Aerospace Materials and Material Technologies (eBook)

Dr. N. Eswara Prasad, FIE,FAPAS,FIIM, a B.Tech. (1985) and a Ph.D. (1993) in Metallurgical Engineering from Indian Institute of Technology (BHU), Varanasi, India, is an innovative and creative researcher and technologist. He is currently serving as Director, Defense Materials and Stores Research and Development Establishment (DMSRDE), DRDO at Kanpur, India.He has made significant and outstanding contributions to the Indian Defense Research and Development Organization (DRDO) in the last 30 years in the fields of design, materials development and characterization, and airworthiness certified production of many advanced aerospace, aeronautical and naval materials and components. The extensive research work conducted  by him has resulted in the development and certified production of  (i) Al & Al-Li alloys for LCA, LCH  and  Indian Space Programme, (ii) Aero Steels, including Maraging and PH Steels for Indian Missile Programmes, (iii)  High strength and high temperature Ti Alloys, including -Ti alloys for LCA’s slat tracks and landing gear, (iv) Advanced  Ultrahigh Temperature materials - Mo & Ti Intermetallics, Monolithic Ceramics (Structural Alumina, Graphite and SiC), Carbon, Silica and SiC based Continuous Fibre-reinforced, Ceramic-matrix Composites (CFCCs) for cutting edge components, systems and technologies. Application of these materials in DRDO has been complemented by him by extensive fundamental research on tensile deformation, fatigue and fracture, correlations between chemical composition-processing-microstructure-texture-deformation, leading to first time scientific explanations on Property Anisotropy. In the last 6 years, Dr. Prasad has been instrumental in the concurrent development and production of several airworthiness certified materials and components of Aero and Naval steels, Al alloys, Ni-base Superalloys, Ti sponge and Special Ti alloys for Indian Defense, Indian Air Force, Indian Navy and ATVP – the Indian Submarine Program, which have resulted in realizing defense hardware worth more than Rs. 12 billion, out of which direct materials production of nearly Rs. 6.2 Billions through 180 provisional clearances and 11 type approvals of CEMILAC. Dr. Prasad’s prolific research resulted over 170 research articles in peer-reviewed national and international journals and conference proceedings, including 30 written/edited books and book chapters as well as 26 classified and unclassified, as also peer reviewed technical reports and a highly acclaimed first International Monograph on Al-Li Alloys in 2014. He has also authored nearly 90 confidential reports and more than 260 certification documents for DRDO. In recognition of his original contributions in the fields of Metallurgy and Materials Engineering, Dr. Prasad had received several national and international awards. He has been the recipient of YOUNG SCIENTIST AWARD (ICSA, 1991), YOUNG METALLURGIST (Ministry of Steel,1994), AvH’s Humboldt Research Fellowship (1998-99), Max-Planck-Institute (Stuttgart)’s Visiting Scientist (1998-99), Binani Gold Medal (IIM, 2006), METALLURGIST OF THE YEAR (Ministry of Steel, 2010), AICTE-INAE Distinguished Visiting Professorship at Andhra University and Mahatma Gandhi Institute of Technology (INAE, 2012-Till Date), IIT-BHU(MET)’s Distinguished Alumnus Award (2013) and the prestigious Dr. VM Ghatge Award of AeSI (in 2014).Dr. Prasad is a Fellow of Institute of Engineers (India) [FIE], Indian Institute of Metals [FIIM] and AP Akademi of Sciences [FAPAS]. Dr. R. J. H. Wanhill is emeritus Principal Research Scientist at the Netherlands Aerospace Centre, formerly the National Aerospace Laboratory NLR, in the Netherlands. He holds two Doctorates, one from