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.
Joint strength of aluminum ultrasonic soldered under liquidus temperature of Sn–Zn hypereutectic solder
Abstract In order to obtain high-strength aluminum joints, ultrasonic soldering of 1070 aluminum was conducted under liquidus temperature of Sn–Zn hypereutectic solder. A device for ultrasonic soldering was assembled, which propagated ultrasonic vibrations in a direction perpendicular to joining surfaces. This device joined 1070-Al using quasi-melting Sn–Zn hypereutectic solder without using any artificial spacers. The strength of the solder joints was evaluated by tensile tests. The optimum joining conditions were determined, and the effects of solder compositions and soldering temperature on the joint strength and the solder layer thickness were examined. In this ultrasonic soldering process, the highest tensile strength was obtained for the solder joints fabricated at 220 °C for the Sn–23Zn and Sn–40Zn solder compositions. The joint strength was equivalent to that of 1070-Al heat treated at 220 °C. The sound joints were obtained at 300 °C using Sn–82Zn solder, the liquid phase volume fraction of which was theoretically only 0.24. The present work also revealed that the thickness of retained solder layer in the joint after ultrasonic soldering could be estimated. Accordingly, ultrasonic soldering under the liquidus temperature of Sn–Zn hypereutectic solder could be a spacer-free soldering method to obtain high-strength aluminum joints.