本文針對四種不同圓孔角度及五種不同圓孔直徑的6061-T6鋁合金圓管作循環彎曲負載的實驗，並觀察其力學行為和損壞破裂的狀況，進而提出預估循環至損壞圈數的理論方程式。本次實驗中考慮的不同圓孔角度分別有:0o、30o、60o及90o，不同的圓形孔直徑分別有:2、4、6、8及10mm，而所分析的力學行為包括有:彎矩-曲度、橢圓化-曲度及控制曲度-循環至損壞圈數的關係。其中方向0o的實驗數據來自於邱易賦【28】的論文。根據實驗彎矩-曲度關係中顯示，當對稱的循環彎曲負載時，6061-T6鋁合金圓管會產生些許的循環硬化現象，且隨圈數增加漸趨於穩定迴圈，同時可以發現不同角度及不同圓孔直徑對曲線影響甚小。從橢圓化-曲度關係中可發現，在對稱循環彎曲負載下，圓孔直徑愈大或角度越小時，橢圓化增長的速度就愈快，且迴圈形成的字形就愈明顯。最後，本文參考Kyriakides 和 Shaw【3】所提出的控制曲度與循環至損壞圈數的關係式，並根據實驗數據提出經驗公式，藉以描述不同圓孔角度與不同圓孔直徑6061-T6鋁合金圓管在循環彎曲負載下的控制曲度-循環至損壞圈數關係。經過與實驗值的比較後發現，理論模式能夠合理的描述出實驗結果。

This paper is mainly to study the response and collapse of 6061-T6 aluminum alloy tubes with four different round-hole directions of 0°, 30°, 60°, and 90° and five different round-hole diameters of 2, 4, 6, 8 and 10 mm under cycling bending. The tube bending machine was used to control, measure and collect the experimental data. During the symmetrical cycling bending, it can be observed from the experimental moment-curvature curves that the loops exhibit a little bit cyclic hardening and become stable after a few bending cycles. Round-hole diameters and directions show minimal influence on the moment–curvature relationship. Next, from the experimental ovalization-curvature curves, the ovalization of the tube’s crosssection increases in asymmetrical and ratcheting manner for tubes with a small diameter and a large direction. However, a larger round-hole diameter and smaller direction leads to a more asymmetrical ovalization- curvature curve. Inaddition, a larger diameter causes a larger ovalization of the tube’s cross section. It is shown from the experimental controlled curvature- number of bending cycles required to ignite failure relationships on a log-log scale that five parallel straight lines can be found for each diameter. Finally, a theoretical formulation was proposed in this thesis to simulate the relationships between the controlled curvature and the number of bending cycles required to produce 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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