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 |  موضوع: كتاب Introduction to the Design and Behavior of Bolted Joints - Non-Gasketed Joints الثلاثاء 03 أكتوبر 2023, 2:12 am | |
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أخواني في الله
أحضرت لكم كتاب
Introduction to the Design and Behavior of Bolted Joints - Non-Gasketed Joints
Fourth Edition
John H. Bickford
و المحتوى كما يلي :
Table of Contents
Preface to the Fourth Edition .xxix
Acknowledgments for Volume 1 of the Fourth Edition .xxxi
Preface to the Third Edition .xxxiii
Preface to the Second Edition .xxxv
Preface to the First Edition .xxxvii
Acknowledgments for the First Three Editions xli
Editor xliii
Abstract .xlv
Chapter 1
Basic Concepts .1
1.1 Two Types of Bolted Joints .1
1.2 Bolt’s Job .1
1.2.1 Tensile Joints 1
1.2.2 Shear Joints 3
1.3 The Challenge 3
1.3.1 Assembly Process 4
1.3.2 In-Service Behavior .5
1.3.2.1 Joints Loaded in Tension .5
1.3.2.2 Shear Joints 5
1.4 Failure Modes 6
1.5 Design 7
1.5.1 In General .7
1.5.2 Specific Goals of the Designer 7
1.6 Layout of the Book 8
Exercises .8
Chapter 2
Materials 11
2.1 Properties That Affect the Clamping Force .11
2.1.1 Magnitude of the Clamping Force .11
2.1.2 Stability of the Clamping Force .12
2.1.2.1 Thermal Expansion or Contraction . 12
2.1.2.2 Corrosion . 12
2.1.2.3 Fatigue Rupture . 12
2.1.2.4 Loss of Strength with Temperature 12
2.1.2.5 Loss of Clamping Force with Temperature . 13
2.1.2.6 Elastic Stiffness of the Parts . 13
xiii2.1.2.7 Change in Stiffness with Temperature 13
2.1.2.8 Brittle Fracture . 13
2.1.3 Miscellaneous Properties .13
2.2 Fastener Standards .14
2.3 Selecting an Appropriate Standard 14
2.4 Bolting Materials 16
2.5 Tensile Strength of Bolting Materials 16
2.5.1 General Purpose=Automotive Group 17
2.5.2 Structural Steel Group 17
2.5.3 Petrochemical=Power Group .17
2.5.4 Metric Group 17
2.5.5 Extreme-Temperature Materials .18
2.5.5.1 American Society for Testing and Materials (ASTM)
F2281 Materials 18
2.5.5.2 Traditional High-Temperature Materials . 18
2.5.6 Corrosion-Resistant Group .19
2.5.7 Two New ASTM Bolting Standards .19
2.5.7.1 Room Temperature Strengths of ASTM F2281
and F2282 Materials . 20
2.6 Metric Fasteners .20
2.7 Equivalent Materials 21
2.8 Some Comments on the Strength of Bolting Materials .21
2.8.1 In General .21
2.8.2 Shear Strength .21
2.8.3 Bearing Yield Strength 23
2.8.4 Hardness versus Strength 23
2.9 Nut Selection 24
2.10 Effects of Temperature on Material Properties 26
2.10.1 Thermal Expansion .27
2.10.2 Miscellaneous Temperature Problems .31
2.11 Other Material Factors to Consider .32
2.11.1 Fatigue Properties .32
2.11.2 Corrosion 32
2.11.3 Miscellaneous Considerations .32
2.12 Joint Materials .32
Exercises .35
References and Bibliography 35
Chapter 3
Stress and Strength Considerations 39
3.1 Types of Strength .39
3.1.1 Tensile Strength 39
3.1.2 Thread-Stripping Strength 39
3.1.3 Shear Strength .40
3.1.4 Brittle Fracture Strength .40
3.1.5 Strengths at High and Low Temperatures 40
3.1.6 Fatigue Strength 40
3.1.7 Stress Corrosion Cracking Strength 40
3.2 Bolt in Tension .41
3.2.1 Elastic Curves for Bolts in Tension .41
3.2.2 Elastic Curves under Repeated Loading .42
xiv3.2.3 Stress Distribution under Tensile Load 42
3.2.4 Stress Concentrations 43
3.2.5 Magnitude of Tensile Stress 43
3.2.6 Stress in the Nut .45
3.3 Strength of a Bolt .48
3.3.1 Proof Strength .48
3.3.2 Tensile Stress Area 49
3.3.3 Other Stress Area Equations .50
3.3.4 Stress Areas—Metric Threads .51
3.3.5 Strength of the Bolt under Static Loads .53
3.4 Strength of the Joint 54
3.4.1 Contact Stress between Fastener and Joint .54
3.4.2 Stresses within and between the Joint Members .56
3.4.3 Static Failure of the Joint .56
3.5 Other Types of Load on a Bolt 57
3.5.1 Strength under Combined Loads 59
Exercises and Problems 59
References and Bibliography 59
Chapter 4
Threads and Their Strength .61
4.1 Thread Forms 61
4.1.1 Thread Forms in General .61
4.1.2 Inch Series Thread Forms .61
4.1.3 Metric Thread Forms 63
4.2 Thread Series 63
4.3 Thread Allowance, Tolerance, and Class .64
4.3.1 Inch Series Threads .64
4.3.1.1 Allowance . 64
4.3.1.2 Tolerance 64
4.3.1.3 Class . 64
4.3.2 Metric Threads 65
4.3.2.1 Tolerance Position (the Allowance) 66
4.3.2.2 Tolerance Grade (the Tolerance) 66
4.3.2.3 Tolerance Class (the Class) . 66
4.3.3 Inch Series and Metric Thread Classes, Compared 66
4.3.4 Coating Allowances 67
4.3.5 Tolerances for Abnormal Lengths of Engagement .67
4.4 Inspection Levels 68
4.5 Thread Nomenclature 69
4.5.1 Inch Series .69
4.5.2 Metric Thread .69
4.6 Coarse- versus Fine- versus Constant-Pitch Threads .70
4.6.1 Coarse-Pitch Threads 70
4.6.2 Fine-Pitch Threads 70
4.6.3 Constant-Pitch Threads 70
4.6.4 Miscellaneous Factors Affecting Choice .70
4.7 The Strength of Threads 71
4.7.1 Basic Considerations .71
xv4.7.2 Thread Strength Equations .71
4.7.3 Thread Strength Computations When Le ¼ D .72
4.7.4 Basic Procedure—An Example .73
4.7.5 Thread Strength Calculations When Le 6¼ D .73
4.7.6 Other Stress Area Formulas 74
4.8 What Happens to Thread Form under Load? .76
4.9 Things That Modify the Static Strength of Threads 76
4.9.1 Common Factors 76
4.9.2 Which Is Usually Stronger—Nut or Bolt? 79
4.9.3 Tables of Tensile Stress and Shear Areas 79
4.10 Other Factors Affecting Strength .81
4.10.1 Pitch Diameter 81
4.10.2 Other Thread Parameters 81
Exercises and Problems 82
References and Bibliography 82
Chapter 5
Stiffness and Strain Considerations 85
5.1 Bolt Deflection .85
5.1.1 Basic Concepts 85
5.1.2 Change in Length of the Bolt .87
5.1.2.1 Effective Length 87
5.1.2.2 Cross-Sectional Areas of the Bolt . 89
5.1.3 Computing Change in Length of the Bolt 89
5.2 Bolt Stiffness Calculations .90
5.2.1 Basic Concepts 90
5.2.2 Example 90
5.2.3 Actual versus Computed Stretch and Stiffness .92
5.2.4 Stiffness of Bolt–Nut–Washer System 92
5.2.5 Alternative Expression for Bolt Stiffness 92
5.2.6 Energy Stored in the Bolt .93
5.3 The Joint 94
5.3.1 Basic Concepts 94
5.3.2 Computing Joint Stiffness .95
5.3.2.1 Stiffness of Concentric Joints . 96
5.3.2.2 Stiffness of Eccentric Joints 97
5.3.3 Stiffness in Practice .100
5.3.3.1 A Quick Way to Estimate the Stiffness of Non-Gasketed
Steel Joints 100
5.4 Gasketed Joints 101
5.5 An Alternate Way to Compute Joint Stiffness 103
5.6 Joint Stiffness Ratio or Load Factor .104
5.7 Stiffness—Some Design Goals .104
5.7.1 Energy Stored in the Joint Members 104
5.7.2 Relationship between Stiffness and Stored Energy .105
5.7.3 Stiffness Ratio .106
Exercises and Problems 106
References 107
xviChapter 6
Introduction to Assembly .109
6.1 Initial versus Residual Preload 109
6.2 Starting the Assembly Process .110
6.2.1 Assembling the Parts 110
6.2.2 Tightening the First Bolt 110
6.3 Bolt Preload versus Clamping Force on the Joint .114
6.3.1 Effects of Hole Interference 114
6.3.2 Resistance from Joint Members .116
