A theoretical analysis of experimental results of shock wave loading of OFE copper relating the observed internal structure to the deformation mechanism

The observations made by Gray and Follansbee of the internal metallurgical changes in oxygen-free electrolytic copper specimens that were subjected to sharply terminated shock loadings of 5, 10 and 20 GPa led to conclusions about the mechanisms of shock loading and its pressure release that may be helpful in formulating the material constitutive equation. Details of the shock load mechanism obtained from these experiments may explain the micro-structure observations made and provide quantitative details for modeling of this important transient process. It was particularly noticed that micro-structural changes caused by the shock front passage through the specimen resulted in a time period after the shock front arrival, called the temporary retardation time, when the material elastic load could not be released by plastic deformation involving internal shearing. This temporary retardation time makes the accumulation of high elastic energy density at high strain rates possible. The accumulated elastic energy may possibly be discharged via shear bands’ formation although occurring of other failure modes of the material cannot be excluded. Formulation is suggested for incorporating the retardation time into material models suitable for hydrocodes.