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一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特定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：反射體幾何形狀、波長變化、以及激發頻率變化等等。根據研究結果顯示反射體形狀以橢圓形最佳，當振動施力於一焦點時，另一焦點會產生極佳的聚焦效果。拋物線聚焦效果較差。同時，激發振動之外力形式以正弦波最佳，方波與衝擊波均會使聚焦效應降低。研究中亦比較頻率與波長偏離正確之波長時，聚焦效應之變化。結果顯示橢圓形反射體聚焦效應十分穩定，既使波長為正確波長之7.1倍仍可在焦點上產生400倍於無反射體聚焦時的能量。

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 form 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 (20kHz) plane shear wave were simulated by finite element analysis (ABACUS). The results show that a fixed reflector can focus the energy to a given location very will. The elliptic reflector focuses the wave energy best than the reflectors with other geometries. The sinusoidal simulation force gives the maximum energy density at the focus, while the rectangular and pulsed force give less energy. The results show the focusing effect by the elliptic reflector is very robust. Even the reflector is designed for a wave length of 7.1 times greater than the true wave length, the energy density at the focus still can be 400 times greater than that of a plate without the reflector.

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