Shock plasticity design of brittle material

Abstract

The mechanical properties of a material are closely related to its internal micro-structure. Enhancing shock plasticity by designing appropriate micro-structure will help to slow down or delay shock failure of brittle material. In this paper, we put forward a method of designing and improving shock plasticity of brittle material by implanting specific micro-voids. A lattice-spring model is adopted, which can represent mechanical properties of brittle materials quantitatively. Simulations reveal how the arrangement modes of micro-voids can affect the shock response of brittle material. By implanting randomly arranged voids, porous brittle material has significantly higher shock plasticity than dense brittle material and the design of the regular arrangement mode of voids will help to enhance the shock plasticity further. The dominant mechanism corresponding to the void collapse in the shocked brittle material is shear slip caused by shear stress concentration, which features the occurrence of shear cracks around the voids. Features of mesoscopic deformation in the sample with 5% porosity indicate that the shock plasticity of porous brittle material comes from the volume shrinkage deformation caused by void collapse and the slippage and rotation deformation caused by extension of shear cracks. The inter-permeation of voids and volume shrinkage deformation play a leading role in the sample with regularly arranged voids. While the shear cracks extends over long distance, slippage and rotation deformation take place dominantly in the sample with randomly arranged voids. The two samples with different arrangement modes of voids both have three stages of response in the Hugoniot stress-strain curves in this paper, i. e., linear elasticity stage, collapse deformation stage, and slippage and rotation deformation stage. The sample with higher porosity has a higher shock plasticity than the sample with lower porosity. When the samples have the same porosity, the collapse deformation stage makes greater contribution to the overall shock plasticity if voids are regularly arranged, while the slippage and rotation deformation stage make greater contribution to the overall shock plasticity if the voids are randomly arranged. The principle of enhancing shock plasticity of brittle material by arranging voids regularly in this paper provides physical knowledge for the designing and preparing new types of brittle materials, thereby helping to prevent the function failure induced by shock in brittle material.