AE4736-L1 2013 -FINAL
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Transcript of AE4736-L1 2013 -FINAL
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AE4736 Experimental Techniques in Structural Analysis
AE4736 Experimental Techniquesin Structural AnalysisLecture 1 Philosophy of easurement
!r "o#er $ro%es
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'n this Lecture
'ntro(uctions )utline of the *ourse
easurement Systems
"e%ie+ of Physical ,nits
!efinitions
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*ourse Lecturers
!r "o#er $ro%es-L".
!r/ir/ aarten0aer -*iT$.
3
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"o#er $ro%es2 ea( ofAerospace !T La5oratory
easurement Technolo#y Al#orithmsfor2
Experimental echanics !T in Pro(uction Assem5ly
!T in aintenance
Structural ealth onitorin#
4
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Experimental echanics 3! )ptical Tomo#raphy of crac #ro+th
in in( Tur5ine 0la(e $8"P
9olume optical elasto#raphy for $8"P
3! strain measurement usin#shearo#raphy
*rac #ro+th an( (eformation of+oo(en structures (ue to temp/ "
:
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Pro(uction Assem5ly Selection of !T;S Technolo#y
*
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aintenance >ey topics for !T assessment2
8laps= lea(in# e(#es of +in#s= 5ir( strie=car#o (oors
ulti
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Structural ealth onitorin#
'nte#ration +ith !T aintenance9i5ration monitorin# of +in( tur5ines
Lam5 +a%e ultrasonic -P@T 8)S.
8i5re optic sensors for #as pipeline repair
!emonstrator ri#s2
in#5ox rotatin# ri#
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AE4736 Experimental Techniques in Structural Analysis
hich aster Trac are youstu(yin#B
C
!onDt no+
Aerospace aterials an(
anufacturin#
Aerospace Structures an(Aircraft !esi#n
)ther
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AE4736 Experimental Techniques in Structural Analysis
@oome( in
1
Aerospace aterials an( anufacturin#
Aerospace Structures an( Aircraft !esi#n)ther
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AE4736 Experimental Techniques in Structural Analysis
Typical Ans+ers to Sur%ey < 1 o+ (o you rate your no+le(#e of
measurement principlesB ee(s'mpro%ement
o+ (o you rate your no+le(#e ofelectronicsB ee(s 'mpro%ement
o+ (o you rate your no+le(#e of optospecs?
-static. !efinition of resolution
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AE4736 Experimental Techniques in Structural Analysis
::
-static. !efinition of resolution
V trans(ucer
%$ =".!S: .esolution is the smallest chan'e ininput that still results in a quanti(iablechan'e at the output
W
The resolution o( a system can be:
G !iscrete: ire
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AE4736 Experimental Techniques in Structural Analysis
:6
*ontinuous resolutionB
The resolution o( the ideal continuous system is in(initesimal
Ioever) in reality the noise puts a limit to it There(ore)the resolution o( a continuous system is also discrete
ideal continuous response noisy continuous response
smallestdetectable
chan'e inresponse
Examples of (iscrete resolution
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Examples of (iscrete resolution
"ee( s+itch
ma#nets
.esolution 8 magnets2N
electric current
rotatin' heel
'
.esolution 8 windD
N 1
V
V
,out
9olt 1 9olt
,out
+ire
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:
Trans(ucer specifications
Sensiti%ity
"esolution*ross tal
ysteresis
*reep an( "elaxationEqui%alent noise= S" (ynamic
ran#e
'naccuracy
=orin' ran'e 8 validity limits (or 'iven speci(ications
The ma#or>specs?
!efinition of cross tal
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:C
!efinition of cross
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6
Trans(ucer specifications
Sensiti%ity
"esolution*ross tal
ysteresis
*reep an( "elaxationEqui%alent noise= S" (ynamic
ran#e
'naccuracy
=orin' ran'e 8 validity limits (or 'iven speci(ications
The ma#or>specs?
!efinition of hysteresis -memory effect.
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!efinition of hysteresis -memory effect.
Iysteresis is the property that a transducer responds di((erentlyto increasin' and decreasin' inputs The transducer there(ore
seems to JrememberK the ma'nitude o( the precedin' input value
input
o
utput
Typical transducer hysteresis
maximum hysteresis
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6&
maximum hysteresis
Iysteresis disadvanta'e: !efines a non
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Trans(ucer specifications
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Trans(ucer specifications
Sensiti%ity
"esolution*ross tal
ysteresis
*reep an( "elaxationEqui%alent noise= S" (ynamic
ran#e
'naccuracy
=orin' ran'e 8 validity limits (or 'iven speci(ications
The ma#or>specs?
*reep an( "elaxation
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*reep an( "elaxation
reep: "esponse W chan#es +hile input V is constant
.elaxation: "esponse W is chan#in# +hile input V is alrea(y Oero
=orse yet: creep is time*rate /(requency1 dependent N
V WS
Time
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0
strain
"KY
L
A
0
p
creep
*
*
strain
time
0 *
! EA
A
plate
#au#e
plate loadin'
Erelax
ation
E
'au'e response
!
!
Trans(ucer specifications
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Trans(ucer specifications
Sensiti%ity
"esolution*ross tal
ysteresis
*reep an( "elaxationEqui%alent noise= S" (ynamic
ran#e
'naccuracy
=orin' ran'e 8 validity limits (or 'iven speci(ications
The ma#or>specs?
Equi%alent noiseK9; K9
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8 X error W X noise),TSX error X noise
K9; K9
K9
"esultin# noise -error. is not easy to compare +ith input quantity/hat (oes it mean2 1 m9 output noise if you +ant to measure 1 B
K
X noise),TW
K
8 X noise),T;S S
This mo(el is simpler an( equi%alent in the accuracy analysis/Equi%alent noise M noise),T;S K
K9
oise in time si#nal
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#
time
noise part
V W X noiseS
K9
oise in time si#nal2
pea
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time
noise part
V W X noiseSK9
oise po+er spectral (ensity M2
n(f)
oise spectral (ensity M n(f)
K9&;O
V/ Hz
2n(f ) df
frequency
noise
oise ener#y M
88T-n.
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orin# ran#es
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7&
S
&ay apply to input or output: speci(y throu'h unit or /pre(erably1 explicitlyN
V Z V Z V1 W Z W Z W1S
ElectricalHmechanical orin' ran'es
S
S W M 7/: 9 X;< si#nal
Bias in output
9olt
1: 9olt
-8ull
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p
Sensiti%ity
"esolution*ross tal
ysteresis
*reep an( "elaxationEqui%alent noise= S" (ynamic
ran#e
'naccuracy
=orin' ran'e 8 validity limits (or 'iven speci(ications
The ma#or>specs?
'naccuracy is H
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1/ 'naccuracy M measurement < cali5rate( %alue-cali5ration is a measurement +ith much hi#her accuracy.
&/ 'naccuracy M measurement < a no+n %alue -intuiti%eB.
3/ 'naccuracy M measurement < stan(ar( %alue -or reference.
4/ The inaccuracy in a #i%en point of a measurement chain is theaccumulation or stochastic mean of all the errors an( noise accompanyin#the si#nal up to that point -assumin# no fee(5ac loops in%ol%e(.
Precision -an( other possi5le
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specifications.B
precise an( accurate not precise an( not accurate precise 5ut not accurate
precision 8 repeatability0
ase 3 su''est a systematic error
M measurement M reference
*omments ?uestions
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