Theoretical and Experimental Vertification for Onset and Extrnsion of Surface Deflections of Sheet Metal in Press Forming

板料冲压成形表面变形发生与扩展的理论与实验验证

基本信息

批准号：
07650086
负责人：
SAWADA Takao
金额：
$ 1.41万
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：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

In this report two results are obtained. First, the experimental method is developed to detect the quantity of surface deflections and its location on the sheet metal. That is, the grating of the parallel straight line are projected on the product of sheet metal after press forming and the reflected image of the grating is taken by an image-sensing camera, from the data of which the quantity and the location of surface deflections are measured by using the successive approximation method. The location of the surface deflection can be connected with the numerical result of the finite element method, which will advance the research more and more. In addition this method is more sensitive to the surface deflections than the needle type contour measuring apparatus because it measures the inclination of the sheet metal surface.Surface deflection is said to be caused by the buckling phenomenon, where the method to detect the surface deflection is developed. The bifurcation point of sheet metal under compression is numerically analyzed. While the sheet metal with imperfection under compression is analyzed, it is shown that the shear stress grows at the instance when the surface deflection becomes large violently. This suggests that the onset of the buckling can be found by the observation of the shear stress. Therefore, the beginning point of the surface deflection of sheet metal under press forming can be easily found instead of using an eigenvalue analysis. Experimentally, the situations of the surface deflection on the flange of sheet metal under embossing are observed.

在本报告中，获得了两个结果。首先，开发了实验方法来检测表面偏转的量及其在钣金上的位置。也就是说，平行直线的光栅在按压后投影在钣金的乘积上，并通过图像感应摄像机拍摄光栅的反射图像，从图中的数据和表面偏转的位置的数据通过使用连续的近似方法来测量。表面挠度的位置可以与有限元方法的数值结果相连，这将越来越多地推进研究。此外，此方法对表面偏转的敏感比测量件金属表面的倾斜度比针状轮廓测量设备更敏感。据说表面偏转是由屈曲现象引起的，其中检测表面挠度的方法为发达。在压缩下，钣金的分叉点进行了数值分析。虽然分析了压缩不完美的钣金，但显示出表面挠度剧烈猛烈地变大的情况下，剪切应力会增长。这表明可以通过观察剪切应力来发现屈曲的开始。因此，可以很容易地找到板金属表面偏转的开始点，而不是使用特征值分析。在实验上，观察到表面偏转在压花下钣金法兰上的情况。