6.4 Continuing the Snugging Pass .119
6.5 Short-Term Relaxation of Individual Bolts .119
6.5.1 Sources of Short-Term Relaxation .119
6.5.1.1 Poor Thread Engagement 120
6.5.1.2 Thread Engagement Too Short 120
6.5.1.3 Soft Parts 121
6.5.1.4 Bending 121
6.5.1.5 Nonperpendicular Nuts or Bolt Heads 121
6.5.1.6 Fillets or Undersized Holes 121
6.5.1.7 Oversized Holes 121
6.5.1.8 Conical Makeups . 121
6.5.2 Factors Affecting Short-Term Relaxation 122
6.5.2.1 Bolt Length 123
6.5.2.2 Belleville Washers . 123
6.5.2.3 Number of Joint Members . 123
6.5.2.4 Tightening Speed 123
6.5.2.5 Simultaneous Tightening of Many Fasteners . 124
6.5.2.6 Bent Joint Members . 124
6.5.3 Amount of Relaxation to Expect 124
6.5.4 Torsional Relaxation 125
6.6 Elastic Interactions between Bolts .127
6.7 The Assembly Process Reviewed .132
6.8 Optimizing Assembly Results 134
Exercises .135
References 135
Chapter 7
Torque Control of Preload .137
7.1 Importance of Correct Preload 137
7.1.1 Problems Created by Incorrect Preload 138
7.1.2 How Much Preload? .138
7.1.3 Factors That Affect the Working Loads on Bolts 139
7.2 Torque versus Preload—The Long-Form Equation 140
7.3 Things That Affect the Torque–Preload Relationship .142
7.3.1 Variables That Affect Friction 142
7.3.2 Geometric Variables .143
7.3.3 Strain Energy Losses 144
7.3.4 Prevailing Torque .144
7.3.5 Weight Effect 144
7.3.6 Hole Interference 145
xvii7.3.7 Interference Fit Threads .145
7.3.8 The Mechanic 145
7.3.9 Tool Accuracy .145
7.3.10 Miscellaneous Factors .145
7.4 Torque versus Preload—The Short-Form Equation 146
7.5 Nut Factors 147
7.5.1 Some General Comments 147
7.5.2 Nut Factor Examples and Case Histories .148
7.5.3 Coefficient of Friction versus Nut Factor .151
7.6 Torque Control in Practice 151
7.6.1 What Torque Should I Use? .151
7.6.2 Initial Preload Scatter .152
7.6.3 Low Friction for Best Control 153
7.6.4 The Lines Aren’t Always Straight .153
7.6.5 Other Problems .154
7.7 Some Tools for Torque Control 155
7.7.1 Some Generalities .155
7.7.2 Reaction Forces Created by the Tool .157
7.7.2.1 Shear Loads Created by Torque Wrenches 157
7.7.2.2 Reaction Torques . 158
7.7.3 In the Beginning—A Search for Accuracy 159
7.7.3.1 Manual Torque Wrenches 159
7.7.4 More Torque for Large Fasteners 160
7.7.4.1 Torque Multipliers and Geared Wrenches . 160
7.7.4.2 Hydraulic Wrenches . 160
7.7.5 Toward Higher Speed .160
7.7.5.1 Impact Wrenches 161
7.7.5.2 Pulse Tools . 161
7.7.5.3 Nut Runners . 161
7.7.6 Add Torque Calibration or Torque Monitoring .162
7.7.7 Add Torque Feedback for Still Better Control .164
7.7.8 For More Information 164
7.8 Fasteners That Limit Applied Torque .164
7.8.1 The Twist-Off Bolt 164
7.8.2 The Frangible Nut 165
7.9 Is Torque Control Any Good? .166
7.10 Testing Tools 166
7.11 The Influence of Torque Control on Joint Design .167
7.12 Using Torque to Disassemble a Joint 168
Exercises and Problems 169
References and Bibliography 169
Chapter 8
Torque and Turn Control 173
8.1 Basic Concepts of Turn Control 173
8.2 Turn versus Preload .175
8.2.1 Common Turn–Preload Relationship .175
8.2.2 Other Turn–Preload Curves 176
8.2.2.1 Sheet Metal Joint 176
8.2.2.2 Gasketed Joint 177
xviii8.3 Friction Effects .177
8.4 Torque and Turn in Theory .179
8.4.1 Torque, Turn, and Energy 179
8.4.2 Torque–Turn–Preload Cube .179
8.4.3 The Broader View .179
8.5 Turn-of-Nut Control 181
8.5.1 The Theory .181
8.5.2 The Practice 182
8.5.2.1 Structural Steel . 182
8.5.2.2 Turn-of-Nut Procedure in Production Operations . 183
8.5.2.3 Turn-of-Nut Procedure in Aerospace Assembly 183
8.6 Production Assembly Problems .184
8.7 Popular Control Strategies .186
8.7.1 Torque–Angle Window Control .186
8.7.2 Torque–Time Window Control 187
8.7.3 Hesitation and Pulse Tightening .187
8.7.4 Yield Control 188
8.7.5 Turn-of-Nut Control 190
8.7.6 Prevailing Torque Control 191
8.7.7 Plus—Permanent Records 191
8.7.8 Meanwhile, Out in the Field .191
8.8 Monitoring the Results 192
8.9 Problems Reduced by Torque–Angle Control .193
8.10 How to Get the Most Out of Torque–Angle Control 193
Exercises and Problems 194
Bibliography and References 194
Chapter 9
Other Ways to Control Preload .197
9.1 Stretch Control: The Concept 197
9.2 Problems of Stretch Control 198
9.2.1 Dimensional Variations 198
9.2.2 Change in Temperature 199
9.2.3 Plastic Deformation of the Bolt 199
9.2.4 Bending and Nonperpendicular Surfaces 199
9.2.5 Grip Length 199
9.3 Stretch Measurement Techniques 199
9.3.1 Micrometer Measurements .199
9.3.1.1 Irregular Measurement Surfaces . 199
9.3.1.2 Operator Feel . 200
9.3.1.3 Measurement Accuracy Required 200
9.3.1.4 Depth Micrometers 200
9.3.2 Other Techniques 201
9.3.2.1 Dial Gages 201
9.3.2.2 Commercially Available Gage Bolt 202
9.3.2.3 Ultrasonic Measurements . 202
9.4 How Much Stretch? .202
9.5 Problems Reduced by Stretch Control .203
9.6 How to Get the Most Out of Stretch Control .204
9.7 Direct Preload Control—An Introduction .204
xix9.7.1 Strain-Gaged Bolts 205
9.7.2 Strain-Gaged Force Washers 205
9.7.3 Direct Tension Indicators .205
9.7.4 Squirter Self-Indicating DTIs 207
9.7.5 Twist-Off Tension-Control Bolts 207
9.7.6 Alternative-Design Fasteners 208
9.8 Bolt Tensioners 208
9.8.1 The Hardware .208
9.9 Bolt Heaters .210
9.10 Problems Reduced by Direct Preload Control .210
9.10.1 Direct Tension Indicators .210
9.10.2 Twist-Off Bolts 211
9.10.3 Hydraulic Tensioners 211
9.10.4 Bolt Heaters 211
9.11 Getting the Most Out of Direct Preload Control 211
9.11.1 Twist-Off Bolts and DTI Washers 211
9.11.2 Bolt Tensioners .212
9.11.3 Bolt Heaters 212
9.12 Ultrasonic Measurement of Stretch or Tension .213
9.12.1 In General .213
9.12.2 Principle of Operation .213
9.12.3 How It’s Used .214
9.12.4 Calibration of the Instrument .214
9.12.5 Presently Available Instruments 215
9.13 Ultrasonic Measurements Using Plasma-Coated, Thin Film Transducers 215
Exercises and Problems 215
References 216
Chapter 10
Theoretical Behavior of the Joint under Tensile Loads .219
10.1 Basic Joint Diagram .220
10.1.1 Elastic Curves for Bolt and Joint Members 220
10.1.2 Determining Maximum and Minimum Residual Assembly Preload 220
10.1.2.1 The Equations . 220
10.1.2.2 An Example 222
10.1.3 Joint Diagram for Simple Tensile Loads 224
10.1.4 The Parable of the Red Rolls Royce .226
10.1.5 Back to the Joint Diagram—Simple Tensile Load 227
10.2 Details and Variations .228
10.2.1 Changing the Bolt or Joint Stiffness .228
10.2.2 Critical External Load 229
10.2.3 Very Large External Loads .230
10.2.4 Another Form of Joint Diagram 230
10.3 Mathematics of the Joint .232
10.3.1 Basic Equations .232
10.3.2 Continuing the Example .234
10.4 Loading Planes .235
10.4.1 Tension Applied to Interface of Joint Members .236
10.4.2 Mathematics of a Tension Load at the Interface 238
10.4.3 Significance of the Loading Planes .238
10.4.4 Loading Planes within the Joint Members 239
