Recommendations for Fatigue Design of Welded Joints and Components (eBook)

Prof. Hobbacher studied mechanical engineering at the Technical University in Stuttgart, Germany. He started his career in industry in chemical plant equipment, heavy machinery and pressure vessels, finally as head of the design office. Later he finalized his doctorate thesis at the Aachen Institute of Technology in aerospace engineering. In 1980 he became full professor at the University of Applied Sciences in Wilhelmshaven, Germany, lecturing welding technology, structural steelwork, pressure vessels and pipes. Here, he established the new Institute for Materials and Production Technology, of which he became the first director. He is chairman of the German Welding Society (DVS) working group on design and analysis, and for a period of ten years he was chairman of the International Institute of Welding (IIW) Commission XV on Design and Analysis of Welded Structures. He served as chairman of an IIW Working Group, which developed the IIW Fatigue Design Recommendations. His scientific work resulted into numerous publications, documents and books. For his efforts and achievements he was rewarded with the “Evgeny Paton Prize” in 2013.

The International Institute of Welding 7
Preface 8
Contents 9
Contributors List 12
1 General 13
1.1 Introduction 13
1.2 Scope and Limitations 13
1.3 Definitions 14
1.4 Symbols 17
1.5 Basic Principles 19
1.6 Necessity of Fatigue Assessment 19
1.7 Application of the Document 20
2 Fatigue Actions (Loading) 22
2.1 Basic Principles 22
2.1.1 Determination of Fatigue Actions (Loading) 22
2.1.2 Stress Range 23
2.1.3 Types of Stress Concentrations and Notch Effects 23
2.2 Determination of Stresses and Stress Intensity Factors 23
2.2.1 Definition of Stress Components 23
2.2.2 Nominal Stress 26
2.2.2.1 General 26
2.2.2.2 Calculation of Nominal Stress 27
2.2.2.3 Measurement of Nominal Stress 28
2.2.3 Structural Hot Spot Stress 29
2.2.3.1 General 29
2.2.3.2 Types of Hot Spots 31
2.2.3.3 Determination of Structural Hot Spot Stress 32
2.2.3.4 Calculation of Structural Hot Spot Stress 32
2.2.3.5 Measurement of Structural Hot Spot Stress 36
2.2.3.6 Tubular Joints 37
2.2.4 Effective Notch Stress 38
2.2.4.1 General 38
2.2.4.2 Calculation of Effective Notch Stress 39
2.2.4.3 Measurement of Effective Notch Stress 40
2.2.5 Stress Intensity Factors 41
2.2.5.1 General 41
2.2.5.2 Determination of Stress Intensity Factors 42
2.2.5.2.1 Standard Configurations 42
2.2.5.2.2 Stress Intensity Factor for Weld Toes 42
2.2.5.2.3 Weight Function Approach 43
2.2.5.2.4 Finite Element Programs 44
2.2.5.2.5 Aspect Ratio 44
2.2.5.2.6 Assessment of Welded Joints Without Detected Imperfections 45
2.3 Stress History 45
2.3.1 General 45
2.3.2 Cycle Counting Methods 46
2.3.3 Cumulative Frequency Diagram (Stress Spectrum) 47
3 Fatigue Resistance 48
3.1 Basic Principles 48
3.2 Fatigue Resistance of Classified Structural Details 49
3.3 Fatigue Resistance Assessed on the Basis of Structural Hot Spot Stress 71
3.3.1 Fatigue Resistance Using Reference S-N Curve 71
3.3.2 Fatigue Resistance Using a Reference Detail 71
3.4 Fatigue Resistance Assessed on the Basis of the Effective Notch Stress 73
