Conventional and probabilistic fatigue life prediction methodologies relevant to the P-3C aircraft. PDF
Preview Conventional and probabilistic fatigue life prediction methodologies relevant to the P-3C aircraft.
NPS ARCHIVE 1997. OS KOUSKY, T. NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS CONVENTIONAL AND PROBABILISTIC FATIGUE LIFE PREDICTION METHODOLOGIES RELEVANT TO THE P-3C AIRCRAFT by Todd R. Kousky March, 1997 Thesis Advisor: Edward M. Wu Thesis K8346255 Approved for public release; distribution is unlimited. DlitMYKNOXLIBRARY NAVALPOSTGRADUATE SCHOOL MONTEREY CA 93943-5101 REPORT DOCUMENTATION PAGE Form Approved OMBNo. 0704-0188 Publicreportingburdenforthiscollectionofinformation isestimatedtoaverage 1 hourperresponse, includingthetimeforreviewinginstruction, searching existingdatasources, gatheringand maintainingthedataneeded, andcompletingandreviewingthecollectionofinformation. Sendcommentsregarding thisburdenestimateoranyotheraspectofthiscollectionofinformation, includingsuggestionsforreducingthisburden,toWashingtonheadquarters Services, DirectorateforInformation Operationsand Reports, 1215Jefferson DavisHighway, Suite1204,Arlington, VA22202-4302,andtotheOfficeof Managementand Budget, PaperworkReduction Project(0704-0188)Washington DC20503. 1. AGENCYUSEONLY(Leaveblank) 2. REPORTDATE 3. REPORTTYPEANDDATESCOVERED March 1997 Master'sThesis titleandsubtitle CONVENTIONAL AND PROBABILISTIC FATIGUE LIFE 5. FUNDINGNUMBERS PREDICTION METHODOLOGIES RELEVANT TO THE P-3C AIRCRAFT N0001996WXCD3YA 6. AUTHOR(S) Kousky, ToddR. PERFORMING 7. PERFORMINGORGANIZATIONNAME(S)ANDADDRESS(ES) 8O.RGANIZATION REPORT NavalPostgraduate School NUMBER Monterey, CA 93943-5000 9N.avSaPlOANiSrORSIysNtGe/mMsOCNoITmOmRaInNdGA(PGMEAN-C2Y90NFAAME/(JSP)1)ANDADDRESS(ES) 1M0O.NSIPTOONRSIONRGING/ Attn: CDRJeffreyKunkel AGENCYREPORTNUMBER 1421 JeffersonDavis Hwy. Arlington, Virginia22243-2900 11. SUPPLEMENTARYNOTES Theviews expressed inthisthesis arethose ofthe authorand do notreflectthe officialpolicyorpositionoftheDepartmentof DefenseortheU.S. Government. 12a. DISTRIBUTION/AVAILABILITYSTATEMENT 12b.DISTRIBUTIONCODE Approvedforpublic release; distributionunlimited. 13. ABSTRACT (maximum 200 words) This thesis investigates conventional and probabilistic methodologies for predicting the fatigue life of critical components in the P-3C aircraft. A probabilistic damage convolution model was developed with the intent ofproviding quantitative predictions oflife-variability. Traditional methodologies, which are based nominally on median values, lack A the capacity to adequately assess variability. Aluminum 7075-T6 was tested using a fatigue Material Test System. fatigue database was compiled fromtests conducted atthe Naval Postgraduate School and from literature sources. 