A modified parallel-sided shear zone model for determining material constitutive law

The Johnson and Cook (J-C) constitutive model is widely employed in finite element analysis for machining. Currently, inverse approach shows greater superiority on identifying the J-C parameters than the traditional way, like the split Hopkinson pressure bar (SHPB) test. In this paper, a modified parallel-sided shear zone model at primary zone is presented for determining J-C parameters. Based on the assumption of nonequidistant primary zone, the distribution of velocity, strain rate, strain, and temperature is successfully predicted. Finite element simulation (FEM) is subsequently used to verify the theoretical prediction. Based on the proposed shear band model, an inverse approach is developed for determining the J-C parameters. In this method, the parameter determining process is taken as an optimization problem. The J-C parameters are considered as the design variable while the optimization objective is cutting force. In conjugation with the measured cutting forces and chip thickness, the particle swarm optimization (PSO) algorithm was introduced to solve the optimization model. The Johnson-Cook's model of nickel-base superalloy Inconel 718 is successfully identified from orthogonal cutting test. Finite element models with seven constitutive models from Deform, references and this work are established to predict cutting force. The results showed that the proposed J-C models have higher prediction precision compared with other constitutive models. With the proposed J-C models, the errors between the simulated and measured cutting forces are controlled within 7.3%.