本研究探討超音波輔助車削技術（Ultrasonic Assisted Turning, UAT）在加工304不鏽鋼時的力學行為，並利用顯式動力學有限元素分析方法進行模擬研究。由於其高硬度和韌性，304不鏽鋼在切削時需要較大的切削力，且刀具容易磨損。此外304不鏽鋼的低熱導率使得切削過程中熱量不易散發，降低了刀具壽命。雖然已有提出多種方法(如切削液的添加)改善上述問題，但會造成環境汙染及切削成本上升，因此仍希望有更佳適合的加工技術，來降低對環境之汙染與加工成本。根據相關文獻回顧，許多研究均指出超音波輔助車削技術能有效降低切削力、改善表面品質和減少工具磨損。而有限元素分析被用來模擬不同切削參數對切削力、剪切角等的影響，從而減少實驗成本和時間。
本研究目的在於以有限元素套裝軟體ANSYS建立有限元素模型，利用顯式動力學探討傳統切削與超音波輔助車削之間的差異，包含切削機制，切削力，剪切角及表面殘留應力等，並分析橢圓振動和摩擦係數對切削性能的影響。在研究方法部分，詳細介紹超音波輔助切削的原理和運動學分析，並描述超音波刀把的設計與增幅桿的設計與二維正交切削模型的力學分析，並使用Johnson-Cook材料本構方程式模擬材料的塑性變形行為。
本研究亦進行網格收斂性分析以確保模擬結果的準確性。分析結果顯示，超音波輔助車削能顯著降低切削力，尤其在低切削速度下效果更為明顯。同時，超音波輔助車削還能增加剪切角，減少切屑厚度，有助於切屑的排除和降低切削溫度。
最後，本研究討論了摩擦係數對切削性能的影響。結果顯示，降低摩擦係數能顯著減少切削力並增加剪切角，並探討了橢圓振動的優勢，指出調整垂直振幅大小可提升剪切角，但對減少切削力方面並無顯著提升，然而可經由相位角的調整改變其運動軌跡，有助於降低切削力，但會因此犧牲表面精度。而對於殘留應力的分析，橢圓振動切削能顯著的降低表面殘留拉應力，使工件在加工後具有更好的壽命與表面精度。
本研究以ANSYS顯示動力學模組開發一個有限元素模型，此模型對於切削力學、切削性能分析具有一定之可靠度，未來可基於此模型進行更深入的探討如三維超音波輔助切削、摩擦熱與熱傳導效應耦合之研究以及進一步的實驗驗證與模型修正。

This study investigates the dynamic behavior of 304 stainless steel during Ultrasonic Assisted Turning (UAT) using explicit dynamic finite element analysis with ANSYS software. Due to the high hardness, toughness, and low thermal conductivity of 304 stainless steel, conventional cutting methods result in significant cutting forces, tool wear, and high temperature issues. UAT, however, has shown to effectively reduce cutting forces, improve surface quality, decrease tool wear and reduce the use of cutting fluids.
In this study, a finite element model to compare conventional turning with UAT was established. The simulation was focused on cutting mechanisms, cutting forces, shear angles, and surface residual stresses. The Johnson-Cook material model was utilized to address the plastic deformation. A mesh convergence study was conducted to ensure the simulation accuracy.
According to the simulation results, it is found that UAT significantly reduces cutting forces at low speeds, increases shear angles. It is also observed that lower friction coefficients also reduce cutting forces and increase shear angles. The use of elliptical vibration can improve shear angles but has a slight impact on cutting force reduction and may affect surface precision. It notably reduces surface residual tensile stress, enhancing workpiece lifespan. For future studies, this work can be extended to three-dimensional UAT and further explore frictional heat and thermal conductivity effects.

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