DYNAMIC CONSTITUTIVE-EQUATIONS AND BEHAVIOR OF BRASS AT HIGH-STRAIN RATES

This paper presents an experimental study of the mechanical properties of brass at high strain rates. The brass tested is the copper-zinc al pha-beta and beta two-phase alloy in the cold-worked state. Experiment s were conducted using an extended tension split Hopkinson bar apparat us. It is found that, at lower strain rates, the stress-strain curve i s smooth, exhibiting no well-defined yield stress, but at higher strai n rates the stress-strain curve not only shows a well-defined yield st ress but also displays a very pronounced drop in stress at yield. The flow stress is found to increase with increasing strain rate, but the increase is more significant for the yield stress than for the flow st ress, showing that the yield stress is more sensitive to the strain ra te than the flow stress away from the yield point. Based on the experi mental results, empirical strain-rate-dependent constitutive equations are recommended. The suggested constitutive equations provide a reaso nable estimate of the strain-rate-sensitive behaviour of materials.