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The present paper analyzes failure observed in polymer rods collided with a steel anvil under the Taylor cylinder impact experiments. The experimental and numerical analysis demonstrates that association of the failure patterns with the loading mode depends on the rod material. Two materials are considered in the paper, specifically, polymethylmethacrylate (PMMA) and polycarbonate (PC). Damage in PMMA rods at the Taylor tests is shown to be dominated by the shear load resulting in plastic deformation. In contrast, the major mechanism of damage in PC rods is governed by omni-directional (pressure) mode of load. Analysis of the damage in sections of the rods associated with the glass transition is also addressed in the present theoretical study. Failure in these polymers follows the traditional fracture wave mechanism for brittle glass-type materials due to load in the corresponding mode. Numerical analysis employs a two-phase model with improved inter-phase thermal balance accounting for the inter-phase mass, momentum, and heat exchanges during the glass phase transition, while damage being accumulated in time. The simulation results demonstrate a good correlation with the experimental results. [ABSTRACT FROM AUTHOR]

The effects of prior deformation on the shock response of silver, whereby a hot forged (low dislocation density) material is compared to a cold rolled (21% reduction in thickness) variant. Results show that the cold rolled material has a higher and more clearly defined Hugoniot Elastic Limit in comparison to the hot forged silver. In contrast the spall response was near identical between states under all conditions of shock loading in this investigation. A comparison with annealed and cold rolled copper, shock loaded under similar conditions showed that a significant quasi-elastic release occurred in the annealed copper that was absent in all other materials. We have suggested that this be due to either twin formation in annealed silver or high initial dislocation densities in the rolled materials creating a Bauschinger effect that would effectively reduce the yield stress on arrival of release waves. [ABSTRACT FROM AUTHOR]