支撑板的冲压模具设计与制造工艺研究-双孔托架落料冲孔复合模、弯曲模含NX三维及20张CAD图
收藏
资源目录
压缩包内文档预览：
编号：89884397
类型：共享资源
大小：33.54MB
格式：ZIP
上传时间：2020-07-20
上传人：QQ14****9609
认证信息
个人认证
郭**（实名认证）
陕西
IP属地：陕西
50
积分
- 关 键 词：
-
支撑
冲压
模具设计
制造
工艺
研究
托架
冲孔
复合
弯曲
NX
三维
20
CAD
- 资源描述：
-
支撑板的冲压模具设计与制造工艺研究-双孔托架落料冲孔复合模、弯曲模含NX三维及20张CAD图,支撑,冲压,模具设计,制造,工艺,研究,托架,冲孔,复合,弯曲,NX,三维,20,CAD
- 内容简介：
-
The Mechanism of Surface Low Defect in Sheet Metal Stamping Hongqing Shen1,2 a, Shuhui Li1,2 b and Guanlong Chen1,c 1Auto Body Manufacturing Technology Center, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China 2State Key Laboratory of Mechanical System and Vibration, Shanghai 200240, PR China ashenhongqing82, blishuhui, cglchen Keywords: surface low; surface deflection; stamping; sheet metal forming; local buckling. Abstract. In this paper, the mechanism of surface low defect in sheet metal stamping is studied. Firstly, we simulate the forming procedure of a stamping component by Finite Element Method (FEM) to observe the growth of surface low defect. And then, we establish an analytical model and deduce the critical stress for local buckling. Finally, we take advantage of the critical stress to detect local buckling areas in the component. The FE simulation result shows that during springback the non-uniform displacement in the thickness direction forms surface low. Moreover, the detected local buckling area agrees with the experimental surface low area. This indicates that the essence of surface low phenomenon is panels local buckling under the residual compressive stress during springback. Introduction Surface low defects are small local deflections in large flat panels containing sudden shape changes. They have a great influence on automobiles appearance. These defects are strictly detected and controlled in body manufacturing. Liu et al. 1 proposed an optical reflection method to evaluate the surface low defect in pressed automobile panels. Andersson 2 used an optical system, called WMS-system, to detect surface low in a sample stamping panel. In addition he also used stylus measurement in his experiment. Fu et al. 3 used stoning method to detect surface low defects around the corner of an embossment. With the development of finite element method, it becomes possible to predict surface low by numerical analysis. Fukumura et al. 4 simulated surface low defects in an automobile door exterior panel. Park et al. 5 developed a curvature-based algorithm to visualize the surface low defects in simulation. Hu et al. 6 developed a stoning algorithm to visualize the surface low defects in simulation. Andersson 2 adopted a curvature-based visualization algorithm to verify the consistence between experiment result and simulation prediction. Nowadays the mechanism of the surface low defect is of great concern. Based on experiment results, Yang Y.Y. et al. 7 pointed out that the residual compression stress was the mechanics condition of the surface deflection initiation. In Numisheet 2008, Wang Huiping et al. 8 made a study on a surface distortion predictor for sheet metals. They believed that the mechanism of surface distortion was panels local buckling. In this paper, the mechanism of surface low defects in sheet metal forming is further studied. FE Simulation In this study, the experiment by Fu et al. 3 is simulated. In Fig. 1 is the section view of the experimental die setup. The radius of the die bottom surface is 170 mm and the draw depth is 40 mm. The embossment at the die bottom is 150150 10 mm3. A sample panel is shown in Fig. 2. The experimental blank is circular. Its radius is 500 mm. Low carbon steel for the automobile exterior panel is adopted. Detailed characteristics of the material are listed in Table 1. Advanced Materials Research Vols. 538-541 (2012) pp 377-381Online available since 2012/Jun/14 at (2012) Trans Tech Publications, Switzerlanddoi:10.4028/AMR.538-541.377All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,. (ID: 7, National Cheng Kung University, Tainan, Taiwan-10/01/14,12:02:33) Fig.1 Section view of the experimental die setup. Fig. 2 A sample panel in the experiment. Table 1 Characteristics of the experiment material Thickness mm Youngs Module GPa Poissons ratio Yield strength MPa Ultimate tensile strength MPa Total elongation, L Normal anisotropy, r Strain hardening exponent, n 0.7 207 0.333 157 520 0.4 1.75 0.23 Since the sample is symmetric, we establish only one quarter of the sample and define symmetric boundary conditions on the symmetry axes. In Fig. 3 is the FE model. The FE model simulates the drawing and springback of the panel. The drawing procedure is simulated with ABAQUS Explicit and the springback is simulated with ABAQUS Standard. For simplicity, the material is assumed isotropic. The linear, finite-membrane-strain, reduced-integration, quadrilateral shell element (S4R) is adopted. This element has been proved robust and suitable in sheet metal forming. Meshes around the embossment are carefully refined to describe the small deflection. The minimum elements are about 11 mm2 Fig. 3 FE model of the stamping test. Fig.4 The analytical model. Analytical Model The surface low problem is simplified as a rectangular plate under plane stress condition, shown in Fig. 4. The length of the plate is a, the wide of the plate is b and its thickness is t. The plate is compressed by a uniformly distributed stress,x, in the x direction and tensioned by a uniformly distributed stress, y, in the y direction. The boundary conditions of the plate model are assumed to be simply supported at the four sides. The depth of surface defect is close to the thickness of the sheet, so the deformation of the middle surface is considered. The