Cavitation effect in two-dimensional ultrasonic rolling process

Abstract

The ultrasonic cavitation effect can improve the machining quality. In order to study the formation process of cavitation in two-dimensional ultrasonic rolling process (TDUR) and its influence on processing, a simulation and experimental study of cavitation in TDUR was conducted to further improve the processing quality. The pressure distribution model and the cavitation model of the two-phase mixed flow around the roller in TDUR were constructed by combining the ideal bubble dynamics theory. And the cavitation intensity was evaluated by the vapor volume fraction (VVF). The formation process of cavitation effect in the flow field was analyzed by finite element analysis, and the effects of different inlet pressures and different pipe structures on the cavitation were studied. TDUR experiments were carried out to study the changes of surface roughness and residual stress of the workpiece under the effect of ultrasonic cavitation, and the positive effect of cavitation effect was verified. The simulation results show that the cavitation effect mainly occurs in the left half of the roller and the rolling area, and the cavitation in the left half of the roller changes from transient cavitation to steady-state cavitation as the inlet pressure increases. Different inlet pressures in the rolling region always show periodic transient cavitation, with obvious cavitation bubbles generation, expansion and collapse processes. The lower the inlet pressures in the straight and inverted trumpet pipe, the stronger the transient cavitation effect. The experimental results show that the cavitation effect can further improve the surface strengthening quality of the workpiece. Under the same process parameters, the surface roughness of the workpiece can be reduced by up to 47.7% and the residual compressive stress of the surface can be increased by up to 10.2%. Therefore, the cavitation effect can be applied in ultrasonic rolling process to further improve the surface strengthening quality, and the straight pipe at atmospheric inlet pressure is preferred in TDUR.