Modeling the effects of Undeformed Chip Volume (UCV) on residual stresses during the milling of curved thin-walled parts

With the increasingly popularized curved thin-walled parts, the control of curved surface residual stress in machining has become more and more demanding. However, it remains to be a major challenge to predict and control curved surface residual stress in the present aerospace research areas. Amidst this backdrop, this paper introduces a residual stress volume model to evaluate the effects of sequential cuts for the generated surface and subsurface residual stresses. Additionally, based on the proposed modeling and calculated results, quantified method is used for superposition of residual stress under different machining conditions. The superposition rates in feed, vertical feed and depth of cut directions are about 10%, 11% and 7%, respectively. In addition, this paper presents a newly constructed mathematical model between the curved surface maximum tensile residual stress and the Undeformed Chip Volume (UCV) (f(z), R, ap and ae) of the ball end milling cutter. Through polynomial fitting for the proposed mathematical model, the influence coefficients alpha and beta can be obtained, which act as the influence factors of machining parameters on residual stress generation. The values of alpha vary from 0.0018 to 0.0087, while the values of beta vary from -3.99 to 0.72. That means that the depth of cut and tool radius can exert the greatest influence on the curved surface maximum tensile residual stress. Finally, with larger tool radius and smaller depth of cut, an experiment of machining curved thin-walled part proves that curved surface residual stress and deformation can be effectively reduced.