Numerical Analysis of Hot Deep Drawing Process of the Thick Hemispherical Head Without the Blank-Holder

In deep drawing process, if the workpiece is not willing to wrinkle due to small drawing ratio, deep drawing is done without the blank-holder. In present paper, numerical analysis of hot deep drawing for the thick hemispherical head from a plate with the thickness of 63.5 mm which is made of alloy steel HY-100 is presented without using the blank-holder. The drawing process of hemispherical head is studied by using three different geometries of drawing die in three positions as (1) increase in the curvature radius of the die, (2) approximate tractrix and (3) exact tractrix. In this research, Johnson-Cook constitutive model is used in order to explain the flow behavior of the material and the damage model of Johnson-Cook is used for prediction of failure probability in the product. Also, it is assumed that the hot deep drawing is done as isothermal and the strain rate is fixed. The results of numerical analysis show that the probability of damage occurrence in the "exact tractrix" design is lower than the other designs. Also, comparison of the thickness distribution in the wall of hemispherical head shows that the "exact tractrix" design has the least fluctuation of change in the wall thickness. Comparison of drawing force obtained by the numerical analysis show that at the same conditions of blank temperature and friction coefficient, using the "exact tractrix" design can significantly reduce the needed force in order to draw the hemispherical head.