the University of Manchester (1968) and the second from the Delft University of Technology (1994). He joined the NLR in 1970, and since then has investigated fatigue and fracture of all classes of aerospace alloys. He is co-author of the book ‘Fracture Mechanics’ (1984), which has run into a second edition; co-author with Simon Barter of the monograph ‘Fatigue of Beta Processed and Beta Heat-treated Titanium Alloys’, published by Springer in 2012; and co-author and co-editor for the book ‘Aluminium - Lithium Alloys: Processing, Properties and Applications’, editors N. Eswara Prasad, Amol A. Gokhale and R. J. H. Wanhill, published in 2014.From 1978 to 1996 Dr. Wanhill was head of the Materials Department of the NLR, and in 1979-80 adjunct professor of materials at Delft University of Technology. From 1997 to 2008 he was a Principal Research Scientist in the Aerospace Vehicles Division of the NLR. From 2008 to 2015 he has been emeritus Principal Research Scientist at the NLR. In 2002 the Board of the Foundation NLR awarded Dr. Wanhill the first Dr.ir.B.M. Spee Prize for outstanding contributions on aerospace materials. In October 2014 he was awarded an Honour Diploma by the Netherlands Aerospace Fund for his long-term contributions to scientific research and knowledge at the NLR, and use of this knowledge for aircraft failure analyses.  In recent years Dr. Wanhill has worked on the analysis of fatigue cracking in GLARE panels from the Airbus 380 MegaLiner Barrel test (presented at ICAF 2009) and, in collaboration with Dr. Simon Barter (Defence Science and Technology Group, DSTG, Melbourne). From November 2009 to May 2010 Dr. Wanhill was a Visiting Academic at the DSTG. The work there included (i) a collaborative report, book chapter, and presentation for the Royal Australian Air Force (RAAF) on fatigue life assessment of combat aircraft; (ii) a book chapter on stress corrosion cracking (SCC) in aerospace; (iii) two seminar presentations, on service failures and the MegaLiner Barrel GLARE cracking (see above); and (iv) preparation of a course on failure analysis, held twice at Auckland Technical University at the beginning of May 2010. This course has been adopted by the RAAF as part of its instruction material. Since 1994 Dr. Wanhill has been investigating fracture phenomena in ancient silver and iron, and has published eight peer-reviewed papers on this topic. The most recent papers have been published in the Journal of Failure Analysis and Prevention (2011), Metallography, Microstructure, and Analysis (2012) and the leading archaeological scientific journal Studies in Conservation (2013). Dr. Wanhill also gives annual lectures on ancient silver for a Master’s Degree course on conservation at the University of Amsterdam. Dr. Wanhill has been an author and speaker on several fatigue and fracture topics and also on fatigue-based design of aircraft structures. In 2012, Dr. Wanhill was a keynote speaker for the International Conference on Engineering Failure Analysis V, held in The Hague. He also had two additional contributions, with co-authors: “Validation of F-16 wing attachment fitting bolts” and “Five helicopter accidents with evidence of material and/or design deficiencies”. All three presentations have been published as papers in Engineering Failure Analysis in 2013. In 2014 he was a keynote speaker at Fatigue 2014, held in Melbourne. In 2015 he gave a Public Lecture at Materials Days 2015, Rostock, with the title “Materials and structural integrity: Milestone aircraft case histories and continuing developments”. This presentation has also been adopted by the RAAF as instruction material, and in written chapter form will be published in ‘The Reference Module in Materials Science and Engineering’.

