冲击压缩下纯铝中微孔洞塌陷的数值模拟

Numerical Simulation of Micro Void Collapse in the Pure Aluminum under the Shock Compression

由于实验中无法观察材料的孔洞在受冲击加载时的变形过程,本文对纯铝中孔洞的变形过程进行了数值模拟.采用了3种材料模型:双线性模型、塑性随动模型和应变率相关塑性模型,分别模拟了它们在冲击压缩下内部微孔洞的塌陷,并对结果作了详细的比较.结果表明:基体材料模型为双线性模型时,孔洞在冲击压缩下会出现射流现象,应变率的变化和材料的硬化方式不影响孔洞的变形;模型为应变率相关塑性模型时,孔洞在冲击压缩下不会出现射流现象,孔洞的变形与当前应变率和应变率历史相关;模型为塑性随动模型时,孔洞在压缩到某一时刻体积不会进一步缩小,孔洞周围单元会因失效而被删除,孔洞反而有变大的趋势,并且用这种模型模拟孔洞变形时,硬化系数会对孔洞变形有影响.通过对使用3种模型计算结果的比较,可以确定影响孔洞变形的主要因素.

Because the deformation process of voids inside the material can not be observed in dynamic shock experiments, the micro void deformation in pure aluminum is simulated under the shock compression by supposing three matrix material models, including the bilinear model, the plasticity kinematic model and the strain rate-dependent plasticity model. The contracting results indicate that： If the matrix material is the bilinear model, the fluidic phenomenon will be displayed in the compressing void, and the change of strain rate and the hardening style of the material will not affect the deformation of the void. If the matrix material is rate-dependent plasticity model, the fluidic phenomenon will not appear in the compressing voids, and the deformation of the voids is dependent on the present strain rate and the strain rate history. If the matrix material is plasticity kinematic model, the void volume will not decrease any more when it reaches a critical size. As the units around the void will be deleted due to its failure, the void will be bigger instead. The void deformation will also be affected by the hardening coefficient in this situation. By comparing the three computing results with different material models, the main factor of void deformation will be determined.