xx10.4.5 Modifying Our Example to Include the Effects of Internal
Loading Planes 243
10.5 Dynamic Loads on Tension Joints .243
10.6 The Joint Under a Compressive Load .245
10.7 A Warning .245
Exercises and Problems 246
References 247
Chapter 11
Behavior of the Joint Loaded in Tension: A Closer Look .249
11.1 Effect of Prying Action on Bolt Loads 250
11.1.1 Definition of Prying 250
11.1.2 Discussion of Prying .251
11.1.3 Prying Is Nonlinear .255
11.2 Mathematics of Prying .256
11.2.1 In General .256
11.2.2 VDI’s Analytical Procedure 256
11.2.3 Critical Loads and the Preloads Required to Prevent Joint Separation .260
11.2.4 Bending Stress in the Bolt before Liftoff 261
11.2.5 Effects of Very Large External Loads .263
11.3 Other Nonlinear Factors 263
11.3.1 Nut–Bolt System .263
11.4 Thermal Effects 266
11.4.1 Change in Elasticity 266
11.4.2 Loss of Strength 267
11.4.3 Differential Thermal Expansion 267
11.4.4 Stress Relaxation .271
11.4.5 Creep Rupture 273
11.4.6 Compensating for Thermal Effects .274
11.5 Joint Equations That Include the Effects of Eccentricity
and Differential Expansion 276
11.5.1 The Equations .276
11.5.2 An Example 277
Exercises and Problems 281
References 281
Chapter 12
In-Service Behavior of a Shear Joint 283
12.1 Bolted Joints Loaded in Axial Shear .283
12.1.1 In General .283
12.1.2 Friction-Type Joints 284
12.1.2.1 Bolt Load in Friction-Type Joints 284
12.1.2.2 Stresses in Friction-Type Joints 285
12.1.3 Bearing-Type Joints 285
12.1.3.1 Stresses in Bearing-Type Joints . 286
12.2 Factors That Affect Clamping Force in Shear Joints 286
12.3 Response of Shear Joints to External Loads .288
12.4 Joints Loaded in Both Shear and Tension .288
12.5 Present Definitions—Types of Shear Joint 290
Exercises .290
References 291
xxiChapter 13
Introduction to Joint Failure .293
13.1 Mechanical Failure of Bolts .293
13.2 Missing Bolts 294
13.3 Loose Bolts .294
13.4 Bolts Too Tight 295
13.5 Which Failure Modes Must We Worry About? .295
13.6 Concept of Essential Conditions 295
13.7 Importance of Correct Preload 297
13.7.1 Corrosion 297
13.7.2 Stress Corrosion Cracking .297
13.7.3 Fatigue Failure 297
13.7.4 Mechanical Failure 297
13.7.5 Self-Loosening of Fastener 297
13.7.6 Leakage .297
13.8 Load Intensifiers 298
13.9 Failure of Joint Members .298
13.10 Galling 300
13.10.1 Discussion .300
13.10.2 Removing Galled Studs .300
Exercises .301
References 302
Chapter 14
Self-Loosening 303
14.1 The Problem .303
14.2 How Does a Nut Self-Loosen? .303
14.3 Loosening Sequence .306
14.4 Junker’s Theory of Self-Loosening .306
14.4.1 The Equations .307
14.4.2 The Long-Form Equation in Practice .308
14.4.3 The Equation When Applied Torque Is Absent .308
14.4.4 Why Slip Occurs? 309
14.4.5 Other Reasons for Slip 310
14.4.6 Other Theories of Self-Loosening 310
14.5 Testing for Vibration Resistance 310
14.5.1 NAS Test .310
14.5.2 Junker Test 311
14.6 To Resist Vibration 312
14.6.1 Maintaining Preload and Friction .313
14.6.1.1 Conventional Wisdom . 313
14.6.2 Preventing Relative Slip between Surfaces 314
14.6.3 Countering Back-Off Torque 315
14.6.3.1 Prevailing Torque Fasteners . 315
14.6.3.2 Nord-Lock Nuts and Washers 318
14.6.3.3 In General . 318
14.6.4 Double Nuts 319
14.6.5 Mechanically Locked Fasteners 319
14.6.5.1 Lock Wires and Pins . 319
14.6.5.2 Welding . 319
xxii14.6.5.3 Stage 8 Fastening System . 319
14.6.5.4 Huck Lockbolt 320
14.6.5.5 Honeybee Robotics . 320
14.6.5.6 A-Lock Bolt and Nut . 321
14.6.5.7 Omni-Lok Fasteners . 322
14.6.6 Chemically Bonded Fasteners .322
14.6.6.1 Rust 322
14.6.6.2 Anaerobic Adhesives 322
14.6.7 Vibration-Resistant Washers 323
14.6.7.1 Washers That Maintain Tension in the Fastener . 323
14.6.7.2 Toothed Washer . 323
14.6.7.3 Helical Spring Washer 324
14.6.7.4 Nord-Lock Washer . 324
14.6.8 Comparison of Options 324
Exercises .324
References and Bibliography 325
Chapter 15
Fatigue Failure .327
15.1 Fatigue Process 327
15.1.1 Sequence of a Fatigue Failure .327
15.1.1.1 Crack Initiation 327
15.1.1.2 Crack Growth . 328
15.1.1.3 Crack Propagation 328
15.1.1.4 Final Rupture . 328
15.1.2 Types of Fatigue Failure .328
15.1.3 Appearance of the Break 329
15.2 What Determines Fatigue Life? .329
15.2.1 S–N Diagrams .330
15.2.2 Material versus ‘‘The Part’’ .332
15.2.3 Summary .332
15.3 Other Types of Diagram 333
15.3.1 Constant Life Diagram .333
15.3.2 Center Portion of Constant Life Diagram 334
15.3.3 Approximate Constant Life Diagram .334
15.3.4 Endurance Limit Diagram 336
15.3.5 Fatigue Life Data for Fasteners 337
15.4 Influence of Preload and Joint Stiffness .338
15.4.1 Fatigue in a Linear Joint .338
15.4.2 Nonlinear Joints 339
15.4.3 What Is the Optimum Preload? 341
15.4.4 Fatigue and the VDI Joint Design Equations .341
15.5 Minimizing Fatigue Problems 343
15.5.1 Minimizing Stress Levels .344
15.5.1.1 Increased Thread Root Radius . 344
15.5.1.2 Rolled Threads . 344
15.5.1.3 Fillets 345
15.5.1.4 Perpendicularity 345
15.5.1.5 Overlapping Stress Concentrations . 345
15.5.1.6 Thread Run-Out . 345
xxiii15.5.1.7 Thread Stress Distribution 345
15.5.1.8 Bending . 347
15.5.1.9 Corrosion 347
15.5.1.10 Flanged Head and Nut . 347
15.5.1.11 Surface Condition . 348
15.5.2 Reducing Load Excursions .348
15.5.2.1 Prevent Prying . 348
15.5.2.2 Proper Selection of Preload 348
15.5.2.3 Control of Bolt-to-Joint Stiffness Ratios 348
15.5.2.4 Achieving the Correct Preload 348
15.6 Predicting Fatigue Life or Endurance Limit 348
15.7 Fatigue of Shear Joint Members 349
15.8 Case Histories 351
15.8.1 Transmission Towers 351
15.8.2 Gas Compressor Distance Piece 351
Exercises .352
References and Bibliography 352
Chapter 16
Corrosion .355
16.1 Corrosion Mechanism 355
16.1.1 Galvanic Series 355
16.1.2 Corrosion Cell .356
16.1.3 Types of Cells 357
16.1.3.1 Two-Metal Corrosion . 357
16.1.3.2 Broken Oxide Film . 358
16.1.3.3 Stress Corrosion Cracking 358
16.1.3.4 Crevice Corrosion . 359
16.1.3.5 Fretting Corrosion 359
16.2 Hydrogen Embrittlement .360
16.2.1 Stress Cracking Failure Modes .360
16.2.2 Hydrogen Embrittlement Mechanism of Failure 360
16.2.3 Susceptible and Safe Materials 361
16.2.4 Testing for Embrittlement .362
16.2.5 Fighting Hydrogen Embrittlement 363
16.3 Stress Corrosion Cracking .363
16.3.1 Mechanism of Failure .363
16.3.2 The Concept of KISCC .364
16.3.3 Factors Affecting KISCC 365
16.3.3.1 Bolt Material . 365
16.3.3.2 The Environment 365
16.3.3.3 Thread-Forming Procedure 365
16.3.3.4 Bolt Strength or Hardness 365
16.3.3.5 Type of Electrolyte 367
16.3.3.6 Temperature 367
16.3.3.7 Bolt Diameter and Thread Pitch . 367
16.3.4 Combating SCC 368
16.3.4.1 Susceptibility of the Material 368
16.3.4.2 Eliminating the Electrolyte . 369
16.3.4.3 Keeping Stress Levels below a Threshold Limit . 370
xxiv16.3.5 Surface Coatings or Treatment .374
16.3.6 Detecting Early SCC Cracks .376
16.4 Other Types of Stress Cracking .376
16.4.1 Stress Embrittlement .376
