Dependence of Measured Lateral Stress on Thickness of Protective “Padding” around Gauge

Earlier work found that lateral stress gauges were unusable when the longitudinal stress in the sample exceeded around 13 GPa in samples of steel. This pressure corresponds to a phase transition found in iron and its alloys. It was hoped that protective padding would allow measurement of stresses higher than this. It was therefore necessary to investigate the effect of the padding on the stress measured. A series of experiments were carried out using mild steel with different thicknesses of mylar or polycarbonate padding. This research has been supported by simulation studies using the Eulerian hydrocode GRIM, which has indicated some issues with the representation of the lateral gauge in the hydrocode. The simulations have confirmed the experimental trends observed with additional padding, but they have also indicated the potential need for additional analysis on the raw lateral gauge data.