Effects of pressing die's boosting function on wall thinning and springback in NC bending process of thin-walled tube with large diameter

Based on FEM code Dynaform, an FEM model of the NC bending and springback process of thin-walled tube with large diameter has been established. The effects of velocity of pressing die and the friction between pressing die and tube on thinning and spring back angle in NC bending process of thin-wall tube with large diameter were studied. The results show that the wall thinning of the tube will exceed the allowable value 0.4375 mm according to the aerial criterion if the tube is formed under the following conditions, there is no friction between the tube and the pressing die, the boosting velocity is 0.9, the boosting velocity is 1.0 and the friction coefficient between pressing die and tube is 0.1. Given fixed value of boosting velocity, as the friction coefficient between pressing die and tube increases to 0.3 from 0.1, the wall thinning can be lessened effectively, but the spring back angle can be increased dramatically. Given fixed value of the friction coefficient between pressing die and tube, the increase in the boosting velocity from 1.0 to 1.2 won't make any obviously improvement in the wall thinning or make any difference in the spring back angle.