Modeling the superposition of residual stresses induced by cutting force and heat during the milling of thin-walled parts

Previous studies on machining-induced residual stress mainly concentrated on qualitative analyses of mechanical load and thermal load. Nevertheless, it remains a major challenge to quantify the influence of cutting force and heat on residual stress generation due to the lack of superposition mechanism. A newly empirical model of milling residual stress superposition was constructed to distinguish the effect of milling force from the effect of milling heat. The influence proportions of milling force and heat on the residual stress generation have been determined. Firstly, the residual stresses induced by the milling force, heat and force-heat coupling load were simulated independently, and the simulation models were verified by experiments. The simulation results presented that the milling force caused both residual compressive stress and residual tensile stress on the machined surface, while milling heat induced mainly residual tensile stress. Then, a mathematical model was put forward to quantify the superposition relationship between the force-induced residual stress and the heat-induced residual stress presented in the simulations. It has been found that the influence of milling force accounts for 53% to 78% in the generation of the surface residual stress when the force-to-heat ratio (RFT) varies from 0.09 to 0.39. Finally, with a constant material removal rate, the conclusion can be drawn that the parameter combination with a higher force-to-heat ratio is more beneficial for the generation of residual compressive stresses on the machined surface, which has been confirmed by the case experiments. Therefore, quantitative analysis of residual stress generation and superposition turns to be possible by using the proposed modeling.