Publication

Abstract : The presented work focuses on numerical modelling and analysis of the forming process of a thin circular disc of negligible thickness, that is later subjected to vibration-induced loading and unloading cycles (fatigue) during application. During the forming process, the material of the pre-form (Mild-Carbon Steel, AISI-1075) is shaped into the required profile of the disc, using a fast moving punch that impacts on a die underneath. The profile consists of a hole at the center of the disc and predefined surface gradations along the periphery. This punching process is followed by heat treatment to relax the residual stresses developed. This paper discusses the development of a detailed thermo-mechanical coupled model using the finite element method, to simulate the different stages of the forming process; namely, the punching process, the instantaneous punch release and structural creep, and the subsequent heat treatment to induce stress relaxation. The numerical model is intended to predict the amount of residual stress and equivalent plastic strain that are developed in the disc at the end of each stage of the forming process. The stress concentration in the disc has serious implications on the subsequent cyclic loading and unloading application. The results obtained from standard tests indicate initiation and propagation of cracks in the disc during application. The intensity and occurrence of crack initiation have a direct connection to the maximum residual stress developed in the disc during the forming process. In addition, the heat treatment model is also intended to investigate the temperature distribution in the disc, during the heating and the subsequent cooling operations. The results of the finite element model are then validated with experimental measurements for each of the stages of the forming process. The finite element packages, Abaqus/Explicit and Abaqus/Standard, are used in conjunction for the aforesaid modeling