Thermo-viscoplastic behavior and constitutive modeling of pure copper under high-strain-rate shear condition

A new double shear specimen (DSS) is used under the traditional Split Hopkinson pressure bar (SHPB) technique to study the constitutive behaviors of pure copper under dynamic shear loading. Shear stress-shear strain curves are obtained at 288-673 K and in a wide range of shear strain rates between 6000-45,000 s(-1). A shear dominated stress state is obtained in the shear zone, in which the stress triaxiality and the Lode angle parameter are both very low. The influence of stress state on the plastic flow properties of the material is observed through comparison of the test results with the experimental data in compression. With the aid of finite element analysis (FEA), it's seen that the determined constitutive model JC1 can give much more precise prediction on the shear testing results than the compression-based model, JC2. The result implies that the commonly adopted compression or tension test data may not be suitable for description of shear dominated deformation conditions. In engineering application, the actual stress/strain state must be considered in the determination or selection of the constitutive models to obtain a precise computation result.