Effect of Steep Reduction on Strain Rate on the Dynamic Flow Stress of Aluminium at Very High Strain Rates.

Abstract

In order to evaluate the effects of the instantaneous strain rate and the structural state reflecting the strain rate history upon the dynamic flow stress, strain rate reduction tests are conducted for high-purity polycrystalline aluminium in a strain rate range from about 8000 to 20000/sec. For the strain rate change tests in such a very high strain rate range, a very steep change in the strain rate is required for the loading system. A new apparatus is devised by which a sharp reduction in the strain rate can be obtained. It is confirmed that the instantaneous strain rate plays a more important role than the structural state in the flow stress at very high strain rates where a steep increase in the strain rate sensitivity of the flow stress is observed.