一种新型的近场声悬浮系统的研究

发布时间：2018-03-28 12:16

本文选题：近场声悬浮系统　切入点：圆盘　出处：《陕西师范大学》2014年硕士论文

【摘要】：早在1886年,就有人对超声悬浮进行了研究。当时,人们就通过实验发现了在声波的作用下,灰尘颗粒可以在谐振腔内悬浮起来。超声波悬浮是在声场辐射力的作用下,使物体悬浮起来的技术,可分为近场声悬浮和驻波悬浮两类。本文主要研究的是近场声悬浮。近场声悬浮在近年来得到了非常广泛的关注。它是利用高强度声场,产生声辐射压力与被悬浮物的重力相平衡,从而使放入声场中的物体被悬浮起来。在精密加工领域,尤其是对表面质量要求较高的工件或产品的应用较多。比方说,在半导体工业中,对硅片的表面粗糙程度和洁净度的要求是极高的。所以,对于近场声悬浮技术的研究具有重要的意义。前面已经有许多学者对近场声悬浮系统做了研究,Whymark教授首次发现了近场声悬浮现象。美国耶鲁大学的Chu和Apfel共同推导并计算出近场声悬浮的辐射声压及悬浮力。Ueha和Hashimoto等人研究了近场声悬浮力与声源表面振幅、悬浮高度之间的关系,得出了当被悬浮物为平面状物体时,其悬浮高度与声源表面的位移振幅成正比,与被悬浮物面密度的平方根成反比。此后,他们还对近场声悬浮系统的稳定性进行了研究,为近场超声悬浮在工业中能够得到广泛的应用奠定了基础。德国学者Reinhart建立了辐射面为凹面的近场超声悬浮系统,用来作为非接触夹具,由于悬浮并不稳定,因此没有在工业生产中大量使用。通过阅读文献,发现近场声悬浮技术的关键问题就是如何提高悬浮系统的稳定性以及如何增大声悬浮力。本文就对此做了以下研究和探讨： (1)根据平面声波垂直入射时的反射原理,得到在近场声悬浮系统中,当入射声波传播到被悬浮物的表面时,在被悬浮物的下表面几乎发生了全反射。根据声学基础中,无限大障板上圆形活塞声辐射压力的计算方法,推导得到指数型旋转激励盘表面的声辐射压力的计算公式。 (2)通过分析,知道如果辐射体表面的位移振幅或振动速度较大,就可以获得较大的声悬浮力。那么如何获得较大的表面振速或振幅,本文通过阅读大量文献,发现运用大振幅超声换能器,可以得到较大的表面振速或振幅。大振幅超声换能器由超声换能器和超声聚能器组成。本文所用到的换能器为纵向复合式换能器,通过换能器的原理及设计,得到了纵向复合式换能器的振速分布、应力分布和频率方程的计算公式。通过计算,得到当工作频率为20kHz时超声换能器的尺寸。采用带有圆锥形过渡段的变幅杆,根据变幅杆的原理和设计,得到变幅杆的位移节点、放大系数、形状因数φ的计算公式。计算得到超声变幅杆在工作频率为20kHz时超声变幅杆的尺寸大小。最后,利用有限元软件,分析得到了大振幅超声换能器的振型,并得到了它的谐振频率。 (3)运用有限元软件,计算了指数型旋转激励盘近场声悬浮系统的谐振频率,并通过路径选择得到指数型旋转激励盘表面附近0.5mm处的位移分布曲线。然后,通过实验验证了其谐振频率与有限元软件计算得出的基本相符。并通过位移测试仪得到了指数型旋转激励盘的三维位移分布。最后,通过加载流固耦合边界条件,得到指数型旋转激励盘表面附近的声场分布,并将其与圆盘表面的声压分布进行了比较。通过比较得到当为指数型旋转激励盘时,指数型旋转激励盘表面的声辐射压力较大于圆盘表面附近的声辐射压力。
[Abstract]:The ultrasonic suspension has been studied in the first place . At that time , it was found that under the action of acoustic wave , the dust particles could be suspended in the resonant cavity . The ultrasonic suspension is a technique which can suspend the object under the action of acoustic field radiation force .

Near - field acoustic levitation system has been widely used in recent years . It is a very important application in the field of precision machining , especially for workpieces or products with high surface quality .

Through reading the literature , it is found that the key problem of near - field acoustic levitation technology is how to improve the stability of the suspension system and how to increase the acoustic levitation force .

( 1 ) In the near - field acoustic levitation system , when the incident sound wave propagates to the surface of the suspended matter , the total reflection occurs almost on the lower surface of the suspended matter when the incident sound wave propagates to the surface of the suspended matter . According to the acoustic basis , the calculation formula of the acoustic radiation pressure on the surface of the exponential rotating excitation disc is deduced .

( 2 ) Through the analysis , it is known that if the displacement amplitude or the vibration velocity of the surface of the radiator is larger , a larger acoustic levitation force can be obtained .

The displacement node , the amplification factor and the form factor 蠁 of the horn are obtained by using the variable amplitude rod with conical transition section . The size of the ultrasonic horn is calculated when the operating frequency is 20 kHz .

Finally , using the finite element software , the vibration mode of the ultrasonic transducer with large amplitude is obtained , and its resonant frequency is obtained .

( 3 ) By using the finite element software , the resonance frequency of the near - field acoustic levitation system of the exponential rotating excitation disk is calculated , and the displacement distribution curve near the surface of the exponential rotating excitation disk is obtained through the path selection . Then , the three - dimensional displacement distribution of the exponential rotating excitation disk is obtained by the experiment . Finally , the acoustic radiation pressure near the surface of the exponential rotary excitation disk is obtained by loading the flow - solid coupling boundary condition .

【学位授予单位】：陕西师范大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB559

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