Optimization of Teeth Shape for Serration Joining

A shape of teeth for serration joining was optimized to improve joining strength as well as to reduce joining load. The serration joining has been proposed to manufacture an automobile shaft with a large disk. The shaft and the disk were joined through the following three processes: a) extrusion of a shaft with serration, b) carburizing of the only outer side including the teeth of the serration, c) penetration of the serrated shaft into a holed disk for joining. Filling up to the teeth shape and strain hardening due to plastic deformation by teeth indentation is a key factor to increase the torsional strength after joining. In this study, experiments about typical tooth shape using clay model brought a rough but nevertheless fundamental result of the valuable top shape of the tooth. Moreover, numerical analyses by FEM were also tried about the several teeth shapes. Thus, it was found that a tooth with a one-side wedge & a small round top enables the joining region to provide large strain by a low joining load.