Foreword by Dr. S. Christopher 7
Foreword by Dr. G. Satheesh Reddy 9
Series Editors’ Preface 11
About the Indian Institute of Metals 11
Genesis and History of the Series 11
Current Series Information 12
About This Book 12
Preface 14
Acknowledgements 16
Contents 18
Editors and Contributors 21
Processing Technologies 27
1 Processing of Aerospace Metals and Alloys: Part 1—Special Melting Technologies 28
Abstract 28
1.1 Introduction 28
1.2 Vacuum Induction Melting (VIM) 29
1.2.1 Functional Principle 29
1.2.2 Melting Process 29
1.2.3 Process Benefits 31
1.2.4 Post-VIM Processing Technologies 34
1.2.5 Manufacture of Nickel-Base Superalloy Investment Castings for Aerospace Gas Turbines—A Case Study 35
1.3 Remelting Technologies 36
1.3.1 Remelting Processes 36
1.3.2 Refining Characteristics 37
1.3.3 Solidification Phenomena 39
1.4 Solidification Defects: Superalloys 41
1.4.1 White Spots 42
1.4.2 Freckles 43
1.4.3 Ring Patterns: ‘Tree Rings’ 43
1.5 Case Study on Melt Processing of a Selected High-Temperature Material, Inconel 718 44
1.6 Titanium and Its Alloys 45
1.7 Secondary Metallurgical Processes 46
1.8 Indian Scenario 46
1.9 Summary 47
Acknowledgments 48
References 48
2 Processing of Aerospace Metals and Alloys: Part 2—Secondary Processing 50
Abstract 50
2.1 Introduction 50
2.2 Fundamentals of Metal Forming 51
2.3 Bulk Deformation Processes 53
2.3.1 Forging 53
2.3.2 Rolling 55
2.3.3 Extrusion 55
2.4 Secondary Processing for Specific Aerospace Materials 55
2.4.1 Titanium Alloys 55
2.4.2 Superalloys 56
2.4.3 Special Steels 58
2.5 Recent Advances in Secondary Processing 58
2.5.1 Rapid Prototyping Using LENS 58
2.5.2 Equal-Channel Angular Extrusion (ECAE) 59
2.5.3 High-Pressure Torsion (HPT) 61
2.5.4 Cryomilling 61
2.5.5 Vacuum Plasma Spray (VPS) Forming 62
2.5.6 Electrodeposition 62
2.6 Summary 62
Acknowledgments 63
Bibliography 63
3 Superplastic Forming of Aerospace Materials 64
Abstract 64
3.1 Introduction 64
3.2 Phenomenology of Superplasticity 65
3.3 A Review of Basic Research on Superplastic Flow 67
3.3.1 Metals and Alloys 67
3.3.2 Intermetallics 68
3.3.3 Ceramics 68
3.3.4 Composites 69
3.3.5 Bulk Metallic Glasses 70
3.3.6 Effect of FSP on Superplastic Forming 70
3.4 Conventional/High Temperature Superplasticity 71
3.5 Low Temperature/High Strain-Rate Superplasticity 72
3.6 Forming Operations 73
3.6.1 Bulge Forming 73
3.6.2 Pressure Forming 73
3.6.3 Sheet Thermoforming 74
3.6.4 Blow (Extrusion) Moulding 75
3.6.5 Deep Drawing 75
3.6.6 Powder Metallurgy Processes 75
3.6.7 Incremental Forming 76
3.6.8 SPF/Diffusion Bonding of Titanium Alloys 77
3.6.9 Superplastic Roll Forming 77
3.7 SPF Tooling 79
3.8 Techno-economic Considerations 80
3.9 Aerospace Applications 80
3.9.1 Aluminium Alloys 80
3.9.2 Titanium Alloys 82
3.10 Additional Remarks 84
3.11 Conclusions 84
Acknowledgments 84
References 84
4 Welding Technologies in Aerospace Applications 89
Abstract 89
4.1 Developments in Welding Processes 89
4.2 Welding of Aerospace Materials 90
4.2.1 Aluminium Alloys 90
4.2.2 Titanium Alloys 93
4.2.3 Nickel-Base Alloys 95
4.2.4 Steels 97
4.2.5 Dissimilar Metals 97
4.2.6 Metal Matrix Composites and Oxide Dispersion-Strengthened Alloys 100
4.2.7 Intermetallics 100
4.3 Innovative Welding Techniques 101
4.4 Ceramic–Metal Joining 102
4.5 Advanced Welding Processes 103
