Dynamic Yield Behavior of Explosively Loaded Metals Determined by a Quartz Transducer Technique

Abstract

Explosively generated plane waves were passed through plates of duraluminum, iron, and steels of variouscompositions and heat treatments. X-cut quartz disks of large diameter-to-thickness ratios (≥5) were usedto obtain continuous stress-time profiles of elastic-plasticwave structures associated with yielding. For timesless than wave transit time through the disk, the short-circuit current output is directly proportional to thespecimen-to-quartz interface stress up to 21 kbar. The incident wave profile in the specimen is then determinedfrom the interface stress-time profile on the basis of an assumed model. Advantages of the techniqueare excellent time resolution, high sensitivity, and relative simplicity of use. The profiles for duraluminum,normalized SAE 1018 steel, and normalized Armco iron exhibit a relatively slow rise to the yield stress,subsequent stress relaxation, except in duraluminum, and then a gradual rising transition into the plasticwave. In comparison, SAE 4340 and other tool steel profiles exhibit a faster initial rise, no stress relaxation,and a steeper transition into the plastic wave. The dynamic yield stress in the tool steels increases withRockwell hardness, and the separation between the elastic and plastic wavefronts decreases. In general, asthe specimen thickness is increased, the dynamic yield stress decreases and the initial rise time increases.