MRF spotting technique for studying subsurface damage in deterministic microground polycrystalline alumina

Abstract

We report on use of the magnetorheological finishing (MRF) spotting technique to estimate subsurface damage (SSD) depth resulting from deterministic microgrinding for polycrystalline alumina (PCA). With various microscopy techniques, we show how surface roughness evolves with the amount of material removed by an MRF spot. Two stages are identified. In the first stage the induced damaged layer and associated SSD from microgrinding are removed, reaching an optimal value of surface roughness. Here, the initial peak-to-valley (p-v) surface roughness from grinding gives a measure of the SSD depth found by spotting. In the second stage, where more material is removed from the nonrotating surface, the resulting surface roughness begins to show the interaction between MRF abrasive particles and the material's microstructure (crystal grains), i.e., the "MRF signature" for a specific material. We can examine the "MRF signature" across grains using power spectral density and characterize surface features that contribute to surface roughness.