Strain Gauge Report1

8/19/2019 Strain Gauge Report1

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University of the highlands and islands perth college

Strain Gauge

Aircraft structural

mechanics Report and

aerothermodynamicsCollins E Mbasha 14014188


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Strain Gauge

Contents

Introduction...................................................................................................................4

Experiment................................................................................................................4

Aim of the experiment...............................................................................................4

Tools and Equipments...............................................................................................4

Procedures...................................................................................................................

Surface preparation...................................................................................................

Installing strain gauge...............................................................................................

Sol!ent degreasing................................................................................................

Surface a"rading...................................................................................................

#ayout lines...........................................................................................................$Surface conditioning..............................................................................................$

%eutrali&ing............................................................................................................$

'andling................................................................................................................(

)onding.................................................................................................................*

Soldering techniques................................................................................................+

Testing.....................................................................................................................,-

Ta"le of alues....................................................................................................,-/alculations.................................................................................................................,,

0ormulas1.................................................................................................................,,

)ending equations...............................................................................................,,

Three point loading..............................................................................................,,

Solution1...................................................................................................................,,

Ta"le of !alues........................................................................................................,2

Graph......................................................................................................................,3

iscussion...............................................................................................................,3

Application of strain gauge.........................................................................................,3

/onclusion..................................................................................................................,

References.................................................................................................................,$

0igure ,1 Strain gauge. E/ircuit centre........................................................................4

0igure 21 Application of degreaser. Instruction )ulletin )5,2(5,4................................

0igure 31 Surface a"rading. Instruction )ulletin )5,2(5,4...........................................$

Collins Elia Mbasha 14014188 Page 2


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Strain Gauge

0igure 41 layout line. Instruction )ulletin )5,2(5,4.......................................................$

0igure 1 %eutrali&ing. Instruction )ulletin )5,2(5,4....................................................(

0igure $1 #ift tape at an angle. Instruction )ulletin )5,2(5,4.......................................(

0igure (1 place tape using reference mar6s. Instruction )ulletin )5,2(5,4.................(

0igure *1 prepare tape to apply adhesi!e 7 )ond. Instruction )ulletin )5,2(5,4........*0igure +1 Apply catalyst. Instruction )ulletin )5,2(5,4.................................................*

0igure ,-1 Apply 7 "ond 2-- Adhesi!e8 Instruction )ulletin )5,2(5,4........................*

0igure ,,1 single 9ipe. Instruction )ulletin )5,2(5,4...................................................*

0igure ,21 thum" pressure on strain gauge. Instruction )ulletin )5,2(5,4..................*

0igure ,31 Remo!e tape. Instruction )ulletin )5,2(5,4...............................................+

0igure ,41 stranded 9ire. )ulletin 3-+E.......................................................................+

0igure ,1 t9isted end. )ulletin 3-+E...........................................................................+

0igure ,$1 /onnecting lead 9ire to gauge. )ulletin 3-+E............................................+

0igure ,(1 Soldering. )ulletin 3-+E..............................................................................+

0igure ,*1 Apply 7 coat A. )ulletin 3-+E...................................................................,-

0igure ,+1 3 point loading...........................................................................................,-

0igure 2-1 stresses on aircraft "ody...........................................................................,4



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Strain Gauge

Introduction

This report co!ers a stress analysis experiment employing the strain gauge as the

main tool. Strain can "e defined as a process of solid deformation due to stress. A

Strain gauge is a sensing de!ice:apparatus 9here"y its resistance changes 9ith

applied force. It applies electrical measurement technique to measure mechanical

quantities. ;nderta6ing measurements on a "eam su"?ected to 3 point loading.

• Plotting graphical data and determining the elastic modulus of the "eam

• iscussing typical applications of strain gauge on aircrafts

!ools and E"uipments

• @or6ing surface

• Strain gauge /EA5-$524->B5,2-C

• Steel "eam

• /S7 egreaser

• Silicon /ar"ide Paper 32- D 4--C

• 75Prep /onditioner A

• 75Prep %eutrali&er A

• Gau&e sponges

• /otton applicators or cotton "uds

• P/T 527 Gage Installation Tape

• Stranded tinned5copper 9ire 32$50C

• iagonal cutter • @ire stripper



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Strain Gauge

• Soldering station

• Solder

• PT5, drafting tape

• ental pro"e

•

T9ee&ers• ernier calliper

• Ruler

• # shape metal

• P3 Strain Indicator and Recorder

• @eight ,--g to ,---gC

#rocedures

The follo9ing is a list of steps that ha!e "een follo9ed in conducting the experiment

to pro!ide data that 9ill "e used for analysis. These steps can "e di!ided into surfacepreparation8 strain gauge installation8 strain gauge soldering techniques and finally

strain gauge tests. These steps are according to 7icro57easurements Instruction

)ulletin )5,2+5*.

