strain gauge report1
TRANSCRIPT
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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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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...........................................$
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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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• 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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. /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
Instruction )ulletin )5,2+5*
$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.
Instruction )ulletin )5,2+5*
&eutrali'ing
,. Add cleaning agent to surface2. @ipe using the cotton tipped applicator.3. @ipe surface gently in one direction
Instruction )ulletin )5,2+5*
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.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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)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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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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!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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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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" "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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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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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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=eferences
,. Ecircuit centre http1::9e".deu.edu.tr:mechatronics:T>R:strainLgauge.htm2.