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Title: | 間隙流體對球體瞬時加速度之碰撞聲壓的影響 Interstitial Liquid Effect on the Collision Sound from Spheres due to Sudden Accelerations |
Authors: | Wei-Ren Su 蘇威任 |
Advisor: | 楊馥菱 |
Keyword: | 麥克風,聲壓訊號,赫茲碰撞,碰撞加速度預測,潤滑理論, microphone,acoustic signals,Hertzian contact,lubrication theory,prediction of contact deceleration, |
Publication Year : | 2013 |
Degree: | 碩士 |
Abstract: | 根據現有之乾碰撞文獻,我們建立一系列的實驗器材量測兩相同球體乾碰撞與在球體表面塗上不同黏度的液體薄膜之濕碰撞的聲音。我們在兩球體的碰撞接觸點塗抹不同黏度的液體,將液體存在之碰撞產生的聲壓與乾碰撞的結果比較發現聲壓隨液體黏滯度上升而下降。為瞭解液體可能會造成的效應,以潤滑理論模擬估算球穿透液體薄膜減速後的碰撞前速度。我們發現碰撞聲壓會隨著間隙流體黏度的增加而降低。我們另外發展出一套方法,藉由量得的壓力歷時曲線反求碰撞過程中球體所受的加速度。對於乾碰撞,我們得到的結果與赫茲加速度相當吻合,但濕碰撞的結果與赫茲加速度有偏差,顯示間隙液體薄膜的減速效果。
關鍵字: 麥克風,聲壓訊號,赫茲碰撞,碰撞加速度預測,潤滑理論 ABSTRACT Based on the existing knowledge of dry impacts, we conducted a series of experiments to measure the sound radiated by identical impacting spheres with dry and liquid-deposited surface results. The thin viscous liquid film of various viscosities was employed. The resulting wet impact sound was compared to the dry sound and the acoustic pressure decrease with viscosity increase. In an attempt to address possible liquid effects, we use classical lubrication theory to estimate a decelerated impact velocity after the sphere penetrates the liquid film to realize a pseudo-dry contact which can then described by existing method. The wet model is feasible to capture the reduced pressure magnitude. We also develop a method to extrapolate the particle acceleration history from the measured pressure time delay. Nearly Hertzian acceleration history is found for dry collisions but deviation is detected for wet collisions, suggesting liquid film decelerating effect. Keywords: microphone, acoustic signals, Hertzian contact, lubrication theory, prediction of contact deceleration |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/59031 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 機械工程學系 |
Files in This Item:
File | Size | Format | |
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ntu-102-1.pdf Restricted Access | 3.49 MB | Adobe PDF |
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