 p S eq

L21 p =Rv p D p

B1 p 1S eq

L22 p =Rv p D p

B2 p 1Seq

L3 p =32

SSeq

: A' p eB1' p 1−B2' p 2−−R' p − KN t p t 1N−1

¿

Finally, p

e puts itself in the form:

p

e=3

2 pD p

Id32 I S p

e I a1 p 1− I a2 p 2

− ⊗ e

H s1 eH a11 1−H a21 2−⊗1−H s2 eH a12 1−H a22 2− ⊗2−

with:

I S p =-32I p .

L1 p L3 p

I a1 p =-32I p L21 p L3 p

I a2 p =-32

I p L22 p L3 p

H s1 p =-3

2H 1 p . L1 p L3 p

H a11 p =-3

2H 1 p L21 p L3 p

H a21 p =- 3

2H 1 p L22 p L3 p

H s2 p =-3

2H 2 p . L1 p L3 p

H a12 p =-3

2H 2 p L21 p L3 p

H a22 p =-3

2H 2 p L22 p L3 p



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Annexe 2 Resolution of the equation F ( p) = 0It is a question of solving a nonlinear scalar equation by seeking the solution in a confidence interval. For that,one proposes to couple a method of secant with a control of the interval of research. That is to say the followingequation to solve:

f x =0 , x∈[a ,b ] , f a 0 , f b 0 éq A2-1

The method of the secant consists in building a succession of points xn who converges towards the solution.It is defined by recurrence (linear approximation of the function by its cord):

xn1= xn−1− f xn−1 xn−xn−1

f x n− f xn−1 éq A2-2

In addition, if xn1 was to leave the interval, then one replaces it by the terminal of the interval in question:

{si xn1a alors xn1 :=asi xn1b alors xn1 :=b éq A2-3On the other hand, if xn1 is in the interval running, then one reactualizes the interval:

{si xn1∈[ a ,b ]et f x n10 alorsa=x n1si xn1∈[a ,b ] et f xn10 alorsb=xn1 éq A2-4One considers to have converged when f is sufficiently close to 0 (tolerance to be informed). As for the firsttwo leader characters, one can choose the terminals of the interval, or, if one has an estimate of the solution,one can adopt this estimate and one of the terminals of the interval.

Note:This method functions well if there is only one solution in the interval [a ,b ] . Without that being formallyshown, one can note that f 0 0 . One seeks then b such as f b 0 .

One leaves for that b= se 23 C11−− 23 C22−eq−R p−

3m

If f b 0 , one multiplies b by 10 and one tests if f b 0 , and so on, until finding a value b suchas f b 0 . One is sure that there is then at least a solution on [a ,b ] .


1 Models élasto-visco-plastics of Chaboche available in Code_Aster2 Description of the models2.1 Description of the models2.2 Addition of the effect of memory2.3 Insertion of the effect of nonproportionality of the loading

3 Integration of the relations of behavior3.1 Integration of the terms taking of account it not radiality3.2 Integration of the effect of memory3.3 Calculation of tangent rigidity3.4 Significance of the internal variables

4 Principle of the identification of the parameters of the model.5 Elements of validation.6 Bibliography7 Description of the versions of the documentAnnexe 1 Tangent matrix of behaviorAnnexe 2 Resolution of the equation F ( p) = 0

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