Strain Rate Dependence of Dynamic Flow Stress of A1070 at Very High Strain Rates

Abstract

In order to evaluate quantitatively the strain rate dependence of the dynamic flow stress of A1070 at very high strain rates, high strain rate and decrement strain rate tests are performed in the strain rate range from 4000/sec to 22000/sec. The reduction ratio caused by the collision between an impact bar and a decelerator is 0.586 of the strain rate before reduction. The flow stress drop obtained by the rate reduction increases with strain rate, and which was assumed to be a response to an instantaneous strain rate. An activation volume is determined from the relation of a thermal activation process and the amount of the flow stress drop obtained from the reduction tests. The activation volume decreases slightly with strain rate. High strain rate tests at high temperatures of 373 K and 473K also performed in the above strain rate range. Calculation curves predicted by thermally activated process show a good agreement with experimental results. The rate controlling mechanism of A1070 at very high strain rates can be represented by the thermal activation process.