Pook Metal Fatigue

What It Is, Why It Matters
1. Auflage 2007
ISBN: 978-1-4020-5597-3
Verlag: Springer Netherlands
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, Band 145, 271 Seiten

Reihe: Solid Mechanics and Its Applications

This book presents important concepts in metal fatigue in a straightforward manner, for the benefit of readers who must understand more advanced documents on a wide range of metal fatigue topics. The text shows how metal fatigue problems are solved in engineering practice. The book assumes no prior knowledge of metal fatigue, requiring only a basic understanding of stress analysis and mathematics covered in engineering undergraduate courses.

Autoren/Hrsg.

Pook, L. P.

Inhaltsverzeichnis

1;Contents;8
2;Preface;14
3;Notation;16
4;1 Introduction;19
5;2 Historical Background;25
5.1;2.1 Introduction;25
5.2;2.2 Experimental Work;26
5.3;2.3 The Modern Era;30
6;3 Constant Amplitude Fatigue;33
6.1;3.1 Notation;33
6.2;3.2 S/N (Wöhler) Curves;33
6.3;3.3 Scatter in Fatigue Data;38
6.4;3.4 Mechanisms of Metal Fatigue;42
6.5;3.5 Effect of Mechanisms on S/N Curves;49
7;4 Variable Amplitude and Multiaxial Fatigue;53
7.1;4.1 Introduction;53
7.2;4.2 Mathematical Description of Fatigue Loadings;55
7.3;4.3 Miner’s Rule;62
7.4;4.4 Standard Load Histories;71
7.5;4.5 Multiaxial Fatigue in Metals;77
8;5 Fatigue Design;85
8.1;5.1 Introduction;85
8.2;5.2 Failure Analysis;86
8.3;5.3 Situations, Philosophies and Approaches;87
8.4;5.4 Product Liability;95
8.5;5.5 Safety Regulations;97
9;6 The Uncracked Situation;101
9.1;6.1 Introduction;101
9.2;6.2 Effect of Surface Finish;102
9.3;6.3 Effect of Mean Stress;103
9.4;6.4 Effect of Multiaxial Fatigue Loading;106
9.5;6.5 Effect of Notches;107
9.6;6.6 Bicycle Crankshaft Analysis;111
9.7;6.7 Scatter under Variable Amplitude Fatigue Loading;114
9.8;6.8 Improvement of Fatigue Life;115
10;7 The Cracked Situation;119
10.1;7.1 Introduction;119
10.2;7.2 Initial Crack Size;120
10.3;7.3 Final Crack Size;121
10.4;7.4 Constant Amplitude Fatigue Crack Propagation;123
10.5;7.5 Variable Amplitude Fatigue Crack Propagation;142
10.6;7.6 Fractography;147
11;8 Fatigue Crack Paths;153
11.1;8.1 Introduction;153
11.2;8.2 Crack Paths in Two Dimensions;156
11.3;8.3 Planar Crack Paths;169
11.4;8.4 Crack Paths in Three Dimensions;173
12;9 Why Metal Fatigue Matters;179
12.1;9.1 Introduction;179
12.2;9.2 Avoidance of Fatigue Failure;180
12.3;9.3 Research and Development;181
12.4;9.4 The Role of Non Destructive Testing;182
12.5;9.5 Current Trends;182
13;A Fracture Mechanics;185
13.1;A.1 Introduction;185
13.2;A.2 Notation for Stress and Displacement Fields;186
13.3;A.3 Stress Intensity Factors;190
13.4;A.4 Corner Point Singularities;204
13.5;A.5 Stress Intensity Factors for Irregular Cracks;213
14;B Random Load Theory and RMS;221
14.1;B.1 Introduction;222
14.2;B.2 Basic De.nitions;222
14.3;B.3 Some Sinusoidal Processes;226
14.4;B.4 Broad Band Random Loading;236
15;C Non Destructive Testing;241
15.1;C.1 Introduction;241
15.2;C.2 Visual Inspection;241
15.3;C.3 Magnetic Particle Inspection;244
15.4;C.4 Dye Penetrant;246
15.5;C.5 Radiography;247
15.6;C.6 Ultrasonics;249
15.7;C.7 Electromagnetic Fields;252
15.8;C.8 Probability of Detection;256
16;References;263
17;Index;277

Leseproben

2 Historical Background (p. 7)

2.1 Introduction

Early in the history of engineering design, there was a recognition of the need to know the different ways in which a material or component could fail. Failure was usually associated with fracture, or with excessive deformation. Failure under static loads, tensile, compressive and shear, became widely known. Much early design aimed at making a component or a structure that would last indefinitely.

Metal fatigue has been of interest for about 170 years. This interest dates back to the development of the steam engine, mechanical transport, and the more extensive use of mechanical devices. This mechanisation meant that many components were subjected to fatigue loads, and fatigue failure was beginning to become a common occurrence. The history of metal fatigue, from an engineering viewpoint, is well documented but early references are often difficult to locate.

Most books on metal fatigue include a historical summary, usually concentrating on mechanical descriptions. The best recent history, on mechanical descriptions of metal fatigue, is by Schütz (1996). It includes over 500 references, mostly in English and German.

The first use of the term fatigue in print appears to be by Braithwaite (1854), although in his paper Braithwaite states that it was coined by a Mr Field. The general opinion had developed (Frost et al. 1974) that the material had tired of carrying the load, or that the continual re-application of a load had in some way exhausted the ability of the material to carry load.

The use of the term has survived to this day. Since fatigue failures also occur in many non metallic materials the term metal fatigue is often used, as in this book, to denote the particular kind of fatigue that occurs in metallic materials, components and structures.

The first known catastrophic fatigue failure, involving major loss of life, was the Versailles (France) railway accident in 1842 (Smith 1990). The train was unusually long, with 17 carriages hauled by two steam engines. The front axle of the leading, four wheeled engine failed due to metal fatigue and the body of the leading engine fell to the ground.

The second engine smashed it to pieces. Following carriages passed over the wreck and some were set on fire. This, and numerous other railway axle failures, led to extensive investigations into the nature of metal fatigue (Parsons 1947, Smith 1990, Schütz 1996).

The first known, reasonably well documented, metal fatigue failures were in clock mainsprings (Wayman et al. 2000). The use of uncoiling springs, rather than descending weights, as a driving force was an important factor in the development of clocks for general use, and appears to have started in the early fifteenth century.

By the late eighteenth century the technology for the manufacture of durable watch and clock mainsprings was well established, a detailed description of the state of the art of making watch springs was published by Blakey (1780). Even so, high quality watches and clocks were designed (and still are) so that a broken mainspring could easily be replaced.