Niemi / Fricke / Maddox Structural Hot-Spot Stress Approach to Fatigue Analysis of Welded Components

Designer's Guide
2. Auflage 2018
ISBN: 978-981-10-5568-3
Verlag: Springer Singapore
Format: PDF
Kopierschutz: Wasserzeichen (»Systemvoraussetzungen)

E-Book, Englisch, 85 Seiten, eBook

Reihe: IIW Collection

This book provides background and guidance on the use of the structural hot-spot stress approach to fatigue analysis. The book also offers Design S-N curves for use with the structural hot-spot stress for a range of weld details, and presents parametric formulas for calculating stress increases due to misalignment and structural discontinuities. 
Highlighting the extension to structures fabricated from plates and non-tubular sections. The structural hot-spot stress approach focuses on cases of potential fatigue cracking from the weld toe and it has been in use for many years in tubular joints.
Following an explanation of the structural hot-spot stress, its definition and its relevance to fatigue, the book describes methods for its determination. It considers stress determination from both finite element analysis and strain gauge measurements, and emphasizes the use of finite element stress analysis, providing guidance on the choice of element type and size for use with either solid or shell elements. Lastly, it illustrates the use of the recommendations in four case studies involving the fatigue assessment of welded structures using the structural hot-spot stress  


Erkki Niemi is Emeritus Professor of Steel Structures in Lappeenranta University of Technology, Finland. Wolfgang Fricke is Professor (retired) of the Institute for Ship Structural Design and Analysis at Hamburg University of Technology, Germany.
Stephen J. Maddox is a Consultant with The Welding Institute (TWI) in the UK and is also Visiting Professor in the Department of Mechanical Engineering at the University of Strathclyde, UK.

Zielgruppe

Professional/practitioner

Autoren/Hrsg.

Niemi, Erkki

Fricke, Wolfgang

Maddox, Stephen J.

