A new Dynamic Plasticity and Failure Model for Metals

Abstract

A new plasticity and failure model is developed herein for metallic materials subjected to dynamic loadings on the basis of the analysis of some available material test data and previous work. The new model consists of two parts: a strength model and a failure criterion. The strength model takes into consideration both tension and shear stress-strain relationships, as well as the effect of Lode angle, while the failure criterion takes into account both the effects of stress triaxiality and Lode angle. Furthermore, the effects of strain rate and temperature are also catered for in the model. In particular, new non-linear functions are suggested for the effects of strain rate and temperature in the strength model in order to describe accurately the mechanical behavior of metallic materials at very high loading rates and temperature. The new model is compared with available material test data for 2024-T351 aluminum alloy, 6061-T6 aluminum alloy, oxygen free high conductivity (OFHC) copper, 4340 steel, Ti-6Al-4V alloys, and Q235 mild steel in terms of stress–strain curves in both tension and shear, strain rate effect, temperature effect and fracture under different loading conditions. The new model is also compared with the JC constitutive model with the respective JC and BW fracture criteria by conducting numerical simulations of quasi-static smooth and notched bar tensile tests and ballistic perforation tests on 2024-T351 aluminum alloy in terms of cup and cone failure pattern, ballistic limit, residual velocity and failure mode. It transpires that the new plasticity and failure model can be used to predict the response and failure of metallic materials and structures under different loading conditions. It also transpires that the new model is advantageous over the existing models.