多孔脆性介质冲击波压缩破坏的细观机理和图像

Mesoscopic picture of fracture in porous brittle material under shock wave compression

本文采用一种具有良好定量性质的离散元模型研究了带孔洞的各向同性脆性介质在细观尺度上的压缩破坏特征.通过对孤立孔洞、三种简单的孔洞排布方式和大量孔洞随机排布等几种情况的模拟,认识到了剪切破坏和局域拉伸破坏是冲击波压缩下多孔介质的基本破坏模式;孔洞之间的损伤贯通会促进孔洞在较低应力下发生塌缩,但损伤区的应力松弛过程却会对一定范围内的介质起到损伤屏蔽作用;不同区域中损伤促进和损伤屏蔽的综合效果是在多孔脆性介质中形成一种高损伤区与低损伤区间错排布的奇特损伤分布.本文的研究结果为深入理解脆性材料冲击波压缩破坏的演化过程和机理提供了细观尺度上的初步物理图像.

Void is one of the most common type of structure flaws existing in brittle materials,which dramatically affects the shock loading response of brittle materials.A quantitative discrete element method is employed in this work to study the fracture characteristics of porous isotropic brittle material under shock wave compression.Scenarios of isolated void,three types of simple distribution and random distribution of voids are computed,from which we find that shear fracture and local tensile fracture are two type of basic fracture modes for brittle material under shock wave compression.Coalescence of damage bands between voids can induce the collapse of voids at relatively low pressure,while stress relaxation caused by damage can shield fracture evolution in a certain zone.The combination of amplification and shielding effects of damage results in a unique pattern of alternate distribution of severe and mild damage zones. These simulation results present a basic physics picture for the understanding of evolution process and mechanism of fracture in porous brittle material under shock wave compression.