Numerical and experimental study on cavitation enhancement of ultrasonic coupled abrasive jet polishing

To enhance the effectiveness of jet polishing, ultrasonic coupled abrasive jet polishing (UC-AJP) was applied. Through high-frequency ultrasonic vibration, pressure lower than saturated vapor was generated in the jet. It made the jet medium cavitation; thus, cavitation-jet composite energy enhanced the material removal rate and reduced the roughness of the workpiece surface. Firstly, the principle of UC-AJP was analyzed, and a numerical model of UC-AJP was established according to the shear-stress transport (SST) k-ω turbulence model, Schnerr-Sauer cavitation model, and discrete phase model (DPM). Through the numerical calculation, the cavitation was enhanced with the increase of ultrasonic amplitude. When the amplitude reached 20 μm, the cavitation bubbles acted on the workpiece surface. Cavitation also increased the velocity and turbulent kinetic energy of the jet. Then, cavitation observation experiments were carried out; the results were consistent with the numerical simulation. Through the fixed-point polishing experiments, it was found that the erosion effect of UC-AJP on the workpiece was enhanced and then weakened. Through continuous polishing experiments, the surface of the workpiece was the smoothest after the polishing with amplitude 20 μm, the roughness decreased from 3.2 μm to 69 nm, and the speed of roughness reduction was also the fastest.