含微孔洞脆性材料的冲击响应特性与介观演化机制

微孔洞显著地影响着脆性材料的冲击响应,理解其介观演化机制和宏观响应规律将使微孔洞有利于而无害于脆性材料的工程应用.通过建立能够准确表现材料弹性性质和断裂演化的格点-弹簧模型,本文揭示了孔洞的演化对于脆性材料的影响.冲击下孔洞导致的塌缩变形和从孔洞发射的剪切裂纹所导致的滑移变形产生了显著的应力松弛,并调制了冲击波的传播.在多孔脆性材料中,冲击波逐渐展宽为弹性波和变形波.变形波在宏观上类似于延性金属材料的塑性波,在介观上对应于塌缩变形和滑移变形过程.样品中的气孔率决定了脆性材料的弹性极限,气孔率和冲击应力共同影响着变形波的传播速度和冲击终态的应力幅值.含微孔洞脆性材料在冲击波复杂加载实验、功能材料失效的预防、建筑物防护等方面具有潜在的应用价值.所获得的冲击响应规律有助于针对特定应用优化设计脆性材料的冲击响应和动态力学性能.

Shock response and evolution mechanism of brittle material containing micro-voids

Micro-voids significantly affect shock responses of brittle materials. Knowledge about the meso-scale evolution mechanism and macro-scale shock behavior will help to utilize micro-void in applications and avoid its disadvantages. A lattice-spring model, which can represent both elastic property and fracture evolution accurately, is built in this work. Simulations reveal that severe stress relaxation, which is contributed from collapse deformation induced by voids and slippage deformation induced by shear cracks extending from voids, modulates the propagation of shock wave. In a porous brittle material, the shock wave broadens into an elastic wave and a deformation wave. On a macro-scale, the deformation wave behaves as a plastic wave in ductile metal; on a meso-scale, it corresponds to the processes of collapse and slippage deformations. It is found that porosity of the sample determines the Hugoniot elastic limit of material; whereas the porosity and shock stress affect the propagation speed of the deformation wave and stress amplitude in a final state of shock. Brittle materials containing micro-voids have potential applications in complex shock loading experiments, precaution of shock induced function failure, and crashworthiness of buildings. Shock behaviors reported in this work will benefit the design and optimization of shock responses and dynamic mechanical properties of brittle materials used in specific applications.
Keywords： micro-voids brittle material shock response evolution mechanism