功率超声珩磨磨削区单空化泡动力学及溃灭温度分析

发布时间：2018-10-20 19:37

【摘要】：功率超声珩磨加工过程中,磨削区常有大量空化泡产生,它们会快速膨胀、压缩直至崩溃,并在崩溃瞬间产生高温高压等现象。为了探讨其对超声珩磨加工过程的影响,本文对其动力学行为及溃灭特性进行了研究。 首先以磨削液为液体介质,研究了超声振动珩磨环境下单个气泡的动力学特性。将气泡大于初始半径的运动过程看作是等温过程,而气泡小于初始半径的运动过程看作是绝热过程,建立了动力学模型,并运用MATLAB软件中的4-5阶Runge-Kutta进行求解,探讨了各影响因素对其运动规律的影响。研究发现,超声珩磨磨削区空化泡的运动较稳定,但频率较快、振幅较小。珩磨压力对空化泡运动规律影响较大,对空化泡溃灭过程有促进的作用。而回转速度、往复速度的影响则相对较小。磨削液的粘滞系数越大,空化泡的振幅越小。环境温度的升高会使得较小的空化泡运动幅度更加剧烈,而较大的空化泡会逐渐变得平稳。声压幅值对空化泡运动规律的影响也比较大,当PαPo+PH时,空化很难发生,当Pα≥Po+PH时,随着声压幅值的增加,空化泡的振幅会明显变大,且更易于被压溃,空化程度更加剧烈。 然后针对磨削区单空泡建立并求解了空泡溃灭瞬间的最大温度、压强公式,运用MATLAB软件分析了各因素对溃灭温度、压强的影响。结果表明：超声珩磨磨削区空化泡溃灭瞬间的最大温度Tmax、最大压力Pmax比普通超声空化的要大,但随着环境温度的升高二者差距会逐渐减小。Tmax、Pmax会随着珩磨压力、声压幅值的增大明显增大,随着环境温度的升高迅速减小,虽然也会随珩磨头回转速度及往复速度的增大有所增大,但增幅较小。 最后建立了超声珩磨环境中单空化泡CFD几何模型,结合己经得到单空泡溃灭瞬间产生的高温,运用FLUENT软件对其扩散过程进行了分析。发现空化泡溃灭瞬间产生的高温会先传递给磨削液,并随着磨削液的流动快速传递给工件和油石,所选研究对象系统温度随着溃灭温度的扩散会提升1-2K。空化泡溃灭所产生的高温区域会随着磨削液的流动而改变位置，并使得工件表面存在瞬时高温，，影响超声珩磨加工。
[Abstract]:In the process of power ultrasonic honing, a large number of cavitation bubbles often occur in the grinding area, which will expand rapidly, compress to collapse, and produce high temperature and high pressure at the moment of collapse. In order to study the effect of ultrasonic honing on the process of ultrasonic honing, the dynamic behavior and collapsing characteristics of ultrasonic honing were studied in this paper. Firstly, the dynamic characteristics of single bubble in ultrasonic vibration honing environment were studied with grinding fluid as liquid medium. The motion process of bubble larger than initial radius is regarded as isothermal process, while that of bubble less than initial radius is regarded as adiabatic process. The dynamic model is established and solved by using 4-5 order Runge-Kutta in MATLAB software. The influence of various factors on its motion law is discussed. It is found that the cavitation bubble in the grinding area of ultrasonic honing is stable, but the frequency is faster and the amplitude is smaller. Honing pressure has great influence on cavitation bubble motion and promotes cavitation bubble collapse process. However, the influence of rotation velocity and reciprocating velocity is relatively small. The larger the viscosity coefficient of grinding fluid, the smaller the amplitude of cavitation bubble. The increase of ambient temperature will make the smaller cavitation bubble motion more intense, and the larger cavitation bubble will gradually become stable. The effect of sound pressure amplitude on cavitation bubble motion is also relatively large. When P 伪 Po PH, cavitation is very difficult to occur. When P 伪 鈮

本文编号：2284178