objective lab1

8/9/2019 Objective Lab1

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ABSTRACT

This experiment is divided into four different individual experiments. Experiment 1 is

Getting to Kno the E!uipment"# here the usage of the four different gauges are $learl%explains and &% $arr%ing out the experiment# the $on$ept is understood. 'n this experiment as

ell# the usage of (ersatile )ata A$!uisition S%stem*()AS+ is explained. Experiment , is

The Bending S%stem" is on the measurement of strain endured &% metals hen experien$ing

&ending for example airplane ings. Experiment - is The Torsion S%stem"# is on the shear

and torsional strain endured &% a metal under tisting or experien$ing tor!ue. Experiment

is The Tension S%stem"# is on measuring the tension experien$ed &% metal.

/or all the experiment# theoreti$al $al$ulation as performed and the reading from the ()AS

s%stem is ta0en to $ompare and measure the a$$ura$% of the s%stem as ell as the $al$ulation.

Throughout the experiment# the ()AS s%stem pla%ed a maor role in the $al$ulation part.

The experiment are &ro0en don $learl% to &e read and understood.


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2B3ECT'(E

There are four parts to this experiment# the respe$tive o&e$tives for the experiments are as

follos4

Experiment 14 Getting to 0no the E!uipment

a+ To use the Bending s%stem to ma0e students &e$ome more familiar ith the use of

e!uipment

&+ To sho the e!uation used &% the strain displa%

$+ To use the Bending S%stem to sho and $ompare different strain &ridge $onne$tion

and sho the linearit% of strain measurement.

Experiment ,4 The Bending S%stem

a+ To sho ho to measure strains in an o&e$t that &ends and $ompare the results ith

theor%.

Experiment -4 The Torsion S%stem

a+ To sho ho to $onne$t and use shear and tor!ue *torsional+ strain gauges to measure

strains in an o&e$t that tists.

&+ To sho ho to $ompare displa%ed strains ith theor% for a torsion &eam.

Experiment 4 The Tension S%stem

a+ To sho ho to $onne$t and use strain gauges to measure strains in to dimensions.

&+ To sho ho to $ompare the displa%ed tensile strains in to dimensions ith theor%

and prove 5oisson6s ratio.


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T7E2R8

The Strain Gauges4

Strain Gauges are ele$tri$al sensors *transdu$ers+ that measure strains. Their ele$tri$alresistan$e $hanges &% a small amount hen an external for$e stret$hes or $ompresses them.

This $hange in resistan$e is dire$tl% proportional to displa$ement *strain+.

Thin metal foil element

The 9heatstone Bridge4

Figure 1 The Wheatstone Bridge

The &asis of most strain measurement is the 9heatstone Bridge# shon in /igure 11. 't has

four identi$al resistan$es *R1# R,# R- and R+ $onne$ted end to end in a diamond shape. An

input voltage *(+ $onne$ts a$ross to opposite $onne$tions. The output voltage is measured

at the other to $onne$tions.


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Figure 2 Voltage Against Resistance

Curve 1shos ho the output of a 9heatstone Bridge $hanges hen resistor R1 $hanges.

The output is not linear# &ut 't ill give good results for small resistan$e $hanges.

Curve 2shos ho the output of a 9heatstone Bridge $hanges hen resistor R1 and an

opposite resistor *R+ $hanges &% the same amount. The output is ti$e as mu$h as ith a

single resistan$e $hange# &ut again the $urve is not linear.

Curve 3shos ho the output of a 9heatstone Bridge $hanges hen resistor R1 and anada$ent resistor *R-+ $hanges &% the same &ut inverse amount. The output voltage of the

&ridge dou&les and the $urve &e$omes almost linear.

Curve 4shos ho the output of a 9heatstone Bridge $hanges hen resistor R1 and an

ada$ent resistor *R-+ $hanges &% the same &ut inverse amount# and also the resistan$e of the

opposite resistors R, and R $hange &% the same amount. The output is four times greater

than ith a single gauge and the $urve is linear.


