SIST-TP CEN/TR 17603-32-23:2022

SLOVENSKI STANDARD
01-september-2022
Vesoljska tehnika - Priročnik za pritrdilne elemente
Space engineering - Threaded fasteners handbook
Raumfahrttechnik - Handbuch zu Befestigungsschrauben
Ingénierie spatiale - Manuel de visserie
Ta slovenski standard je istoveten z: CEN/TR 17603-32-23:2022
ICS:
49.030.01 Vezni elementi na splošno Fasteners in general
49.140 Vesoljski sistemi in operacije Space systems and
operations
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT CEN/TR 17603-32-23

RAPPORT TECHNIQUE
TECHNISCHER BERICHT
June 2022
ICS 49.030.10; 49.140
English version
Space engineering - Threaded fasteners handbook
Ingénierie spatiale - Manuel de visserie Raumfahrttechnik - Handbuch zu
Befestigungsschrauben
This Technical Report was approved by CEN on 13 April 2022. It has been drawn up by the Technical Committee CEN/CLC/JTC 5.

CEN and CENELEC members are the national standards bodies and national electrotechnical committees of Austria, Belgium,
Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia,
Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.

CEN-CENELEC Management Centre:
Rue de la Science 23, B-1040 Brussels
© 2022 CEN/CENELEC All rights of exploitation in any form and by any means
Ref. No. CEN/TR 17603-32-23:2022 E
reserved worldwide for CEN national Members and for
CENELEC Members.
Table of contents
European Foreword . 15
Introduction . 16
1 Scope . 17
2 References . 18
3 Terms, definitions and abbreviated terms . 19
3.1 Terms from other documents . 19
3.2 Terms specific to the present document . 19
3.3 Abbreviated terms. 21
3.4 Variables . 22
3.4.1 Uppercase variables . 22
3.4.2 Lowercase variables . 24
3.4.3 Symbols . 25
3.4.4 Subscripts . 27
4 How to use the guidelines . 28
4.1 Introduction . 28
4.2 Procedure . 28
4.2.1 Stage 1 . 28
4.2.2 Stage II . 29
4.2.3 Stage III . 29
4.2.4 Stage IV . 30
4.3 Annexes . 30
5 General Fastener Analysis Guidelines . 31
5.1 Introduction . 31
5.2 Main Joint Categories . 31
5.2.1 Overview . 31
5.2.2 Concentric Axially Loaded Joints . 32
5.2.3 Eccentric Axially Loaded Joints . 32
5.2.4 Shear Loaded Joints . 32
5.2.5 Combined Loaded Joints. 32
5.2.6 Low Duty Joints . 33
5.3 Joint Analysis Procedure . 37
5.3.1 Overview . 37
5.3.2 Margins of Safety . 37
5.4 Joint Geometry . 39
5.4.1 Fastener Geometry . 39
5.4.2 Thread Geometry . 40
5.5 Safety Factors . 43
5.5.1 Overview . 43
5.5.2 The Joint Fitting Factor . 43
5.6 References . 44
6 The Preload . 45
6.1 Overview . 45
6.2 Coefficient of Utilisation . 45
6.3 Theoretical Aspects . 46
6.3.1 The Relation between Torque and Preload . 46
6.3.2 Determining the Design Torque Level . 49
6.3.3 Locking Devices and Prevailing Torque . 51
6.3.4 Sources of Error . 53
6.3.5 Forces Induced by Thermal Fluctuation . 54
6.4 Mechanisms of Preload Loss . 56
6.4.1 Overview . 56
6.4.2 Embedding . 56
6.4.3 Fastener Group Interaction . 62
6.4.4 Gaskets . 64
6.4.5 Metallic Creep . 64
6.4.6 Washers . 64
6.4.7 Torsional Relaxation . 65
6.5 Margin of Safety on Tightening . 65
6.6 Worked Example . 67
6.7 References . 67
7 Concentric Axially Loaded Joints . 68
7.1 Overview . 68
7.2 Joint Stiffness . 68
7.3 The Joint Diagram . 69
7.3.1 Overview . 69
7.3.2 Compressive Loading . 72
7.4 The Force Ratio . 73
7.5 The Compliance of the Fastener . 73
7.6 The Compliance of the Clamped Parts . 75
7.6.1 Overview . 75
7.6.2 Compression Zone Configurations . 76