16.4.2 Hydrogen-Assisted Cracking 376
16.5 Minimizing Corrosion Problems 377
16.5.1 In General .377
16.5.2 Detailed Techniques 377
16.6 Fastener Coatings 379
16.6.1 In General .379
16.6.2 Organic Coatings 380
16.6.2.1 Paints 380
16.6.2.2 Phos-Oil Coatings . 381
16.6.2.3 Solid-Film Organic Coatings 381
16.6.3 Inorganic or Metallic Coatings .381
16.6.3.1 Electroplated Coatings 382
16.6.3.2 Hot-Dip Coatings . 382
16.6.3.3 Mechanical Plating . 382
16.6.3.4 Miscellaneous Coating Processes 383
16.6.4 Composite Coatings 383
16.6.5 Rating Corrosion Resistance 387
16.6.6 Substitutes for Cadmium Plate .387
Exercises .388
References and Bibliography 388
Chapter 17
Selecting Preload for an Existing Joint 391
17.1 How Much Clamping Force Do We Want? 391
17.1.1 Factors to Consider 391
17.1.1.1 Joint Slip . 392
17.1.1.2 Self-Loosening 392
17.1.1.3 Pressure Loads 392
17.1.1.4 Joint Separation 393
17.1.1.5 Fatigue 393
17.1.2 Placing an Upper Limit on the Clamping Force .393
17.1.2.1 Yield Strength of the Bolt . 394
17.1.2.2 Thread-Stripping Strength 394
17.1.2.3 Design-Allowable Bolt Stress and Assembly Stress Limits . 394
17.1.2.4 Torsional Stress Factor . 394
17.1.2.5 Shear Stress Allowance . 395
17.1.2.6 Stress Cracking . 395
17.1.2.7 Combined Loads . 395
17.1.2.8 Damage to Joint Members . 395
17.1.2.9 Distortion of Joint Members 395
17.1.2.10 Gasket Crush 396
17.1.3 Summarizing Clamping Force Limits .396
17.2 Simple Ways to Select Assembly Preloads .397
17.2.1 Best Guide: Past Experience .397
17.2.2 Second Best: Ask the Designer .398
17.2.3 Unimportant Joint: No Prior Experience .398
xxv17.2.4 When More Care Is Indicated 398
17.2.5 If Improvements Are Required .400
17.2.6 Selecting Preload for Critical Joints 400
17.3 Estimating the In-Service Clamping Force 400
17.3.1 Basic Assumptions 402
17.3.2 Combining the Scatter Effects 402
17.4 Relating Desired to Anticipated Bolt Tensions 408
17.5 Which Variables to Include in the Analysis .410
17.5.1 In General .410
17.5.2 Possible Factors to Include .411
17.5.3 Which Should We Include? .411
17.6 ASTM F16.96 Subcommittee on Bolting Technology .412
17.7 A More Rigorous Procedure 412
17.7.1 Experiments Required for True Accuracy 413
17.7.2 The Equations .413
17.7.3 Minimum Clamping Force—Some Examples .414
17.7.3.1 First Example—Using Worst-Case Values . 414
17.7.3.2 Second Example—Using Statistically Combined Values 415
17.7.3.3 Third Example—Using Average Values . 416
17.7.3.4 Fourth Example—Using Feedback Control Values . 417
17.7.4 Maximum Bolt Tension 417
17.8 NASA’s Space Shuttle Preload Selection Procedure 418
17.8.1 Calculating Maximum and Minimum Preloads 418
17.8.2 Confirming the Preload Calculations 420
17.8.3 Discussion .420
Exercises .421
References and Bibliography 421
Chapter 18
Design of Joints Loaded in Tension .423
18.1 A Major Goal: Reliable Joints .423
18.1.1 Checklist for Reliable Bolted Joints 423
18.2 Typical Design Steps 424
18.2.1 Initial Definitions and Specifications 425
18.2.2 Preliminary Design 425
18.2.3 Load Estimates .425
18.2.4 Review Preliminary Layouts: Define the Bolts .426
18.2.5 Clamping Force Required .426
18.2.5.1 Minimum Clamp 426
18.2.5.2 Maximum Clamp 427
18.3 Joint Design in the Real World .427
18.4 VDI Joint Design Procedure 427
18.4.1 Terms and Units .428
18.4.2 Design Goals .429
18.4.3 General Procedure 429
18.4.4 Estimating Assembly Preloads: Preliminary Estimate of Minimum
and Maximum Assembly Preloads 430
18.4.5 Adding the Effects of the External Load 431
18.4.6 Is the Required Force Good Enough? 432
18.4.7 Further Considerations .433
xxvi18.4.7.1 Static Strength of the Bolt 433
18.4.7.2 Fatigue 433
18.4.7.3 Bearing Stress 434
18.4.7.4 Shear Stress . 434
18.4.7.5 Bending Stress . 434
18.4.7.6 Eccentric Loading . 434
18.4.8 Revised Bolt Specifications .435
18.5 An Example .435
18.5.1 Inputs 435
18.5.2 Calculations .436
18.5.2.1 Maximum and Minimum Assembly Preloads . 436
18.5.2.2 Static Strength of the Bolts . 436
18.5.2.3 Fatigue Strength . 437
18.5.2.4 Contact Stress . 437
18.6 Other Factors to Consider When Designing a Joint 437
18.6.1 Thread Strength 437
18.6.2 Flexible Bolts 438
18.6.3 Accessibility .438
18.6.4 Shear versus Tensile Loads .438
18.6.5 Load Magnifiers 438
18.6.6 Minimizing Embedment 438
18.6.7 Differential Expansion 438
18.6.8 Other Stresses in Joint Members .438
18.6.9 Locking Devices 439
18.6.10 Hole Interference .439
18.6.11 Safety Factors .439
18.6.12 Selecting a Torque to be Used at Assembly 439
Exercises .440
References 440
Bibliography .440
Chapter 19
Design of Joints Loaded in Shear 443
19.1 An Overview 443
19.2 The VDI Procedure Applied to Shear Joints .444
19.3 How Shear Joints Resist Shear Loads .446
19.3.1 In General .446
19.3.2 Concept of Slip-Critical Joints 446
19.4 Strength of Friction-Type Joints 448
19.4.1 In General .448
19.4.2 Allowable Stress Procedure .449
19.4.3 Other Factors to Consider 449
19.4.4 Slip Coefficients in Structural Steel .450
19.4.5 An Example 451
19.4.5.1 Minimum Preload Required to Prevent Slip . 453
19.4.5.2 Alternate Using the Allowable Stress Procedure 454
19.5 Strength of Bearing-Type Joints 455
19.5.1 Shear Strength of Bolts .455
19.5.1.1 Distribution of Load among the Bolts 455
19.5.1.2 Shear Strength Calculations 456
xxvii19.5.2 Tensile Strength of Joint Plates .457
19.5.3 Bearing Stress 457
19.5.4 Tearout Strength .458
19.5.5 Summary .459
19.5.6 Clamping Force Required by a Bearing-Type Joint .459
19.6 Eccentrically Loaded Shear Joints .459
19.6.1 Rotation about an Instant Center .459
19.6.2 Rotation about the Centroid of the Bolt Group .461
19.6.2.1 Find the Centroid of the Bolt Group . 461
19.6.2.2 Estimating the Shear Stress on the Most Remote Bolt . 462
19.7 Allowable Stress versus Load and Resistance Factor Design 465
Exercises .466
References 466
Appendix A
Units and Symbol Log .467
Appendix B
Glossary of Fastener and Bolted Joint Terms 475
Appendix C
Sources of Bolting Information and Standards 483
Appendix D
English and Metric Conversion Factors .485
Appendix E
Tensile Stress Areas for English and Metric Threads with Estimated ‘‘Typical’’
Preloads and Torques for As-Received Steel Fasteners .487
Appendix F
Basic Head, Thread, and Nut Lengths .497
Index .505
Index
A
A325 bolt, elastic curve for, 183
Acme thread, 61–62
Airframe, 115
Air-tool control system, 188
AISC allowable stress limit, 464
AISC bolt specifications, 449
AISI H-11 bolts, 364
Allowable stress, 465
A-lock bolt and nut, 321
American Bureau of Shipping, 14
American Institute of Steel Construction (AISC)
Load, 290
American National Standards Institute
(ANSI), 14
American Society for Testing and Materials
(ASTM), 14–17
American Society of Mechanical Engineers
(ASME), 14
Anaerobic adhesives, 322–323
ANSI washer, standard thickness, 56
Anticipated loads and strength, 465
ASME Boiler and Pressure Vessel Code, 50
Assembly
stress limits, 394
