Influence of Material Flow on Forming Conditions in Backward Cup Extrusion

Backward cup extrusion occurs high pressure, high temperature, and a large surface expansion ratio during forming. Thus, this forming provides the severe tribological conditions because lubricant film between the punch and the specimen is broken. This study investigates the influence of the material flow on forming conditions using the FEM analysis data and the previous experimental data in the cold backward cup extrusion at the extrusion ratio of 2.8. Additionally, suitable punch nose shape is also verified to keep good lubricant condition between the punch and the specimen during the forming. The friction between the punch and the specimen of the punch with corner radius is lower than that with nose angle.