中文摘要：

基于闭孔泡沫铝的显微CT扫描信息,考虑胞孔的不规则形貌及胞孔分布的不均匀性,以及胞孔尺寸和壁厚沿泡沫高度的梯度分布,建立了梯度泡沫金属材料的二维细观有限元模型,分析了梯度泡沫金属材料在动态压缩过程中的变形、塑性波的传播和能量变化特征。对于平均相对密度0.3、平均梯度系数0.4的梯度泡沫铝,低速（10 m/s）加载时,梯度泡沫金属在变形的整个过程中吸收的总能量均低于均匀泡沫金属;高速加载时,梯度泡沫金属沿负梯度方向压缩的早期吸能比均匀泡沫金属有优势,而且速度越高,优势越明显。

英文摘要：

Based on tomographic images of closed-cell aluminum foams, a two-dimensional mesoscopic finite element （FE） model is created for idealized density-graded aluminum foams, with cell shape and geometric distribution accounted for. Numerical simulations are carried out to investigate the compressive deformation mechanisms, shock wave propagation and energy absorption capacity of the model density-graded foam under impact loading, with its average relative density and gradient coefficient fixed at 0.3 and 0.4, respectively. At relatively low impact velocity （10m/s）, the density-graded foam absorbs smaller total energy than its homogeneous counterpart. At sufficiently high impact velocities, however, the density-graded foam compressed along the negative gradient direction exhibits superior energy-absorbing performance. Such superiority is strengthened with increasing impact velocity.