A criterion for void coalescence in anisotropic ductile materials
A criterion for void coalescence in anisotropic ductile materials
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DOI：
10.1016/j.ijplas.2016.03.003
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发表时间：
2016-07
影响因子：
9.8
通讯作者：
S. M. Keralavarma;S. Chockalingam
中科院分区：
文献类型：
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作者：
S. M. Keralavarma;S. Chockalingam
塑性各向异性的形式纹理发展和孔隙形状演变可以显着影响损伤增长率和总应变破坏韧性材料。一个标准的开始聚结，这是过渡的扩散塑性变形的局部塑性连接相邻的空隙的韧带中的空隙增长，是一个关键组成部分的任何预测模型的韧性断裂。在本文中，一个新的细观力学为基础的标准，结合上述两种形式的各向异性，开发使用均匀化和极限分析的一个空心圆柱形的代表性体积元的正交各向异性材料的希尔型。两种可能的合并模式，对应于颈缩不稳定性和剪切应变局部化的横向空隙间韧带，占在分析中。的最终形式的合并标准有一个有趣的对称性与Gurson型多孔材料的屈服准则，并示出为是一个改进现有的模型的特殊情况下的各向同性矩阵的行为。为了验证的分析模型，准精确的数值合并轨迹计算使用有限元为基础的极限分析方法的特殊情况下的横观各向同性材料。分析模型被证明是在良好的协议与数值数据，除了高度扁圆形接近硬币形裂纹的空隙形状。提出了一种启发式修改模型，这显着提高了模型的预测在该限制。
Plastic anisotropy in the form of texture development and void shape evolution can significantly affect damage growth rates and overall strain to failure in ductile materials. A criterion for the onset of coalescence, which is the transition from void growth by diffuse plastic deformation to localized plasticity in the ligament connecting neighboring voids, is a critical component of any predictive model for ductile fracture. In this paper, a new micromechanics-based criterion for void coalescence, combining both forms of anisotropy above, is developed using homogenization and limit analysis of a hollow cylindrical representative volume element made of an orthotropic material of the Hill type. Two possible modes of coalescence, corresponding to necking instability and shear strain localization in the transverse inter-void ligament, are accounted for in the analysis. The final form of the coalescence criterion has an interesting symmetry with Gurson-type yield criteria for porous materials and is shown to be an improvement over existing models for the special case of isotropic matrix behavior. For validation of the analytical model, quasi-exact numerical coalescence loci are computed using a finite elements based limit analysis method for the special case of transversely isotropic materials. The analytical model is shown to be in good agreement with the numerical data, except for highly oblate void shapes approaching penny shape cracks. A heuristic modification for the model is proposed, which significantly improves the model predictions in that limit.