Foundation Research Of Cavitation Effect In The Grinding Area Of Power Ultrasonic Honing

Power ultrasonic honing during grinding often uses the kerosene or emulsified liquid as the cutting fluid. When the ultrasonic wave passes the grinding zone, the cavitation effect can happen. The cavitation bubbles in the grinding area usually are unstable, constantly grow, expend, compress and even collapse. When the cavitation bubble collapsed, shock wave can be generated and a fluid microjet can be released, which attract enough attention in the power ultrasonic vibration industry. The study on the technology of power ultrasonic honing from the perspective of cavitation effect is very important for the grinding mechanism of the power ultrasonic honing. The cavitation mechanism in the grinding zone can be explained. The dynamics of cavitation bubble and the effects of cavitaiton can be also discussed.The work of this paper and main results are as follow:(1) The mechanism of cavitation in the grinding region of power ultrasonic honing was explained. The process of cavitation occurrence was explained. The continuous cooling liquid can be dispersed into a large number of tiny liquid for the perturbation of the ultrasonic honing head body, and then the cavitation can occur with the ultrasonic vibration. The cavitaion threshold value in the grinding area was calculated. The pressure of the oilstone surface was greater than the cavitaion threshold value of cutting fluid with Flow and Bernoulli equation and the Laplace’s equation, which verified the cavitation effect occured on the oilstone surface, and this theoretical result fits the experiments well.(2) The dynamic model of an individual cavitation bubble in the grinding zone was established. The desired closed time range of the spherical cavitation bubble completely and its collapse distance were obtained. And then, the dynamics model of the hemispherical cavitation bubbles cluster on the oilstone surface can also be established. The numerical results show that the distance between the center of the bubbles cluster and its boundary of cavitation bubbles cluster was about the dimensionless radius r=70～80, which can generate significant local pressure pulse phenomenon.(3) The influence of the cavitation noise, cavitation erosion and chatter caused by cavitation on the power ultrasonic honing can be discussed. Taking the reflection, refraction and mirroring principle of ultrasonic in the solid surface into consideration, the radiated acoustic pressure model of single and double cavitation bubbles near the oilstone wall was studied. The occurrence probability of the pressure pulse generated by collapsing cavitation bubbles on the oilstone was calculated. The collapsed pressure released by a few large cavitation bubbles can generate cavitation erosion on a rigid wall, and even bring ductile deformation and brittle fracture.Comparing the model of power ultrasonic honing chatter with considerations of power ultrasonic cavitation noise, it is observed that the chatter time domain should be short when considering cavitation noise, but there is not obvious effect to the ultrasonic vibration amplitude.(4) The fluid-coupled acoustic model of resonant system, fluid medium and rigid cylindrical absorbing boundary were established. The acoustic field distribution of the renonant system and its relationship between the resonant frequency and the vibrational state can be obtained. The results show that the sound field of resonant system is uniformly distributed in the outer line of the oilstone and oilstone seat, and that the amplitude values focus on the surface of the oilstone, when the resonant system is located in the optimal vibration status. It presents that the strength of the cavitations can be determined by the distribution of the resonant system directly, and the optimal resonant state can also be evaluated. This method provides a crucial support for the designing and optimization of resonant system.(5) The cavitation acoustic field in the grinding area was measured qualitatively by a weak acid paper method. The acoustic distribution by different ultrasonic frequency can be obtained, and the maximum sound pressure on the oilstone surface amplitude is1.3Mpa. Compared with the experiments, the method used for acoustic field analysis of resonant system is verified reasonable and feasible.