Plastic behavior and failure mechanism of Ti-6Al-4V under quasi-static and dynamic shear loading

摘要

A new kind of double-shear specimen (DSS) is used to study quasi-static and dynamic behaviors of Ti-6Al-4V under simple shear conditions. With different loading techniques, a wide range of shear strain rates are covered from 0.002 s(-1) to 60,000 s(-1). The flow stress curves are determined under different conditions. Its observed that the work-hardening effect on the flow stress is weakened gradually with the increasing strain rates. Both the yield stress and the failure initiation stress show an increasing tendency with the strain rates. On the contrary, the failure initiation strain and the fracture strain both decrease with strain rates. From numerical simulation, it's seen that a shear dominated stress/strain state is formed in the shear zone, where the stress triaxiality and the Lode angle parameter basically keep constant for different strain rates. Based on the fracture morphology, it's concluded that with the increasing shear strain rates the failure mechanism changes from a ductile fracture to an ASB dominated process. The macro regularities of the failure properties can be explained well by the different micro-mechanisms.