Abstract
In order to evaluate quantitatively the relation between the dynamic flow stress and the activation distance of Aluminums 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 the strain rate, and which was assumed to be a response to an instantaneous strain rate. High strain rate tests at high temperatures of 373 K and 473K are also conducted 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 Aluminums at very high strain rates can be represented by the thermal activation process. The activation distance is determined from the activation volume which is derived from the amount of the flow stress drop obtained from the reduction tests. The activation distance decreases with increasing flow stress. The force – displacement curves of A1070 and A6061 – O are presented.