torque selection for, 439–440
Assembly preloads
calculations for, 436
estimation of, 430–431
selection of, 398–400
Assembly process, 4, 6, 22, 114
first bolt tightening, 110–114
optimizing assembly outcomes, 134–135
parts assembling, 110
tool work and clamping force, factors affecting
relationship, 133
Association of American Railroads, 14
ASTM A193 B7 bolts, 110
ASTM A325 bolts, 206
ASTM A490 bolts and strength loss, 42
ASTM A193 materials and temperature
limits, 18
ASTM B-117 and corrosion resistance
rating, 387
ASTM B7 fasteners, 200
ASTM F2281 and F2282 materials, room
temperature strengths, 18–20
ASTM F16.96 subcommittee, on bolting
technology, 412
Automotive-tightening procedures, 191
Average assembly preload, 223
Axial bolt load, 250, 252
Axial shear
bolted joints loaded in, 283–284
joints, static failure modes of, 56–57, 299
load, 450, 452
Axial tension load for bolt, 255
Axis of gyration of joint, 256–257
B
Bearing stress, 434, 457–458
Bearing-type joints, 285
clamping force for, 459
static failure of, 56
strength determining factors for, 455
stresses in, 286
Belleville washer, 123, 275, 316
Bending stresses, 262, 434
Bent bolt, ‘‘radius of curvature’’, 58
Bent joint members, 124
Bolted joints
behavior and life of, 2
clamping force and, 4, 426–427
design of, 7
failure on Skylab program, 155
load estimation, 425–426
preliminary design, 425
problems in, 3
types of, 1–2 (see also Shear joints; Tensile
joints)
typical design steps for, 424
Bolt head and nut, contact surfaces, 54–55
Bolt-hole interference, 193
Bolting information and standards, 483–484
Bolting materials
hardness and strength of, 23
properties of, 16
505resistance to corrosion, 12
shear strength of, 21
temperature effect on, 12–13, 26
tensile strength of, 16
Bolting spec by RCSC, 290
Bolting standards, see Fastener standards
Bolting technology, ASTM F16.96 subcommittee
on, 412
Bolting Technology Council (BTC), 143, 412
Bolt loads and interface clamping force, thermal
effects on
compensation for, 274–276
creep and stress relaxation, 271–273
differential thermal expansion and contraction,
267–271
modulus of elasticity and tensile strength,
266–267
Bolt-nut system, 24–25
Bolt-nut-washer system, stiffness of, 92
Bolt preload
and clamping force, 114–118
limits, 444
in shear joint, 286
Bolt(s)
clamping capacity of, 12
cross-sectional areas of, 89, 453
deformation of, 85, 93
design allowable stresses for, 394
diameter, thread pitch and, 367–368
diameter of, 72
dimensions, 497
distribution of load, 455–456
effective length of, 87–89
elastic curves for, 87
elastic interactions between, 127–132
elongation of, 91, 173
energy storage capacity of, 8, 93
flexible, 438
and hole, 114–116
hydrogen embrittlement cracking of, 7
length, 123
load types on, 57
mechanical failure of, 293
shear strength of, 455
short and stubby, 89
short-term relaxation of
amount to expect, 124–125
factors affecting in, 122–124
sources of, 119–120
torsional relaxation, 125–127
static strength of, 53, 433, 436–437
stiffness of (see Bolt stiffness)
strength, KISCC value and, 365–367
tension in (see Bolt tension)
tightening, 48, 111, 140
yield strength of, 394
Bolts and joint members
differential expansion between, 5
elastic deformation of, 3
shear strength of, 3
stiffness of, 27
Bolt stiffness, 87, 175
calculations of, 90–91
design goals of, 104–106
expression for, 92–93
Bolt stretch component, of reaction
torque, 141
Bolt tension, 2, 256
anticipated, 408–410
elastic curves for, 41–42
at initial preload, 137
maximum, 417–418
at residual preload, 137
in service, 137
tension and compression stress in, 43
Bolt tensioners, see Tensioners
Bolt thread root stresses, 76
Bolt-to-bolt preloads, 143
Bolt-to-joint stiffness ratios, 287
Bolt yield, 256
Brittle fracture, 13, 40
Broken bolt, examination, 329
BS 4882 and equivalent materials, service
temperature limits, 29
Butt joint, see Shear joint
Buttress thread, 61–62
C
Centroid, of bolt group, 461–464
Clamping force, 4, 114, 219–221, 226, 234, 240,
261–262, 274, 444, 459
bolted joints design and, 426–427
considering factors, 391–393
instability of, 28
limits, 396–397
loss of, 13, 30
magnitude of, 11
properties affecting, 11
requirements for joint, 393–396
in shear joints, 3, 286–288
stability of, 12
Clutch, types of, 162
C-Micrometer, see Micrometers
Coarse-and fine-inch series and metric fastener
series, 68
Coarse-pitch threads, 63, 70
Combined loads, 395
Compressive force and deflection, of blocks,
94–95
506 Introduction to the Design and Behavior of Bolted JointsConcentric joints, stiffness of, 96–97
Conical makeups, preloaded fastener relaxation
in, 121–122
Constant-pitch threads applications, 70
Contact stress, 437
Conventional nut, relative stress level in, 47
Corrosion, 12, 32, 297
cadmium plate, substitutes for, 387–388
composite coatings, 383–387
hydrogen-assisted cracking, 376
hydrogen embrittlement, 360–363
inorganic coatings, 381–383
mechanism (see Corrosion mechanism)
organic coatings, 380–381
reduction of, 377–379
resistance rating, 387
SCC
combating, 368–374
early cracks, detection of, 376
failure mechanism, 363–364
KISCC concept, 364–368
surface coatings, 374–376
stress embrittlement, 376
Corrosion mechanism
corrosion cell, 356–360
galvanic series, 355–356
Corrosion protection, 451
Corrosion-resistant materials, 19, 378
Crack growth monitoring, computer-controlled
equipment for, 362
Cracking susceptibility and temperature, 367
Crack initiation, 327
Crack propagation, 328
Creep, 27, 120, 123, 271, 445
relaxation, 433
rupture, 273
Crevice corrosion, 359
Critical external load, 229
Critical hardness, 23
Critical joints, preload selection for, 400
Cryogenic bolting materials, room temperature
strengths for, 31
Cryogenic temperatures, 18, 31
Cut and rolled threads, 143
D
Deformations, in joint and bolt, 174–175
Depth micrometers, 200
Differential expansion, 258, 265, 268, 269, 271,
275, 433, 438
Direct tension indicators (DTI), see Washers,
tension indicating
Double nut, 316, 319
Drunken thread, 81
Ductile bolts, 185
Ductile fastener, 41
E
Eccentric joints, stiffness equations of, 97–100
Eccentric load, 434–435, 460, 463
Eccentric nut, 316
Elastic curves, for bolts, 221
Elastic interactions, 152, 445
Elasticity modulus, 13, 27, 87–88
Elastic limit, 41
Elastic stiffness, 13
Electroplated coatings, 382
Elongated expansion bolt, 275
Elongation chart, for bolts, 203
Embedment, relaxation, 4, 119–120, 122,
152, 189
Endurance limit, 12, 32, 330–332, 335, 342–344,
348–349
Engine head bolts, preloads in, 149
Equi-torq motor, 188
Exotic aerospace bolting materials, service
temperature limits of, 29
Expansion, coefficients of, 445
F
Fastener, 208
chemically bonded, 322–323
diameter of, 16, 71
initial preload scatter for, 152
international metric standard for, 20
and joint, contact stress between, 54
length change for, 90
limiting torque of, 164
shape of, 16
standards, 14–15
static failure of, 138