$urface preparation

To a!oid contamination all tools and equipments need to "e cleaned. In this case the

9or6ing surface 9as thoroughly cleaned "y using sponge gau&e 9ith %eutrali&er 75

/leaner. This is repeatedly done until satisfied. Instruction )ulletin )5,2+5*

Installing strain gaugeInstallation is executed in the follo9ing order to o"tain the most accurate data.

$olvent degreasing

,. Apply degreasing material to surface2. @ipe thoroughly using gau&e

0igure 21 Application of degreaser. Instruction )ulletin )5,2(5,43. This is carried out to remo!e greases8 oils and organic contaminants.

Instruction )ulletin )5,2+5*

$urface abrading

,. A"rade 9ith 32- grit silicon car"ide paper at the "onding position2. Add an adequate amount of 75Prep /onditioner A3. A"rade using the 9etted 32- grit silicon car"ide paper.

4. Repeat using the 9etted 4-- grit silicon car"ide paper.



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Strain Gauge

. /leaned "y using the 75Prep /onditioner A and gau&e sponge

0igure 31 Surface a"rading. Instruction )ulletin )5,2(5,4Instruction )ulletin )5,2+5*

%ayout lines

,. #ocate the desired position of strain gauge2. 7ar6 a straight perpendicular line using a "all point pen.

0igure 41 layout line. Instruction )ulletin )5,2(5,4


$urface conditioning

,. /lean test surface using 75Prep /onditioner A2. Scru" surface clean using cotton applicators until.3. @ipe in slo9 motion using 9ire gau&e.


&eutrali'ing

,. Add cleaning agent to surface2. @ipe using the cotton tipped applicator.3. @ipe surface gently in one direction




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Strain Gauge

.0igure 1 %eutrali&ing. Instruction )ulletin )5,2(5,4

(andling

,. >sing t9ee&ers remo!e gauge from protector co!er 2. Attach gauge to a piece of 7icro57easurements P/T27 tape3. #ift the tape 9ith the gauge attached to it at an angle

0igure $1 #ift tape at an angle. Instruction )ulletin )5,2(5,44. Place tape on surface aligning the triangles on the strain gauge 9ith your

mar6ed point.

0igure (1 place tape using reference mar6s. Instruction )ulletin )5,2(5,4

. prepare tape to apply adhesi!e 7 )ond

0igure *1 prepare tape to apply adhesi!e 7 )ond. Instruction )ulletin )5,2(5

,4



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Strain Gauge

)onding

,. Apply a thin uniform coat of 75)ond 2-- /atalyst.

0igure +1 Apply catalyst. Instruction )ulletin )5,2(5,42. Apply a thin uniform "ond of adhesi!e

0igure ,-1 Apply 7 "ond 2-- Adhesi!e8 Instruction )ulletin )5,2(5,43. Single 9ipe the tape using gau&e 9hile attaching it to surface

0igure ,,1 single 9ipe. Instruction )ulletin )5,2(5,44. Apply thum" pressure for a"out 2 minuites

0igure ,21 thum" pressure on strain gauge. Instruction )ulletin )5,2(5,4. Remo!e tape gently at an angle



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Strain Gauge

0igure ,31 Remo!e tape. Instruction )ulletin )5,2(5,4

$oldering techni"ues

,. 0irst strip and separate the lead 9ire strands in color

0igure ,41 stranded 9ire. )ulletin 3-+E

2. T9ist the 9hite and "lac6 strands together and the red separate

0igure ,1 t9isted end. )ulletin 3-+E3. Place the t9isted end on the gauge

0igure ,$1 /onnecting lead 9ire to gauge. )ulletin 3-+E4. Solder the lead 9ire to gauge

0igure ,(1 Soldering. )ulletin 3-+E. 0inally apply protecti!e coat o!er the gauge and soldering ?oints

0igure ,*1 Apply 7 coat A. )ulletin 3-+E



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Strain Gauge

!esting

• 7easure the "eam geometry and record !alues

• /onnect the three 9ire quarter "ridge circuit to the p3 indicator as follo9s

• Red 9ire PF8 9hite 9ire S58 "lac6 9ire ,2-C

•

Place "eam on support• )alance and &ero the gauge measure your span #

• Record !alues for different 9eights

*igure 1+, - point loading

!able of .alues

Parameter alues

" "readth of the "eamC 2-

d depth of the "eamC 3

# SpanC 3--

7ass 6gC StrainHC

- -

-., ,4

-.2 2(

-.3 4,

-.4

-. $*

-.$ *2

-.( +

-.* ,-*-.+ ,23

, ,3$



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Strain Gauge

Calculations

Gi!en the a"o!e data from the tests8 calculate the stress for each load increment

and plot it against the strain.

