Analytical modeling and experimental verification of surface roughness in the ultrasonic-assisted ball burnishing of shaft targets

摘要

Ultrasonic-assisted ball burnishing (UABB) is a promising surface strengthening technology for improving the properties of components. This method superimposes ultrasonic vibration to the traditional deep rolling; it can improve the surface roughness of a material, enhance its surface hardness, and introduce a high compressive residual stress, thereby improving the fatigue performance of components. A mathematical model should be established to predict and analyze the relationship between the experimental process parameters and results and to predict the effect of UABB on surface roughness. In the present work, a mathematical model of surface roughness after UABB was established on the basis of Hertz contact theory, comprehensively considering the process parameters, dynamic vibration forces, and elastic rebound of the targets. UABB experiments were carried out to verify the correctness of the mathematical model. Results showed that UABB can significantly reduce the surface roughness of the material, and the values calculated from the derived mathematical model showed good agreement with the experimental findings. The surface roughness decreased with the burnishing force (50-250 N) and amplitude (4-10 mu m) increased, whereas the feed rate decreased. The increases of radii of component and ball were detrimental to the improvement of the surface roughness. And elastic rebound was not conducive to roughness reduction and its influence was negligible. Finally, the derived surface roughness model can be used to predict the component values after UABB and understand the effects of machining parameters on the shaft targets during processing.