Experimental study on deformation evolution and fracture behaviors of pure titanium at different stress triaxialities

Abstract

In this study, the deformation and fracture behaviors of pure titanium sheet specimens under different stress triaxialities are experimentally investigated. Digital image correlation (DIC) technique is used to determine the strain maps on the surface of the specimens during the deformation and failure process. The experimental results show clearly that the strain localization occurs in different specimens which leads to the formation of the crack in the localized region (LR). The characteristics of the LR are quantitatively identified by the strain distribution along axial and transverse directions, the evolution of effective strain is successfully used to obtain the strains of diffuse necking, local necking and strain at fracture. The fracture features of the specimens with different stress triaxialities are studied by the analysis of fracture surface morphology. The nucleation and growth of micro-voids in pure titanium is significantly dependent on the applied stress conditions. The slip mechanism dominates the failure of shear specimens. For tensile loading conditions, the higher stress triaxiality accelerates the growth and coalescence of micro voids which induce the decrement of fracture strain.