Damian DT Lecture PS60_A

7/25/2019 Damian DT Lecture PS60_A

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1/29/2009 1TASSIncTraining

DamageToleranceAnalysisofRepairsandModifications

DamianHorriganPh.D

[email protected]

TASSInc
mailto:[email protected]:[email protected]


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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


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


FatigueandDamageToleranceAnalysisconceptually:


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AnalysisConsiderations


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

1/29/2009 7TASSIncTraining From T. Swift


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Proprietarydata:(OEM,legallyavailabletooperators)

TCDS SRM

SOPM

MM NDT

RAG

SSID

Drawings

Specifications

(AIPC)

Information


Zone Factors

737C RAG


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AnalysisConsiderations


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


ConsidersomeexamplesofDTanalysisforwhichactualfuselage

stressesarerequired AntennaInstallation

Corner

Rivet

Cablecutout

Stresses
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StressAnalysis


Dissimilarsizestructureaffectslocalstresses lapsplice

Stressinnominal0.063skinvariesby4%from0.063/0.08

mixedat

lap.

Recall:1.044 =0.86ora14%errorincrackgrowthcycles.

LapSplice
http://www.tassinc.com/resourceshttp://www.tassinc.com/resourceshttp://www.tassinc.com/resourceshttp://www.tassinc.com/resourceshttp://www.tassinc.com/resourceshttp://www.tassinc.com/resourceshttp://www.tassinc.com/resources


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StressAnalysis


Dissimilarsizestructureaffectslocalstresses padupordoubler

Stressneighboringthepadupis7%higherthannominal

Thisequatesto24%reductionincrackgrowthcycles.


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StressAnalysis


1. Longitudinalcracksaretypicallydrivenbypressurization

2. Circumferentialcracksgrowduetopressurizationandbending

3. Analysisofcircumferentialcracksrequiresspectrumloading

4. Considerananalysisofabuttspliceplate:

nz

L

ButtSplice

L
http://www.tassinc.com/resourceshttp://www.tassinc.com/resourceshttp://www.tassinc.com/resourceshttp://www.tassinc.com/resourceshttp://www.tassinc.com/resourceshttp://www.tassinc.com/resourceshttp://www.tassinc.com/resources


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ComparativeAnalysis


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


1. ThereisalargeamountofinformationavailableforDT

2. Toobtainrealisticresultsrequiresrealisticstressvalues

3. Crackgrowthrateequationshighlysensitivetostresses

4. Longitudinalstressesmagnifiedbyspectrumloading

5. Nominalstressesaffectedbylocalgeometry

6. Comparativeanalysisrelativelyeasytoconduct but

cautionrequired

7. Comparativeanalysiscanhelpsubstantiateabsolute

analysis


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DamageToleranceAnalysisofRepairsandModifications

DamianHorriganPh.D

[email protected]

TASSInc
mailto:[email protected]:[email protected]

Damian DT Lecture PS60_A

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