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To $al$ulate the strain from the d$ voltage a$ross the &ridge# the Strain )ispla% uses a

standard e!uation4

*1+

)ire$t Stress# Strain and 8oung"s :odulus

Stress *;+

This is the for$e applied to a material over a 0non area. 't is found &% the e!uation4

Compressive stress is here the material is $ompressed. 't has a negative value.

Tensile stress is here the material is stret$hed. 't has a positive value.

Strain *


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:odulus of Rigidit% or Shear :odulus *G+

The Shear :odulus or :odulus of Rigidit% is a measure of the rigidit% of the material hen

in 6shear6 = hen it is tisting. 't is a ratio of the shear stress and the shear strain of the

material4


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E>?'5T:E@T

The equipment used for this experiment is a Strain Gauge Trainer SM1009

that is connected to the Versatile Data cquisition S!stem "VDS#$

The Tension System

The tension s!stem has a tensile test specimen$ This sho%s the strain in

di&erent materials %hen the! are stressed "or stretched# along their axis$

clamp holds the test specimen$ 'eights are added to the %eight hanger

connected to the (ottom of the specimen$ The %eights appl! a stretching

"tensile# force to the specimen$


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The Torsion System

The torsion s!stem is a solid) circular section torsion (eam$ torsion

(eam is a (ar or rod held (et%een t%o *xings$ +ne or (oth *xings can

rotate or t%ist independentl! of each other (! small amounts$ moments

arm *ts into the (earing so that the students can add %eights to t%ist the

(eam$ T%o sets of special torsion gauges measure the torsional "t%isting#

shear strainon the surface of the (eam at ,- degrees to the (eam length$

+ne set of gauges is underneath the (eam and the other is on top of the

(eam$

The Bending System

This is a solid) rectangular section cantile.er (eam$ This is a specimen

(eam held securel! at one end$ cantile.er can (end or /deect

up%ards or do%n%ards) (ut in this guide) the experiments %ill (end the

(eam do%n%ards$ 2our standard strain gauges measure the tensile and

compressi.e strains directl! in line %ith the (eam$ T%o gauges measure

thetensile strainon the top of the (eam$ The other t%o gauges measure

the compressive strain underneath the (eam$


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The Strain Display

The strain displa! is a metal (ox %ith a displa!) controls and input soc3ets$

The input soc3ets accept the signals from the color4coded strain gauges

on the three di&erent s!stems of the Strain Gauge Trainer$ The multiple

displa! sho%s the output .oltage measure across the strain (ridge and

automaticall! calculates and displa!s the strain$

The (ox also has a soc3et for connection to the hard%are of the VDS) to

allo% data to (e transferred to a computer$


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Virtual Data Acquisition System (VDAS)

The VDS is a t%o4part product"hard%are and soft%are# that %ill5

6 automaticall! log data from the experiment6 automaticall! calculates the data6 sa.e time6 reduce error6 create charts and ta(les from the data6 export data for processing in other soft%are


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Experiment 1 - Getting to Know the Equipment

5R2CE)?RE

1. Create four &lan0 results ta&les# ea$h similar to Ta&le ,. 'f %ou are to use ()AS# sele$t the

6Bending S%stem Experiment6. The softare ill $reate the ta&le as %ou do the experiment.

,. Conne$t the strain $onne$tion $a&le to the output so$0et of the Bending S%stem.

Quarter Bridge Connection

-. Conne$t onl% the red gauge *red ire and plug+ to the strain displa% as a !uarter &ridge$onne$tion. /it dumm% plugs to the other three so$0ets.

. Sit$h on the poer to the strain displa%. Adust the $onfiguration $ontrol to 1 *1 a$tivearm+. Adust the gauge fa$tor to &e the same as ritten on the &a$0 plate near the&ending s%stem.

. 'n %our results ta&le# note the gauge fa$tor and a$tive arms setting. 'f %ou are to use()AS# the softare ill automati$all% re$ord these for %ou.

