Optimization of Ti-6Al-4V ring rolling process by FE simulation using RSM

Ring rolling is a process to manufacture seamless rings. The process is characterised by high non-linearity, asymmetry, unsteady state and non-uniformities in plastic strain and temperature distribution in the ring cross-section. Inhomogeneities in distribution of plastic strain and temperature have significant effects on deformation behavior, microstructure and mechanical properties. Fishtail defect, one of the form defects, is also a major concern. In this study, a reliable coupled 3D thermo-mechanical finite element model of the ring rolling process was developed using dynamic explicit code in ABAQUS/Explicit environment. Nine simulations with different combinations of feed rate and rotational speed were ascertained using Central Composite Design (CCD). CCD model is an integral part of Response Surface Methodology (RSM). Strain and temperature heterogeneities and fishtail defect were predicted using the simulated models. Coefficient of Variation (CoV) was introduced as a heterogeneity index for strain and temperature analysis. The fishtail coefficient was used to quantify fishtail defect. ANOVA was carried to find out the significant factors and interactions affecting the ring rolling process. Feed rate was found to be the only significant factor in the range of parameters studied. Multi-response optimization was performed to find out the feed rate at which the process is most optimized with an aim to minimize both strain and temperature heterogeneity and fishtail defect. Feed rate of 1.61 mm/s was found to be the most optimized process parameter.