3.4.1 Steel 73
3.4.2 Aluminium 73
3.5 Fatigue Strength Modifications 74
3.5.1 Stress Ratio 74
3.5.1.1 Steel 74
3.5.1.2 Aluminium 75
3.5.2 Wall Thickness 75
3.5.2.1 Steel 76
3.5.2.2 Aluminium 77
3.5.3 Improvement Techniques 77
3.5.3.1 General 77
3.5.3.2 Applicability of Improvement Methods 77
3.5.3.3 Grinding 79
3.5.3.4 TIG Dressing 80
3.5.3.5 Hammer Peening 80
3.5.3.6 Needle Peening 81
3.5.4 Effect of Elevated Temperatures 82
3.5.4.1 Steel 82
3.5.4.2 Aluminium 83
3.5.5 Effect of Corrosion 83
3.6 Fatigue Resistance Assessed on the Basis of Crack Propagation Analysis 84
3.6.1 Steel 84
3.6.2 Aluminium 85
3.6.3 Correlation of Fracture Mechanics to Other Verification Methods 85
3.7 Fatigue Resistance Determination by Testing 86
3.7.1 General Considerations 86
3.7.2 Evaluation of Test Data 87
3.7.3 Evaluation of Data Collections 88
3.8 Fatigue Resistance of Joints with Weld Imperfections 90
3.8.1 General 90
3.8.1.1 Types of Imperfections 90
3.8.1.2 Effects and Assessment of Imperfections 90
3.8.2 Misalignment 91
3.8.3 Undercut 93
3.8.3.1 Steel 93
3.8.3.2 Aluminium 93
3.8.4 Porosity and Inclusions 94
3.8.4.1 Steel 94
3.8.4.2 Aluminium 95
3.8.5 Crack-like Imperfections 95
3.8.5.1 General Procedure 95
3.8.5.2 Simplified Procedure 96
4 Fatigue Assessment 101
4.1 General Principles 101
4.2 Combination of Normal and Shear Stress 101
4.3 Fatigue Assessment Using S-N Curves 102
4.3.1 Linear Damage Calculation by the “Palmgren-Miner” Rule 106
4.3.2 Nonlinear Damage Calculation 109
4.4 Fatigue Assessment by Crack Propagation Calculation 110
4.5 Fatigue Assessment on the Basis of Service Testing 112
4.5.1 General 112
4.5.2 Acceptance Criteria 113
4.5.3 Safe Life Assessment 114
4.5.4 Fail Safe Assessment 114
4.5.5 Damage Tolerant Assessment 115
5 Safety Considerations 116
5.1 Basic Principles 116
5.2 Fatigue Design Strategies 117
5.2.1 Infinite Life Design 117
5.2.2 Safe Life Design 117
5.2.3 Fail Safe Design 117
5.2.4 Damage Tolerant Design 117
5.3 Partial Safety Factors 118
5.4 Quality Assurance 119
5.5 Repair of Components 119
6 6 Appendices 121
6.1 Loading History 121
6.1.1 Markov Transition Matrix 121
6.1.2 ‘Rainflow’ or ‘Reservoir’ Counting Method 122
6.2 Fracture Mechanics 123
6.2.1 Rapid Calculation of Stress Intensity Factors 123
6.2.2 Dimensions of Cracks 123
6.2.3 Interaction of Cracks 124
6.2.4 Formulae for Stress Intensity Factors 125
6.2.4.1 Standard Solutions 125
6.2.4.2 Weight Function for a Surface Crack 132
6.2.5 Stress Distribution at a Weld Toe 134
6.3 Formulae for Misalignment 135
6.4 Statistical Considerations on Safety 137
6.4.1 Statistical Evaluation of Fatigue Test Data 137
6.4.2 Statistical Evaluation of Results from Component Testing 138
6.4.3 Statistical Considerations for Partial Safety Factors 140
6.5 Fatigue Resistance of ISO 5817 Quality 141
7 Erratum to: Recommendations for Fatigue Design of Welded Joints and Components 147
Erratum to:& #6
8 Erratum to: Recommendations for Fatigue Design of Welded Joints and Components 148
Erratum to: A.F. Hobbacher, Recommendations for Fatigue Design of Welded Joints and Components, IIW Collections, https://doi.org/10.1007/978-3-319-23757-2 148
References 149