Modeling of material removal based on multi-scale contact in cylindrical polishing

Abstract

In this paper, the material removal and the surface roughness in the cylindrical polishing with a soft pad and free abrasives are investigated theoretically and experimentally. Existing our studies have suggested that there is different contact deformation at dimension scales of millimeter, micrometer and nanometer. On that basis, the material removal model is proposed by integrating the contact at different scales in accordance with the Hertz contact, the Greenwood and Williamson's model (G-W model) of rough contact and the single grain's cutting depth. Furthermore, a model of surface roughness is built based on the idea that more materials are removed at the peak on the workpiece's surface, whereas few materials are removed at the valley. The polishing experiments and simulation of cylindrical AISI 52100 steel using the polyurethane polishing pad and the free abrasives of aluminum oxide powder were performed through the Taguchi orthogonal tests, which indicated that the simulation results were well consistent with the experimental results. Under the optimal conditions, the material removal rate (MRR) of 0.40 μm/min was achieved, and the surface roughness Ra was reduced from 104.90 to 20.22 nm after the polishing for 12 min. The contributions of the loading force, the abrasives concentration and the grain size on the MRR and the surface roughness are investigated in accordance with the variance and the level average response, and their reasons are discussed at different scales. It is revealed that the influences of loading force and grain size are significantly different at multi-scale. Furthermore, the parameters related to the contact (e.g., nominal contact area, average contact gap and single grain's cutting depth) under different conditions are studied.