Effect of mandrel diameter on non-circularity of hollow shafts in cross wedge rolling

摘要

Because of the need for lightweight design, the application of hollow shaft parts rapidly increases. The mandrel plays an important role in the process of forming hollow shafts using cross wedge rolling (CWR). This paper presents the experimental and numerical analysis on the effect of the mandrel diameter on non-circularity in CWR for the hollow shafts with mandrel. A thermomechanical finite element (FE) model was developed to simulate the CWR process of hollow shaft. The experiments and numerical analysis suggest that the diameter of mandrel has a great effect on the non-circularity of hollow shafts. During the CWR process, because of the effect of the mandrel, the workpiece is compressed in radial direction and extended along the circumferential direction, which lead to the increase of the non-circularity. With increasing diameters, the workpieces show larger non-circularity. The non-circularity slowly increases when mandrel diameter is small. However, when the mandrel diameter exceeds a certain value, the non-circularity increases rapidly. Besides, the non-circularity of the inner hole is larger than that of the outer circle. According to the strain curves during the forming process, it can be found that circumferential compressive strain plays an important role in the rounding forming stage. Larger compressive strains decrease the non-circularity of the rolled pieces.