Finite-element investigation of the wear and elastic deformation of dies in metal forming

Abstract

In the held of metal forming, reliable predictions of the amount of wear and its distribution in dies are very important, since such factors greatly affect the life of dies. In this study, the wear profile in dies during upsetting was calculated by implementing Archard's wear model into a rigid-thermo-viscoplastic finite-element analysis program for metal forming. According to the simulation results, the numerically-determined wear profile was consistent with the trend of experimental results available in the literature. The current approach was used to obtain the wear profiles and the pressure distributions at the workpiece and dies interface for two cold extrusion processes. Based on the pressure information at the interface, further elastic finite-element analyses were carried out to investigate local stress concentration regions and elastic deformations of the two extrusion dies. Examination of the wear profiles and local stress concentrations for the two cold extrusion processes revealed that wear would most likely be the primary cause of die failure for the case of a lower extrusion ratio. On the other hand, it was found that a sudden failure might occur due to fatigue fracture in the case of a higher extrusion ratio, since the stress concentration in the transition region was critical. From this study, it was found that the failure mode in the extrusion dies could be governed by wear or fatigue depending on the die geometry, namely, the extrusion ratio and the radius of the transition region. (C) 1999 Elsevier Science S.A. All rights reserved.