14. SUBJECTTERMS 15. NUMBEROF P-3C Aircraft, Fatigue Life Prediction, Aluminum7075-T6, FatigueDataBase, Probability, Reliability PAGES 159 16. PRICECODE R17E.PSOERCTURITYCLASSIFICATIONOF T18H.ISSEPCAUGREITYCLASSIFICATIONOF O19F.ASBESCTURRAITCYTCLASSIFI-CATION 2O0F.ALBISMITTRAATCITON Unclassified UL Unclassified Unclassified NSN7540-01-280-5500 StandardForm298 (Rev.2-89) PrescribedbyANSIStd.239-18 Approved for public release; distribution is unlimited CONVENTIONAL AND PROBABILISTIC FATIGUE LIFE PREDICTION METHODOLOGIES RELEVANT TO THE P-3C AIRCRAFT Todd R. Kousky Lieutenant, United States Navy B.S., United States Naval Academy, 1989 Submitted in partial fulfillment ofthe requirements for the degree of MASTER OF SCIENCE IN AERONAUTICAL ENGINEERING from the NAVAL POSTGRADUATE SCHOOL March 1997 DUDLEYKNOXLIBRARY NAVAL POSTGRADUATE SCHOOL MONTEREY CA 93943-5101 ABSTRACT This thesis investigates conventional and probabilistic methodologies for predicting A the fatigue life of critical components in the P-3C aircraft. probabilistic damage convolution model was developed with the intent ofproviding quantitative predictions of life-variability. Traditional methodologies, which are based nominally on median values, lack the capacity to adequately assess variability. Aluminum 7075-T6 was tested using a fatigue Material Test System. A fatigue data base was compiled from tests conducted at the Naval Postgraduate School and from literature sources. VI TABLE OF CONTENTS INTRODUCTION I. 1 BACKGROUND AND PERSPECTIVE A. 1 B NPS P-3 LIFE EXTENSION PROGRAM 3 C. SCOPE OF THIS RESEARCH 4 II. CONVENTIONAL FATIGUE LIFE PREDICTION 7 PROBABILISTIC APPROACH TO FATIGUE III. 13 INTRODUCTION A. 13 PROBABILITY CONCEPTS B. 18 WEIBULL DISTRIBUTION C. 19 MODERN DAMAGE ACCUMULATION METHODOLOGY IV. 21 A. PROBABILISTIC MODEL 21 B. FLAW DISTRIBUTION 21 C. LIFE DISTRIBUTION 22 D DAMAGE ACCUMULATION VIALIFE CONVOLUTION 23 1. Power Law Damage Function 24 2. Exponential Form Damage Function 26 V. PROBABILISTIC INFORMATION THEORY 27 A. BAYESIAN ANALYSIS 27 B. AN EXAMPLE OF BAYESIAN INFERENCE 27 C. MAXIMUM LIKELIHOOD ESTIMATION 29 D. AN APPLICATION OF MAXIMUM LIKELIHOOD ESTIMATION 31 VI. ALUMINUM 7075-T6 FATIGUE DATA BASE 33 A. INTRODUCTION 33 B. NOTATION AND TERMINOLOGY 34 C. PRELUDE TO APPENDIX A 36 D. PRELUDE TO APPENDIX B 36 E. PRELUDE TO APPENDIX C 37 vn PRELUDE TO APPENDIX D F. 37 CONCLUSIONS AND RECOMMENDATIONS VII. 39 CONCLUSIONS A. 39 RECOMMENDATIONS B. 39 LIST OF REFERENCES 41 BIBLIOGRAPHY 45 APPENDIX A. CONSTANT AMPLITUDE, AXIAL FATIGUE 47 APPENDIXB. SPECTRAL, AXIAL FATIGUE 93 APPENDIX C. CONSTANT AMPLITUDE, ROTATIONAL FATIGUE 115 APPENDIXD. SPECTRAL, ROTATIONAL FATIGUE 119 APPENDIXE. SPECIMEN DRAWINGS 125 APPENDIXF. NACA"SAWTOOTH" LOAD SHAPES 141 APPENDIX G. DEVELOPMENT OF GUST AND MANEUVERLOADING SPECTRA 143 APPENDIXH. ROTATIONAL LOAD SHAPE SPECTRA 145 INITIAL DISTRIBUTION LIST 147 Vlll
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