平板高頻彈性剪力波在銲接與常溫材料殘留應力消除等等應用方面極具發展的前景。然而其振動能量隨距離發散與高功率超音波致動元件價格昂貴等問題，經常導致高頻彈性剪力波應用上的限制。因此如何避免能量發散以節約超音波致動元件功率始終困擾研究者。故本研究之主要目的在於發展確實有效的方法將平板高頻彈性剪力波能量聚焦於特定範圍，以避免振動能量發散導致功率散失現象產生。本研究中利用有限元素方法模擬平板高頻彈性剪力波的行為，並成功地應用固定於平板上方橢圓形狀之反射體將振動能量聚焦於設定位置。研究所使用之有限元素分析軟體為ABACUS，變化之參數為：反射體大小、反射體伸出的臂長、邊界影響、以及激發頻率變化等等。根據研究結果顯示橢圓形反射體效果很好，當振動施力於一焦點時，另一焦點會產生極佳的聚焦效果。研究中亦比較反射體大小與反射體伸出手臂長度改變時，聚焦效應之變化。結果顯示橢圓形反射體放大倍數為3倍時，聚焦效過最好，且伸出臂長越長，能反射更多的能量聚集於另一焦點。

High frequency shear wave on a flat plate can be an advance approach to improve the structure on the weld and release the residue stress of a machine part. However, the energy of the high frequency wave decays rapidly with increasing distance from the acting point of vibration actuator. Hence, how to transport the vibration energy to a given location is a problem needed to be solved.
The purpose of this research was to develop an effective method to focus the energy of plane shear wave at a pre-defined position on a flat plate. The behaviors of the high frequency (20k Hz) plane shear wave were simulated by finite element analysis (ABAQUS). The results show that elliptic reflector can focus the energy to a given location very well.
And the results show the focusing effect by the elliptic reflector is very robust, when the reflector is designed for a wave length of 3 times greater than the true wave length and the elliptic reflector’s hand extended, the elliptic reflector can focus the energy to a given location is very good.

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