Numerical simulation study on the cause of ellipse generation in two-roll cross wedge rolling the hollow parts with uniform inner diameter

This article focuses on the ellipse problem in two-roll cross wedge rolling the hollow shafts with uniform inner diameter. Numerical simulation by a finite element method was performed to study the forming process and the stress-strain conditions of the hollow parts. It is found that the mismatching between radial compression and axial flow leads to easier tangential metal flow and growing up in the circumferential direction, which is the main cause for forming the ellipse. The study is useful to choose proper process parameters in two-roll cross wedge rolling the hollow parts.