Numerical Damage Prediction and Experiments in Deep Drawing of Irregular Square Cup
Deep drawing is an important sheet metal forming process in the industry. The deep drawing of irregular square cup was investigated in this paper. To predict the damage of irregular square cup, different blank hold forces and blank shapes were studied in the numerical model. The experiment was carried out with the optimized blank force holder and blank shapes, the crack and thickness distribution were investigated. The results of the experiment accorded with those of the numerical simulations, which show the validity of the simulation to predict where the damaged zones will appear in the part during the deformation.
Effect of blank holder force control in deep-drawing process of magnesium alloy sheet
Abstract A circular cup deep-drawing process was investigated using a magnesium alloy material, which is the lightest practical material for use in manufacturing structural components. An improvement in the limiting drawing ratio (LDR) at 300 °C was observed, by controlling a variable blank holder force (BHF) during the process, in comparison with the constant BHF conditions. The reason for the improvement of the LDR is that the magnesium alloy material has a low F -value, which was obtained from tensile tests when it was warmed to the elevated temperature. When the experimental conditions are not appropriate, such as when BHF is high, the experimentally drawn cup fractured at the wall part (β-rupture). The LDR of the magnesium alloy sheet was improved using the BHF control technique and verified using a finite element method (FEM) simulation. It is confirmed that the FEM simulations behaved in a similar manner to the experiments, with β-rupture being observed during the fracture at the wall part.
Hapten inhibition of passive antidextran dextran anaphylaxis in guinea pigs. Role of molecular size in anaphylactogenicity and precipitability of dextran fractions.
High titred antidextran antisera have been raised in rabbits by prolonged immunization with soluble conjugates between isomaltose oligosaccharides or dextran mw 4,400 and bovine serum albumin in complete Freund’s adjuvant. Guinea pigs sensitized with such antisera exhibited anaphylactic shock on i.v. challenge with fractions of hydrolyzed B512 dextran. The severity of anaphylaxis depended on the amount of sensitizing antibody and the dose and molecular size of the challenging dextran fraction. In maximally sensitized animals, fractions of mw 3,600 or larger were anaphylactogenic and smaller molecular size fractions were nonanaphylactogenic. In submaximally sensitized animals, dextran fractions of mw 10,500 or less were foundnonanaphylactogenic. In addition, nonanaphylactogenic dextran fractions produced desensitization, i.e. protection from anaphylaxis due to subsequent or simultaneous injection of more high molecular and anaphylactogenic dextran fractions. When the molar ratio in a mixture of nonanaphylactogenic/anaphylactogenic fractions was about 7.6, protection was complete with reduction of mortality from 100 to 0%. A molar ratio of 1.9, corresponding to a 13-percent by weight admixture of nonanaphylactogenic dextran, still significantly reduced mortality from 100 to 50%. From the ability to form precipitates with antidextrans and to elicit anaphylaxis in sensitized guinea pigs, and from the absence of these properties, the approximate molecular size range of bivalent and monovalent dextran B512 fractions was found to correspond to mw 3,600 and mw 1,430, respectively. The practical applicability of hapten inhibition is discussed.