Finite Element Based Fatigue Calculations

Fatigue analysis procedures for the design of modern structures rely on techniques, which have been developed over the last 100 years or so. 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.