Abstract: The fracture behaviors and associated mechanisms of metallic materials under biaxial stress are vital for their manufacturability and service performance. In this work, the fracture behaviors of commercially pure titanium (CP-Ti) under quasi-uniaxial and equi-biaxial tension were investigated by using the digital image correlation technique and finite element modeling. The fracture behaviors under quasi-uniaxial tension were characterized by a general normal fracture. In contrast, normal fracture firstly occurred perpendicular to the rolling direction (RD) under equi-biaxial tension, followed by secondary shear fracture along the 45° direction relative to the RD. The normal fracture was attributed to the lower strain hardening ability in RD compared to the transverse direction (TD) induced by the TD-split type basal texture. The different hardening abilities introduced large shear stress in the 45° direction, which contributed significantly to the secondary shear fracture. An anisotropy parameter K (∆Ss/σs), defined as the ratio of the equivalent effective traction stress to the yield strength, was proposed for the first time, to predict the fracture path with the impact of crystallographic preferred orientation.

Key words: Titanium, Biaxial tension, Fracture behavior, Digital image correlation (DIC) technique, Finite element modeling