T-shape upsetting-extruding test for evaluating friction conditions during rib-web part forming

Since the deformation features of existing friction testing methods are not as similar as those of the closed die forging process of rib-web parts, the friction conditions evaluated by these methods are not consistent with the actual situation. In this paper, a new friction testing method, the T-shape upsetting-extruding process employing a rectangular blank, is proposed for evaluating the friction conditions during rib-web part forming process. It was found that rib height and the web width are both sensitive to friction conditions. Therefore, the ratio of rib height to web width was chosen as a criterion for friction evaluation. With the utilization of a commercial FEM program, DEFORM, the effects of the geometrical parameters and testing variables on the friction sensitivity were investigated, and the friction conditions between different interfaces were analyzed. In order to verify the proposed method, friction factors of a water-based graphite lubricant measured by three different methods (the proposed one, the ring compression test and the double-cup extrusion test) at 723 K were used to simulate the isothermal deformation process of a cross-rib part. The experimental results suggest that the proposed method is more accurate than the other two methods for rib-web part forming process.