Material removal mechanism elucidated by a novel cross-scale model using a unified physical framework linking macroscopic stress distribution and microscopic motion states of abrasives for polishing

Abstract

The effect of polishing pads is generally incorporated as a coefficient in the conventional Preston equation and its modified forms during the past century, and macroscopic stress distribution and microscopic motion states are discussed separately. To solve this challenge, we propose a novel cross-scale model using a unified physical framework integrating the macroscopic and microscopic states. The proposed model decomposes the effect of polishing pads into stress transfer and abrasive constraint factors. It connects microstructure, stress transfer, abrasive constraint and material removal in sequence and establishes a relationship between the microstructure of pads and the evolution of a polished surface. Finite element simulations show that the maxima of von Mises stresses on fused silica are 0.171, 0.749 and 0.446 MPa for non-woven, polyurethane, and asphalt pads, respectively, corresponding to the support of discrete fibers, local stress concentration and continuous transfer of stress. Furthermore, single-abrasive scratching confirms that the maxima of equivalent stress exerted by the associated three pads are 2.059, 4.701 and 7.771 MPa, respectively, relevant to weak, unstable and strong constraints of abrasives. Polishing experiments were performed on fused silica with ceria slurry. They demonstrate that the peak-to-valley value obtained using an asphalt pad decreases from 385.976 to 115.237 nm and the attenuation of power spectral density is 88%. The surface roughness S_a achieved using a non-woven pad is reduced from 2.145 to 0.721 nm. The predictions of the proposed model are in good agreement with the simulation and experimental results. Our outcomes provide new insights into achieving error convergence of full bands on polished surfaces using different polishing pads.