超音波加工為硬脆性材料中最常見的加工方式之一。其工件品質會因刀具振幅、磨料種類與粒徑大小等加工參數不同而受到影響，因此以往的文獻多半與優化加工參數以提升表面品質有關，鮮少有人討論加工時產生的訊號與工件品質之關連性。此外目前並無有效方法監控超音波製程，往往須等到加工結束後才有辦法得知工件品質好壞，而且無法對超音波機台進行校正動作。
本研究藉由動力計擷取超音波加工玻璃材料時產生的力量訊號，並透過經驗模態分解(Empirical Mode Decomposition)解析出「空蝕作用」及「衝擊與鎚擊作用」之振動模態。經由擷取上述兩種模態所對應之邊際頻譜、能量大小與平均頻率之特徵，建立一套能夠由力量訊號辨別超音波機台穩定性及工件品質的機制，可用於監控超音波加工製程。此外實驗中所使用的變幅桿與刀具均為自行設計，除了利用ANSYS的模態分析(Modal Analysis)與簡諧響應分析(Harmonic Response Analysis)外，也量測當變幅桿於無負載狀態時，其振幅與頻率大小是否與模擬結果相符，達到提升設計準確性之目的。

Ultrasonic machining is one of the most common methods in brittle materials. The quality of workpiece is usually influenced by processing parameters, such as abrasive particle and tool amplitude. In the past, most of the literature focused on optimization of processing parameters to improve the surface quality and few people studied in the connection between signals and workpiece quality. Besides, there is no way to monitor the ultrasonic process. In general, we can’t understand the workpiece quality and calibrate the machine before the end of machining.
This study will use the dynamometer to capture force signal during machining, and the Empirical Mode Decomposition is applied to analyze the vibration mode, including cavitation effect, impact and hammer effect. After capturing the characteristics of the vibration mode, such as Marginal Spectrum, power, and mean frequency, we establish a measurement mechanism which can distinguish the stability of machine and workpiece quality by force signal. This measure mechanism can be also applied to monitor the ultrasonic machining process. Furthermore, the tool and horn are self-designed. In order to enhance the design accuracy, we not only used modal analysis and harmonic response analysis in ANSYS but ensure the result is as same as the measurement when the horn is without loading.

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