Variations in the shear strength of shock loaded niobium

The shock response of the body centred cubic (bcc) metal, niobium, and in particular its shear strength has been measured using manganin stress gauges. Whilst the shear strength increases with shock amplitude, as would be expected, its shear strength behind the shock front has been observed to be near constant. This is in contrast with other bcc metals such as tantalum or tungsten where a significant reduction has been observed. It has been suggested that the low Peierls stress in this metal (compared to Ta or W) enables the material to generate more new dislocations which reduces the decrease in shear strength.