Lateral stress and shear strength behind the shock front have been measured in three face centered cubic alloys. Results show different behaviors according to microstructure. A hardening response has been shown in pure nickel, while in stainless steel (SS) 304L, hardening has been shown to be minimal. This has been explained in terms of the stacking fault energy effecting the motion and generation of dislocations. In the high stacking fault energy nickel, dislocation motion is comparatively easy, and hence the microstructure consists of dislocation cells, with a pronounced hardening postshock. In SS 304L with its lower stacking fault energy, dislocation motion is more restricted, and hence deformation is dominated by deformation twins. The behavior behind the shock front correlates with the low degree of hardening observed by others during mechanical testing of preshocked samples. The aluminum alloy 6082-T6 also shows a low degree of hardening behind the shock front. This is believed to occur due to the presence of fine intermetallic particles suppressing the formation of dislocation cells but rather forming a random distribution throughout the microstructure.

The effect of prior cold work on the shock response of tantalum has been investigated via plate impact. As-received and 50% cold-rolled material has been studied to determine the Hugoniot Elastic Limit (HEL), shear strength evolution behind the shock front, and spall strength. Results show that there is a significant drop in both HEL and shear strength due to cold-rolling, but as the thickness of the target (or time) increases, results converge between the two states. Results suggest that this is due to the cold-rolling process moving dislocations away from the surrounding interstitial solute atoms that collect there, thus reducing the initial stress to initiate yield. In other words, the main contribution of cold-rolling is to increase the population of mobile dislocations within the microstructure rather that just increase the dislocation density as a whole. In contrast, the spall strength in both states appears almost identical. It is suggested that the high Peierls stress prevents a large increase in dislocation density during rolling and hence reduces any post rolling strengthening that might be observed in the spallation response. Finally, we observe a significant change in spall response below a pulse width of 150 ns. We believe that this represents a change from a nucleation and growth of ductile voids type mechanism to one based on ductile fracture of atomic planes. The fact that at these low pulse durations, results appear to trend towards the theoretical strength of tantalum would lend support to this hypothesis.

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The shock-induced shear strength of a commercial silastomer, trade name Sylgard 184™, has been determined using laterally mounted manganin stress gauges. Shear strength has been observed to increase with increasing shock amplitude, in common with many other materials. Shear strength has also been observed to increase slightly behind the shock front as well. It is believed that a combination of polymer chain entanglement and cross linking between chains is responsible. Finally, a ramp on the leading edge of the lower amplitude stress traces has been observed. It has been suggested that this is due to shock-induced collapse of free space between the polymer chains. Similar explanations have been used to explain the apparent non-linearity of the shock velocity with particle velocity at low shock amplitudes.

Manganin stress gauges in lateral orientation have been used to monitor the shock response of Ti–6Al–4V when loaded either parallel to or radial to the long axis of the original bar stock studied in this investigation. Materials characterization has shown that the c-axis of the hexagonal unit cell is preferentially orientated radially to the axis of the bar. Shear strengths measured along the long axis of the bar were found to be in agreement with previous data in the literature, while strength in the radial direction was found to be significantly lower. It was also noted that the lateral stress, when measured in the radial direction, displayed a pronounced drop in the lateral stress after reaching the peak shock stress unlike the longitudinal orientation. This decrease is indicative of an increase in shear strength behind the shock front. In both instances, it is postulated that extensive deformation twinning during the early stages of deformation in the shock and thereafter c+a slip and dislocation tangling builds up over a longer time period, resulting in the higher degree of hardening noted.