A Physically Based Constitutive model for FCC metals with Applications to Dynamic Hardness

摘要

A constitutive model is developed in this work to describe the mechanical behavior of face centerd cubic (fcc) metals under a wide range of temperatures and strain rates. The model is basically based on the dependence of activation energy on temperature, strain rate, and stress. An expression for flow stress is proposed in terms of micromechanical terms such as mobile dislocation density and the Burgers vector as well as macromechanical based state variables such as stress and material constants such as threshold and transition temperature. The proposed model was used to simulate the experimental results of Oxygen Free High Conductivity (OFHC) Copper at different temperatures and strain rates in order to obtain the different model parameters. The model shows good capability in capturing the coupling between strain rate and temperature, plastic strain and strain rate, and plastic strain and temperature. Finally, the model is used to characterize the hardness at low and high strain rates. The model gives good predictions of hardness at both low and high strain rates at a representative strain of 8%, but tends to underestimate the hardness at higher strain levels. The underestimation is attributed to the work hardening produced by indentation process itself which is not accounted for in the model.