tensile force of, 48
Fastener coatings, 379
cadmium plate, substitutes for, 387–388
composite, 383–387
corrosion resistance, rating, 387
inorganic, 381–383
organic, 380–381
Fastener control, production method of, 191
Fastener joint system, energy delivered to, 112
Fastener materials; see also Bolting materials
relative weights of, 33
selection of, 32
shear strength of, 71
Fatigue, 6, 393, 433–434
break surface of bolt, failed in, 329
Index 507case histories of, 351–352
cracks, 329, 344, 352
cracks and failures, 329
eliminating problems, 343–348
factors affect life, 332–333
failure, 138, 327–328
life, 32, 329–337
in linear joint, 338–339
loading conditions, variety of, 335
and mechanical failure of joint, 297, 327
process of, 327–328
resistance, 332
resistant fasteners, 344
rupture, 12
of shear joint members, 349–351
strength, 32, 40, 332, 350, 433–434
types of, 328–329
and VDI joint design equations, 341–343
Federal Standard FED-STD-H 28=2B, 61
Fillets, 121
Fine-pitch threads, 63
applications of, 70
lengths for, 67
Finite-element analysis, 413
Flanged nut, 316
Flange rotation, 250
Force ratio, see Load factor
Fracture mechanics, 350
Frangible nut, 165
Free-spinning lock nuts and bolts, 317
Fretting corrosion, 359–360
Friction
coefficient, 451
effects, 177
joints, 56
restraint, 141, 175
variables affecting, 142–143
Friction-type joints, 447, 449
bolt holes, 284–285
stresses in, 285
G
Galling, 300–301
Galvanic series, 355–356
Galvanized coating, 450–451
Gasket creep, 274
Gasket crush, 396
Gasketed joints, 6, 56, 174–175
relaxation of, 178
stiffness of, 101–103
turn–preload curve for, 177
Gaskets, 274
creep and relaxation of, 177
force-deflection behavior of, 103
Geared wrenches, 156, 160
Graphite-based lubricants, friction coefficient
for, 149
H
Heaters, bolt, 210
Helical spring washer, 324
Hex bolts, 498
finished, 499
heavy, 499, 500
metric, 501–502
Hex cap screws, 499–500
metric, 502–503
High-temperature materials, 18
Hole–bolt interface problems, 115
Hole interference, 114, 439
Honeybee robotics, 320
Hooke’s law, 85, 93, 197, 269
Hot-dip coatings, 382
Hot torque, 275
Huck lockbolt, 320
Hydraulic tensioners, 117–119; see also
Tensioners
Hydraulic wrenches, torque accuracy of,
159–160
Hydrogen-assisted cracking, 376
Hydrogen embrittlement
combating, 363
failure mechanism, 360–361
materials, safe and susceptible, 361–362
stress cracking failure modes, 360
testing for, 362
Hysteresis effects, 265
I
IFI, see Industrial Fastener Institute
Impact wrenches, torque accuracy for, 161
Inch series and metric thread classes, 66–67
Inch series external (bolt) thread code, 69
Inch series thread forms, 61
Inch series threads
allowance of, 64
class of, 64
coatings of, 67
tolerance of, 64
Inconel bolts, 53, 116
Industrial Fastener Institute, 14, 316, 362
Infinite life, 336, 342
Inorganic coatings, see Metallic coating
Inorganic zinc-rich paint, 451
In-service clamping force, estimation
basic assumptions of, 402
508 Introduction to the Design and Behavior of Bolted Jointsscatter effects and, 402–408
variables in, 401
In-service tension in bolts, 109
Interference fit holes, 115
International Standards Organization (ISO), 14
J
Joint
behavior, 249
design, 452
designer goals and problems of, 4, 7
eccentrically loaded, 257
hardness, on torque tool selection, 157
plates, 457
separation, 138, 393
slip, 138, 392
yields, 153
Joint behavior, under loads
compressive load and, 245
critical external load and, 229–230
equations, for studying, 232–235
fluctuating external load and, 243–244
joint diagrams, 220–225
loading planes and, 235–242
residual assembly preload determination,
220–224
Rolls Royce example, 226–227
simple tensile loads and, 244–266
stiffness, effect of, 228
Joint diagram, and joint behavior
axial compression, load under, 246
fluctuating loads and, 244–245
joint surface, external load at, 237
for preloaded joints, 220–221
for simple tensile loads, 224–227
stiffness change and, 228
Joint failure, 293
essential conditions for, 295–297
failure mode and preload, relationship, 297
failure modes, types of, 295
fatigue and mechanical, 297
Joint loaded in tension
analysis of behavior on prying action, 250–255
impact of change in temperature, 266–276
joint equations for eccentricity and differential
expansion, 276–280
mathematics of prying in, 256–263
nonlinear behavior of, 263–266
Joint materials
bearing yield strength of, 23
failures of, 35
room temperature strength of, 32–35
Joint members, 123
bolt preload and clamping force on, 114
classification of, 157
damage and distortion, 395
deflection of, 95, 105
disassembly of, torque to, 168–169
energy stored in, 104
equal compressive stress in, 54
failure of, 298
interface contact pressure, 258
relative interface pressure between, 55
resistance from, 116–118
snugging of, 175
as springs, 94
static failure of, 56
strength of, 54
stresses in, 438–439
stresses of, 56
Joints loaded in tension, design
calculations, 436–437
considering factors, 437–440
in real world, 427
reliable bolted joints, checklist for, 423–424
steps for, 424–427
VDI joint design procedure, 427–435
Joint stiffness, 276, 250, 253, 265
computation of, 95, 103
and deformation, 96
estimation of, 100
influence of preload and, 338–343
ratio, 104
Joint-to-bolt deflection ratio, 223
Joint-to-bolt stiffness ratio, 100, 102
Junker vibration test machine, 311–312
K K
ISCC concept, 364–365; see also Stress corrosion
cracking
bolt material and hardness, 365–367
electrolyte, type of, 367
environment, 365
temperature, 367
thread-forming procedure, 365
thread pitch, bolt diameter and, 367–368
L
Lap joint, see Shear joint
Lead screw, 174
Leakage, 297; see also Gaskets
Levers to pry bolt, 250–251
Linear elastic fracture mechanics (LEFM)
equation, 364–365; see also KISCC concept
Load
cycles, 328, 337, 341
Index 509excursion, 338–342, 348
factor, 104, 233
intensifiers, 298
magnifiers, 438
Load and Resistance Factor Design (LRFD)
specification, 290, 465
Loading plane factor, 240, 242
Loading planes, and joint behavior
definition of, 236
effects of, 243
joint members and, 239–243
significance of, 238–239
Locking fasteners, 312, 318, 320
Lock wires and pins, 319
Loose bolts, 294
Low-alloy, quenched, and tempered steels (LAQT
steels), 21
thermal expansion for, 27
ultimate strength and hardness for, 24
yield strength and hardness for, 22, 24
Low-alloy quenched and tempered (LAQT) steels,
365–367, 370
Low-weight fasteners, 13
LRFD specification, 448
Lubricants
preloads and stresses for, 488
torque for, 487–488
Lubricants and antiseize compounds, break out
torques for, 147–148
Lubricated and unlubricated bolts, torque in, 154
M
Manual torque wrenches; see also Torque
wrenches
torque accuracy of, 159–160
Manual turn-of-nut techniques, 192
Maximum bolt load, 276, 280
Mechanically locked fasteners, 319–320, 319–322
Metallic coating, 381; see also Fastener coatings
