Effect of Steep Reduction in Strain Rate on Dynamic Flow Stress of BCC Metals at Very High Strain Rates.

Abstract

In order to evaluate the effects of the instantaneous strain rate and strain rate history on the dynamic flow stress in BCC metals at very high strain rates, strain rate change tests are performed for low carbon iron and niobium in a strain rate range from about l0000 to 20000/s. The results indicate that the instantaneous strain rate plays a dominant role. Furthermore, the σ-log ε curve calculated using activation energy E(γ) for deformation of pure iron obtained by Aono et al. shows good agreement with experimental data. It can be concluded that the deformation in the BCC metals at high strain rates is controlled by dislocation motion which surmounts the Peierls potential barriers with the aid of the thermally activated formation of kink pairs