4.6 Fixturing, Automation and Post-weld Heat Treatments 104
4.7 Summary 104
Acknowledgments 105
References 105
5 Nanomanufacturing for Aerospace Applications 108
Abstract 108
5.1 Introduction 108
5.2 Nanomanufacturing Processes 109
5.2.1 Bottom-up Method 109
5.2.2 Top-Down Method 112
5.2.3 Graphene: A Special Case 114
5.2.4 Challenges 114
5.3 Nanoporous Aerogels 116
5.3.1 Preparation of Aerogels 116
5.3.2 Properties of Aerogels 117
5.4 Electrodeposited Nanostructured Coatings 118
5.5 Potential Aerospace Applications: A Concise Survey 119
5.5.1 Nanostructured Alloys 119
5.5.2 Carbon Nanocomposites 119
5.5.3 Aluminium-Based Propellant Materials 120
5.5.4 Aerogel Thermal Insulation 120
5.5.5 Electrodeposited Coatings 120
5.6 Indian Scenario 121
5.7 Summary and Conclusions 122
Acknowledgments 122
References 123
Characterisation and Testing 125
6 Microstructure: An Introduction 126
Abstract 126
6.1 Introduction 126
6.2 Microstructures: General Remarks 127
6.3 Optical Microscopy 128
6.4 Scanning Electron Microscopy 129
6.4.1 SEM and Failure Analysis 130
6.5 Transmission Electron Microscopy 133
6.5.1 Transmitted and Diffracted Beam Imaging 133
6.5.2 Bright-Field and Dark-Field Images 134
6.5.3 Diffraction Patterns 135
6.5.4 Characterization of Defects 137
6.6 High-Temperature Microscopy 137
6.7 Field Ion Microscopy 139
6.7.1 FIM Image Interpretation 139
6.7.1.1 3D Atom Probe Microscopy (3DAP) 141
6.8 Microstructural Studies in Aerospace Alloys: An Overview 142
6.9 Concluding Remarks 143
Acknowledgments 144
References 144
7 Texture Effects in Important Aerospace Materials 145
Abstract 145
7.1 Introduction 145
7.1.1 Texture Definition and Representations 146
7.1.2 Methods of Measuring Texture 147
7.2 Aluminium Alloys 148
7.2.1 Processing of Aerospace Aluminium Alloys 148
7.2.2 Texture Effects on Aerospace Aluminium Alloy Properties 151
7.3 Titanium Alloys 152
7.3.1 Types of Commercial Titanium Alloys 153
7.3.2 ? + ? Titanium Alloy Processing 153
7.3.3 Processing Effects on Texture 153
7.3.4 Texture Effects on Aerospace Titanium Alloy Properties 157
7.4 Nickel-Base Superalloys 159
7.5 Summary 160
References 160
8 Physical Property Significances for Aerospace Structural Materials 163
Abstract 163
8.1 Introduction 163
8.2 Aerospace Structural Components 164
8.3 Density and Stiffness 165
8.3.1 Aerospace Alloy Density and Stiffness Data 165
8.3.2 Alloy Classes and Applications 167
8.3.3 Inadvisable Alloy Selection: A Case History 169
8.4 Thermal Properties 170
8.4.1 Thermal Expansion Mismatch: Airframes 172
8.4.2 Thermal Barrier Coatings (TBCs) 174
8.5 Concluding Remarks 176
References 176
9 Structural Alloy Testing: Part 1—Ambient Temperature Properties 178
Abstract 178
9.1 Introduction 178
9.2 Mechanical Properties 180
9.2.1 Tension Testing 180
9.2.2 Compression Testing 181
9.2.3 Stress–Strain Curve Moduli 181
9.2.4 Shear and Bearing Strengths 181
9.2.5 Hardness 182
9.3 Fatigue 182
9.3.1 Some Important Remarks About the Commencement of Fatigue Cracking 182
9.3.2 Fatigue Test Approaches 183
9.4 Fatigue Crack Growth: Part I–Constant Amplitude Testing 185
9.4.1 Long/Large Cracks 185
9.4.2 Short/Small Cracks 186
9.5 Fatigue Crack Growth: Part II–Variable Amplitude Testing 188
9.5.1 Introduction 188
9.5.2 Long/Large Cracks 189
9.5.3 Short/Small Cracks 189
9.6 Fracture Toughness Testing 191