electroplated coatings, 382
hot-dip coatings, 382
mechanical plating, 382–383
miscellaneous coating processes, 383
Metallized aluminum and zinc, 451
Metric fasteners, 15, 20
Metric series threads, coatings of, 67
Metric standards, 20
Metric thread forms, U.S. standards for, 63
Metric threads
code for, 69
stress areas of, 51
tolerance class, grade and position for, 66
types of, 65
Micrometers, 199–201
Microprocessor control, for torque–angle tools,
185
MIL-STD-1315-5A, hydrogen embrittlement
testing and, 362
Minimum clamping force, using
average values, 416–417
feedback control values, 417
statistically combined values, 415–416
worst-case values, 414–415
Minimum per-bolt clamping force, 276
Missing bolts, 294
Molydisulfide lubricants, coefficients of friction
for, 149
Motosh equation, 309
MP35N, SCC and, 369
MP35N bolt
nut factor in, 149
re-tightening of, 149
M12 steel bolts, torque in, 153
Multispindle air-tool control system, 190
N
NASA’s space shuttle preload selection
procedure, 418–420
NAS vibration test, 311
National Institute of Standards and Technology
(NIST), 14
Non-gasketed joints, 100, 102
Nonlinear joints, 339–341
Nonstandard fasteners, design limits for, 49
Nord-Lock nuts and washers, 316, 318
Nut, 501
stress in, 45–48
tension in (see Tension nuts)
torque-turn curve of, 103
turning of, 173
vibration loosening of, 138
Nut and bolt
flank angles of, 76
relative motion of, 173
Nut and bolt threads, pitch of, stress distribution
in, 45, 47
Nut-bolt systems, nonlinear factors, 263
combined stiffness and hysteresis effects, 265
distance, washers (DLW) of system as function
of applied load, 264–265
Superbolt torquenut as model for, 266
Nut dilation, 4, 26, 76–77
Nut factors, 150, 323
accuracy of, 148
case histories of, 148–151
for ceramic-based material, 147–148
and coefficient of friction, 151
lubricity effect on, 151
510 Introduction to the Design and Behavior of Bolted Jointsfor moly-based material, 147–148
for steel fasteners, 146–147
for unlubricated steel, 148
Nut friction torque, 141
Nut-joint friction, 142
Nut materials
proof load of, 26
selection of, 24
strength of, 26
Nut runner, multispindle, 162
Nut runner multipliers, see Torque multipliers
Nuts or bolt heads, nonperpendicular, 121
Nut strength and bolt strength, 79
Nut threads, diameter of, 71
Nut-to-bolt threads
coefficient of friction between, 77
relative strength of, 77
rotary motion of, 77
thread bending factor for, 77
Nylon insert nut, 316
O
Omni-lok fasteners, 322
Optimum preload, 341
Organic coatings; see also Fastener coatings
paints, 380
phos-oil, 381
of solid-film lubricant, 381
Oversized holes, 121
Oxide film, broken, 358
P
Petrochemical bolting materials and stress
relaxation, 28
Phos-oil coatings, 381
Pipe stress, 118
Pitch diameter, of thread, 81
Plastic deformation, 2, 182
Polytetrafluoroethylene (PTFE), 381, 383
Power Dyne instrument, 215
Preload
control of, 173
eccentric elastoplastic joint, 257
in engine head bolts, 149
friction and maintaining of, 313–314
initial and residual, 109
in joint, step-by-step buildup of, 176
preventing relative slip, 314–315
problems of, 138
in SAE Grade 8 bolt, 152, 184
torque control of, 140, 166
Preload, for existing joint
assembly preloads selection, 397–400
bolting technology, ASTM F16.96
subcommittee on, 412
bolt tensions
anticipated, 408–410
maximum, 417–418
clamping force
considering factors, 391–393
limits, 396–397
minimum, 414–417
upper limit on, 393–396
equations, 413–414
experiments for, 413
in-service clamping force estimation, 400–408
NASA’s space shuttle preload selection
procedure, 418–420
variables for, 410–412
Preload, in bolts
direct control of, 204–208
optimizing, 211–213
problems solved by, 210–211
stretch control of, 197–199
Preload-indicating washer (PLI), 206
Pressure loads, 392–393
Pressure vessel joint, 110
Pressure Vessel Research Committee (PVRC), 147
Pretensioned joints, 290
Prevailing torque, 144; see also Torque
control of, 191
Proof loads, 48
Proof strength, 16, 48
Proportional limit, 41
Prying
action on bolt loads, 250
external load and reaction force for, 252
forces, 252–254
load, 253
mathematics of
bending stress in bolt before liftoff, 261–263
critical loads and preloads, 260–261
equations for load factor F, 259–260
and external loads, effects of, 263
VDI’S analytical procedure, 256–260
nonlinear nature, 255–256
Puget Sound Naval Shipyard, 117
Pulse tools, 161
R
Reaction torques, 157–159
Relaxation processes, 5
Reliable bolted joints, checklist for, 423–424
Remote bolt and calculation shear stress, 462–464
Research Council on Structural Connections
(RCSC), 207, 290, 443, 451, 465
Index 511Residual assembly preload, 223
Residual preload, 139
bolt tension at, 137
in structural steel bolts, 30
Residual stress, 28
Resilience, 104, 258–260, 271, 277, 278
Room temperature strengths, 21
Rust, 322
S
SAE Grade 8 bolt
preload in, 152, 184
stiffness and change in length of, 90
SAE’s J429, 15, 17
Scatter effects, combining, 402–408
SCC, see Stress corrosion cracking
Screwdrivers, 161
Self-loosening, 459
Junker’s theory of, 306–309
loosening sequence, 306
occurrence of, 303–306
relative resistance to, 316
testing for vibration resistance, 310
Self-loosening, 292
Shear joints, 1, 283, 443
bolt’s job in, 3
clamping force in, 3
eccentrically loaded, 459–465
failing of., 287
in-service behavior of, 5–6
response to external loads, 288
slip-critical joints, load resistance for, 446–448
VDI procedure for, 444–446
Shear-loaded joints, fatigue failure of, 115
Shear loads, in structural steel joints, 57
Shear strength, calculation, 3, 21–22, 35, 40, 58,
71, 455–457
Shear stress, 287, 434, 462
allowance, 395
and tensile loads, 438
Sheet metal joint, turn–preload curves of, 176–177
Simple tensile loads, joint diagram for, 224, 227
Skidmore–Wilhelm device, 163, 207
Slip, 6
coefficient, 450–452
and preload, 453–454
resistance, 448–449, 450
Slip, thread and nut or joint
helix angle of threads, reducing of, 315
preventing or minimizing of, 314
sequence of events, 309–310
Slip-critical joints, 290, 446–440
S–N diagrams, 330–332
Snugging pass, 119
Snugging torque, 110, 119, 181
Snug-tightened joints, 290
Society of Automotive Engineers (SAE), 14
Spring constant, 86, 173–174, 232
Spring washer, 316
Square bolts, 498
Stage 8 fastening system, 319
Steel fasteners, nut factor K value for, 146–147
Stiff joint, torque–preload behavior of, 176
Stiffness
bolt, 225, 232, 264–265, 270
bolt–nut–washer system, 92
concentric joints, 96
eccentric joints, 97–100
joint (see Joint stiffness)
of non-gasketed steel joints, 100
and stored energy, 105–106
and stretch, 92
Stiffness ratio, 8, 106
bolt and joint, 252–253, 270, 274–275
joint (see Load factor)
Strain energy losses, 144
Strain-gauges, 205; see also Stretch,
measurement of
Strength
of bolt, 78
at high and low temperatures, 40
of threads, 71
types of, 39–40
Stress
amplitude, 343
concentrations, 43, 329
