High Strain-rate Test of Sinter-forged Cu-Cr Material with Split Hopkinson Pressure Bar

Abstract

Vacuum interrupters are used in various switchgear systems such as circuit breakers, distribution switches and contactors. Electrodes of vacuum interrupters are manufactured of sinter-forged Cu-Cr materials that have good electrical and mechanical characteristics. Since the deformation of the electrode depends on the strain-rate at the closing stroke, the dynamic characteristics of the sinter-forged Cu-Cr material need to be specified in order to investigate the impact behavior in contact. Due to the inertia effect and the stress wave propagation, an adequate experimental technique is necessary to obtain the dynamic response for the corresponding level of the strain-rate. In this paper, a split Hopkinson pressure bar apparatus was used to acquire the high strain-rate material properties of the sinter-forged Cu-Cr material. The dynamic response of the material at the high strain-rate is obtained from the high strain-rate compression test using disc type specimens. Experimental results from both quasi-static and dynamic tests are interpolated to construct the Johnson-Cook and a modified Johnson-Cook model as the constitutive relation for numerical simulation of the impact behavior of electrodes.