. Carefull% slide a 0nife=edge hanger onto the &eam to the , mm position. Deave thee!uipment to sta&ilie for approximatel% one minute# then press and hold the 6ero6

&utton until the displa% readings &e$ome *ero+.

F. @ote the output voltage and strain readings into %our ta&le. 'f %ou are to use ()AS#$li$0 on the 6Re$ord )ata (alues6 &utton.

. 7oo0 a small eight hanger to the 0nife=edge hanger.H. The small eight hanger is 1 g. Add x 1 g eights to the eight hanger to give a

total eight *load+ of g. @ote the output voltage and strain readings into %our ta&le.'f %ou are to use ()AS# adust the load setting# then $li$0 on the 6Re$ord )ata (alues6

&utton.

1.'n in$rements of g# add more eights to the eight hanger until %ou rea$h g.At ea$h in$rement# note the output voltage and strain readings into %our ta&le. 'f %ouare to use ()AS# remem&er to adust the load setting at ea$h in$rement# then $li$0on the 6Re$ord )ata (alues6 &utton.

Half Bridge 1 Connection - Opposite Arms (two gauges measure the same strain)

11. Repeat the experiment &ut4

7 Conne$t the red gauge *red ire and plug+ and the &lue gauge *&lue ire andplug+ to the strain displa% as a half &ridge *opposite arms+ $onne$tion.

7 /it dumm% plugs to the other to so$0ets.

7 Adust the $onfiguration $ontrol to A$t I , *, a$tive arms+.

Half Bridge 2 Connection - Adjacent Arms (two gauges measure opposite strain)

1,.Repeat the experiment &ut4

7 Conne$t the red gauge *red ire and plug+ and the green gauge *green ire and

plug+ to the strain displa% as a half &ridge *ada$ent arms+ $onne$tion.

7 /it dumm% plugs to the other to so$0ets.


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7 Adust the $onfiguration $ontrol to A$t I , *, a$tive arms+.

ull Bridge Connection

1-.Repeat the experiment &ut4

7 Conne$t the red gauge *red ire and plug+ and the &lue gauge *&lue ire and

plug+# to opposite so$0ets.

7 Conne$t the %ello gauge *%ello ire and plug+ and the green gauge *green ire andplug+ to opposite so$0ets# to $omplete a full &ridge $onne$tion.

7 Adust the $onfiguration $ontrol to A$t I * a$tive arms+.

)ATA# 2BSER(AT'2@ A@) RES?DTS

Table 1 Quarter Bridge Connection

Table 2 Hal Bridge 1 Connection ! "pposite Arms #t$o gauges measure the same strain%


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Table & Hal Bridge 2 Connection ! Ad'acent Arms #t$o gauges measure opposite strain%

Table ( Full Bridge Connection


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0 1 00 800 00 , 00 - 00 :0 00

800

,00

:00

;00

1000

1800

1,00

1:00

f"x# < 0$=x > 0$==

f"x# < 1$,x 4 :$;:f"x# < 1$,8x 4 0$=

f"x# < 8$;8x > 1$;8

output voltage vs load

2ull ?ridge @inear "2ull ?ridge#Aalf ?ridge "adBacent# @inear "Aalf ?ridge "adBacent##

@inear "Aalf ?ridge "adBacent## Aalf ?ridge "opposite#

@inear "Aalf ?ridge "opposite## Cuarter

@inear "Cuarter#

@oad "3g#

Voltage "V#

)raph 1

Sample alculation5

Esing equation "1# to calculate the calculated strain5

4 36

2.110.51

13.64


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)'SC?SS'2@

The results o&tained shos o&serva&le differen$es hen the t%pes of $onne$tion of the &ridge

$hanges. Though the stain re$orded for all the &ridge are similar and $lose to ea$h other# the

output voltage *(o+ varies from one to another.

The o&tained data is used to plot output voltage vs load graph# and the graph is displa%ed as

Graph 1. Graph 1 shos that &% using /ull Bridge Conne$tion gives out highest output

voltage $ompared to all the other $onfiguration hile >uarter Bridge Conne$tion had the

loest voltage output and 7alf Bridge Conne$tion falls in &eteen this to $onfiguration.