9.6.1 Introduction 191
9.6.2 Plane-Strain/Plane-Stress Fracture Toughness 191
9.6.3 KR Curves 192
9.6.4 Examples of KIc and KR Curve Use 193
9.7 Corrosion and Stress Corrosion Cracking (SCC) 194
9.7.1 Introduction 194
9.7.2 Corrosion 195
9.7.3 Stress Corrosion Cracking (SCC) 196
9.7.4 Some SCC and Corrosion Issues 198
9.8 Summary 199
References 199
10 Structural Alloy Testing: Part 2—Creep Deformation and Other High-Temperature Properties 203
Abstract 203
10.1 Introduction: Creep 203
10.2 Secondary (Steady-State) Creep 205
10.2.1 Modelling Steady-State Creep for Particle-Strengthened Alloys: A Summary 206
10.3 Creep Fractures 207
10.4 Experimental Determination of Creep Properties 209
10.5 Creep Life Prediction Methods 211
10.5.1 Data Correlations Using ‘Classical’ Methods 211
10.5.2 Developments in Correlation Methods 214
10.6 Other Important High-Temperature Properties: A Brief Survey 216
10.6.1 Creep–Fatigue Interactions (CFI) 216
10.6.2 Thermal Fatigue (TF) 216
10.6.3 Thermomechanical Fatigue (TMF) 218
10.6.4 Dwell Cracking 219
10.6.5 Creep Crack Growth 221
10.7 Summary 222
References 222
Bibliography 225
11 Non-destructive Testing and Damage Detection 226
Abstract 226
11.1 Introduction: The Role of NDT 226
11.2 Generic NDT Systems 227
11.3 Surface Techniques 228
11.3.1 Visual Evaluation 228
11.3.2 Optical Testing Techniques 228
11.3.3 Liquid Penetrant Technique 229
11.3.4 Magnetic Particle Technique 229
11.3.5 Eddy Current Technique 230
11.3.5.1 Other Types of Eddy Current Testing 234
11.3.5.2 Summary 234
11.3.6 Infrared Thermography Technique 235
11.4 Volumetric Techniques 235
11.4.1 Acoustic Testing Techniques 236
11.4.2 Acoustic Emission Technique 236
11.4.3 Ultrasonic Testing Technique 237
11.4.3.1 Advanced Ultrasonics 238
11.4.4 X-Radiography Technique 239
11.4.5 Isotope Radiography Technique 240
11.4.6 Neutron Radiography 240
11.5 Certification of NDT Personnel 241
11.6 Recent Advances and Future Trends 241
11.7 An Overview of NDT Techniques 242
11.8 Summary 244
Acknowledgments 244
References 244
Structural Design 246
12 Design of Aircraft Structures: An Overview 247
Abstract 247
12.1 Introduction 247
12.2 Major Structural Components of an Aircraft 248
12.2.1 Semi-monocoque Structures 248
12.2.2 Functions of Semi-monocoque Structural Components 249
12.3 Materials for Aircraft Applications 250
12.3.1 Experimental Methods for Material Characterization 251
12.4 Idealization of Thin Stiffened Shell Aerospace Structures 253
12.4.1 Idealization of Structures 253
12.4.2 Buckling in Aerospace Structures: Design Motivation 255
12.4.3 Role of the Frames, Spars, and Ribs 256
12.4.4 Aircraft Landing Gear Design 260
12.5 Aeroelastic Considerations 262
12.6 Conclusions 265
References 265
13 Aircraft Mechanical Systems 267
Abstract 267
13.1 Introduction 267
13.2 Environmental Control Systems 268
13.2.1 Different Types of ECS 269
13.2.2 Life Support Systems 271
13.3 Anti-/de-icing Systems 272
13.3.1 Ice Protection Systems 272
13.4 Aircraft Hydraulic Systems 272
13.4.1 Hydraulic Fluids 273
13.4.2 Hydraulic System Components 274
13.5 Aircraft Fuel Systems 277
13.5.1 Aircraft Fuels 278
13.5.2 Fuel System Components 279
13.5.2.1 Valves 280
13.5.3 Gauging of Fuel 281
13.6 Undercarriage, Wheels and Brakes 282
13.6.1 Undercarriage (Landing Gear) Arrangement 283
