UPPER-BOUND ANALYSIS OF COMBINED EXTRUSION-FORGING PROCESS: PENTAGONAL HEAD WITH ROUND SHAFT PRODUCT FROM CYLINDRICAL BILLET

摘要

Corresponding to higher demands for strength, resistance to fatigue, heat and corrosion, extrusion-forging process becomes more popular among different metal forming process. In general practice, the shaft and the head of rotating elements are manufacture separately and then assembled. In this process, the chance of failure increases due to stress concentration occurs at shaft and rotating element junction. To minimize the rate of failure extrusion-forging processes are used where, the head element is made by forging processes and shaft is made by extrusion processes. In this study, an upper bound solution for extrusion-forging of the pentagonal head with round shaft from cylindrical billet through square/flat die is found. The rigid-perfectly plastic model of the material is assumed, and the Spatial Elementary Rigid Region (SERR) techniques are presented for the kinematically admissible velocity field is found out by minimizing the plastic dissipation of power. Optimized values of the non-dimensional average extrusion pressure at various area reductions have been computed and compared with experimental results and by FE analysis. An extrusion-forging setup is designed and fabricated for the said purposes and commercially available lead (98% purity) is used as modelling material. Results obtained by proposed theoretical analysis, experiment and finite element analysis have shown good agreement.