Analysis of Strains,Strain Rates and Temperatures during the early stages of shaped charge liner collapse

In trying to understand the extraordinarily high dynamic ductility of a copper shaped charge jet, prior work by the authors has utilized the Eulerian MESA 2D code with a novel form of the LaGrangean tracer particle technique as well as the experimental “soft recovery” and metallurgical examination of partially collapsed copper liners. This work had indicated that localized material processing occurs during the earliest stages of liner collapse and causes dramatic visible grain size refinement, evident in the photomicrographs. Further computational analysis shows that the localized plastic flow is accompanied by very high localized engineering strains (>200), extremely high (>4 × 10⁷ s⁻¹) localized strain rates, as well as elevated temperatures, all of which favor a dynamic recrystallization process. In this paper, the focus is on a detailed quantitative analysis of strain, strain rate and temperature distribution history within the collapsing liner, in the region of the inner liner apex and the early location of the moving collision zone, where the early material conditioning first occurs. Correlations are sought between the computed, time-dependent values of these three paremeters and the microstructures observed in the interiors of the partially collapsed liners, in those regions where the grain size changes are observed. This data may ultimately permit quantitative comparisons with the predictions of dynamic recrystallization models.