A numerical scheme for extracting strength model coefficients from Taylor test data

Abstract

A simple pair of ordinary differential equations describing a one-dimensional model of a deforming Taylor impact specimen were numerically integrated. The Johnson-Cook strength model was assumed to apply and was used to estimate material strengths and plastic wave speeds during the deformation process. The material constants of the Johnson-Cook model were adjusted using an optimizer so that experimentally measured deformed geometries were matched with those calculated by the integrator. In this fashion Taylor test data were used to back-out strength model coefficients. Event durations, and peak values of stresses, equivalent plastic strains, equivalent plastic strain rates, and temperatures were also obtained from the simple numerical model. The EPIC finite element code was used to investigate the validity of the predictions of the simple model. Three different materials are considered (OFE copper, 6061-T6 aluminum, and 4340 steel) and the results obtained are reasonable.