An Analysis of Hydroforming Process

• Main Authors: Shian-Jiann Hsieh, 謝先建
• Other Authors: Tze-Chi Hsu
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/92608002192860009332

碩士 === 元智大學 === 機械工程研究所 === 81 === The permissibl operating pressure path of a controlled pressurized fluid in the hydroforming process was investigated. The favorable pressure path subteded between rupture loci and wrinkling loci is affected by both geomatrical and material paramaters. The analysis is based on limite theorems of plasticity with a power law hardening material and Tresca criterion. The parametric study include a wide range of physical variables such as friction coefficient and anisotropic parameters as well as operating condition such as blank holding force. Some of the parameters have a significant influence on the two failure loci. Experiment of axisymmetric drawing operation with a hemisperical punch were conducted by using a hydroforming press. Experimental variable which include mechanical property and geometry of the blank were measured before the deformation. Several different fluids ranging from high viscosity to law viscosity were used to provide different friction condictions at the interface of the blank and the fluid. The holding force of the blank was applied at the surrounding as a independent variable .Various paths of imposed fluid pressure were then tested in actual deep-drawing operations in order to demontrates the importance of the proper preselected path for ensuring a sound product. Different geometrical and material parameters are all view through their effect on these critical fluid pressure. The "working zone" confined within these two failure loci is enlarged by law friction forces, high strain-hardening exponnents,small drawing ratios, thick workpieces and orthotropic materials. The comparisons between the experiments and theoretical predicitions are very close and the premature failure by wrinkling and rupture is avoidable if the pressure path is confined within the suggested bounds.