Effects of Forming Conditions on Wrinkling in Necking of Tube End

Abstract

The effects of forming conditions on wrinkling in the neck of stainless-steel tubes were investigated using experiments and three-dimensional finite element simulations. The materials used for this study were tubes designed for automotive exhaust parts. When the axial or radial forming pitch of the rollers is large, the outside of the tube is subjected to considerable compressive stress in the circumferential direction by contact with the rollers. Simultaneously, the inside of the tube is subjected to considerable tensile stress in the circumferential direction. Consequently, the tube is subjected to excessive localized forming, which causes the curvature to become uneven in the circumferential direction, thereby resulting in wrinkling. The number of contact points with the rollers was determined. Results show that the optimum forming conditions were easily determined to achieve short forming times and high dimensional accuracy.