cracking, 6, 395
embrittlement, 376
gradient, 350
levels, factors increase of, 298
procedure, 449, 454
relaxation, 13, 27–28
Stress area equations, for fastener
materials, 50
Stress corrosion cracking, 40, 138, 297, 355,
358–359
combating
electrolyte elimination, 369–370
material susceptibility, 368–369
threshold limit, 370–374
failure mechanism, 363–364
KISCC concept (see KISCC concept)
SCC cracks, early detection of, 376
surface coatings, 374–376
Stress design procedure, allowable, 465
Stress–strain performance, 332
Stretch, measurement of
dial gages and, 201–202
ultrasonic measurement, 202
512 Introduction to the Design and Behavior of Bolted Jointsultrasonic technique, 213–215
using micrometers, 199–201
Stretch control
advantages of, 198, 203–204
basic concept, 197
optimizing, 204
problems with, 198–199
Stripped thread, 71
Structural steel bolts
residual preload in, 30
temperature effect on, 30
turn-of-nut procedure for, 182
Structural steel bolts and modified Goodman
curve, 337
Structural strength, 465
Superbolt torquenut, 265
T
Tapped holes, see Nut
Target preload, see Average assembly preload
Tearout strength, 458–459
Tensile capacity of bolt to shear stress, 289
Tensile joints
bolt’s job in, 1
in-service behavior of, 5
Tensile loads, 42, 57, 250, 251, 253, 256, 258,
276–277, 280
Tensile loads, and joint behavior
equations, for studying, 232–235
imple tensile loads and, 244–266
joint diagrams of, 220–225
loading planes and, 235–242
residual assembly preload determination,
220–224
Rolls Royce example, 226–227
stiffness, effect of, 228
Tensile strength, 16, 39, 59
in automotive group, 17
joints plates for, 457
in metric group, 17
in petrochemical=power group, 17
in structural steel group, 17
Tensile stress, 88, 289
along lines parallel to bolt axis, 43
magnitude of, 43–45
in rod of nonuniform diameter, 85–86
Tensile stress area
for higher-strength steels, 52
of standard thread, 49
Tensile-tensile (nonreversing) load, 343
Tensioners, for bolts, 208–212
Tension-monitoring device, 192
Tension nuts
relative stress level in, 47
stress distribution in, 45–46
Thermal expansion, 12, 27
Thin joints, stiffness ratio vs. slenderness
ratio for, 102
Thread
and bolt, stress areas of, 51
characteristics of, 70
class 2A, stress area of, 49, 67
engagement, 72, 120
friction torque, 141, 144
inspection levels for, 68–69
lubricants, 153
root, pitch, and nominal diameter of, 52
series, 63
static strength of, 76–79
strength of, 71
Thread bending, strength reduction factor
for, 78
Threaded fasteners, 24, 61
torque to, 155
Thread forms, 61
applications of, 61
under load, 76
Threadless fastener, 45
Threads per inch, of UNC and UNF thread, 63
Thread strength, 437–438
computation procedures, 72–73
equations, 71
factors affecting, 81
loss of, 80–81
Thread stress and shear areas
metric M series, 75
UNC=UNF=8UN, 74
Thread stress area, 74–75
Thread-stripping
areas, 72, 79
strength, 39–40, 70, 80, 394
Threshold limit, SCC combating and, 370–374
Tightening speed, 123
Titanium alloys, 369
Titanium tension nuts, 45
Tolerance
abnormal lengths of engagement, 67
inch series threads, 64
metric threads, 66
Tool work on bolt or nut and clamping force,
133
Toothed washer, 316, 323
Torque
and angle, 179
back-off, 312, 315
for different lubricants, 487–488
equations applied, 307–308, 315
fasteners, 315, 322
feedback control on, 164
Index 513monitoring (see Torque calibration)
multipliers, 159–160
nut, 312, 317
preloads and stresses for, 488
prevailing, 304, 312, 315
selection for assembly, 439–440
units (see Torque units)
Torque and preload
long form equation of, 140–142
short-form equation of, 146
Torque and turn, theory of, 179–181
Torque-angle control, see Torque-turn control
Torque-angle tools, production assembly
problems of, 184–186
Torque-angle window control, 186–187
Torque calibration, 162
disadvantage of, 163
for structural steel torque wrenches, 162
Torque–clamping force relationship., 114–117
Torque control, 151
advantages of, 166
on joint design, 167–168
low friction for, 153
tools for, 155
Torque-preload relationship, factors affecting,
154–155
friction, 142
geometric variables, 143
hole interference, 145
interference fit threads, 145
mechanic, 145
prevailing torque, 144
strain energy losses, 144
tool accuracy, 145
weight effect, 144
Torque-time curve, 187
Torque-time window control, 187
Torque tools, 156
for high speed production applications, 160
maintenance of, 156
power supplies for, 156
reaction forces, 157
testing of, 166
Torque transducer, 164, 184
Torque-turn air tools, 183
Torque-turn control, 179
advantages of, 193
optimization of, 193–194
techniques of, 176, 181
Torque-turn curve, 185
Torque-turn-preload cube, 179
friction change in, 180
Torque-turn system, 186
Torque-turn tool, 192
Torque units
english tensile stress areas, 489–495
metric tensile stress areas, 496
Torque wrenches, shear loads of, 157–158
Torquing operations, hard-copy records of, 191
Torsional energy, 178
Torsional stress, 58, 182, 394–395
Turn control, 173, 178
Turn-of-nut control, 179, 181
in aerospace assembly, 183
for automotive joints, 191
nut rotation from snug tight condition for, 182
in production operations, 183
in structural steel applications, 181
for structural steel bolts, 182
theory of, 181–182
Turn-past-snug tightening procedure, 183
Twist-off bolt, 164–165
Twist-off fastener, in airframes, 165
Two-metal corrosion, 357–358
U
Ultimate strength, 16, 41; see also Tensile strength
of exotic bolting materials, at cryogenic
temperatures, 31
and hardness for LAQT steels, 24
Ultimate tensile strength (UTS), 332–333, 336,
402, 409
Ultrasonic extensometers, 192
Ultrasonic measurement, of stretch,
214–215, 215
UN, UNR, and UNJ, threads form, 61
UN and UNJ threads, tensile stress and thread
root areas for, 50–51
Undersized holes, 121
V
VDI Directive 2230, 413, 435
VDI equations, use of, 435–437
VDI joint design procedure, 427
assembly preloads, estimation of, 430–431
bolt, static strength of, 433
design goals, 429
eccentric loading, 434–435
external load effects, 431–432
fatigue, 433–434
force required for, 432–433
revised bolt specifications, 435
stress, 434
terms and units, 428–429
VDI procedure, for shear joints, 446–448
Verein Deutscher Ingenieure (VDI), 97, 100, 256
Vibration loosening, see Self–loosening
514 Introduction to the Design and Behavior of Bolted JointsVibration resistance, testing for, 310
Junker test, 311–312
NAS test, 310–311
Vibration-resistant nuts, 316
Vibration-resistant washers, 323–324
Vinyl coatings, 451
W
Washers
strain gaged, 205
tension indicating, 205–208
Whitworth thread, 61–62
Working loads on bolts, factors affecting, 139
Wrenches, torque range for, 156
Y
Yield control, 188–190
Yield strength, 16, 41
of bolt, 394
of inconel 600 bolt, 53
of joint material, 23
vs. hardness for LAQT steels, 22, 2
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