功率超声加工中空泡溃灭的冲击波特性分析

Analysis on the shock wave characteristics for collapsing cavitation bubble of power ultrasonic machining

研究空化冲击波效应对于功率超声加工具有重要意义。为揭示功率超声加工参数与冲击波压强之间的关系,考虑声压在空泡压缩过程中的作用,建立冲击波压强模型。通过试验与数值方法,对超声声压在功率超声加工中的作用以及功率超声加工参数对冲击波压强的影响进行分析。在此基础上,对空泡在被加工固体表面附近球形溃灭产生的冲击波进行分析,结果表明:超声声压通过改变空泡的运动来影响冲击波压强的大小;冲击波压强最大值随着声压幅值的增加而增加,随着超声频率、润滑液表面张力系数的增加而减小;冲击波经过衰减后,作用于固体表面的压强仍然可以达到吉帕级以上。

Shock wave effect induced by cavitation is of great significance for power ultrasonic machining. In order to determine the relationship between power ultrasonic machining parameters and shock wave pressure, a pressure model of the shock wave induced by ultrasonic cavitation considering acoustic pressure is established. The effect of ultrasonic sound pressure in power ultrasonic machining is analyzed by experiments and numerical methods. Numerical simulations of the shock wave characteristics of a bubble are performed under various conditions of acoustic pressure, ultrasonic frequency, initial bubble radius and surface tension coefficient to explain the effects of these key parameters of power ultrasonic machining. The ultrasonic pressure influences the pressure of shock wave by affecting the movement of cavitation. With the increase of the acoustic pressure amplitude, the maximum pressure of the shock wave increases. With the increase of ultrasonic frequency and surface tension coefficient of lubricant, the maximum pressure decreases. Furthermore, the shock wave caused by a spherically collapsed bubble near a solid surface is analyzed. Results demonstrate that the pressure on the solid surface can still reach more than one gigapascal after the shock wave decays.