K11 Strain Rate Sensitivity of Dynamic Flow Stress of FCC Metals at Very High Strain Rates

Abstract

The strain rate sensitivity in FCC metals is known to increase dramatically when the strain rate exceeds about 5×10^3/s. In order to evaluate the effect of a instantaneos strain rate upon the dynamic flow stress, strain rate reduction tests are conducted for high-purity aluminum. The instantaneous strain rate plays dominant role in the flow stress at very high strain rates where a steep increase in the strain rate sensitivity of the flow stress observed. A simplified model for the kinetics of dislocations is used to consider the transition mechanism. The flow stress calculated using the expression derived from the model shows fairly good agreement with the directly measured flow stress over the high strain rate range.