本文主要利用彎管試驗機與曲度-橢圓化量測器，對兩種不同外徑/壁厚比及各五種不同深度之局部尖銳凹痕6061-T6鋁合金圓管做對稱循環彎曲負載實驗，進而探討其相關的力學與損壞行為。從實驗之彎矩-曲度關係圖中可觀察出，在對稱循環彎曲負載下，測試圓管試件皆會產生些許循環硬化的現象，經反覆的循環彎曲加載後，其關係圖中曲線迴圈會漸漸趨於穩定的狀態，而當凹痕深度或外徑/壁厚比增大時，彎矩-曲度關係曲線圖會呈不對稱。由橢圓化-曲度關係圖中可發現，橢圓化之圖形曲線會隨循環彎曲圈數的增加，曲線會呈現不對稱棘齒狀的成長。此外，外徑/壁厚比或凹痕深度越大時，橢圓化增加的速度就越快也更不對稱。由控制曲度-循環至損壞圈數的雙對數關係圖中得知，當外徑/壁厚比或凹痕深度越大時，循環至損壞圈數就越少。對個別外徑/壁厚比的五種凹痕深度，上述關係則呈現五條不平行的直線，而當外徑/壁厚比增加時，五條直線則越接近平行。最後，本文參考李致頤【20】論文中所提出的理論架構，再導入不同外徑/壁厚比因素後，提出一個新的理論方程式，可準確描述不同外徑/壁厚比不同深度局部尖銳凹痕6061-T6鋁合金圓管在循環彎曲負載下，控制曲度與循環至損壞圈數之間的關係。此理論分析與實驗數據值對照後發現，理論能充分表現實驗結果。

In this thesis, two kinds of diameter-to-thickness ratios and five different dent depths of local sharp-dent 6061-T6 aluminum alloy tubes were subjected to symmetrical cyclic bending. In order to study the response and　failure, the tube-bending machine and curvature-ovalization measurement apparatus were used to measure and collect the experimental data. From the moment-curvature relationship, it can be observed that the tubes exhibit a little cyclic hardening and become stable after a few bending cycles. When the dent depth or diameter-to-thickness ratio increases, the moment-curvature curve becomes more asymmetrical. In addition, it can be discovered from the ovalization- curvature graph that the ovalization increases with the number of bending cycles, and the curve demonstrates in an asymmetrical and ratcheting way. The larger the diameter-to- thickness ratios or the dent depths, the faster and more asymmetrical the ovalization- curvature curve. In the controlled curvature-number of bending cycles required to produce failure relationships on a log-log scale, the larger the diameter-to-thickness ratios or the dent depths, the less the number of bending cycles required to produce failure. In addition, the aforementioned relationship shows five nonparallel straight lines for each diameter-to-thickness ratio. Finally, a theoretical formulation was proposed in this thesis to simulate the aforementioned relationship. By comparing the theoretical analysis with the experimental data, it is shown that the theoretical formulation can properly simulate the experimental results.

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