13.6.1.1 Fixed and Retractable Landing Gears 283
13.7 Drag Parachute Systems 285
13.8 Flight Control Systems 285
13.9 Armament Systems 287
13.9.1 Armament Construction: Pylons 287
13.9.2 Gun Systems 288
13.10 Emergency Escape System 288
13.11 Materials for Mechanical Systems 290
13.12 Future Trends in Mechanical Systems and Their Design 292
13.13 Summary and Conclusions 293
Acknowledgments 294
References 294
14 Design and Structures of Aircraft Engines 295
Abstract 295
14.1 Background 295
14.2 Gas Turbine Engine Components and Operating Environment 296
14.3 Requirements for Gas Turbine Materials 297
14.4 Engine Design Phases 298
14.4.1 Engine Structural Design 300
14.4.2 Design Reliability Requirements 301
14.4.3 Component Design Approach 302
14.4.4 Specific Design Tools and Methodologies 304
14.5 Testing and Validation 314
14.6 Current Trends in Structural Design 315
14.7 Conclusions 317
Acknowledgments 317
References 317
15 Missile Propulsion Systems 320
Abstract 320
15.1 Introduction 320
15.1.1 Operational Principle for Rockets 322
15.1.2 Nozzle Design 322
15.2 Solid Rocket Propulsion System 323
15.2.1 Rocket Motor Casing 323
15.2.2 Thermal Insulation 324
15.2.3 Nozzle 324
15.2.4 Igniter 325
15.2.5 Grain Design (Propellant Geometric Form) 325
15.2.6 Thrust Vectoring 326
15.2.7 Motor Static Test 326
15.3 Liquid Rocket Propulsion 326
15.3.1 Types of Liquid Propulsion Feed Systems 328
15.3.2 Turbopump Feed System 329
15.3.3 Pressure Feed System 330
15.3.4 Liquid Propulsion Subsystems 330
15.3.4.1 Thrust Chamber 332
15.3.4.2 Injectors 333
15.3.4.3 Propellant Tanks 333
15.3.4.4 Air Bottles (Pressurized Gas Storage Tanks) 333
15.3.4.5 Turbopump Feed System 333
15.3.4.6 Valves 334
15.3.4.7 Controls 334
15.3.5 Engine System Calibration 334
15.3.6 Testing of Liquid Propulsion Systems 335
15.4 Ramjet Propulsion Technology 335
15.4.1 Liquid Fuel Ramjets 336
15.4.1.1 Ramjet Air Inlet 336
15.4.1.2 Ramjet Fuel Tank 337
15.4.1.3 Ramjet Combustion Chamber 337
15.4.1.4 Ramjet Insulation 338
15.4.2 Solid Fuel Ducted Rockets (Ramrockets) 338
15.4.2.1 Solid Propellant (Grain) 339
15.4.2.2 Ducted Rocket Fuel Flow Control Valve 339
15.4.3 Ramjet Testing 340
15.5 Scramjet Propulsion 340
15.5.1 System Description 340
15.5.2 Subsystems 342
15.5.3 Other Critical Areas 343
15.5.4 Development at DRDL in India 343
15.6 Summary 345
Acknowledgments 345
Bibliography 345
16 Fatigue Requirements for Aircraft Structures 346
Abstract 346
16.1 Evolution of Fatigue Requirements 347
16.1.1 Civil Aircraft Milestone Accidents 348
16.1.2 Military Aircraft Milestone Accidents 350
16.2 Continuing Developments 351
16.2.1 Fatigue Analyses for Conventional Alloys 351
16.2.2 Airframe Materials 352
16.3 Fatigue Lifing Methods for Metallic Airframe Structures 354
16.4 Fatigue Lifing Analyses for Metallic Airframe Structures 356
16.4.1 Safe-Life Estimations 356
16.4.2 Damage Tolerance Estimations 357
16.4.3 Operational Damage Estimations 359
16.5 Testing Requirements 361
16.5.1 ‘Building Block’ Testing Procedure 362
16.6 Summary 365
Acknowledgments 365
References 365
17 Full-Scale Fatigue Testing 368
Abstract 368
17.1 Why Testing and Why FSFT? 368
17.2 Evolution of FSFT 369
17.2.1 Initial Approach 369
17.2.2 Hydraulics in FSFT 369
17.2.3 Advent of Servo-Hydraulics and Computer Control 370
17.2.4 ASIP and Consideration of Damage Tolerance 370