7.6.3 Determining the Compression Zone Configuration . 79
7.6.4 The Compression Zone Compliance . 80
7.6.5 Gasket Compliance . 81
7.7 Calculation of the Loading Plane Factor . 83
7.7.1 Introduction . 83
7.7.2 Simple Calculation of the Loading Plane Factor . 87
7.7.3 Analytical Calculation of the Loading Plane Factor . 89
7.8 Joint Separation . 91
7.8.1 Introduction . 91
7.8.2 The Margin of Safety for Joint Separation . 92
7.9 Fastener Tensile Failure . 92
7.9.1 External Vs Overall Load. 92
7.9.2 Margin of Safety on Fastener Failure . 93
7.10 Thread Failure by Shear Pull-Out . 94
7.10.1 Introduction . 94
7.10.2 Failure of the Female Thread . 94
7.10.3 Failure of the Male Thread . 96
7.10.4 Margin of Safety on Thread Pull-Out . 96
7.11 Crushing of Flanges . 97
7.12 Repeated Loading to a Point above Yield . 97
7.13 Dynamic Loading . 99
7.14 Worked Examples. 100
7.14.1 Preload in a Concentric Axially Loaded Joint . 100
7.14.2 Thread Shear Pull-Out Example. 107
7.15 References . 108
8 Eccentric Axially Loaded Joints . 109
8.1 Effects of Eccentricity . 109
8.1.1 Overview . 109
8.1.2 Prying. 112
8.2 Joints with Large Areas of Contact . 112
8.2.1 Compliance of the Clamped Parts . 112
8.2.2 The Joint Diagram . 117
8.2.3 The Force Ratio . 118
8.2.4 Loading Plane Factor . 118
8.2.5 The Interface Opening Limit . 119
8.2.6 Preload Considerations . 119
8.3 Cantilevered Flange Joints . 120
8.3.1 Overview . 120
8.3.2 Compliance of Circular Flanges . 120
8.3.3 Force Ratio for Circular Cantilever Flanges . 124
8.3.4 Simplified Joint Diagram for Eccentric Joints . 125
8.3.5 Joint Diagram for Eccentric NonLinear Joints . 125
8.4 Fastener Loads in Eccentric Joints . 126
8.4.1 Bending Moments . 126
8.5 References . 129
9 Shear Loaded Joints . 130
9.1 Introduction . 130
9.1.1 Overview . 130
9.1.2 Analysis Approach . 131
9.2 Friction Grip Joints . 132
9.2.1 Design Principles . 132
9.2.2 Slip Resistance . 134
9.2.3 Friction Grip Strength Analysis . 137
9.3 Bearing Joints . 138
9.3.1 Design Principles . 138
9.3.2 Fastener Shear Failure . 140
9.3.3 Net Tension Section Failure of FlangeS . 144
9.3.4 Hole Bearing Failure . 146
9.3.5 Shear-Out or Tear-Out Failure . 150
9.4 Eccentrically Loaded Shear Joints . 151
9.4.1 Overview . 151
9.4.2 Fastener Group Centroid. 152
9.4.3 Bearing Design of Eccentric Shear Joints . 152
9.4.4 Friction Grip Design of Eccentric Shear Joints . 153
9.5 Worked Examples. 155
9.5.1 Shear Loaded Joint Example . 155
9.5.2 Net Tension Section Failure Example . 158
9.5.3 Eccentric Shear Bearing Joint Example . 159
9.6 References . 161
10 Low Duty Joints . 162
10.1 Introduction . 162
10.2 Low Duty Joint Design Guidelines . 162
10.2.1 Overview . 162
10.2.2 Insert Pull out Strength . 162
10.2.3 Joint Thermal Conductivity . 164
10.2.4 Joint Electrical Conductivity . 164
10.2.5 Handling Size . 165
10.2.6 Stiffness . 166
10.2.7 Tolerances . 166
10.2.8 Redundancy . 166
10.3 Non-Metallic Joints . 166
10.4 Low Duty Threshold . 167
10.5 Example: Low Duty Thermal Joint . 167
10.5.1 Overview . 167
10.5.2 Initial Assumptions . 169
10.5.3 Thermal Conductivity . 169
10.6 References . 170
11 Fatigue and Fracture Mechanics of Fasteners . 171
11.1 Introduction . 171
11.2 Fastener Fatigue . 171
11.2.1 Fundamentals . 171
11.2.2 Palmgren – Miner rule . 174
11.2.3 Fatigue Design Principles. 174
11.3 Fundamentals of Fracture Mechanics . 176
11.3.1 The Stress Intensity Factor . 176
