Investigations on the mechanism and behavior of dynamic energy absorption of metal foam

Abstract Metal foams have been widely used in the engineering fields due to its excellent energy absorption capacity under impact. Under different impact velocities, metal foam exhibits different energy absorption properties. It is important to investigate the mechanism and behavior of energy absorption of metal foam under impact. In this study, a 3D microscopic finite element model (FEM) of metal foam is first established to study energy absorption properties of metal foam. It is shown that the impact energy transfers into kinetic and internal energy of metal foam which varies under impact. The variation can be explained by plastic shock wave, which is produced and then propagates under impact. The theoretical model is proposed to discuss and predict kinetic energy and the difference between dynamic and quasi-static energy absorption behavior of metal foam. Effects of inertia and base material strain rate on plastic shock wave are investigated, and the mechanism of the two effects on dynamic energy absorption properties are studied. The results indicate that base material strain rate effect resists the formation of plastic shock wave, and leads to smaller kinetic energy, but higher internal energy.摘要 金属泡沫因其在冲击载荷下优异的吸能性能，已被广泛应用于工程领域。在不同冲击速度条件下，金属泡沫展现出各异的吸能特性。研究冲击载荷下金属泡沫的吸能机制与行为具有重要意义。本研究首先构建了金属泡沫的三维微观有限元模型（Finite Element Model, FEM），以探究其吸能特性。研究发现，冲击能量会转化为金属泡沫的动能与内能，且二者随冲击进程发生动态变化。该变化可通过塑性冲击波予以阐释：冲击过程中会产生塑性冲击波并使其向外传播。本研究提出理论模型，用以探讨并预测金属泡沫的动能，以及其动态与准静态吸能行为间的差异。研究了惯性与基体材料应变率对塑性冲击波的影响，并揭示了这两类因素对动态吸能特性的作用机制。结果表明，基体材料的应变率效应会抑制塑性冲击波的形成，使得体系动能更低，但内能更高。