CONSIDERATION OF MULTIAXIALITY IN FATIGUE LIFE PREDICTION USING THE CLOSURE CONCEPT

Based on fracture mechanics a model has been developed for predicting the fatigue lifetime to initiate a crack of technical size (2a 0.5 mm) in engineering components under multiaxial-proportional loading. Using material data determined for uniaxial loading, the model describes and evaluates the elasto-plastic multiaxial notch stresses and strains using the effective range of the J-integral, ΔJ eff , as a crack tip parameter. Mean stresses, load sequence effects and various modes of crack propagation due to variable amplitude loading with individual multiaxiality ratios can be explicitly considered. The prediction accuracy of the model is demonstrated using experimental fatigue life data determined with unnotched specimens of FeE460 and Al5083 for proportional fully-reversed constant and variable amplitude loading with various multiaxiality ratios.

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