11.3.2 The Stress Intensity Correction Factor . 177
11.3.3 Crack Growth Calculations . 181
11.3.4 Corrosion Considerations . 181
11.4 Worked Examples. 181
11.4.1 Fatigue of a Threaded Fastener Example . 181
11.4.2 Threaded Fastener Fracture Mechanics Example . 182
11.5 References . 184
12 Preloded Fastener Installation . 185
12.1 Overview . 185
12.2 Yield Load Controlled Tightening . 185
12.2.1 Introduction . 185
12.2.2 Method of Operation . 185
12.2.3 Preload Developed in Fastener . 187
12.3 Angle of Rotation Controlled Tightening . 188
12.3.1 Introduction . 188
12.3.2 Elastic Range Tightening . 188
12.4 Ultrasonic Methods . 190
12.4.1 Introduction . 190
12.4.2 Ultrasonic Extensometers . 190
12.5 Direct Measurement . 193
12.5.1 Overview . 193
12.5.2 Method of Application and Practical Considerations . 194
12.6 Reuse of Fasteners . 194
12.6.1 Overview . 194
12.6.2 Effects on Friction Coefficients . 194
12.6.3 Effects on Prevailing Torques . 195
12.6.4 Recommended Practice for Fastener Resuse . 197
12.7 References . 197
13 Corrosion . 199
13.1 Overview . 199
13.2 Galvanic Corrosion . 201
13.2.1 Introduction . 201
13.2.2 Factors Which Affect the Rate of Corrosion . 201
13.2.3 Prevention of Bimetallic Corrosion . 202
13.3 Stress Corrosion Cracking . 205
13.3.1 Introduction . 205
13.3.2 Factors Affecting Stress Corrosion Cracking . 205
13.4 Crevice Corrosion . 209
13.4.1 Introduction . 209
13.4.2 Methods of Avoiding Crevice Corrosion . 209
13.5 Pitting corrosion . 209
13.5.1 Introduction . 209
13.5.2 Alloy Susceptibility . 210
13.5.3 Prevention of Pitting Corrosion . 210
13.6 References . 210
14 Lubricants for Space Use . 211
14.1 Introduction . 211
14.2 Lubricant Selection . 211
14.3 Plating and Coatings for Fasteners . 212
14.4 Liquid Lubricants . 213
14.5 Dry Lubricants . 213
14.6 Codification of Space Lubricant Systems and Processes. 213
14.7 References . 214
15 Manufacturing Quality Control . 215
15.1 Introduction . 215
15.2 Manufacturing and Quality Assurance . 215
15.3 Quality of Threaded Fastener Joints . 215
15.3.1 Overview . 215
15.3.2 Process Variations . 216
15.3.3 Material Variations . 216
15.3.4 Tolerancing . 216
15.4 References . 217
16 Joint Validation by Testing . 218
16.1 Introduction . 218
16.2 Types of Testing . 218
16.3 Development Testing . 218
16.3.1 Overview . 218
16.3.2 The Test Factor . 219
16.3.3 Specific Development Tests . 220
16.4 Production Testing . 221
Annex A Recommended Starting Values for Seating Torque . 222
A.1 Recommended values . 222
A.2 References . 223
Annex B Measured Friction Coefficients of Fasteners . 224
Annex C Typical Friction Coefficients for Joint Materials . 225
Annex D Material Data of Fasteners Typically Used in Aerospace Industry . 227
D.1 Overview . 227
D.2 Stainless Steel . 227
D.3 Nickel and Nickel/Cobalt Based Alloys . 230
D.4 Titanium Alloys . 232
D.5 References . 232
Other Useful References . 233

Figures
Figure 5-1 - Joint Categories (1 to 6) . 34
Figure 5-2 - Joint Categories (7 to 12) . 35
Figure 5-3 - Joint Categories (13 to 17) . 36
Figure 5-4 - Definitions of Forces and Moments Acting on a Joint . 37
Figure 5-5 – Fastener Dimensions . 39
Figure 5-6 – Definition of the under-head bearing angle . 39
Figure 5-7 – Thread Geometry . 41
Figure 6-1 – Forces Present During Tightening (the Wedge Model) . 47
Figure 6-2 - Typical Preload vs. Applied Torque Graph . 54
Figure 6-3 - Fastener Faying Surfaces . 57