To displa% the slope pre$isel%# the gradient of ea$h line is shon in Graph 1. All the gradient

o&tained for all the $onne$tion as linear.


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Experiment 2: The Bending Sytem

5R2CE)?RE

1$ reate a (lan3 results ta(le$ Ff !ou are to use VDS) select the ?endingS!stem Hxperiment$ The soft%are %ill create the ta(le as !ou do theexperiment$

8$ Ese the Vernier instrument "supplied# to accuratel! measure thedimensions of the specimen (eam$ Iecord !our measurements into !ourresults ta(le$ Ff !ou are to use VDS) enter the specimen dimensions into

the soft%are$

$ onnect the (ending s!stem strain gauges to the strain displa! as a full (ridge$

,$ arefull! slide the 3nife4edge hanger onto the (eam to the ,80 mm position$

-$ @ea.e the equipment to sta(iliJe for approximatel! one minute) then press andhold the Jero (utton until the displa! readings (ecome 0 "Jero#$

:$ Kote the strain reading into !our ta(le$ Ff !ou are to use VDS) clic3 on theIecord Data Values (utton$

=$ Aoo3 the small %eight hanger to the 3nife4edge hanger$

;$ The small %eight hanger is 10 g$ dd , x 10 g %eights to the %eight hanger togi.e a total %eight "load# of -0 g$ Kote the strain reading into !our ta(le$ Ff !ouare to use VDS) adBust the .alue of the mass to -0 g$

9$ Fn -0 g steps) add more %eights to the %eight hanger until !ou reach -00 g$ teach step) note the strain reading into !our ta(le$ Ff !ou are to use VDS)remem(er to increase the .alue of the mass (! -0 g at each increment$


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Table * the Bending +,stem

Calculate

d Strain(

Measure

d Strain(

Percenta

ge rror

(!"

0 0 0

11$: 1 18$0:

8$8 8= 1:$=

,$; ,0 1,$9,

,-$; - 1-$=8

-=$, := 1:$=8

:9 ;0 1-$9,

;0$: 9 1-$;

98$8 10= 1:$0-

10$; 180 1-$:0

11,$; 1 1-$;-Table - .ercentage /rror bet$een calculated and measured strain


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0 80 ,0 :0 ;0 100 180 1,00

-

10

1-

80

8-

f"x# < 0$1;x > 0$08

alculated Stress .s Displa!ed Strain

Strain

Stress

)raph 2

Sample alculation5

2orce5

< 0$0-3g x 9$;1 mLs8

< 0$,9 K

Second moment of Fnertia5

205

3

12

208.33mm4


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)'SC?SS'2@

The strain reading and $al$ulated strain reading as $om&ined to $he$0 for the per$entage

differen$e# although the readings are not ver% deviated there $al$ulated per$entage error as

a&out 1.J the most. The higher error o$$urred hen the load as in$reased and the

highest error as hen the load of g as pla$ed.

Graph , as plotted $al$ulated stress and displa%ed strain in order to o&tain the 8oung"s

:odulus of the &eam. /rom the gradient of the graph# it as noted that the 8oung"s :odulus

o&tained is 1F. G@m,and the a$tual modulus of the &eam is ,F G@m,. The per$entage

of error is 1-.J.


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Experiment 3: The Torion Sytem

!rocedure 1 - "o #se $hear and "or%ue $train &auges1 Stud% the strain gauge pattern for the Torsion S%stem. @ote that the gauges

underneath the &eam are identi$al to the gauges a&ove the &eam. 7oever# note that

the% are ea$h a rosette of to gauges. Ea$h gauge in the rosette ill measure the

same amount of strain# &ut their polarit% is inverted# as one measures $ompressive

tisting strain and the other measures tensile tisting strain.

, Create a &lan0 results ta&le# to re$ord the data. 'f %ou are to use ()AS# sele$t the

6Torsion S%stem Experiment6. The softare ill $reate the ta&le as %ou do the

experiment.

