Effect of elastohydrodynamic characteristics on surface roughness in cylindrical shear thickening polishing process

The shear thickening fluid exhibits a non-Newtonian characteristic, i.e. the viscosity follows a power law with the increasing shear rate. The shear thickening polishing technology has been proposed and developed to realize the precision finishing, utilizing the slurry with free abrasives prepared by the shear thickening fluid. In this paper, the formation mechanism and evolution of surface roughness in the cylindrical shear thickening polishing process is investigated in the elastohydrodynamics theoretically and experimentally. The elastohydrodynamic properties and the surface roughness are modeled by a novel solution method, based on the integration of polishing pad's elastic deformation and slurry's hydrodynamics. The Taguchi orthogonal tests of polishing the cylindrical AISI 52100 steel with the foam polyurethane pad were conducted, and the experimental surface roughness Ra of 9.689 nm was achieved under conditions of loading force 10 N, α-Al2O3 powder with grain size 1 μm and concentration 20 wt%, starch powder with concentration 25 wt%. According to the comprehensive analysis of variance and level average response, it is revealed that the slurry's viscosity has a great influence on the surface roughness. The effecting mechanisms of processing factors on the surface roughness are interpreted from the perspective of effects transition in aspects of viscosity, pressure distribution and single grain's cutting depth, interestingly exhibiting significant differences from that of traditional polishing methods.