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Evaluation for Nonlocal Damaged State in terms of Voronoi Porygon

用 Voronoi Porygon 评估非局部损坏状态

基本信息

批准号：
09650103
负责人：
NAGAKI Shigeru
金额：
$ 2.18万
依托单位：
Tokyo University of Agriculture & Technology (1999)Okayama University (1997-1998)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

For ductile fracture of materials, the influence of damage due to voids on the mechanical property of materials is very important, and it is necessary to clarify the relation between quantitative evaluation of damage and void growth.In this project, we propose a new method to evaluate the local damage state due to voids using the voronoi tessellation and the stereology. Perforated sheets were set up as the plane models of damaged materials and were examined under the condition of uniaxial tension, where the deformation of circular holes is measured. The experimental results show that the distance and the direction between adjacent holes are well described in this method. The deformation of circular holes becomes larger in severely damaged domain. The part where fracture of models starts is evaluated as severely damaged part. It is shown that the fracture of perforated sheets and local plastic deformation is well corresponding to the part with large damage estimated by means of the voronoi tessellation and the stereology.Elastic - Plastic deformation of perforated sheet, where circular holes are distributed regularly, were also analyzed numerically under the plane stress condition by means of finite element method introducing the periodic boundary conditions. It is shown that the deformation behavior depends highly on the distribution of holes and the arrangement of holes results in the anisotropy of yield stresses of perforated sheets, which is related to the stress concentration near the holes. It is also shown that the highly deformed regions in perforated sheets corresponds with the voronoi porygon where the value of local damage tensor componets are especially large.

对于材料的韧性断裂，孔洞损伤对材料力学性能的影响是非常重要的，有必要阐明损伤的定量评估与孔洞生长之间的关系，在本项目中，我们提出了一种新的方法来评估局部损伤状态的孔洞voronoi镶嵌和体视学。建立了损伤材料的平面模型--开孔板，并在单向拉伸条件下进行了试验，测量了圆孔的变形。实验结果表明，该方法能很好地描述相邻孔之间的距离和方向。在损伤严重的区域，圆孔的变形变大。将模型开始断裂的部分评价为严重损坏部分。结果表明，用Voronoi网格和体视学方法估计的大损伤部位与开孔板的断裂和局部塑性变形有很好的对应关系，并采用有限元法引入周期性边界条件，对平面应力条件下开孔板的弹塑性变形进行了数值分析。结果表明，开孔板的变形行为与开孔的分布密切相关，开孔的排列方式导致开孔板屈服应力的各向异性，这与开孔附近的应力集中有关。研究还表明，穿孔板中的高度变形区域对应于局部损伤张量分量值特别大的voronoi porygon。