17.2.4.1 Five Tasks of ASIP 371
17.2.5 Adaptation of ASIP to Composite Structures and Its Impact on FSFT 374
17.2.5.1 Differences in Damage Mechanisms Between Metals and Composites 375
17.2.5.2 Statistical Aspects of Fatigue of Composites and Adaptation to FSFT 375
17.3 Organization of FSFT 380
17.4 Summary 385
References 386
18 Residual Strength Requirements for Aircraft Structures 387
Abstract 387
18.1 Introduction 388
18.2 Case Histories 388
18.2.1 Civil Aircraft Milestone Accidents 388
18.2.2 Military Aircraft Accidents 390
18.3 Residual Strength Definitions 391
18.4 Residual Strength Methods for Metallic Airframe Structures 392
18.4.1 Civil Aircraft Fail-Safe Design (1956–1978) 393
18.4.2 Damage Tolerance Design in the 1970s 394
18.4.3 Widespread Fatigue Damage (WFD) 396
18.5 Helicopters: A Short Note 398
18.6 Summary 398
References 399
19 Stress Corrosion Cracking in Aircraft Structures 401
Abstract 401
19.1 Introduction 401
19.1.1 Background to Aircraft SCC 402
19.2 Structures, Materials and Environments 402
19.2.1 Primary Structures 403
19.2.2 Mechanical Systems 404
19.2.3 Fluid Systems 404
19.2.4 Environmental Protection: Corrosion and SCC 404
19.3 Aircraft SCC Case Histories 406
19.3.1 Aluminium Alloys 406
19.3.1.1 Aluminium Alloy SCC Characteristics 408
19.3.1.2 Repair and Inspection Possibilities 409
19.3.2 Stainless Steels 411
19.3.2.1 Background Information 411
19.3.2.2 Stainless Steel Case Histories 411
19.3.2.3 Stainless Steel SCC Characteristics 412
19.3.3 High-Strength Low Alloy Steels 415
19.3.3.1 Background Information 415
19.3.3.2 High-Strength Low Alloy Steel Cases 415
19.3.3.3 High-Strength Low Alloy Steel SCC Characteristics: A Case History 416
19.3.4 Magnesium Alloys 417
19.3.4.1 Background Information 417
19.3.4.2 Magnesium Alloy Case Histories 418
19.3.4.3 Magnesium Alloy SCC Characteristics 419
19.4 Preventative and Remedial Measures to Avoid SCC 419
19.4.1 Preventative Measures 419
19.4.2 Remedial Measures 420
19.5 Summary 422
References 423
Special Technologies 425
20 Aero Stores (Materials) Inspection and Quality Assurance 426
Abstract 426
20.1 Introduction 426
20.2 Importance of QA for Aero Materials 427
20.3 General Categories of Aero Stores 427
20.4 Quality Management System Requirements for Aero Stores 428
20.5 Modes of Inspection 428
20.6 Phases of QA 429
20.6.1 Inspection and QA During the Development Phase 429
20.6.2 Inspection and QA During the Production Phase 430
20.6.3 Inspection and QA During the In-Service Exploitation Phase 430
20.7 Inspection/Test Stages for an Aero Material 431
20.8 Salient QA Attributes 433
20.9 Important Inspection and Quality Control Attributes 434
20.9.1 Aluminium Alloys 434
20.9.2 Titanium Alloys 436
20.9.3 Nickel/Iron-Based Superalloys 438
20.9.4 Steels 440
20.9.5 Composites 442
20.10 Summary 443
Acknowledgments 443
References 443
21 Fatigue Life Enhancement for Metallic Airframe Materials 445
Abstract 445
21.1 Introduction 445
21.2 Life Enhancement via Residual Stress Application 446
21.2.1 Application of Residual Stresses 450
21.3 Life Enhancement via Stress Concentration Reduction 451
21.4 Life Improvement Factors for Residual Stress Methods 452
21.5 Conclusions 457
References 457
22 Structural Health Monitoring 461
Abstract 461
22.1 Introduction 461
22.2 Health and Usage Monitoring Systems (HUMS) 463
