Experimental and crystal plasticity studies of deformation and crack nucleation in a titanium alloy

Abstract

This paper presents recent developments in crystal plasticity modelling to incorporate a non-local crack nucleation criterion and the comparison of experimental observations and model predictions for deformation and crack nucleation in a near-alpha titanium (Ti) alloy polycrystal. The model polycrystal was established so as to have grain morphology and crystallography nominally identical to that in the experiment, enabling direct interpretation and comparison of the results. The experimental measurements of strain fields were obtained using electronic speckle pattern interferometry on a large-grained polycrystalline sample.

The crystal plasticity model predictions and experiments show strong agreement in a number of important features relating to crack nucleation: the location of crack nucleation, the direction changes in crack growth when the crack crosses two grain boundaries, and the important role of crystallographic orientation in nucleation site and in growth directions. There was also good agreement in the establishment of strain heterogeneity and in localization; both experiment and crystal plasticity predictions demonstrate that the heterogeneity is established early in the loading history and that the localization correlates closely with the crack nucleation site.