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ABSTRACT Finite Element Analysis Model of Rotary Forging for Assembling Wheel Hub Bearing Assembly

In the past the wheel hub bearing assembly was assembled by incredible method which was much dependent on the manual experience. Thus the tolerance changed from situation to situation. It has passed quite long time since rotary forging approach was used to fabricate the wheel hub bearing assembly. The shaft clinching technology was developed to meet the requirement of customers on light weight and improved wheel bearing performance (Toda et al., 2001). The rotary forging approach needs quite much assembly time compared to a kind of simple forging approach. However, rotary forging requires relatively small forming load with the result that precision assembly can be achieved. Of course, due to quite large assembly time of the rotary forging approach, a direct forging method has been studied but failed because of difficulty in controlling the preload within the required accuracy and frequent fracture of the hub bearing unit (Shim et al., 2012) An assembly process of the wheel hub bearing assembly is affected by many factors, especially including die geometry, feed rate, initial shape of material and metallurgical state of material, which are much correlated with each other. Thus a systematic approach to determine the factors and to reveal their relationship is needed. The important factors from standpoint of process design engineers include plastic deformation history of the hub, some information about the possibility of ductile fracture occurrence at the end of the hub, and the pushing force on the hub bearing unit, which are complicatedly coupled with each other. Of course, metal forming simulation technology may be appropriate to satisfy the need of the process design engineers.

Several researchers studied rotary forming processes by experiments and/or predictions (Hawkyard et al., 1977; Zhou et al., 1992; Choi et al., 1997; Yuan et al., 1998; Toda, 2001; Guangchun and Guoqun, 2002; Liu et al., 2004; Wang et al., 2005; Munshi, 2005; Moon et al, 2007; Nowak et al., 2008; Han et al., 2013). However, few researchers (Toda et al., 2001; Munshi et al., 2005; Moon et al., 2007) applied the technologies to predicting plastic deformation occurring during rotary forging of wheel hub bearing assembly. Toda et al. (2001) predicted the clamping force by applying the given force on the wheel hub bearing assembly using a dynamic analysis software but they did not mentioned the plastic deformation during rotary forging process itself. Munshi et al. (2005) employed a so-called rigid-super-element scheme for reducing computational time drastically in simulating the similar orbital forming process but the predictions did not look as good as the number of elements.

In spite of remarkable contributions by many researchers, there still stand some strong obstacles against metal forming process design engineers in simulating such difficult forming processes as the rotary forging process for assembling the hub bearing assembly. It should be emphasized that it takes inherently quite long computational time to conduct the process simulation with its entire solution domain considered in such incremental forming processes as rotary forging (Munshi et al., 2005). In recent, Cho et al. (2011) developed a method of artificial planes of symmetry for simulating a sort of incremental forming processes and showed that it predicts quite reliable solutions at the midplane of the solution domain defined by two planes of symmetry when the plastic deformation occurs only around the local contact area.

In this paper, an analysis model of the rotary forging for fabricating wheel hub bearing assembly is presented, based on the method of artificial planes of symmetry and the predictions are compared with experiments.