Abstract
A continuum damage mechanics (CDM) model for high-cycle fatigue (HCF) is presented to study crack initiation in AA7075-T651. This study is based on the experimental observation of dependence of crack initiation life on microstructure of alloys. We investigate the effect of microstructural features such as grain size and grain orientation on crack initiation life. A crystal plasticity finite element model (CPFEM) is implemented in conjunction with CDM model to simulate damage evolution at grain scale. Finite element program ABAQUS has been used and the CPFEM–CDM model is written using a user material subroutine. Simulations are performed for constant amplitude, completely reversed loading. In order to provide a prediction for fatigue scatter, we consider different realizations of the microstructure as well as uncertainty in fatigue parameters. Given probability density function of damage parameters, we can transport it into a lifetime probability density function using simulations results. Good agreement is observed between simulations results and available experimental data. Further investigation is needed to develop the CPFEM–CDM model for HCF under variable loading conditions.
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