Recess swaging method for manufacturing the internal helical splines

With the advantages of minimized stress concentration and allowing a combination of rotation and axial motion, internal helical splines have been widely used in automotive and aeronautic industries. However, this type of splines can only be manufactured using machining or extrusion method. This paper studied the recess swaging method, a net-shape forming process, for manufacturing the internal helical splines. In order to investigate the deformation tendency of workpiece along the thickness direction, Finite Element (FE) simulations and experiments were firstly performed on the recess swaging of tube without mandrel. Results show that the stress state in the forging zone is triaxial compressive except for the tensile axial stress at the inner surface of the tube. Moreover, during the recess swaging process material mainly flows along the axial and thickness direction, but the axial flow dominates. With increasing the reduction in outer radius and the wall thickness, metal flow along the axial direction increases but along the thickness direction decreases. Furthermore, based on the fundamental research on recess swaging experiments and FE simulations on the recess swaging method for manufacturing the internal helical splines were conducted. After the recess swaging, the hardness at the bottom of the tooth improved approximately 56.9%, while that at other zones increased 41%. The strength and the wear resistance of tooth were also improved. In summary, the recess swaging process provides an effective method for manufacturing the internal helical splines.