Influence of Process Parameters and Viscosity on Radial Stresses in Fluid Assisted Deep Drawing Process
Deep drawing is an important process used for producing cups from sheet metal in large quantities. The process parameters and viscosity of fluid is maintained the major role in the hydro forming-deep drawing process. Hydraulic pressure can enhance the capabilities of the basic deep drawing process for making metal cups. Hydraulic pressure contributes positively in several ways to the deep drawing process. In fluid assisted 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 pressure is generated in fluid due to punch movement with in the fluid chamber and directed through the bypass path to blank periphery and is to reduce tensile stresses acting on the wall of the semi drawn 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. The blank holder pressure is controlled by the radial pressure of fluid and these are equal for 1858 R. Uday Kumar, P. Ravinder Reddy and A. V. Sita Ramaraju uniform deformation of blank to obtained required shape and also elimination of failure of blank in deformation. 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. In this paper the radial stresses are determined in terms of process parameters and viscosity of different fluids for magnesium alloys and then influence of viscosity of fluid, process parameters and fluid pressure on these stresses incorporated. This analysis is carried through theoretically.
Buckling prevention by lateral fluid pressure in deep-drawing
Abstract An instability analysis of flange buckling against lateral fluid pressure in deep drawing is considered. It is intended to explain the experimental fact that relatively low fluid pressure when applied to the flange area can suppress buckling. The analysis is based on the approximate ‘energy method’ with the inclusion of the work against the fluid. The attention is focused on the initiation of the deep drawing process, where buckling (of non-hardening material) is most susceptible. A special apparatus which enables the replacement of a rigid blank-holder by a lateral fluid-pressure was used for testing. A general solution to the critical pressure, above which the deep drawing can be terminated without buckling, is provided. The prediction of the critical pressure and the number of the associated buckling ‘waves’ (wrinkles) agree very well with the experiments. The pertinent geometrical and material variables (as blank thickness, drawing ratio, Young modulus, yield strength, etc.) are grouped in nondimensional form and plotted for various parameters to provide an engineering-type solution for potential users.
Plasticity Analysis of Sheet Metal Forming
The paper surveys the application of plasticity theory to sheet metal forming problems and attempts to highlight those areas where knowledge is lacking. From an engineering standpoint the most valuable analyses would seem to be those which predict trends in deformation behaviour. It is only rarely that the material properties and lubrication characteristics are known with sufficient accuracy to make correlations between theory and practice worthwhile in a particular case. There would, however, seem to be definite advantages in the same research team following both theoretical and experimental paths.