Post on 27-Feb-2018
7/25/2019 Damian DT Lecture PS60_A
1/22
1/29/2009 1TASSIncTraining
DamageToleranceAnalysisofRepairsandModifications
DamianHorriganPh.D
damian.horrigan@tassinc.com
TASSInc
mailto:damian.horrigan@tassinc.commailto:damian.horrigan@tassinc.com7/25/2019 Damian DT Lecture PS60_A
2/22
TASS,Inc
Incorporatedin1997
Engineering SpecializedinStructuralAnalysis(Design)
FiniteElementModeling
FatigueandDamageTolerance
Certificationservices
FAASTCMajorAlterationandRepair
FAAApprovedQualityandPMASystem
MaintenanceProgramoptimizationandextension
Fleetmanagement
LongtermBoeingrelationship Onsitesupport
BoeingApprovedforoffloadengineeringpackages
Boeing
Approved
to
level
5
(independent
certification)
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DamianHorrigan
20+yearsofanalysisexperience Stressanalysis
Finiteelementanalysis(nonlinear)
Developmentof
analysis
methods
and
tools
(software)
Fatigueanalysis
Damagetoleranceanalysis
Structuresdesignandrepair
Experience
in
managing
an
Approved
Design
Organization SupplementalTypeCertificate(STC) BoeingapprovedEngineering(Level5)andManufacturedPartsSupplier
MajorAlterations,PMAsetc.
Repairs
Experiencein
Fleet
Management
and
Operator
Engineering
Fleetissues
CustomeruseofBoeingproductsandservices
Customerindependence
CustomerissueswithLeaseCompanies
Avoidableworkload
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Introduction
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Abriefoutlineofpresentationmaterial:
1. Basicconcepts
of
F&
DT
analysis
2. Analysisconsiderations
3. Availabilityof
information
4. Absolutestressanalysismethods
5. Comparativemethods
of
analysis
6. Substantiationofabsolutemethods
7. Summary
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BasicConcepts
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FatigueandDamageToleranceAnalysisconceptually:
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AnalysisConsiderations
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ConductofarealisticFatigueandDamageToleranceAnalysis
requiresactualstructuralstressesfor:
1. FatigueAnalysis S/N,/Norda/dN
2. ResidualStrengthAnalysis KcandFty
3. CrackGrowthAnalysis da/dN
Compare
therequirements
to
conduct
an
ultimate
static
analysis.
1. KnowledgeofFtuorFsu
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ThispresentationlooksatavailableresourcesforDTAnalysis:
Publicdomain
data:
(FAA,
NASA,
Military,
Uni)
Crackgrowthsoftware
Fatiguedata(S/N,/N)
Geometrycorrectionfactors
Materialproperties
Aircraftspectra
Measuredcrackgrowthdata
StressMethods
Information
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Proprietarydata:(OEM,legallyavailabletooperators)
TCDS SRM
SOPM
MM NDT
RAG
SSID
Drawings
Specifications
(AIPC)
Information
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Zone Factors
737C RAG
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AnalysisConsiderations
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Considerabasiccrackgrowthequation(Walker):
( )nm
RKC
dNda
=
1( ) aaK =
HandbookSolutions
Detectability&
ResidualStrength
TypicalWalkerequationhasm~4 mCN = 0
Considera10%
error
in
the
stress:
( ) mm CCN == 00 52.19.0
Crackgrowthisextremelysensitivetostresshowdoyougetreal
valuesfor
accurate
analysis?
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StressAnalysis
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ConsidersomeexamplesofDTanalysisforwhichactualfuselage
stressesarerequired AntennaInstallation
Corner
Rivet
Cablecutout
Stresses
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StressAnalysis
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Dissimilarsizestructureaffectslocalstresses lapsplice
Stressinnominal0.063skinvariesby4%from0.063/0.08
mixedat
lap.
Recall:1.044 =0.86ora14%errorincrackgrowthcycles.
LapSplice
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StressAnalysis
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Dissimilarsizestructureaffectslocalstresses padupordoubler
Stressneighboringthepadupis7%higherthannominal
Thisequatesto24%reductionincrackgrowthcycles.
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StressAnalysis
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1. Longitudinalcracksaretypicallydrivenbypressurization
2. Circumferentialcracksgrowduetopressurizationandbending
3. Analysisofcircumferentialcracksrequiresspectrumloading
4. Considerananalysisofabuttspliceplate:
nz
L
ButtSplice
L
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ComparativeAnalysis
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Dataexistsforpurposesofcomparativeanalysis,typically:
1. ExistingrepairsfromSRM,RAGetc
2. Previouslyapprovedrepairsandmodifications
3. ServiceBulletins
Comparisonneedstoassess:
1. Applicabilityoftheexistingdatatothecurrentanalysis
2. Geometricaldifferences
3. Location
4. Stresslevels
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CargoDoorLatchFitting
Basehas
been
machined,
reducingthickness
StressIncrease
Bendingstressinthebase
hasbeen
increased,
due
toreducedthickness
ComparativeAnalysis
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AbsoluteAnalysis
Knowingthe
lug
loads
for:
Operatingpressure
1gmaneuverloadcases
Bendingstress
in
the
base
for
each
case
Construct
Fatigue
Flight
Spectrum CalculateFatigueLife
FatigueBasedThreshold=FatigueLife/4
ComparativeAnalysis
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AbsoluteAnalysis(continued)
UsingFatigue
Spectrum,
run
crack
growthanalysis
W=basewidth
t
=
base
thickness a=0.125inch
a/c=1
CrackGrowthBasedThreshold=FlightstoFailure/2
CrackGrowthBasedRepeats=FlightstoFailure/Factor
FactorperFAAGuidelines(i.e.2,3,or4)
ComparativeAnalysis
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ComparativeAnalysis
Findrelative
increase
in
bending
stress
due
to
thicknessreduction(noloadsneeded)
FindcurrentinspectionintervalsperMPD(Noriginal)
Solvefornewinspectioninterval(Nrepair):
4
=repair
original
original
repair
S
S
N
N
ComparativeAnalysis
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CrackGrowthRateData Ratedataisreasonablywellknown(m~4)
Somedanger
in
reverse
engineering
from
crack
data
Exampleofthinsheetcracking
y=1.6625x7.1659
R=0.8179
5.9
5.7
5.5
5.3
5.1
4.9
4.7
4.5
0.8 0.9 1 1.1 1.2 1.3 1.4 1.5
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0 1000 2000 3000 4000 5000
Data
Paris Power = 1.6885
ComparativeCheck
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Statisticalcomparisonofgrowthratedata
AnalysisCheck
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Summary
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1. ThereisalargeamountofinformationavailableforDT
2. Toobtainrealisticresultsrequiresrealisticstressvalues
3. Crackgrowthrateequationshighlysensitivetostresses
4. Longitudinalstressesmagnifiedbyspectrumloading
5. Nominalstressesaffectedbylocalgeometry
6. Comparativeanalysisrelativelyeasytoconduct but
cautionrequired
7. Comparativeanalysiscanhelpsubstantiateabsolute
analysis
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1/29/2009 22TASSIncTraining
DamageToleranceAnalysisofRepairsandModifications
DamianHorriganPh.D
damian.horrigan@tassinc.com
TASSInc
mailto:damian.horrigan@tassinc.commailto:damian.horrigan@tassinc.com