Heterogeneous deformation in a commercially pure titanium sheet under dwell fatigue loading: Crystal plasticity modeling and experiment

Abstract

The heterogeneous deformation in a hot-rolled commercially pure titanium grade 1 sheet has been experimentally and numerically investigated under dwell fatigue loading in current paper. The residual strain fields within two regions of interest are probed by digital image correlation (DIC) after interrupted dwell fatigue test. These measurements essentially agree with predictions of a dislocation mechanism based crystal plasticity model incorporating deformation twinning. The simulated results further indicate that axial strain localization at grain scale mainly derives from prismatic slip activity, followed by pyramidal <a>, basal slip and {1122} compression twinning activities. On this basis, a weighted averaged Schmid factor is proposed to correlate the axial strain accumulation with active plastic deformation modes in individual grains. Besides, the cyclic load shedding within a soft-hard-soft grain pair is captured by crystal plasticity modeling. The stress redistribution from soft to adjacent hard grain implies that the influence of deformation twinning on dwell facet nucleation is limited. The presented study confirms a robust crystal plasticity model and deepens the quantitative analysis of cold dwell fatigue in titanium and its alloys.