The density uniformity and the corresponding size effect were analyzed for two different foam aluminum materials. Analyzed results show that the more non-uniform the density distribution of the foam aluminum, the more significant the size effect. But if the density distribution interval is smaller and in line with normal distribution, the size effect is weaker. Based on the assumption of the stress uniformity in the split Hopkinson pressure bar tests, the quartz pieces were used to measure the time required by the stress uniformity process at the two ends of the specimens. It is found that the larger the axial size of the foam specimen, the more evident the influence of the inertial effect. And the right axial sizes were chosen to decouple the inertial effect of the specimen (wave effect) from the strain rate effect. The experimental results display that the foam materials have obvious strain rate effects.%通过材料密度均匀性分析得知,泡沫材料密度分布的均匀性越差,尺寸的影响越明显,对于密度分布区间小、并符合正态分布的试件,尺寸的影响较小.根据Hopkinson杆动态测试的应力均匀性假定,利用石英片监测试件左右端面达到应力均匀所需的时间,试件轴向尺寸越大,惯性效应的影响也越大.选择合适的尺寸,将试件的惯性效应(波动效应)与应变率效应解耦,结果表明,泡沫材料具有一定的应变率效应.
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