Elastoplastic finite element simulation of rotary forging process for an assembling hub bearing unit with an emphasis on residual stress

In this paper, finite element analysis of a rotary forging process is conducted for an assembly process of hub bearing assembly unit (HBAU) by rotary forging with an emphasis on the residual stress of bearing parts as well as the structural parts. A theoretical analysis model is given, based on rate-independent assumption of the material to minimize the numerical effect. An elastoplastic finite element method with MINI-tetrahedral elements is employed. The multi-body function is employed to prevent the predictions from being numerically affected by the interface treatment scheme. Two inner races of duplex pair taper-roller bearings as well as the hub shaft are treated as elastoplastic materials. To remove the numerical effects of convergence and volume consistency on the finite element prediction, which may occur during near-idling rotational motion of materials, the material is fixed while the relative tool velocities are maintained. The predictions are discussed to reveal the characteristics of the assembly process. It is to be noted that the cavity between the hub shaft and the bearing inner race could be predicted and that it generated two distinctly separable normal stresses around the bearing race shoulder, which are related to the anti-play stress between the two parts and the joining stress of the duplex pair bearing races.