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.
Rupture instability in hydroforming deep-drawing process☆
Abstract The critical fluid-pressure locus above which rupture by tensile instability may occur in the hydroforming deep-drawing process, is formulated and tested. The formulation is based on the classical theory of plasticity (with simple power-law hardening and Mises-Hill normal anisotropic yielding) assuming plane strain tensile failure. Further simplifications, such as assuming constant blank thickness and a constant Coulomb friction coefficient, enable one to account for the coupling effect between the self-adjusted blank curvature and the governing material parameters on rupture. Experiments with copper blanks are aimed to demonstrate that under certain conditions, failure by rupture may be prevented if the path of the working fluid pressure nowhere exceeds the predicted critical-pressure locus path. On the other hand, it is shown that the working fluid pressure should nowhere be lower than a predetermined minimum pressure locus to prevent wrinkles at the rim. Thus a distinct operating zone, lying between the upper and the lower pressure loci, is identified and recommended for practical use.
Endodontic regeneration: hard shell, soft core
A loss of organs or the destruction of tissue leaves wounds to which organisms and living things react differently. Their response depends on the extent of damage, the functional impairment and the biological potential of the organism. Some can completely regenerate lost body parts or tissues, whereas others react by forming scars in the sense of a tissue repair. Overall, the regenerative capacities of the human body are limited and only a few tissues are fully restored when injured. Dental tissues may suffer severe damage due to various influences such as caries or trauma; however, dental care aims at preserving unharmed structures and, thus, the functionality of the teeth. The dentin–pulp complex, a vital compound tissue that is enclosed by enamel, holds many important functions and is particularly worth protecting. It reacts physiologically to deleterious impacts with an interplay of regenerative and reparative processes to ensure its functionality and facilitate healing. While there were initially no biological treatment options available for the irreversible destruction of dentin or pulp, many promising approaches for endodontic regeneration based on the principles of tissue engineering have been developed in recent years. This review describes the regenerative and reparative processes of the dentin–pulp complex as well as the morphological criteria of possible healing results. Furthermore, it summarizes the current knowledge on tissue engineering of dentin and pulp, and potential future developments in this thriving field.