Investigation on the effect of mandrels on hollow shafts in cross-wedge rolling

Abstract

Cross-wedge rolling (CWR) hollow shafts with mandrels can control the hole contour and reduce internal defects so that the working conditions for the shafts can be met. The diameter of the mandrel plays an important role in this forming process. In this study, numerical simulations and experimental trials were conducted as part of a detailed investigation on the mechanism of a mandrel and its influence on the forming quality of CWR hollow shafts. The contact areas between the mandrel and workpiece, the rolling forces of the mandrel, stress-strain fields, metal flows and temperatures were analysed in detail. The gaps on the surface of dies designed to prevent torsion failure of the rolled piece lead to noticeable steps on the surface of the rolled piece, as the relative diameter of the mandrel is too large. The diameter and non-circularity of the outer and inner surface increase with the increase of the relative diameter of the mandrel. The results can provide theoretical guidance for the production application of cross-wedge rolling hollow shafts with mandrels.