Current Aeronautical Fatigue Problems (eBook)

Front Cover 
1 
Current Aeronautical Fatigue Problems 4
Copyright Page 
5 
Table of Contents 6
PREFACE 8
PART I: ELEVATED TEMPERATURE EFFECTS 10
TECHNICAL PREFACE TO PART I 12
CHAPTER 1. CREEP AND FATIGUE PROPERTIES UNDER CYCLIC LOADING AT ELEVATED TEMPERATURES 14
I. INTRODUCTION 14
II. MECHANISMS OF DEFORMATION AND FRACTURE UNDER STATIC AND FATIGUE LOADING 26
III. DYNAMIC CREEP UNDER STATIC AND PERIODIC LOADING CONDITIONS AT CONSTANT TEMPERATURE 33
IV. RUPTURE AND FATIGUE FRACTURE UNDER COMBINED STATIC AND PERIODIC LOADING AT CONSTANT TEMPERATURE 43
V. SYNERGISMS ASSOCIATED WITH VARIABLE TEMPERATURE 49
VI. NON-PERIODIC, RANDOM, AND ACOUSTICAL FATIGUE 52
VII. CLOSING REMARKS 52
REFERENCES 53
DISCUSSION 56
AUTHOR'S CLOSURE 56
CHAPTER 2. SOME EFFECTS OF KINETIC HEATING ON FATIGUE LIFE ASSESSMENT OF TRANSPORT AIRCRAFT 58
INTRODUCTION 58
FLIGHT PLANS 59
GUST DATA 63
S-N DATA AND FATIGUE DAMAGE 66
EFFECT OF TEMPERATURE ON S-N CURVES 71
THERMAL STRESS CYCLE 75
INTERACTION CREEP AND FATIGUE 81
CONCLUSIONS 83
RECOMMENDATION S FOR FURTHER STUDY 85
REFERENCES 85
CHAPTER 3. FATIGUE STRENGTH AND CRACK PROPAGATION IN AU2GN ALLOY AS A FUNCTION OF TEMPERATURE AND FREQUENCY 86
1. GENERAL 86
2. ALLOY INVESTIGATED 88
3. INFLUENCE OF SOAKING PERIODS ON THE FATIGUE STRENGTH 91
4. RATE OF CRACK PROPAGATION 98
5. INFLUENCE OF FREQUENCY ON FATIGUE STRENGTH 102
6. CONCLUSION 108
REFERENCES 109
DISCUSSION 109
CHAPTER 4. FATIGUE STRENGTH AT ELEVATED TEMPERATURE OF L.65 ALUMINIUM ALLOY NOTCHED AND LUG SPECIMENS 112
1. INTRODUCTION 112
2. MATERIALS 113
3. SPECIMENS 114
4. TESTING EQUIPMENT 115
5. MEASUREMENTS 116
6. PROGRAMME AND TESTING PROCEDURE 117
7. RESULTS 118
8. DISCUSSION 123
9. CONCLUSIONS 127
REFERENCES 127
APPENDIX 1: COMPOSITION AND PROPERTIES OF L.65 ALUMINIUM ALLOY 128
APPENDIX 2: APPEARANCE OF FRACTURE SURFACES OF NOTICHED AND LUG SPECIMENS 128
DISCUSSION 137
CHAPTER 5. FATIGUE RESISTANCE OF LIGHT ALLOY COMPRESSOR BLADES AT 20° AND 150°C, USING A CONSTANT AMPLITUDE AND A STANDARD INCREMENTAL AMPLITUDE TEST 140
INTRODUCTION AND PURPOSE OF THIS RESEARCH 140
TESTING PROGRAM 141
TEST EQUIPMENT 143
SPECIMEN AND MATERIAL SPECIFICATIONS 144
DISCUSSION OF RESULTS 145
CONCLUSIONS 149
REFERENCES 150
DISCUSSION 150
AUTHOR'S CLOSURE 151
WRITTEN CONTRIBUTION BY AUTHOR 151
CHAPTER 6. FATIGUE BEHAVIOUR OF THE Ti-Al 6-V 4 ALLOY AT NORMAL AND HETERONORMAL TEMPERATURES 152
1. DESCRIPTION OF SAMPLES 154
2. ELASTIC MODULUS 155
3. MECHANICAL PROPERTIES 156
4. FATIGUE TESTS 158
5. CONCLUSIONS 168
PART II: CRACK PROPAGATION AND RESIDUAL STATIC STRENGTH 170
TECHNICAL PREFACE TO PART II 172
CHAPTER 7. OBSERVATION OF CRACK PROPAGATION ON THE FRACTURE SURFACE 174
1. INTRODUCTION 175
2. MACROFRACTOGRAPHY 176
3. MICROFRACTOGRAPHY 178
4. CHARACTERISTIC FEATURES OF A FATIGUE FRACTURE SURFACE 182
5. APPLICATIONS OF MICROFRACTOGRAPHY 192
6. CONCLUSIONS 204
REFERENCES 204
DISCUSSION 206
CHAPTER 8. FURTHER INVESTIGATIONS INTO FATIGUE CRACK PROPAGATION IN SHEET SPECIMENS 210
DISCUSSION 220
CHAPTER 9. A STATISTICAL THEORY OF FATIGUE CRACK PROPAGATION 224
I. INTRODUCTION 224
