Initially these techniques were relatively simple procedures, which compared measured constant amplitude stresses (from prototype tests) with material data from test coupons. These techniques have become progressively more sophisticated with the introduction of strain based techniques to deal with local plasticity effects. Nowadays, variable amplitude stress responses can be dealt with.

Furthermore, techniques exist to predict how fast a crack will grow through a component, instead of the more limited capability to simply predict the time to failure. Even more recently techniques have been introduced to deal with the occurrence of stresses I more than one principal direction (multi-axial fatigue) and to deal with vibrating structures where responses are predicted as PSDs (Power Spectral Densities) of stress.

Today, 95% of all fatigue design calculations are covered by one of three approaches, i.e., Stress-Life or Crack-Propagation. Furthermore, since stress or strain are governing variables it has been usual to test prototype components in order to obtain the required data needed for the fatigue analysis.

However, with the introduction of Finite Element Analysis (FEA) techniques, has come the possibility of doing fatigue calculations long before a prototype exists. Furthermore, a dramatic improvement in computing power has made FE based fatigue life calculations a routine task. FE has been around for some time and is now a mature technology. The purpose of this book is to provide an introduction to the basic underlying concepts of fatigue analysis within the FE environment.

This goal can be stated further as to give engineers involved in FE a basic understanding of fatigue; and to give engineers involved in fatigue a basic understanding of FE. A number of examples are used throughout the text to illustrate the concepts and potential applications.

Contents

• Introduction
  
• Why FEA based fatigue design?
  
• Different Philosophies ad Life Estimation Models.
  
• The Stress-Life (S-N) Approach.
  
• The Strain-Life ( e -N) Approach.
  
• Crack Propagation Analysis Using LEFM
  
• Multi-axial Fatigue Analysis.
  
• Vibration Fatigue Analysis.
  
• FE Model Building and Post Processing Issues.
  
• Bibliography