结构特征参数和应变速率对泡沫铝压缩力学性能的影响

摘要

A series of uniaxial compression experiments of open-and close-cell aluminum foams were conducted by using a MTS hydraulic pressure machine and a split Hopkinson pressure bar (SHPB) at different strain rates. Results show that the quasi-static compressive behaviors of aluminum foams depend on the aspect ratio of the sample. With the decrease in the aspect ratio of the sample, the plastic yield stress becomes higher and the plastic yield plateau becomes smaller in length, which is attributed to the influence of the friction force between the end face of sample and the loading plateau. The density of aluminum foams has a significant influence on the quasi-static compressive behavior and results in the appearance of the smooth plastic plateau phase. With the increase in the density, the deformation mechanism is changed from the localized plastic collapse to the whole plastic yield. The plateau stress of aluminum foams shows an apparent strain rate dependence.%采用MTS万能材料试验机和分离式霍普金森压杆(SHPB)对具有不同结构特征参数的泡沫铝进行准静态和动态单轴压缩试验,分析了试样高径比、初始密度以及应变速率对其力学行为的影响.实验结果表明:在准静态压缩试验中,高径比越小,塑性屈服应力越高,塑性屈服平台长度越短,归因于端面摩擦效应;初始密度微小的变化都会对泡沫铝的力学性能有较大的影响,同时密度的大小还直接影响泡沫铝是否具有平坦的塑性屈服平台段,其原因是随着密度增大,泡沫铝的塑性变形机理从逐层坍塌变形转为整体塑性屈服变形;无论是开孔还是闭孔结构,泡沫铝的力学行为都表现出了明显的应变率效应,屈服强度与应变速率的对数呈双直线关系.