Figure 6-4 - Microscopic View of Surface Asperities Initially in Contact . 57
Figure 6-5 - Embedding Preload Decay . 58
Figure 6-6 - Joint with Conical Mating Surfaces . 60
Figure 6-7 - Effect of Fastener Stiffness on Preload Loss Due to Embedding . 60
Figure 6-8 - Increasing Joint Compliance Using Belleville Washers . 61
Figure 6-9 - Initial and Final Preload of a Typical Flange Joint for the First Tightening Pass. 63
Figure 6-10 - Initial and Final Preload Levels after Four Tightening Passes. . 63
Figure 6-11 - Self Tightening by Torsional Relaxation . 65
Figure 7-1 - Typical Joint Components . 69
Figure 7-2– Fastener Stiffness . 69
Figure 7-3 – Clamped Parts Stiffness . 69
Figure 7-4 - Growth of the Joint Diagram Illustrating the Tightening Process . 70
Figure 7-5 – Application of external axial load . 71
Figure 7-6 - Joint Diagram Showing the Effect of an External Axial Load . 71
Figure 7-7 – External Load Causing Gapping . 72
Figure 7-8 – Joint Diagram for Compressive Loading . 72
Figure 7-9 – Dimensioning of the Fastener for Compliance Calculations . 74
Figure 7-10 - Compression zones in cylindrical clamped parts . 76
Figure 7-11 - The compression zone when multiple edge distances are present . 77
Figure 7-12- Approximation of the Compression Zone for Insert Joints . 78
Figure 7-13 - The compression zone with multiple interacting fasteners . 78
Figure 7-14 - Typical Gasket Deflection . 82
Figure 7-15 – Gasket Showing Hysteresis . 82
Figure 7-16- Joint Diagram for a Gasket Joint Showing Gasket Creep . 82
Figure 7-17 - Tension Joint Loading Planes and the Forces Acting within the Joint . 83
Figure 7-18 - Joint Diagram for Loading Planes within the Joint (n < 1) . 84
Figure 7-19 - Geometry for Determination of Loading Plane Factor . 85
Figure 7-20 – Extraction of the Joint from its Environment . 86
Figure 7-21 - The Basic and Connector Bodies . 87
Figure 7-22 – Joint Types According to the Points of Force Introduction . 88
Figure 7-23 – Basic and Connector Bodies of a Flange . 89
Figure 7-24- Moment Conduction Factor Variation with the Connector Body Position . 90
Figure 7-25 - Joint Diagram at Onset of Separation Failure . 92
Figure 7-26 – Joint Diagram Showing Repeated Loading into the Plastic Region . 98
Figure 7-27 – Preload Loss with Repeated Loading into Yield . 98
Figure 7-28 – Joint Diagram Showing a Dynamic External Load . 99
Figure 7-29 – Typical S-N Curve (For a Given Mean Stress) . 100
Figure 7-30 - Example problem of concentric axially loaded joint . 100
Figure 8-1 - A Typical Eccentric Joint . 109
Figure 8-2 - Interface Pressure Distribution after Preloading . 110
Figure 8-3 - Typical Joint Eccentrically Loaded . 110
Figure 8-4 - Redistribution of interface pressure (with force F not sufficient to cause
A1
gapping) . 111
Figure 8-5 - An Eccentrically Loaded Joint with Gapping . 111
Figure 8-6 - Redistribution of Interface Pressure (Force F Causes Gapping) . 112
A2
Figure 8-7 - Limitations of the Eccentric Joint Analysis Method . 113
Figure 8-8 - The Interface Area for Multiple Fastener Joints . 114
Figure 8-9 - An Eccentrically Loaded Joint where s = a . 115
Figure 8-10 - The General Eccentrically Loaded Joint . 116
Figure 8-11 - The Joint Diagram for Eccentrically Loaded Joints showing the Non-Linearity
of the Clamped Parts. 117
Figure 8-12 - Joint Diagram with a Higher Preload . 118
Figure 8-13 - An Eccentrically Joint Loaded to the Interface Opening Limit with the Loading
