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Evaluation for Nonlocal Damaged State in terms of Tesellation Analysis and an Anisotropic Yield Function

根据曲面细分分析和各向异性屈服函数评估非局部损坏状态

基本信息

批准号：
12650073
负责人：
NAGAKI Shigeru
金额：
$ 2.18万
依托单位：
Tokyo University of Agriculture and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12650073/
关键词：
Damage Mechanic Damage Tensor Voronoi Polygon Yield Function Plastic Anisotropy Non locality 降伏関数

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 equivalent net stress. The equivalent net stress can be calculated from the applied stress and the damage tensor which is obtained form voronoi tessellation and the stereological method.Perforated sheets were set up as the plane models of damaged materials and were examined under the biaxial tensile condition in bulge testing machine, where the deformation of circular holes is measured. 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 domain where the value of equivalent net stress is large. It is also 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.As the three dimensional ideal model for real materials with damage, tensile specimens with the irregular distribution of holes are made by rapid prototyping method. Tensile test was carried out and the fracture state and the deformation of each hole are compared to the damage tensor distribution. It is found that the highly deformed region in the specimen corresponds to the part where the values of local damage tensor component 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，有必要阐明孔洞损伤定量评价与孔洞生长之间的关系。在这个项目中，我们提出了一种新的方法来评估局部损伤状态，由于空洞使用等效净应力。利用Voronoi网格法和体视学方法得到的损伤张量和外加应力计算等效净应力，建立了多孔板的平面损伤模型，在胀形试验机上进行了双向拉伸试验，测量了圆孔的变形。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，穿孔板的断裂和局部塑性变形与等效净应力值较大的区域有很好的对应关系。作为真实的含损伤材料的三维理想模型，本文采用快速成形技术制备了不规则分布孔洞的拉伸试件。进行了拉伸试验，并将断裂状态和各孔的变形与损伤张量分布进行了比较。结果表明，试件中的高变形区域对应于局部损伤张量分量值特别大的部位。