MULTI-TIME SCALING IMAGE BASED CRYSTAL PLASTICITY FE MODELS DWELL FATIGUE INITIATION IN POLYCRYSTALLINE TI ALLOYS

摘要

This work develops a crystal plasticity finite element simulation based prediction of fatigue crack nucleation in polycrystalline alloys. The novel framework paves the way for a paradigm change in fatigue modeling of metals and alloys. Two specific topics are at the core of this development. The first is a non-local fatigue crack nucleation model at the scale of grains in a polycrystalline microstructure based on post-processing results of crystal plasticity finite element simulations under cyclic loading. The second development is a unique wavelet transformation based multi-time scaling algorithm for accelerated crystal plasticity finite element simulations.It is motivated by the large number of cycles that may be required to initiate a fatigue crack in a polycrystalline sample.Simulating such large number of cycles remains intractable to conventional single time scale finite element analysis. The unique aspect of the developed method is that the algorithm does not require inherent scale separation as with other conventional methods that assume averaging,periodicity or near periodicity.