Plane Inside the Joint . 119
Figure 8-14 - Definition of Flange Compliance due to Bending Loads at Different Points . 121
Figure 8-15 - Dimensions of a Fixed Circular Flange (with a Weldneck) . 122
Figure 8-16 - Bending Deformation of Circular Loose Flange . 123
Figure 8-17 - Simplified Joint Diagram for Cantilevered Flanged Joints . 125
Figure 8-18 - The Joint Diagram for Non-Linear Gasket Joints . 126
Figure 8-19 - Idealised Linear Pressure Distribution across an Eccentrically Loaded Joint’s
Interface . 128
Figure 9-1 - Typical Double Lap Shear Joint . 130
Figure 9-2 - Load Deformation Curve for a Fastener in Direct Shear . 131
Figure 9-3 - A Symmetrical Shear Joint . 133
Figure 9-4 - The Joint Diagram for Each Fastener in Figure 6.3 . 133
Figure 9-5 - Typical Unsymmetrical Friction Grip Shear Joint . 133
Figure 9-6 - Fastener Bending and Tension in an Unsymmetrical Shear Joint . 134
Figure 9-7 - Simple Friction Grip Joint with Added Tension Loading . 135
Figure 9-8 - Reduction of Shear Capacity with Increasing External Axial Load . 136
Figure 9-9 - Joint Design Features that Increase Slip Resistance . 137
Figure 9-10 - Shear Joint in Bearing . 138
Figure 9-11 - Long Bearing Shear Stress Distribution . 139
Figure 9-12 - Graphical Determination of the Margin of Safety on Combined Loads . 142
Figure 9-13 - Fastener Group with hole clearance . 143
Figure 9-14 - Shear load parameter versus hole clearance . 144
Figure 9-15 - Nomenclature for Net Tension Section Calculation . 145
Figure 9-16 - Ultimate Strength Reduction Factors for Net Tension Section Failure . 146
Figure 9-17 - Initial Bearing Contact Elastic Stresses and Deformations . 147
Figure 9-18 - Elastic / Plastic Stresses and Deformations After Increased Loading . 148
Figure 9-19 - Idealised Bearing Stresses . 149
Figure 9-20 - Shear-Out Failure . 150
Figure 9-21 - Tear-Out Failure . 150
Figure 9-22 - Nomenclature for Plate Shear Out Calculation . 150
Figure 9-23 - A Typical Eccentric Loaded Shear Joint . 151
Figure 9-24 - Load v Rotation Curve for a Typical Eccentric Loaded Shear Joint . 152
Figure 9-25 - Shear Resistance Relative to the Centre of Rotation . 154
Figure 9-26 - Shear loaded joint example . 155
Figure 9-27 - Shear Joint Example to Show the Method of Net Tension Section Calculation158
Figure 9-28 - Offset Loads on Fastener Groups . 160
Figure 9-29 - Vector addition of the fastener loads . 161
Figure 10-1 - Types of Inserts Used in Honeycomb Panels . 163
Figure 10-2 - Typical Earthing Arrangements . 165
Figure 10-3 - Typical Low Duty Clamp Connections . 166
Figure 10-4 - Equipment Mounting Box Geometry . 168
Figure 11-1 - Typical Fatigue Curve at Constant Mean Stress . 172
Figure 11-2 - Typical Constant Amplitude Loading . 172
Figure 11-3 - Typical Stress Ratio – Mean Stress Diagram . 173
Figure 11-4 - Typical Preload Effects on Fatigue Life of Fasteners . 173
Figure 11-5 - Joint Diagram Comparing Steel and Titanium Fasteners . 175
Figure 11-6 - Typical Fatigue Comparison . 175
Figure 11-7 - ESACRACK Model of a Circumferential Crack . 178
Figure 11-8 - ESACRACK Model of a Thumbnail Crack . 179
Figure 11-9 - ESACRACK Model of a Fillet Crack under a Fastener Head . 180
Figure 12-1 - Yield Load Controlled Tightening . 186
Figure 12-2 - Torque and Gradient Values as a Function of e . 186
Figure 12-3 - Variation of Strain al
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