A new drop weight tester system was developed to obtain compression stress-strain curves of the aluminum alloy A2024 (JIS) and PMMA (polymethyl methacrylate) at a medium strain rate of approximately 100 s-1. To evaluate the strain rate or the strain of the specimen it has been necessary to measure the motion parameters, i.e., velocity or displacement, of the tup and anvil. In this new method, the velocity and displacement of the tup and anvil, which were in contact with both end surfaces of the specimen were computed on the basis of the equations of motion of the tup and anvil, respectively. The differential equation, in which the measured dynamic force versus time characteristics were contained, was integrated by the Runge-Kutta method using Microsoft Excel. For the aluminum alloy A2024, stress was not markedly affected by strain rate. On the other hand for PMMA the stress was affected significantly by strain rate.
