ANALYSIS OF TAPERED PREFORMS IN COLD UPSETTING

Upset forging is usually carried out with a sequence of stages and the tapered preforms are commonly used. The preforms should be free from flash formation and buckling injuries. :In this paper, the results tha t depend on elastic-plastic finite element analysis of taper upset for ging are given. The buckling analysis was realized by using the Modifi ed Riks method. For a given upset ratio which is the ratio of unsuppor ted length to diameter of the initial billet, reduction in the height of the billet and the diameter ratio are the important design paramete rs in taper upsetting. For several values of the design parameters, th e analysis has been carried out and the results have been compared wit h the results of the well-known Meyer's experiment and Gokler's sugges tions. In the analysis, the perfectly square end (ideal billet case) a nd the end with face inclination angle were considered as two differen t end conditions of the billet. The results for the ideal billet case are in good-agreement with Meyer's results. The end-face inclination a ngle, which is a significant imperfection on the billet, reduces the l imits of allowable upset ratio. It has been observed that although the tapered header dies designed at the limits suggested by Meyer produce flashless preforms, in some of the cases, injuries due to buckling ar e not eliminated. However, Gokler's suggested limits provide eliminati on of both flash formation and injuries due to buckling. (C) 1998 Else vier Science Ltd. All rights reserved.