Discrepancy between fatigue and dwell-fatigue behavior of near alpha titanium alloys simulated by cellular automata

Cellular automata were used to simulate microstructure heterogeneities at local (one grain) and global (aggregate of grains) levels in an attempt to better understand the large discrepancies observed between fatigue and dwell-fatigue behaviors of some titanium alloys. Eshelby theory was used to estimate the local stresses and strains developed in the microstructure. In the case of simple fatigue tests, loading and unloading stages were used to calculate and describe the strain accumulation history. For dwell fatigue analysis, a thirty second steady state at maximum load was applied to simulate the dwell period. In the present study, the local stress, strain and creep rate in each grain are calculated as a function of the mechanical properties of the neighboring grains. The data are then compiled and the overall behavior of the aggregate is predicted. The results can reproduce and explain some specific features observed experimentally in fatigue and dwell-fatigue tests of near alpha titanium alloys.