High speed compression behaviour of metallic cellular materials under impact loading
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摘要: 基于微CT扫描影像信息，建立泡沫金属材料二维细观有限元模型，考虑不规则胞孔的不均匀分布，根据实验结果拟合孔壁材料的弹塑性本构参数。研究了泡沫金属在不同加载速度下的压缩变形机理，重点讨论泡沫金属中弹塑性波的传播、惯性效应和从冲击端传递到静止端的应力变化特征。对于相对密度为0.3的泡沫铝，弹性波速约为5 km/s，与孔壁材料的弹性波速相当，塑性波速表现为随着加载速度的增大而增大。在加载速度为50~100 m/s间变形模式从准静态模式转变为动态模式，未发现明显的临界速度，动态锁死应变随着加载速度的增大而增大。由于塑性波发生反射，试件会发生二次压缩过程，相应地，静止端产生二次应力平台。受惯性作用的影响，二次应力平台也随着加载速度的增大而提高。Abstract: A two-dimensional finite element model was created from a tomographic image of the aluminum foams, which represents the cell shape and geometric distribution of real foams.To determine the mechanical properties of cell wall material, the uniaxial stress versus strain curve, predicted numerically for aluminum foam, was fitted to that measured experimentally.We mainly discuss the shock wave propagation, the inertial effect and the strength of the stress on the stationary end of metallic cellular materials under high speed compression.As for aluminum foams with relative density 0.3, the elastic wave speed is calculated to be 5 km/s, whilst the plastic wave speed increases from 83 to 294 m/s, with the compression velocity increasing from 50 to 200 m/s.Within the compression velocity range of 50-100 m/s, the deformation modes change from random mode to progressive mode.However, no distinct critical velocity are observed.The dynamic locking strain increases with the increasing compression velocity.Second compression process occurs in metallic cellular materials when the plastic wave reflects on the stationary end.Accordingly, the second stress plateau appears on the stationary end, which increases with the increasing compression velocity due to inertia effect.
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图 1 泡沫金属材料二维细观有限元模型
Figure 1. Two-dimensional mesoscale finite element models of metallic cellular materials
图 2 泡沫金属单轴压缩的名义应力应变曲线
Figure 2. Numerically predicted and experimentally measured uniaxial compressive stress versus strain curves for closed-cell aluminum foams
图 3 泡沫金属在不同速度压缩下的变形图
Figure 3. Simulated deformation modes of aluminum foam (relative density of 0.3)under different impact velocities
图 4 泡沫金属动态压缩的名义应力应变曲线
Figure 4. Numerically predicted uniaxial compressive stress versus strain curves for aluminum foams
图 5 冲击波传播示意图
Figure 5. Schematic diagram of shock wave propagation in metallic cellular materials
表 1 泡沫金属高速冲击加载计算结果
Table 1. Summary of FE predictions for aluminum foam (relative density of 0.3) under impact loading
vi/(m·s-1) vp/(m·s-1) εlock ρlock/(kg·m-3) σy(εlock)/MPa 50 83 0.60 2 025 34.5 100 167 0.60 2 025 34.5 150 234 0.64 2 314 40.1 200 294 0.68 2 700 52.7 
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