EVALUATION OF THE PREFORM DESIGN OF A STEPPED FORGING PART BY COUPLEDTHERMOVISCOPLASTIC FINITE-ELEMENT ANALYSIS AND VISIOPLASTICITY

To achieve a sound product without lap defects, both finite-element an alysis and the visioplasticity technique were adopted in this article as a design tool to execute the preform design of a stepped forging pa rt, which is a simplified modeled to simulate one piece of five-finger -span part applied widely in the bicycle industry. The physical modell ing of the real material, performed by visioplasticity for four sets o f preliminary preform designs, was preformed first. Subsequently, one of the preliminary preforms was simulated numerically using the rigid- viscoplastic finite-element method under both uncoupled and coupled th ermomechanical conditions. It was seen the numerical results evaluated by the finite-element method were consistent with the experimental da ta obtained by visioplasticity. Moreover, the lap defect, as well as a local high-effective-strain condition due to improper design of the p reform geometry, were observed by both visioplasticity and finite-elem ent analyses. Consequently, four sets of re-designed preforms were eva luated numerically in the coupled thermomechanical condition, and the optimal preform design obtained. Finally, the rules for improving the preform design of a stepped forging were proposed as discussed.