724 Strain Rate Dependence of Dynamic Flow Stress of SS400 at Very High Strain Rates

Abstract

In order to evaluate a strain rate sensitivity of a dynamic flow stress "d σ/dlog ε" of SS400 at very high strain rates, constant strain rate tests and strain rate reduction tests are conducted in the strain rate range from about 2×10^3/s to 2×10^4/s. The flow stress depends strongly on the instantaneous strain rate and further, the "d σ/dlog ε" can be expressed by a thermally activated process of a formation of kink pairs. Alloying and impurity atoms contribute to the increase in an athermal component of flow stress.