The use of dynamic impact experiments in the determination of the strain rate sensitivity of metals and alloys

The deformation of a metal target under an impacting hard elastic ball is analyzed to show that simple measurements can lead to valid stress-strain and stress-strain rate data. It is found that pure metals, exhibit the highest strain rate sensitivity while the solid solution alloys show intermediate strain rate sensitivity. On the other hand, in the case of precipitation hardened and dispersion strengthened alloys, the flow stress is insensitive to strainrate. The observed strainrate effects are rationalized in terms of a three component flow stress model incorporating the athermal, thermally activated and viscous components