Fracture evaluation of metallic materials at intermediate strain rates

This paper evaluates existing dynamic hardening models and fracture strains for metallic materials of typical crystalline structures: 4130 steel (BCC); OFHC copper (FCC); and Ti6Al4V (HCP). Uniaxial tensile and fracture tests of the representative materials are carried out at intermediate strain rate. In order to describe the dynamic hardening characteristics, several models are compared for each material and the most applicable model for a specific material has been recommended. The fracture tests at strain rates ranging from 0.001s to 100s are conducted with several types of the pure shear, dog bone and grooved specimens for the strain paths of the pure shear, uniaxial tension and plain strain conditions. The fracture strain and the strain path are measured on the surface of the specimen and the Lou-Huh ductile fracture criterion is implemented to describe the fracture loci with respect to the strain rate.