Microcumulation at Impact Loading As a Method of Comparative Evaluation of Dynamic Plasticity of Metallic Materials: Case of Copper

A novel experimental laboratory technique for evaluating the ultimate dynamic plasticity of materials, under the conditions of cumulative jet flow and without using explosives, is described. To perform the microcumulative tests, miniature cylindrical specimens with conical pits were used. The dynamic loading of the specimens was performed using a gas gun with a striker accelerated up to speeds in the range of 600-800 m/s. The optimal specimen geometry and testing regimes, including the focal distance during microcumulation testing, were then determined. The flow speed of the microcumulative jet was found to be equal to its theoretical value calculated within the framework of the Lavrent'ev hydrodynamic theory. The novel technique was demonstrated to enable the study of the relationship between the initial specimen microstructure and the ultimate dynamic plasticity magnitude at the cumulative jet flow using high-purity copper as an example. The penetration depth of the cumulative microjet into a steel barrier was shown to depend on the parameters of the copper microstructure. A preliminary analysis of the effects of copper purity and processing regimes on the ultimate dynamic plasticity characteristics was performed.