Study on constitutive relations and spall models for oxygen-free high-conductivity copper under planar shock tests

It is indicated that the constitutive relations for shear modulus G as functions of thermodynamic state were not given in the Johnson-Cook model and the Zerilli-Armstrong model while the constitutive relations for yield strength Y as functions of strain and strain rate were not given in the Wallace model and the Straub model. Seven constitutive models are constructed based on Y∕G=constant and on G∕B=constant (B-bulk modulus), respectively. The variations of longitudinal stress, transverse stress, and yield strength of oxygen-free high-conductive (OFHC) copper with time under planar shock loading are obtained using the manganin stress gauges and compared with the predicted results by the constructed seven constitutive models. It seems that the pressure, density, temperature, and plastic strain dependence of the yield strength for OFHC copper subjected to planar shock loading is essential to the constitutive description. Planar spall tests for OFHC copper are also performed and the void coalescence-based spall model presented by the authors are applied to numerical simulations of planar spall tests including tests given by Seaman et al. [Phys. Rep. 147, 253 (1987)]. The Steinberg-Cochran-Guinan constitutive model is proved appropriate to the planar shock loading and is adopted in the numerical simulations of planar spall tests.