I I . CRACK PROPAGATION: POISSON PROCESS 225
I I I . DISTRIBUTION LAW FOR FATIGUE LIVES 230
IV. RELATIONS BETWEEN K, a AND STRESS 232
V. FATIGUE LIFE IN THE CASE OF A RANDOM LOAD 235
DISCUSSION 236
CHAPTER 10. NOTCH EFFECTS ON FATIGUE AND STATIC STRENGTH 238
INTRODUCTION 238
SYMBOLS 240
METHOD OF NOTCH ANALYSIS 241
APPLICATIONS TO CLASSES OF MATERIALS 249
SPECIAL APPLICATIONS 260
CONCLUDING REMARKS 265
APPENDIX 265
REFERENCES 266
DISCUSSION 267
AUTHOR'S CLOSURE 272
CHAPTER 11. AN ANALYSIS OF FATIGUE CRACK PROPAGATION IN SHEET MATERIAL, USING FAMILIAR CONCEPTS 274
1. INTRODUCTION 274
2. NOTATION 275
3. STRAIN CONCENTRATION FACTORS 275
4. UNSTABLE CRACK PROPAGATION 279
5. FATIGUE CRACK PROPAGATION 290
6. CONCLUSIONS 294
ACKNOWLEDGMENT 295
REFERENCES 295
CHAPTER 12. CRACK PROPAGATION AND RESIDUAL STATIC STRENGTH OF STIFFENED AND UNSTIFFENED SHEET 296
INTRODUCTION 296
CRACK PROPAGATION PROGRAM 297
CRACK-ARRESTING PROGRAM 310
CONCLUSIONS 321
APPENDIX A 322
APPENDIX B 325
APPENDIX C 330
ACKNOWLEDGMENT 332
REFERENCES 333
DISCUSSION 333
CHAPTER 13. INVESTIGATION OF CRACK PROPAGATION IN STRUCTURE AND SPECIMENS 334
1. INTRODUCTION 334
2. SYMBOLS 335
3. FULL-SCALE FATIGUE TEST ON A REAR-FUSELAGE STRUCTURE 335
4. CRACKS IN ALUMINIUM ALLOY FORGINGS 339
5. FATIGUE CRACKS IN SHEET SPECIMENS 342
6. PROPOSED EVALUATION OF CRACK GROWTH FROM FATIGUE CURVES 347
7. CONCLUSION 350
REFERENCES 350
DISCUSSION 350
PART III: STRUCTURAL FATIGUE TESTING 352
TECHNICAL PREFACE TO PART III 354
CHAPTER 14. SIMULATION OF RANDOM AIRCRAFT SERVICE LOADINGS IN FATIGUE TESTS 356
1. INTRODUCTION 356
2. PRELIMINARY INVESTIGATION 357
3. MAIN INVESTIGATION 372
4. ADDITIONAL DATA 399
5. FATIGUE TESTING OF STRUCTURE 400
6. PROBLEMS IN THE DEVELOPMENT OF ADVANCED AIRCRAFT 407
7. CONCLUSION 409
REFERENCES 410
CHAPTER 15. FATIGUE LIFE AND CRACK PROPAGATION UNDER RANDOM AND PROGRAMMED LOAD SEQUENCES 412
1. INTRODUCTION 413
2. TEST PROGRAMS 414
3. APPARATUS AND SPECIMENS 416
4. THE LOAD SEQUENCES 419
5. TEST RESULTS 422
6. DISCUSSION 429
7. CONCLUSIONS 434
REFERENCES 435
DISCUSSION 436
CHAPTER 16. THEORY AND PRACTICE IN FAIL-SAFE WING DESIGN 438
INTRODUCTION 438
COMPARATIVE DESIGN PARAMETERS OF THE TWO WINGS 439
FAIL-SAFE WING 441
GENERAL DESIGN OF THE FAIL-SAFE WING 441
TENSION FLANGE DESIGN 445
DESIGN FOR INSPECTABILITY 449
WEIGHT COMPARISON 450
FATIGUE DESIGN 451
CRACK PROPAGATION 453
DETAIL TESTS AND ESTIMATIONS OF RESIDUAL STRENGTH 457
INTERPRETATION OF DETAIL TESTS 460
CHAPTER 17. THEORETICAL ESTIMATE OF THE EFFECT OF STRINGERS ON THE RESIDUAL STRENGTH OF FLAT SHEET 464
ASSUMPTIONS 464
SKIN CRACK BETWEEN TWO STRINGERS 465
SKIN CRACK ASSOCIATED WITH ONE STRINGER FAILED 466
FULL SCALE TESTING 467
ACKNOWLEDGEMENTS 468
DISCUSSION 468
AUTHOR'S CLOSURE 470
CHAPTER 18. FATIGUE TESTING AND SERVICE BEHAVIOUR OF THE NORATLAS AIRCRAFT WING STRUCTURE 472
INTRODUCTION AND GENERAL OUTLINE 472
1. THE N-2502 474
2. FATIGUE TESTING AT TOULOUSE 478
3. INCIDENTS IN SERVICE —ANALOGY WITH FATIGUE TESTING — CONCLUSION 495
REFERENCES 498
APPENDIX 499
DISCUSSION 504
SUBJECT INDEX 506
INTERNATIONAL SERIES OF MONOGRAPHS IN AERONAUTICS AND ASTRONAUTICS 510