本文選題：近場聲懸浮系統(tǒng)　切入點：圓盤　出處：《陜西師范大學(xué)》2014年碩士論文

【摘要】：早在1886年,就有人對超聲懸浮進行了研究。當(dāng)時,人們就通過實驗發(fā)現(xiàn)了在聲波的作用下,灰塵顆�？梢栽谥C振腔內(nèi)懸浮起來。超聲波懸浮是在聲場輻射力的作用下,使物體懸浮起來的技術(shù),可分為近場聲懸浮和駐波懸浮兩類。本文主要研究的是近場聲懸浮。 近場聲懸浮在近年來得到了非常廣泛的關(guān)注。它是利用高強度聲場,產(chǎn)生聲輻射壓力與被懸浮物的重力相平衡,從而使放入聲場中的物體被懸浮起來。在精密加工領(lǐng)域,尤其是對表面質(zhì)量要求較高的工件或產(chǎn)品的應(yīng)用較多。比方說,在半導(dǎo)體工業(yè)中,對硅片的表面粗糙程度和潔凈度的要求是極高的。所以,對于近場聲懸浮技術(shù)的研究具有重要的意義。前面已經(jīng)有許多學(xué)者對近場聲懸浮系統(tǒng)做了研究,Whymark教授首次發(fā)現(xiàn)了近場聲懸浮現(xiàn)象。美國耶魯大學(xué)的Chu和Apfel共同推導(dǎo)并計算出近場聲懸浮的輻射聲壓及懸浮力。Ueha和Hashimoto等人研究了近場聲懸浮力與聲源表面振幅、懸浮高度之間的關(guān)系,得出了當(dāng)被懸浮物為平面狀物體時,其懸浮高度與聲源表面的位移振幅成正比,與被懸浮物面密度的平方根成反比。此后,他們還對近場聲懸浮系統(tǒng)的穩(wěn)定性進行了研究,為近場超聲懸浮在工業(yè)中能夠得到廣泛的應(yīng)用奠定了基礎(chǔ)。德國學(xué)者Reinhart建立了輻射面為凹面的近場超聲懸浮系統(tǒng),用來作為非接觸夾具,由于懸浮并不穩(wěn)定,因此沒有在工業(yè)生產(chǎn)中大量使用。 通過閱讀文獻,發(fā)現(xiàn)近場聲懸浮技術(shù)的關(guān)鍵問題就是如何提高懸浮系統(tǒng)的穩(wěn)定性以及如何增大聲懸浮力。本文就對此做了以下研究和探討： (1)根據(jù)平面聲波垂直入射時的反射原理,得到在近場聲懸浮系統(tǒng)中,當(dāng)入射聲波傳播到被懸浮物的表面時,在被懸浮物的下表面幾乎發(fā)生了全反射。根據(jù)聲學(xué)基礎(chǔ)中,無限大障板上圓形活塞聲輻射壓力的計算方法,推導(dǎo)得到指數(shù)型旋轉(zhuǎn)激勵盤表面的聲輻射壓力的計算公式。 (2)通過分析,知道如果輻射體表面的位移振幅或振動速度較大,就可以獲得較大的聲懸浮力。那么如何獲得較大的表面振速或振幅,本文通過閱讀大量文獻,發(fā)現(xiàn)運用大振幅超聲換能器,可以得到較大的表面振速或振幅。大振幅超聲換能器由超聲換能器和超聲聚能器組成。本文所用到的換能器為縱向復(fù)合式換能器,通過換能器的原理及設(shè)計,得到了縱向復(fù)合式換能器的振速分布、應(yīng)力分布和頻率方程的計算公式。通過計算,得到當(dāng)工作頻率為20kHz時超聲換能器的尺寸。 采用帶有圓錐形過渡段的變幅桿,根據(jù)變幅桿的原理和設(shè)計,得到變幅桿的位移節(jié)點、放大系數(shù)、形狀因數(shù)φ的計算公式。計算得到超聲變幅桿在工作頻率為20kHz時超聲變幅桿的尺寸大小。 最后,利用有限元軟件,分析得到了大振幅超聲換能器的振型,并得到了它的諧振頻率。 (3)運用有限元軟件,計算了指數(shù)型旋轉(zhuǎn)激勵盤近場聲懸浮系統(tǒng)的諧振頻率,并通過路徑選擇得到指數(shù)型旋轉(zhuǎn)激勵盤表面附近0.5mm處的位移分布曲線。然后,通過實驗驗證了其諧振頻率與有限元軟件計算得出的基本相符。并通過位移測試儀得到了指數(shù)型旋轉(zhuǎn)激勵盤的三維位移分布。最后,通過加載流固耦合邊界條件,得到指數(shù)型旋轉(zhuǎn)激勵盤表面附近的聲場分布,并將其與圓盤表面的聲壓分布進行了比較。通過比較得到當(dāng)為指數(shù)型旋轉(zhuǎn)激勵盤時,指數(shù)型旋轉(zhuǎn)激勵盤表面的聲輻射壓力較大于圓盤表面附近的聲輻射壓力。
[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 .

【學(xué)位授予單位】：陜西師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TB559

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相關(guān)博士學(xué)位論文 前1條

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本文編號：1676286