微磨粒对超声空化冲击波衰减作用研究OA北大核心CSTPCD

The effect of cavitation shock waves during power ultrasonic vibration machining can be produced.The presence of micro-abrasive particles can enhance the machining efficiency and impact the propagation of shock waves.The work aims to investigate the mechanism of micro-abrasive particles on shock waves during power ultrasonic vibration machining.By utilizing the Gilmore-Akulichev equation,the bubble dynamic equation under power ultrasonic vibration machining and the mathematical model of shock waves generated by the collapse of bubble were established.Subsequently,a propagation model for shock waves in the mixed medium of micro-abrasive particles and water was developed.The mathematical model was solved by the sixth-order Runge-Kutta method,providing insights into the dynamic evolution of bubble radius and the internal pressure of the bubble.The results indicated that a bubble with an initial radius of 8 μm exhibited nonlinear oscillations under the effect of the ultrasonic field.After a series of oscillations,the change in radius gradually diminished over time,indicating a convergence towards equilibrium between the pressure inside the bubble and the surrounding environment.When the bubble radius decreased from 8 μm to 3 μm,the pressure on the bubble wall remained relatively stable.Upon compression approximate to 1 μm,the internal pressure of the bubble could reach 1 000 MPa,surpassing the ambient pressure.Consequently,the cavitation bubble rebounded outward,compressing the surrounding water and generating a shock wave that propagated radially.By solving the shock wave pressure at a distance of 1.5R0 from the cavitation wall,it was found that the shock wave pressure rapidly decreased from the initial 1 000 MPa to 80 MPa within a short time of 0.07 μs,covering a propagation distance of 17 μm.Comparing the shock wave propagation speed in a pure water medium with that in a mixed medium of SiO2 micro-abrasive particles and water,it was discovered that the addition of SiO2 micro-abrasive particles reduced the maximum speed of the shock wave from 2 976 m/s to 2 681 m/s,resulting in a reduction rate of 10%.Subsequently,power ultrasonic vibration processing experiments were conducted on Ti-Ta alloy to validate the aforementioned numerical results.Through a comparative analysis of the surface structure and three-dimensional surface morphology of the Ti-Ta alloy before and after the addition of SiO2 micro-abrasive particles,it was observed that the number of cavitation pits decreased from 34 to 21.This indicated that the addition of SiO2 micro-abrasive particles reduced the occurrence of cavitation pits.The software ImageJ was utilized to measure the projected area of cavitation pits with diameter greater than 1 μm on the Ti-Ta alloy surface.The results showed that the addition of SiO2 micro-abrasive particles led to a decrease in the projected area of cavitation pits from 497.132 μm2 to 434.84 μm2,corresponding to a reduction rate of 12.5%.This reduction rate was in line with the 10% calculated by the model,demonstrating consistency.The observed discrepancy mainly arose from the uneven distribution of SiO2 micro-abrasive particles in the machining area during the machining due to factors such as gravity,resulting in varying obstacles to the shock wave.This study confirms that micro-abrasive particles effectively attenuate the propagation of shock waves and become a key factor affecting the material surface.The findings of this research hold both theoretical significance and practical value in the field of ultrasonic processing.