Wavelet transformation based multi-time scale crystal plasticity FEM for cyclic deformation in titanium alloys under dwell load

摘要

Titanium alloys are used in high end applications due to their desirable properties. However under dwell fatigue loading, these alloys exhibit premature crack initiation and failure when compared to normal cyclic loading. This early crack initiation can be attributed to the inhomogenous plastic deformation occurring in these alloys during the hold period of dwell cyclic loading and is strongly influenced by the underlying micro-structure. This necessitates the consideration of micro-structural features and their influence on the response, for accurate life prediction in these alloys. Crystal plasticity based finite element simulations capture the micro-structural influence on the response and can prove effective for accurate prediction of crack initiation in these alloys. However 70-80% of total life in Ti-alloys based components is spent in crack initiation and this may involve crystal plasticity based finite element simulations for large number of cycles. Such simulations using conventional single scale time integration schemes can be computationally intractable. A multi-time scale method using wavelet based decomposition is thus developed in this work for accurate and computationally efficient dwell fatigue simulations of these alloys for large number of cycles.