动态断裂过程的数值分析及LY-12铝的层裂

 本文从文献1]中用于分析柱壳动态膨胀断裂过程的损伤度函数出发，将它推广到对一维应变下层裂过程的数值模拟研究。试件材料为LY-12铝，其特性方程取为含粘性的本构方程形式。数值计算结果很好地再现了实测自由面速度u_fs随时间t的变化过程，并表现出层裂强度σ_c及层裂面上的临界损伤度α_c都分别是应变率ε_c'的单调递增函数关系。σ_c~ε_c'的这种变化规律在许多文献中已屡见报道，例如可见文献2-3]。在10⁵ s^-1~10⁶ s^-1应变率范围内，σ_c~ε_c'关系可以表示为ε_c'exp(-11.4α_c)=2 100 s^-1，这个式子可以作为一种层裂判据使用。数值计算还给出了层裂片的损伤度剖面，其形状特征与Barbee等对回收试件的细观测量结果在定性上一致。

NUMERICAL ANALYSIS FOR DYNAMIC DAMAGE PROCESSES AND LY-12 ALUMINUM SPALLATIONS

In Ref1], a damage-level function is proposed for analyzing the dynamic fracture processes of expanding cylindrical shell. In this paper, we extend the model to the case of planar geometry and perform numerical simulation. for the dynamic damage processes under uniaxial strain case.The studied material is LY-12 aluminum and a kind of constitutive equation with viscous effect is utilized. The calculated free-surface velocity versue time relation is consistent with the experimental results. The calculated results also indicate that the spall strength ac and the critical damage-level at fracture plane, ac, are both monotone increase function of strain rate ec, respectively. This kind of ac ~ec relation has been reported in many other articles, for example in Ref2,3].The relation ac-ec can be expressed as ecexp -11.4ac] =2100s-1 in the strain-rate range from 105s-1 to 106s-1.We think this expression could be used as a.kind of spall criterion.The damage-level profiles in the spalled layer are also given from the numerical results, and the specific feature of the profiles are qualitatively in accord with that of the microphotographic results from recovery specimens reporded by Barbee, et al.