1Dept. of Mechanical Engg., Mahatma Gandhi Institute of Technology, Andipet, Hyderabad, A.P., India
2Dept. of Mechanical Engg., Chaitanya Bharathi Institute of Technology, Gandipet, Hyderabad, Andhra Pradesh, India, E-mail: reddy_prr@yahoo.com
3Dept. of Mechanical Engg., JNTUH College of Engg., Kukatpalli, Hyderabad, A.P., India. E-mail:avsrraju_2008@rediffmail.com
1Corresponding Author E-mail: u_kumar2003 @yahoo.co.in
In this paper the drawing stress of magnesium alloys are presented through fluid assisted deep drawing process. It is the process used for production of cups from sheet metal in large quantities.The advantages of hydraulic pressure assisted deep drawing techniques, increased depth to diameter ratio's and reduces thickness variations of the cups formed are notable. In addition, the hydraulic pressure is applied on the periphery of the flange of the cup, the drawing being performed in a simultaneous push-pull manner making it possible to achieve higher drawing ratio's then those possible in the conventional deep drawing process. The pressure in the die cavity can be controlled very freely and accurately, with the approximate liquid pressure as a function of punch position, the parts can drawn without any scratches on the outside of the part and also obtained in good surface finish, surface quality, high dimensional accuracy and complicated parts. In the fluid assisted deep drawing process the pressurized fluid serves several purposes are supports the sheet metal from the start to the end of the forming process, thus yielding a better formed part, delays the on set of material failure and reduces the wrinkles formation. The pressure is generated in fluid due to punch movement with in the fluid chamber and directed through the bypass path to blank periphery and also apply the fluid pressure in radial direction on the periphery of the blank. This fluid creates the fluid film on the upper and lower surfaces of the blank and subsequently reduces frictional resistance. During the process, the blank is taking at centre place in between blank holder and die surface with supporting of pressurized viscous fluid. In this process the radial and hoop stresses are produced in the blank due to punch force applied on it, the shear stresses acted by viscous fluid on the both sides of blank, so apply viscosity phenomenon to this analysis for evaluation of stresses and forces in the direction of drawing of a cup. The blank holder pressure is controlled by the radial pressure of fluid and these are equal for uniform deformation of blank to obtained required shape and also elimination of failure of blank in deformation. In this paper drawing stresses are determined in terms of viscosity and process parameters for magnesium alloys and studied. The method of analysis is carried through theoretically.
Deep drawing process, drawing stress, hydro forming; viscosity, shear stress, pressurized fluid
