超音波手術刀是一種利用高頻率超聲波震盪產生的能量來進行手術的醫療器械。現今它被廣泛應用於外科手術中，特別是在神經外科、泌尿外科及微創手術。其原理是利用在器械刀尖傳輸高頻（如55,500 Hz）超音波能量振動，使蛋白質氫鍵變性、斷裂，進而分割組織，並使變性蛋白凝固，實現血管的密封，達到止血的效果。超聲波手術刀的主要優點是它可以實現高精度和準確的切割，同時也能夠快速止血和減少手術時間。此外，由於它的切割方式不會產生明顯的熱量和電流，因此對周圍組織的損傷較小，並且可以減少術後的疼痛和恢復時間。
本研究透過Ansys的模態分析探討超音波手術刀內芯的共振頻率，及利用諧振響應分析探討內芯之振幅放大率，並將模擬結果與實際量測值進行比較及探討。比較結果顯示共振頻率模擬值與量測值誤差為0.42 %，振幅放大率模擬值與量測值在高低兩種功率模式下誤差為0.88 %-1.3 %。由結果可知本研究所建立的有限元素模型及模擬方法在給定適當的材料性質以及幾何條件下應可正確預測超音波手術刀之共振頻率及振幅放大率。本研究並透過模擬與實驗量測手術刀內芯因操作導致升溫(從20°C至60°C)對刀尖端面位移之影響，模擬結果顯示升溫至60°C造成刀尖最大位移下降3.32 %，而實驗量測結果指出在高低兩種功率模式下，刀尖位移下降1.24 %-3.15 %。
此外，本研究嘗試以所建立的有限元素模擬探討改善超音波手術刀內芯可能發生的裂痕及疲勞破壞。透過改變幾何特徵，包含導入圓角及開槽，模擬結果顯示內芯振動應力可下降8.1 %，夾持應力可下降5.9 %，及總應力可下降7.2 %。改善後的總應力值小於內芯材料Ti-6Al-4V的最大抗拉強度，期望能因此降低裂痕生成的機率，改善超音波手術刀的可靠性及使用壽命。

關鍵字:超音波、手術刀、Ti-6Al-4V、Ansys、模態分析、LS-DYNA、應力集中、諧振響應分析

The ultrasonic dissector is a medical device that can perform surgery with the energy generated by ultrasonic vibrations. It is currently being applied widely in surgery, especially in neurosurgery, urologic surgery and other minimally invasive surgery. The principle is to use the blade tip of the instrument to transmit high-frequency (such as 55,500 Hz) ultrasonic vibrations to denature and break protein hydrogen bonds, further segment tissues, achieve sealing of blood vessels and hemostasis. The main advantage is that it allows for accurate dissection with blood coagulation and shorter surgical time. In addition, because its cutting method does not generate significant heat and current, it causes less damage to surrounding tissues and can reduce the pain and recovery time.
This study used the modal analysis of Ansys to simulate and study the resonant frequency of the ultrasonic dissector's inner core, and used the resonance response analysis to explore the amplitude ratio of the inner core. The simulation results were compared with the measured values experimentally. The difference of resonant frequency between the simulated value and measured value is 0.42%, and the difference of amplitude ratio, in the high and low power modes, is between 0.88% and 1.3%. The comparison results show that the finite element model and simulation method established in this study can predict the resonance frequency and amplitude ratio correctly with appropriate material properties. This research also studied the effect of the operating temperature rise from 20°C to 60°C on the blade tip displacement with simulation and experiment. The simulation results showed that the maximum tip displacement decreased 3.32% when the temperature increased to 60°C, and the tip displacement decreased by 1.24%-3.15% in the high and low power modes from experiments.
In addition, this study attempted to use the established finite element simulation to improve the inner core design to avoid possible cracks and fatigue damage. By changing the geometric features, including rounding and slotting, simulation results show that the inner stress due to core vibration can be reduced by 8.1%, and the inner stress from clamping can be reduced by 5.9%, and the total reduced stress is reduced by 7.2%. The improved total stress is less than the ultimate strength of Ti-6Al-4V, the inner core material, and it could reduce the possibility of crack and improve the reliability and useful life of the ultrasonic dissector.

Keywords: Ultrasound, dissector ,Ti-6Al-4V, Ansys, modal analysis, LS-DYNA, stress concentration, Harmonic response

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