A Comprehensive Sensitivity Analysis of Johnson-Cook Plasticity Parameters on Orthogonal Cutting Simulations

Abstract

The Johnson-Cook material model, which is the most widely used constitutive model in machining simulations, describes the yield stress as a function of the thermomechanical load spectrum without any further influence of structural material parameters. It is a purely empirical model and contains five independent material parameters which govern the material-specific flow stress. The parameters have a significant effect on the simulation results and quality. Current research in this field is mostly focused on experimental approaches to determine these parameters whereas the results often differ widely even though the parameters describe comparable materials. It is therefore of great interest to understand how differences between material parameters affect machining simulations in detail. The approach in this work follows these questions and uses a full factorial test design to perform and analyze two-dimensional cutting simulations with respect to the sensitivity of the material parameters. The influence of all five Johnson-Cook parameters on cutting forces, temperatures, chip thickness and contact length is investigated. To ensure the significance of the results, the approach does not focus on the effect of a single change in one parameter while the other parameters remain constant. Rather, it shows the influence of each material parameter after analyzing all possible permutations of the full factorial test design. The results are supplemented with an investigation of the correlation coefficients between model parameters and simulation results. This provides information about the extent to which simulation results can be influenced independently. It turns out that the Johnson-Cook parameters affect the results in different ways and in different magnitudes. It also shows that some simulation results can be influenced separately, while others always change together.