- Conne$t the &lue strain gauge to the strain displa% as a !uarter &ridge. Adust the

Strain )ispla% to sho the $orre$t gauge fa$tor and ACT I 1.

S$re the tor!ue arm into the threaded hole at the end of the torsion s%stem *see /igure

-+.

Deave the e!uipment to sta&ilie for approximatel% one minute# then press and hold

the 6ero6 &utton until the displa% readings &e$ome *ero+. 'f %ou are to use ()AS#

$li$0 on the 6Re$ord )ata (alues6 &utton.

Add a small eight hanger to the end of the tor!ue arm *the end of the tor!ue arm hasa smaller diameter part to a$$ept the eight hanger hoo0+.

F The small eight hanger is 1 g. Add H x 1 g eights to the eight hanger to give

a total eight *load+ of g. @ote the strain reading into %our ta&le and its polarit%

*L or =+. 'f %ou are to use ()AS# adust the value of the mass to g and $li$0 on

the 6Re$ord )ata (alues6 &utton.

Remove the eights and repeat the experiment# &ut use the red# %ello and green gauges.

!rocedure 2 - Compare $trains

1 Create a &lan0 results ta&le# similar to Ta&le . 'f %ou are to use ()AS# start a ne data

series and the softare ill $reate a ne ta&le for %ou.

, ?se the vernier instrument *supplied+ to a$$uratel% measure the dimensions of the

spe$imen &eam. Re$ord %our measurements into %our results ta&le. 'f %ou are to use

()AS# enter the measurements into the softare.

- Conne$t the torsion s%stem red and green gauges 6tensile tist6 as opposites. Conne$t the

&lue and %ello gauges 6$ompressive tist6 as opposites to $omplete a full &ridge.

Deave the e!uipment to sta&ilie for approximatel% one minute# then press and hold the

6ero6 &utton until the displa% readings &e$ome *ero+.

@ote the strain reading into %our ta&le. 'f %ou are to use ()AS# $li$0 on the 6Re$ord

)ata (alues6 &utton.


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Add a small eight hanger to the end of the tor!ue arm. The end of the tor!ue arm has a

smaller diameter part to a$$ept the eight hanger hoo0 at a 0non length and tor!ue

radius.

F The small eight hanger is 1 g. Add , x 1 g eights to the eight hanger to give atotal eight *load+ of , g. @ote the strain reading into %our ta&le. 'f %ou are to use

()AS# adust the value of the mass to , g and $li$0 on the 6Re$ord )ata (alues6

&utton.

Add more eights to the eight hanger until %ou rea$h g. @ote the strain reading

into %our ta&le. 'f %ou are to use ()AS# adust the mass to g and $li$0 on the

6Re$ord )ata (alues6 &utton


5art 1

Table 0

#auge $actor% 2&05

Strain#auge

Strain'eading

Polarit()*+"

,pe o- Strain(Co.pressive*,en

sile"/lue 48, 4 ompressi.e

'ed 8 > Tensile

ello 48 4 ompressi.e

#reen 8 > Tensile

Table


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5art ,

Table

Sample Cal$ulation4

I0.370.01

2981.75E-12 I1.88M

79.6G

I 1. :@m, I,-.E=

)'SC?SS'2@

'n the first part of the experiment - e are o&serving the t%pe of the strain experien$ed &% the

rod. There are four gauge on the rod and hen fixed in !uarter $onfiguration e"re a&le to

differentiate the polarit%. The o&tained strain value are similar ith all the gauges measured

&ut the negative and positive value indi$ates eather it $ompressive tisting strain or tensiletisting strain. /rom this understanding# e"re a&le to determine the gauges to &e used for

the se$ond part of the experiment.

'n the se$ond part of the experiment# the differen$es &eteen theoreti$al and displa%ed stain

are small and the values are $lose to ea$h other. The per$entage of error is &elo J for ea$h

of the values.


