Investigation on the hole evolution and forming dimensions during cross wedge rolling hollow shaft with mandrel

Abstract

The cross wedge rolling (CWR) is an efficient and green process for manufacturing hollow shafts. The mandrel plays an important role in controlling hole shape during the process of CWR hollow shafts with mandrel. To obtain precise dimensions of rolled parts, the hole evolution during rolling in different parameters is need to be investigated further. This paper deeply studied the effect mechanism of mandrel on hole of hollow shaft. A finite element model (FEM) was developed to analyse the evolution process of inner hole during CWR hollow shaft, and the results shown that the wall of hollow shaft is rolled and the hole dimensions is grow after inner hole contacts mandrel. The hole evolution process can be considered as the rolling of wall under the effect of CWR dies and mandrel. A layer gap between the mandrel and the hole of rolled parts, defined as diameter difference, is caused because of the hole expansion. The effect of process parameters on the diameter difference was investigated by conducting CWR experiments. It shown that the diameter difference increases with stretching angle and mandrel diameter; and decreases with forming angle, compression ratio and wall thickness. The results reveals the hole evolution and the causes of the diameter difference during CWR hollow shafts with mandrel, and can provide theoretical guidance for the production application.