Simulation and experimental study of ultrasonic-assisted shear thickening polishing of cemented carbide

In order to obtain a good surface quality of carbide inserts, an ultrasonic-assisted shear thickening polishing (UASTP) method is proposed in this paper. Using the shear thickening property of non-Newtonian fluids and combining with the principle of ultrasonic vibration, the abrasive grains wrapped by the polishing slurry carry out both flexible micro-cutting and high-frequency micro-collision on the material surface. This enables more efficient polishing of the microscopic surface of the material. In this paper, the polishing principle of this method is analyzed. The rheological characteristics of shear thickening polishing slurry are studied, and a continuity model that can adapt to nonlinear rheological behavior is proposed based on the Gross constitutive equation. The effects of fluid velocity, ultrasonic amplitude and ultrasonic frequency on polishing speed and polishing pressure in the Preston equation are studied by COMSOL Multiphysics simulation software. This method's material removal rate model is established based on the high-frequency periodic characteristics of ultrasonic action, combining the simulation results with polishing experiments, which accurately describe the variation law of material removal rate with polishing time. After polishing the carbide insert for 60 min with this method, a smooth surface is obtained with continuous surface ripple measurements and small floating values; the surface roughness is reduced from 195 nm to 16.1 nm with an improvement rate of 91.7 %, and the material removal rate reached 0.71 μm/h, which improved the surface roughness improvement rate and material removal rate by 27.6 % and 44.9 %, respectively, compared with the STP method. The experimental results show that the UASTP method is an efficient composite polishing technology to enhance the cemented carbide's surface quality further.