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Experiment 4: The Tenion Sytem

!rocedure 1 - "ensile $trains Onl' (ed and ellow &auges)

1 Create a &lan0 results ta&le to ta&ulate the data o&tained. 'f %ou are to use ()AS#

sele$t the 6Tension S%stem Experiment6. The softare ill $reate the ta&le as %ou do

the experiment.

, ?se the vernier instrument *supplied+ to a$$uratel% measure the dimensions of the

spe$imen *its idth and thi$0ness+. Re$ord %our measurements into %our results

ta&le. 'f %ou are to use ()AS# enter the measurements into the softare.

- Conne$t the red and %ello gauges of the Tension S%stem to the Strain )ispla% as a

half &ridge *opposite+. Set ACT I ,. @ote that these gauges ill onl% measure the

strain in the dire$tion of the for$e.

Deave the e!uipment to sta&ilie for approximatel% one minute# then press and hold

the 6ero6 &utton until the displa% readings &e$ome *ero+.

@ote the strain reading into %our ta&le. 'f %ou are to use ()AS# $li$0 on the 6Re$ord )ata

(alues6 &utton.

/it the large eight hanger to the &ottom of the Tension S%stem spe$imen. The large

eight hanger is g. Add . 0g to the eight hanger to give a total load of 1 0g. 'f

%ou are to use ()AS# adust the value of the mass to 1 0g.F @ote the strain reading into %our ta&le. 'f %ou are to use ()AS $li$0 on the 6Re$ord )ata

(alues6 &utton.

Add more eights in to the eight hanger in 1 0g steps# until %ou rea$h 1 0g. At ea$h

step# note the strain reading into %our ta&le. 'f %ou are to use ()AS remem&er to in$rease

the value of the mass &% 1 0g at ea$h step and then $li$0 on the 6Re$ord )ata (alues6

&utton.

!rocedure 2 - Compressi*e $trains Onl' (Blue and &reen &auges)

1 Create a &lan0 results ta&le# to ta&ulate the data. 'f %ou are to use ()AS# start a ne

data series. The softare ill $reate a ne ta&le for %ou., Repeat 5ro$edure 1 = Tensile Strains 2nl% *Red and 8ello Gauges+# &ut use the &lue

and green gauges.

!rocedure + - ull Bridge "ensile and Compressi*e $train

1 Create a &lan0 results ta&le# similar to Ta&le . 'f %ou are to use ()AS# start a ne data

series. The softare ill $reate a ne ta&le for %ou.

2 !epe"t #ro$edure 1 - Teni%e Str"in &n%y '!ed "nd (e%%ow G"uge)*+ut $onne$t "%%,our

gauges as a full &ridge. Set the $onfiguration $ontrol so that ACT I @.


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5art 1

Table 13

5art ,

Table 11


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)raph &

Sample Cal$ulation

= 1(2.99)

=0.33


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5art -

Table 12

)'SC?SS'2@

'n part 1# half &ridge $onfiguration as used to measure the stain. The strain o&served is

tensile strain# this as found through the polarit% of the values o&tained. The o&tained value

has a $lose proximit% ith the real value of the strain.

'n part ,# the gauges are repla$ed and the experiment as repeated again. The strain o&served

is $ompressive strain# this as found through the polarit% of the values o&tained. The

o&tained value has large deviation to the real value of the strain. After loo0ing through the

data and $on$luding# the reason $ould &e due to the rong gauge made on the ()AS s%stem

hi$h gave fairl% a large deviation from the theoreti$al reading. ?sing the data o&tained to

plot a graph# ta0ing the gradient of the graph hi$h is =,.HH. Su&stituting that values into

the formula to o&tain 5oisson"s Ratio# gives a values of vI.-- hi$h is found to &e in $lose

proximit% if $opper"s 5oisson"s# =0.35 .

'n part -# using all four gauge gives us a more pre$ise reading. Setting the Strain )ispla% to

mat$h %our $hosen strain gauge $onne$tions and their gauge fa$tor. Supplied ith the

e!uipment are spe$ial plugs ith &uilt=in high pre$ision dumm% resistors# for use hen %ou

onl% measure one or to a$tive arms *gauges+.


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objective lab1

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