Dynamic Behavior of Polycrystalline Metals Under Combined Compression and Shear Impact Loading at Elevated Temperatures*

In this paper, we will present results of a series of elevated temperature combined compression-and-shear plate impact experiments conducted on commercial purity polycrystalline aluminum (99.999{\%}) and magnesium (99.9{\%}) at test temperatures in the range from room to near melt. These experiments are designed primarily to study the effect of temperature on the shearing resistance of polycrystalline metals at ultra-high shear strain rates and high shear strains. In order to conduct these experiments, the single-stage gas-gun facility at Case Western Reserve University was modified to include a breech-end sabot heater system and a fully fiber-optics based combined normal and transverse displacement interferometer. The measured shear-stress versus shear-strain profiles in commercial purity aluminum and magnesium samples, as inferred from the transverse particle velocity record measured at the free surface of a fully elastic tungsten carbide target plate, reveal that the flow stress in both sample materials thermally soften when heated to approximately 50{\%} of their melt temperatures. The flow stress attained at higher temperatures up to melt will be discussed in the presentation.