*ormulas,

)ending e"uations

M

I =

σ

Y = E

R

Therefore

σ = MY

I

@here"y1

7 "ending moment

I second moment of area

σ stress

distance from neutral axis

E elastic modulus

R radius of cur!ature

!hree point loading

M =WL

4

I =bd

3

12

Y =d

2

@here"y1

@ applied load 7ass J -.+*,

# span



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Strain Gauge

" "readth of the "eam

$olution,

Applying the set of formulas gi!en a"o!e "y first calculating the applied force in %e9t

on to use it to o"tain the "ending moment8 distance from the neutral axis and thesecond moment of inertia8 using these !alues the stress and thus the elastic

modulus 9ill "e calculated.

I =bd

3

12=

20×33

12=45

Y =d

2

=3

2

=1.5

E=σ

strain

!able of values

/alculations are executed on excel spread sheet to o"tain the follo9ing !alues.

Mass(g!

"eight(#!

Strain($%! M& "'4(#)!

*&M+,(M-a!

E&*strain(G-a!

0 0 0 0 0 0

0.1 0.981 14 73.575 2.453 175.2

0.2 1.962 27 147.15 4.905 181.6

0.3 2.943 41 220.725 7.358 179.4

0.4 3.924 55 294.3 9.81 178.4

0.5 4.905 68 367.875 12.263 180.3

0.6 5.886 82 441.45 14.715 179.5

0.7 6.867 95 515.025 17.168 180.7

0.8 7.848 108 588.6 19.62 181.6

0.9 8.829 123 662.175 22.073 179.5

1 9.81 136 735.75 24.525 180.3

The a!erage modulus of elasticity is 1/+2 3pa



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3raph

0 20 40 60 80 100 120 140 160

0

5

10

15

20

25

30

Stress(Mpa) against strain(µε)

Stress against strain

The slope of the graph is 1802 3pa gi!ing the elastic modulus of the of the

material.

iscussion

The plot on the a"o!e graph of $tress 5Mpa6 against strain 576 produces a straight

line implying that stress is directly proportional to stress therefore an increase in loador force applied to the material result to increase in solid deformation. The material

o"eys (oo9e:s la; 9hich states that stress is directly proportional to stress pro!ided

the elastic limit is not exceeded. The gradient of the line 1802 3pa is the modulus

of elasticity 9hich is the stiffness of this material8 it increases as the material

"ecomes stiffer. /omparing this !alue to that of steel


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Strain Gauge

deflections8 etc this are fe9 stress forces acting on a 9ing8 loo6ing at the 9hole

aircraft there are many stress forces in action 9hich can "e measured "y the using

the strain gauge and hence "e controlled "y introducing safety margins for flight

operations8 construction for future de!elopments. The follo9ing are "asic aircraft

"ody stresses

0igure 2-1 stresses on aircraft "ody

Strain gauges are used in to gi!e the life time of these structures of the aircraft gi!ing

a margin for replacement "efore structural failure.


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Strain Gauge

Conclusion

Studying the "eha!iour of material structure against stress can "e achie!ed using

strain gauging step "y step8 as this report has co!ered. The main aim is to sho9

efforts directed to9ard measuring loads on aircraft utili&ing strain gauges.

There are fe9 things to "e a9are such as the experiment requires cleanliness from

contamination of any sort therefore ma6es it delicate to conduct and requires

attention8 the experiment can "e impro!ed in order to o"tain more accurate readings

this is "y ha!ing 9eights placed on the "eam at a designated point for a change in

position !aries the result gi!ing a less accurate readings. There may "e unnoticed

faults during the "onding process.

Strain gauge has no mo!ing parts it is small and inexpensi!e8 simply a relia"le

sensor or measuring de!ice.



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Strain Gauge

=eferences

,. Ecircuit centre http1::9e".deu.edu.tr:mechatronics:T>R:strainLgauge.htm2.

Strain Gauge Report1

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