本文主要針對五種局部切痕深度之 6061-T6 鋁合金管作對稱循環彎曲負載實驗，以探討其力學行為與裂縫損壞關係。透過彎管實驗機與曲度-橢圓化量測器來進行實驗數據的控制、量測及蒐集。從實驗之彎矩-曲度曲線圖顯示，在對稱循環彎曲負載時，實驗試件皆會發生少量的循環硬化現象，且經過反覆的加載與卸載行為後，其迴圈會漸趨於穩定。其次，由實驗之橢圓化-曲度曲線圖發現，橢圓化值會隨著循環彎曲的圈數增加而成棘齒狀增加，且當橢圓化值增加到某一臨界值時，圓管便會發生裂縫而導致管件損壞。此外，由實驗之控制曲度-循環至損壞圈數關係圖可看出，控制曲度越大則損壞圈數越小，且由其雙對數座標關係圖中可發現，當切痕深度較小至較大時，控制曲度-循環至損壞圈數曲線關係斜率呈現不平行的直線。最後，本文參考 Shaw 和 Kyriakides【9】、Lee et al.【13】與范揚東【17】論文中所提出的理論方程式，並導入切痕深度後提出一個可以描述不同切痕深度圓管在循環彎曲負載時，控制曲度與循環至損壞圈數關係的理論方程式，在與實驗值做比較後發現，理論分析能充分的描述實驗結果。

This thesis investigates the mechanical behavior and buckling failure of 6061-T6 aluminum alloy tubes with five different chopped depths subjected to cycling bending. The tube bending machine and curvature-ovalization measurement apparatus were used to control, measure and collect the experimental data. From the experimental moment-curvature curve, the test specimen shows vary little cyclic hardening and becomes steady loop after a few bending cycles. From the experimental ovalization-curvature curve, the ovalization of the tube cross-section increases in a ratcheting manner with the number of cycles. When the tube ovalization reaches to a critical amount, the tube failures due to the cracks. In addition, from the controlled curvature-number of cycles to failure relationship, a higher controlled curvature leads to a lower number of cycles to produce buckling. From the aforementioned relationship on log-log scale, the controlled curvature-number of cycles to produce buckling relationships show unparallel lines from a small to a large chopped depth. Finally, by referring the theoretical formulations proposed by Shaw and Kyriakides [9], Lee et al. [13] and Y. D. Fan [17] and including the factor of the chopped depths, a theoretical formulation was proposed to simulate the relationship between the controlled curvature and the number of cycles to failure. 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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