Inhaltsverzeichnis

1;Preface;6
2;Contents;9
3;Abstract;13
4;1 Introduction;14
4.1;1.1 General;14
4.2;1.2 Safety Aspects;16
4.3;References;16
5;2 The Structural Hot-Spot Stress Approach to Fatigue Analysis;18
5.1;2.1 Field of Application;18
5.2;2.2 Types of Hot Spot;19
5.3;2.3 Definition of the Structural Stress at a Type “a” Hot-Spot;20
5.4;2.4 Use of Stress Concentration Factors;22
5.4.1;2.4.1 Modified Nominal Stress;22
5.4.2;2.4.2 Structural Stress Concentration Factors, Ks;22
5.4.3;2.4.3 Stress Magnification Factor Due to Misalignment Km;23
5.5;2.5 Effect of Component Size on the Fatigue Resistance;25
5.6;References;25
6;3 Experimental Determination of the Structural Hot-Spot Stress;26
6.1;3.1 General;26
6.2;3.2 Type “a” Hot Spots;26
6.3;3.3 Type “b” Hot Spots;28
6.4;References;29
7;4 Structural Hot-Spot Stress Determination Using Finite Element Analysis;30
7.1;4.1 General;30
7.2;4.2 Choice of Element Type;31
7.3;4.3 Methods for Determination of Structural Hot-Spot Stress;32
7.3.1;4.3.1 Determination of the Structural Stress at the Weld Toe Using Through-Thickness Linearization;33
7.3.2;4.3.2 Determination of the Structural Stress at the Weld Toe Using Surface Stress Extrapolation;34
7.3.3;4.3.3 Determination of the Structural Stress at a Single Point Close to the Weld Toe;38
7.4;4.4 Use of Relatively Coarse Element Meshes;39
7.4.1;4.4.1 Solid Element Modelling;39
7.4.2;4.4.2 Thin Shell (or Plate) Element Modelling;40
7.4.3;4.4.3 Hot-Spot Stress Extrapolation;40
7.5;4.5 Use of Relatively Fine Element Meshes;41
7.5.1;4.5.1 Solid Element Modelling;41
7.5.2;4.5.2 Thin Shell (or Plate) Element Modelling;42
7.5.3;4.5.3 Hot-Spot Stress Extrapolation;42
7.6;4.6 Modelling Fillet Welds in Shell Element Models;42
7.7;References;43
8;5 Parametric Formulae;45
8.1;5.1 Misalignment;45
8.1.1;5.1.1 Axial Misalignment Between Flat Plates of Equal Thickness Under Axial Loading;45
8.1.2;5.1.2 Axial Misalignment Between Flat Plates of Differing Thickness Under Axial Loading;46
8.1.3;5.1.3 Axial Misalignment Between Tubes or Pipes Under Axial Loading;46
8.1.4;5.1.4 Axial Misalignment at Joints in Pressurized Cylindrical Shells with Thickness Change;47
8.1.5;5.1.5 Angular Misalignment Between Flat Plates of Equal Thickness Under Axial Loading;47
8.1.6;5.1.6 Angular Misalignment at Longitudinal Joints in Pressurized Cylindrical Shells;48
8.1.7;5.1.7 Ovality in Pressurized Cylindrical Pipes and Shells;49
8.2;5.2 Structural Discontinuities;49
8.3;References;50
9;6 Structural Hot-Spot S-N Curves;51
9.1;6.1 General Principles;51
9.2;6.2 Recommended S-N Curves for the Conventional Structural Hot-Spot Stress Approach;54
9.2.1;6.2.1 Hot-Spot S-N Curves;54
9.2.2;6.2.2 Hot-Spot S-N Curves for Tubular Joints in Steel;55
9.3;6.3 Recommended S-N Curves for the Other Structural Stress Approaches;55
9.3.1;6.3.1 Structural Stress Approach According to Dong;55
9.3.2;6.3.2 Structural Stress Approach According to Xiao and Yamada;56
9.3.3;6.3.3 Structural Stress Approach According to Haibach;56
9.4;References;56
10;7 Case Study 1: Box Beam of a Railway Wagon;58
10.1;7.1 Introduction;58
10.2;7.2 Materials and Methods;58
10.2.1;7.2.1 Description of the Structure;58
10.2.2;7.2.2 Angular Misalignment in the Web;58
10.2.3;7.2.3 Strain Gauge Measurements;59
10.2.4;7.2.4 Structural Hot-Spot Stress Determination;60
10.2.5;7.2.5 S-N Curve;61
10.2.6;7.2.6 Partial Safety Factors;62
10.3;7.3 Results;62
10.3.1;7.3.1 Stress Concentration Factor, Ks;62
10.3.2;7.3.2 Results for a Perfectly Straight Web;62
10.3.3;7.3.3 Effective Magnification Factor, Km;63
10.3.4;7.3.4 Results for a Web with Angular Misalignment;64
10.4;7.4 Discussion and Conclusions;64
11;8 Case Study 2: Hatch Corner Design for Container Ships;66
11.1;8.1 Introduction;66
11.2;8.2 Materials and Methods;66
11.2.1;8.2.1 Description of the Structure;66
11.2.2;8.2.2 Service Loads;66
11.2.3;8.2.3 Experimental Investigation;67
11.2.4;8.2.4 Structural Hot-Spot Stress Determination;68
11.2.5;8.2.5 S-N Curve Based on Nominal Stress;69
11.3;8.3 Fatigue Assessment;70
11.4;8.4 Conclusion;70
11.5;Reference;70
12;9 Case Study 3: Web Frame Corner;71
12.1;9.1 Introduction;71
12.2;9.2 Computation of the Structural Hot-Spot Stress;72
12.2.1;9.2.1 Finite Element Modelling;72
12.2.2;9.2.2 Computation of Structural Hot-Spot Stresses;73
12.3;9.3 Fatigue Tests;74
12.3.1;9.3.1 Performance of the Tests;74
12.3.2;9.3.2 Observed Fatigue Lives;74
12.3.3;9.3.3 Comparison with Design S-N Curves;75
12.4;Reference;76
13;10 Case Study 4: Loaded Stiffener on T-Bar;77
13.1;10.1 Introduction;77
13.2;10.2 Computation of the Structural Hot-Spot Stress;77
13.2.1;10.2.1 Finite Element Modelling;77
13.2.2;10.2.2 Determination of the Structural Hot-Spot Stress by Extrapolation;79
13.2.3;10.2.3 Determination of the Structural Stress According to Dong;80
13.2.4;10.2.4 Determination of the Structural Stress According to Xiao/Yamada;82
13.3;10.3 Estimation of the Design Fatigue Life;82
13.3.1;10.3.1 Fatigue Life Determined from Extrapolated Stress;82
13.3.2;10.3.2 Fatigue Life Determined from Dong’s Approach;82
13.3.3;10.3.3 Fatigue Life Determined from Xiao/Yamada’s Approach;83
13.3.4;10.3.4 Comparison with Test Results;83
13.4;References;83
14;Appendix;84
14.1;Symbols;84

Introduction.- The Structural Hot-Spot Approach To Fatigue Analysis.- Experimental Determination Of The Structural Hot- Spot Stress.- Structural Hot-Spot Stress Determination Using Finite Element Analysis.- Parametric Formulae.- Structural Hot-Spot 
S-N 
Curves.- Case Study 1.- Case Study 2.- Case Study 3.- Case Study 4.

Über Autor(innen)

Erkki Niemi
 is Emeritus Professor of Steel Structures in Lappeenranta University of Technology, Finland.
Wolfgang Fricke
is Professor (retired) of the Institute for Ship Structural Design and Analysis at Hamburg University of Technology, Germany.
Stephen J. Maddox
 is a Consultant with The Welding Institute (TWI) in the UK and is also Visiting Professor in the Department of Mechanical Engineering at the University of Strathclyde, UK.