缺陷形状对金属板极限应变影响研究。.PDF

1991年11月 Vo1．1 4．N9．6 第1 4卷第6期 重 庆 大 学 学 报 JOURNAL OF CHONGQING UNIVERSITY NOV．199l 缺陷形状对金属板极限应变影响的研究。 A RESEARCH oN THE EFFECT oF A DEFECT SHAPE oN LIMIT STRAIN FoR SHEET METALS 汪凌云 W ang Linyun (重庆大学冶金及材料工程系) 摘 要 在研究板料的极限应变时，提出了一种新的初始几何缺陷模型——椭圆缺陷 模型。用大变形弹塑性有限元法，按大变形t， 塑性流动理论，大变开t，z塑性变形理论分析了 具有不同长短半轴椭圆缺陷模型，标准的 一 缺陷、模型，圆形缺陷模型对双向受拉金属 板极限应变的影响，分析结果表明 椭圆缺陷对双向受拉金属板极限应变的影响与椭圆的长 短半轴比及椭圆区板厚有关。根据圆形缺陷模型算出的极限应变值是上限，根据标准的 — 缺陷模型算出的极限应变值是下限。圆形缺陷模型和标准的 一 缺陷模型是椭圆缺 陷模型的特殊情况。分析还表明，大变形t， 塑性流动理论对缺陷比大变形t， 塑性变形理论 更敏感。分析时，假定双向受拉 金垦 处于平面应力状态，在弹性、塑性状态下都是体积不可 压缩的。 关键词 椭圆缺陷模型；极限应变；大变形 中国图书资料分类法分类号 TG301 · ABSTRACT A new initial geometric defect m0del—— elliptic defect model for research on the limit strain of sheet metals is first presented．The effects of the elliptic defect models of various ratioes of major axis to minor axis。the standard M—K defect model and the circular defect models on the limit strains for a biaxially-stretched sheet are studied with large—Strain FEM，large strain ver= sions of J2 flow theory and J2 deformation theory of plasticity．The results show that the effects of the elliptic defect on th_e limit strain for biaxially—stretched sheet metals are related to the ratio of major axis to minor axis of ellipse and the sheet thickness in elliptic region．The results also indicate that the circular defect mod el gives an upper bound to limit strain。while the standard M— K defect mod el gives a lower bound to limit strain。and that the circular defect mod el and the M— K defect model are special P．．ases of the elliptical defect models．The study proves that the J2 flow theory of large strain plasticity is more sen