The method of depressing the hole deformation caused by residual tensile stress in sheet metal.

• Main Authors: Chung-Yi Dai, 戴仲義
• Other Authors: Sy-Wei Lo
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/80985164745919736502

碩士 === 國立雲林科技大學 === 機械工程系碩士班 === 100 === Punching holes on the drawer slides, which are pre-produced by stamping or rolling, will induce outward expansion of the entire frame and make the ball groove dimension fail to fulfill the accuracy requirement when the slides are assembled. In view of this, the outward expansion of the slide frame must be controlled within 0.04mm. This is set as the research objective of the thesis and a finite element software package is used to calculate the dimensions, stress, and deformation of the workpiece before and after punching the holes. The concept of adding reinforcement ribs is adopted and two ribs are placed along the hole to conceal the release of the residual tensile stress. At first the Taguchi method is employed to identify the appropriate size and position of the ribs for circular as well as rectangular holes with various aspect ratios on a metal plate. The results are then applied to the drawer slide to stamp ribs around the hole on a plane surface. For large holes which do not have a sufficient space to print the coplanar ribs, an alternative choice of stamping the rib on the adjacent inclined plane is studied to check their constraints on the hole and frame expansions. The results show that the releasing of the internal stress around the punched hole can bring up the hole deformation and frame expansion. Using ribs of appropriate size and location can hold the tensile stress and reduce the warp. In the implement to the practical product, it is found that the plastic strains from rib stamping will make the slide frame shrunk and the follow-up punching can release the residual tensile stress to expand the frame. The two opposite effects almost cancel each other out so that the final form error can be controlled under 0.04mm. In the case of large hole where the reinforcing ribs must be stamped on the inclined surface can also accomplish the accuracy requirements.