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Construction and Application of Wrinkling Limit Diagram (WLD)

起皱极限图（WLD）的构建及应用

基本信息

批准号：
05555034
负责人：
TOMITA Yoshihiro
金额：
$ 3.58万
依托单位：
Kobe University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05555034/
关键词：
Sheet Metal Forming Wrinkle Formation Forming Limit Wrinkling Limit Diagram (WLD)Plastic Instability Bifurcation Computational Simulation Anisotropy

项目摘要

This research aims at to provide a computational tool for predicting the onset of wrinkles during the general forming processes used on thin-walled bodies. It is assumed that the bodies are thin enough to deform along a completely lubricated tool surface to satisfy the membrane stress condition until wrinkling. A corner type constitutive equation with a general anisotropic quadratic yield function for a thin-walled bodies is developed. The onset of wrinkles is assumed to be a bifurcation from the membrane type of deformation to the bending type of deformation. Hill's general theory of bifurcation and uniqueness is employed in conjunction with Donnell-Mushtari-Vlasov's thin shell theory and Naghdi's linear thin shell theory to formulate the problem.An analytical solutions have been presented to the condition of the onset of wrinkling for the curved sheets with different thickness under the variety of stress conditions. The results are summarized as the wrinkling limit diagram (WLD) which present the combinations of the critical principal stresses for the assumed mode of wrinkles. This can be used to predict the onset of wrinkling during the sheet metal forming processes as is done for the prediction of the forming limit of sheet metals with Forming Limit Diagram (FLD) by using the local stresses estimated by the computational simulations.For the complicated problems, direct numerical searching strategies of the critical stress conditions for the onset of wrinkling have been employed. This can be also introduced to the computational simulation of shin sheet metal forming processes. Furthermore, to clarify the growth rate of wrinkles three dimensional analysis with isoparametric shell element and the same constitutive equation has been done. Parametric studies have been performed to investigate the effect of material characteristics, boundary condition and shape of the sheet metal on the wrinkling processes.

这项研究旨在提供一种计算工具，用于预测薄壁体通用成型过程中皱纹的出现。假设物体足够薄，可以沿着完全润滑的工具表面变形，以满足膜应力条件，直到起皱。建立了薄壁体具有一般各向异性二次屈服函数的角型本构方程。假设皱纹的出现是从膜型变形到弯曲型变形的分叉。采用Hill的分岔和唯一性一般理论，结合Donnell-Mushtari-Vlasov的薄壳理论和Naghdi的线性薄壳理论来阐述该问题。针对不同厚度的弯曲板材在不同应力条件下起皱的发生条件给出了解析解。结果总结为起皱极限图 (WLD)，它呈现了假设的起皱模式的临界主应力的组合。这可以用来预测金属板材成形过程中起皱的发生，就像使用成形极限图（FLD）通过计算模拟估计的局部应力来预测金属板材的成形极限一样。对于复杂的问题，采用了起皱发生的临界应力条件的直接数值搜索策略。这也可以引入到薄板金属成形过程的计算模拟中。此外，为了阐明皱纹的增长率，进行了等参壳单元和相同本构方程的三维分析。已进行参数研究来研究材料特性、边界条件和金属板材形状对起皱过程的影响。