22.3 Damage Monitoring 465
22.4 Sensing Systems: An Overview 466
22.5 Acoustic Waves for Damage Detection 467
22.5.1 Passive Acoustic Techniques: Acoustic Emission (AE) 468
22.5.2 Active Acoustic Techniques: Acousto-Ultrasonics and Guided Waves 471
22.5.3 Emerging Applications of Acoustic Waves for SHM 472
22.6 Fibre Optics for Damage Detection 475
22.6.1 Interferometric Sensors 476
22.6.2 Grating-Based Sensors 476
22.6.3 Distributed Sensing 479
22.6.4 Practical Examples 480
22.7 Fibre Optics and Acoustic Sensing 481
22.8 Issues and Strategies 482
22.8.1 Metallic versus Composite Structures 482
22.8.2 Online versus Offline 482
22.8.3 SHM as a Part of IVHM 483
22.8.4 Diagnosis versus Prognosis 484
22.8.5 Certification 484
22.9 Concluding Remarks 484
References 485
23 Failure Analysis and Prevention 490
Abstract 490
23.1 Introduction 490
23.2 Fracture of Metals and Alloys 491
23.2.1 Ductile Fracture 491
23.2.2 Brittle Fracture 492
23.2.3 Fatigue Fracture 494
23.3 Major Causes for Component Failures 495
23.3.1 Poor Material Quality 495
23.3.2 Manufacturing Defects 496
23.3.3 Operational Overload/Abuse 498
23.3.4 Fatigue 499
23.3.5 Corrosion 499
23.3.6 Hydrogen Embrittlement and Stress Corrosion Cracking (SCC) 501
23.3.7 Wear 503
23.3.8 Overheating 504
23.4 Tools and Techniques of Failure Analysis 505
23.5 Case Studies 508
23.5.1 Steel Inner Gear of an Aeroengine 508
23.5.2 Inner Flange of Flame Tube 512
23.5.3 Centre Main Bearing of an Aeroengine 518
23.6 Concluding Remarks 522
Acknowledgments 523
References 523
Bibliography 523
24 Airworthiness Certification of Metallic and Non-metallic Materials: The Indian Approach and Methodologies 525
Abstract 525
24.1 Introduction 527
24.2 Aeromaterial Production in India 528
24.3 Airworthiness Regulators in India 529
24.4 Certification Methodology 529
24.5 Airworthiness Certification Methodology 531
24.6 Metallic Materials Case Studies 533
24.6.1 Aluminium Alloy Investment Castings for an Antenna Platform (APL) 533
24.6.2 Aluminium Alloy HF 15 Forgings 537
24.6.3 Nickel-Base Cast Superalloy Supercast 247A 540
24.6.4 Titanium Alloy—Ti 1023 542
24.7 Airworthiness of Non-metallic Materials and Certification Methodology [Case Study on Carbon–Carbon Composite Brake Discs for TEJAS] 543
24.8 Type Clearance Process 547
24.9 Significance of Metallurgical Evaluation 548
24.10 Summary and Conclusions 548
Acknowledgments 548
References 549
Bibliography 549
25 Lightweight Ballistic Armours for Aero-Vehicle Protection 551
Abstract 551
25.1 Introduction 551
25.2 Threats to Helicopter Structures 552
25.2.1 Ballistic Threats 552
25.3 Armour Systems 553
25.3.1 Passive Armour Systems 553
25.3.2 Reactive Armour Systems 553
25.3.3 Active Armour Systems 554
25.3.4 Summary 555
25.4 Lightweight Armour Materials 555
25.4.1 Ceramics for Armour 556
25.4.2 PMCs for Armour 557
25.4.3 Ceramic—PMC Armour 559
25.4.4 Transparent Armour 561
25.5 Examples of Ballistic Armour for Helicopters 563
25.6 Test Requirements for Ballistic Armour Protection Systems 564
25.7 Concluding Remarks 565
References 565
26 Erratum to: Failure Analysis and Prevention 568
Erratum to: Chapter 23 in: N. Eswara Prasad and R.J.H. Wanhill (eds.), Aerospace Materials and Material Technologies, Indian Institute of Metals Series, DOI 10.1007/978-981-10-2143-5_23 568