Optimal Blank Shape Prediction Considering Sheet Thickness Variation for Multistage Deep Drawing

Deep drawing is one of the very old and widely practiced processes in the sheet metal industries for producing beverage cans and automobile components. Many of the deep drawn components need multiple draws to achieve the required dimensions, because often it is not possible to obtain the desired reduction in the first draw. Among several defects that occur during the process, earing is one of the prominent and common defect. In the present work, analysis has been carried out by dividing the total deformation region into several zones. Analysis of each zone is carried out by proposing kinematically admissible velocity field, i.e. the velocity field satisfying the condition of normal velocity continuity and volume constancy. The input material (already drawn cup) for redrawing is pre-strained from the previous stage drawing operation and this has been considered while carrying out the analysis. Thickness and punch load predictions are validated by comparing them with the published results and are found to be in good agreement. The optimal blank shape, that will result in earing free cup after the final drawing operation, has been determined. For the prediction of optimal blank shape for multistage deep drawing, addition-subtraction scheme has been developed and successfully implemented; the modification of the initial blank is done after each stage of drawing. The optimal blank shape obtained has been tested, using simulation, to draw the cup and it yields the final cup height with percentage earing less than 1%. However, in a few cases, three or four iterations for the modification of blank may be required, to bring the percentage earing within the specified limit.

USING OF BEZIER FORMULATION FOR CALCULATION OF STREAMLINE, STRAIN DISTRIBUTION AND EXTRUSION LOAD IN RECTANGULAR CROSS SECTION OF ECAE PROCESS

In this research, a general solution of volume constancy differential equation is presented based on the equation of deformation field for a general process. As the Bezier method is suitable for construction of complex geometries, the solution is used in conjunction with the Bezier method to analyze the equal channel angular extrusion (ECAE) process of rectangular cross section. Thus, a generalized kinematically admissible velocity field is derived from the equation of deformation zone such that the compatibility of the surface representing the deformation zone is fulfilled. The effects of die angle, friction between the billet and die wall, and the angle of outer curved corner, on extrusion pressure are all considered in the analysis. It is found that extrusion pressure decreases with increasing both the die angle and the outer curved corner angle and with decreasing the friction coefficient. Also, the effect of die curvature on inhemogenity of strain is assessed. It is exhibited that increasing the angle of outer curved corner decreases the extrusion pressure and increases the inhomogeniety of strain field of deformation zone. A good agreement is found between the predicted and experimental results pertaining to two dies of different outer curved corner.

A New Punch Profile Design for Orbital Forging of a Bevel Gear Part

The difficulty in forging of bevel gear with an outside diameter larger than 75mm is due to the high forming load requirement. In this paper, a new intuitive method for the punch and preform design of the bevel gear warm orbital forging is proposed to lower the forging load and improve the die filling. The geometry of the forged bevel gear are divided into characteristic features and mapped to the main dimensions of the preform design. The exact dimensions of the preform are determined utilizing constraints of the volume constancy and the section centroid balance. The surface of punch tip is designed using the section profile described by a Bezier curve with five control points which are related to the preform and the forged part geometry simultaneously. The forming process was analyzed via the FEM simulation. The die stress was also calculated to prevent die failure and improve tool life. A PXW-200 orbital forging press was adopted for the experimental tests of the proposed designs. The unfilled area at the teeth faces were examined via the laser scanner. The experimental results of the maximum unfilled distances were varied from 0.3 mm to 0.8mm depending on the different punch tip profile design. The predicted tooth profiles were in good agreement with the experimental measurements.

Functional Significance of Cell Volume Regulatory Mechanisms

Lang, Florian, Gillian L. Busch, Markus Ritter, Harald Völkl, Siegfried Waldegger, Erich Gulbins, and Dieter Häussinger. Functional Significance of Cell Volume Regulatory Mechanisms. Physiol. Rev. 78: 247–306, 1998. — To survive, cells have to avoid excessive alterations of cell volume that jeopardize structural integrity and constancy of intracellular milieu. The function of cellular proteins seems specifically sensitive to dilution and concentration, determining the extent of macromolecular crowding. Even at constant extracellular osmolarity, volume constancy of any mammalian cell is permanently challenged by transport of osmotically active substances across the cell membrane and formation or disappearance of cellular osmolarity by metabolism. Thus cell volume constancy requires the continued operation of cell volume regulatory mechanisms, including ion transport across the cell membrane as well as accumulation or disposal of organic osmolytes and metabolites. The various cell volume regulatory mechanisms are triggered by a multitude of intracellular signaling events including alterations of cell membrane potential and of intracellular ion composition, various second messenger cascades, phosphorylation of diverse target proteins, and altered gene expression. Hormones and mediators have been shown to exploit the volume regulatory machinery to exert their effects. Thus cell volume may be considered a second message in the transmission of hormonal signals. Accordingly, alterations of cell volume and volume regulatory mechanisms participate in a wide variety of cellular functions including epithelial transport, metabolism, excitation, hormone release, migration, cell proliferation, and cell death.

Viability of the vascularly perfused, recirculating rat intestine and intestine-liver preparations

Function and stability of vascularly perfused, recirculating in situ rat intestine (I) and intestine-liver (IL) preparations were evaluated in fasted and nonfasted rats because these techniques may be readily applied in drug metabolism studies. The rat intestine was perfused with blood medium (7.5 ml/min) via the superior mesenteric artery, with the venous outflow draining into the portal vein, which, together with hepatic arterial flow (2.5 ml/min), constituted the total blood flow (10 ml/min) to the liver. Maintenance of intestinal membrane integrity was observed. Rapid [14C]glucose absorption against a concentration gradient and a lack of [3H]-polyethylene glycol 4000 (PEG 4000, less than 4%) and Evans blue absorption by the recirculating I and IL preparations resulted after bolus injections of these markers into the pyloric end of the duodenum. Other indexes that revealed stable intestinal and liver functions were the following: preservation of reservoir perfusate volume, constancy in perfusion pressure, bile flow, and hemoglobin concentrations, evidence of intestinal glucose utilization and liver glucose production, and a lack of significant leakage of serum glutamic oxalic transaminase. The intestine and liver consumed oxygen at relatively constant rates, but the consumption rates for the fasted tissues (I or L) were significantly higher than those for nonfasted tissues. These results indicate that the vascularly perfused I and IL preparations were maintained in a viable and stable state for a 2-h perfusion period.