balance differential equation is 34442222422422(2)212(1)xyxyEtNNNxxyyxyx y+=+ (1) where is the deflection, Nx, Ny and Nxy are membrane stress resultants. In this model, Nx, Ny are assumed uniformly distributed along thickness direction and Nxy equals to zero. So Nx, Ny and Nxy can be expressed as 378Materials Processing Technology II0xxyyxyNtNtN= = (2) According to the boundary condition of the model, the deflection surface of the buckled plate can be represented as 11sinsinmnmnm xnyAab= (3) where mnA represents the amplitude of deflection. Combining equations (1), (2), (3), we can obtain 22222111sinsin0mnxymnmnmnm xn yAttabDabab=+= (4) where D is the bending stiffness, 3212(1)EtD=. When mnA = 0, the equation has a unique solution, 0. This indicates that the plate keeps flat. When mnA 0 and 2222210xymnmnttabDab+= (5) the solution of the equation is not unique. This means the plate buckles. From Eq. (5) we can deduce the buckling compressive stress, 22222222222112(1)BuckleyEtnanaavmbmb=+ . (6) Each pair of n and m represents a buckling mode of the model. The critical compressive stress is the minimum value of all the buckling stresses for all the buckling modes. Since 22200ynamb , (7) we can deduce from Eq. (6) that 22222222222112(1)BuckleyEtnanaavmbmb=+ 22222222112(1)Etnaavmb+ 2222.12(1)Etav (8) So the critical compressive stress can be expressed as: 222212(1)crEtav= (9) Results and Discussion In order to observe the growth of the surface low defect, we measure the displacement in the Z direction (drawing direction) at two representative points. The location of the two measure points are shown in Fig. 5. Point A is around the corner of the embossment, where surface low occurs according Advanced Materials Research Vols. 538-541379to the experimental work by Fu et al. 3. Point B is near Point A, but surface low does not occur at this point. The difference of the displacement in the Z direction, Z=ZA-ZB, represents the surface deflection of the local area. Fig. 5 The selected measure points. Fig. 6 The history of surface deflection In Fig. 6 is the history of surface deflection during the entire forming process. During the drawing procedure, the surface deflection fluctuates about the zero value within 0.1mm. At the end of drawing, the surface deflection is only 0.01 mm. During springback, the absolute value of surface deflection increases dramatically. At the end of springback, the absolute value of surface deflection increases from 0.01 to 0.1 mm (negative value means concave and positive value means convex), 10 times the original value. This indicates that the panel trembles during drawing, but surface low does not grow in this stage. It is during springback that the non-uniform displacement in thickness direction forms surface low. local buckling surface low (stoning) Fig. 7 Minor stress distribution. Fig. 8 The surface low areas and the local buckling areas. In Fig. 7 is the minor stress distribution around the embossment corner. Different from other areas, the minor stress in the surface low area is negative. This indicates that the surface low area is under a plane stress status of compression and tension. According to the analytical model in Fig. 4, buckling may happen if the local compressive stress is larger than the critical value. Table 2 Calculation of the critical stress Sub-domain Compressive stress x (MPa) The compressive length, a (mm) The critical stress, cr (MPa) Buckle or not 1 234 12 645 No 2 210 15 412 No 3 190 18 286 No 4 170 22 191 No 5 150 26 137 Yes 6 100 27 127 No 7 50 34 80 No 380Materials Processing Technology IIAccording to the stress distribution in Fig. 7 and Eq. (9), we can calculate the critical stress for the sub-domains divided by the compressive stress level (shown in Table 2). According the results, buckling occurs in the sub-domain 5 whose boundary compressive stress is 150 MPa. Fig. 8 shows the predicted local buckling area and compares it with the experiment results by Fu et al. 3. It is obvious that the local buckling area agrees with the detected surface low area. This indicates that the essence of surface low phenomenon is panels local buckling under the compressive residual stress during springback. Conclusion Our work in this paper focuses on the mechanism of surface low defect in sheet metal stamping. Based on the finite element simulation results, theoretical analysis and the referred experiment result, the following conclusions apply: ? The stamping panel trembles during drawing, but surface low does not grow in this stage. It is during springback that the non-uniform displacement in thickness direction forms surface low. ? The panel local buckling under the compressive residual stress during springback is one of the major reasons for surface low in sheet metal stamping. Acknowledgements The authors acknowledge the support from Research Project of State Key Laboratory of Mechanical System and Vibration MSVMS201101, Doctoral Fund of Ministry of Education of China 20100073110034 and Shu Guang project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation 10SG13. References 1 Liu L., Sawada T., Sakamoto M.: Journal of Materials Processing Technology 103, 280-287. 2 Andersson A.: Journal of Materials Processing Technol
- 温馨提示:
1: 本站所有资源如无特殊说明，都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等，如果需要附件，请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸，网页内容里面会有图纸预览，若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供信息存储空间，仅对用户上传内容的表现方式做保护处理，对用户上传分享的文档内容本身不做任何修改或编辑，并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容，请与我们联系，我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
人人文库网所有资源均是用户自行上传分享，仅供网友学习交流，未经上传用户书面授权，请勿作他用。
川公网安备: 51019002004831号