Use of creep-plastic analysis methods to predict complex non-isothermal loading cycle crack growth and nucleation behaviour

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Models developed by RR for creep and plasticity have been shown to provide a valuable insight into nominally complex fatigue and crack growth behaviour. Using stabilised stresses predicted by creep-plastic finite element analyses as the basis for lifing correlations has resolved many of the unusual observed trends in fatigue tests such as longer dwell times giving higher fatigue lives at all but extreme temperatures. Creep-plastic modelling of crack tip stress fields has allowed high temperature retardation models to be developed that predict incubation periods where no time dependent crack growth occurs following unloading from a high to an intermediate stress levelThis project proposes to explore the capabilities of non-linear stress analyses of crack tips and notches further to resolve a number of long-standing issues related to complex loading cycles such as threshold behaviour, low and high temperature retardation, fatigue scatter and mean stress effects. The understanding gained from the non-linear FE analyses will be used to develop models for the above effects that will be suitable for component lifing.