INFLUENCE OF PUNCH ON BLANK HOLDER PRESSURE IN HYDROFORMING
Dr. R. Uday Kumar
Associate Professor Dept.of Mechanical Engineering Mahatma Gandhi Institute of Technology Gandipet, Hyderabad. 500075 , IN
Keywords: Deep drawing, Hydro forming process, Fluid pressure, Blank holder pressure, Cfd model Analysis
Abstract
The hydro formed components are used in the aerospace, automotive, marine and other industries. In hydro forming deep drawing process, applying the hydraulic pressure in radial direction on the periphery of the blank is obtained through the punch movement with in the fluid chamber. The fluid is taking place in the die cavity and punch chamber and these are connected with the bypass path provided in the die. The gap is provided between die surface and blank holder bottom surface for movement of pressurized fluid and blank in the process. The pressure is generated in fluid due to punch movement within the fluid chamber and directed through the bypass path to the blank periphery and is to reduce tensile stresses acting on the wall of the semi drawn blank. The fluid pressure is obtained through ANSYS Flotran CFD analysis software for castor oil. The evaluation of fluid pressure with changing the punch speed at onstant punch radius. The pressure of fluid is acting radially on surface of blank during the process. The radial pressure of fluid is controlled by the blank holder pressure. This pressure of fluid is used to evaluate the blank holding pressure. In this process of hydro forming deep drawing the fluid pressure is equal to blank holder pressure is to be obtained. The deformation of blank is uniform to get a required shape and also it prevents the blank failure during deformation due to these two pressures are being equal. The pressure of fluid and blank holder pressure depends on punch speed. The fluid pressure and blank holder pressure increases with increasing in the punch speed. The fluid pressure and blank holder pressures are the dominant parameter for failure and success of forming of cups from the cylindrical blanks
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