本文研究不同外徑/壁厚比與不同圓孔直徑的6061-T6鋁合金圓孔管在不同曲率比循環彎曲負載下的響應與失效，其中的不同外徑/壁厚比有:16.5、31.0與60.0，不同圓孔直徑有: 2、4、6、8與10 mm，而不同曲率比有:-1、-0.5、0與0.5。根據實驗結果顯示，不同圓孔直徑對於彎曲-曲率的關係幾乎沒有影響，但對橢圓化-曲率的關係則有顯著的影響。當曲率比為-1時，從第一個循環圈數開始，彎曲-曲率關係即呈現為一個穩定的迴圈關係，而橢圓化-曲率的關係則呈現棘齒、增長與不對稱的趨勢。當曲率比為 -0.5、0或0.5時，由於曲率範圍變小，導致彎矩-曲率從第二個循環圈數起即呈現線彈性的關係，且隨著循環圈數的增加，該關係會有些許鬆弛但之後很快又會回到一個穩定的狀態。此外，當固定外徑/壁厚比時，各別圓孔直徑的曲率範圍-循環至損壞圈數雙對數座標關係顯示，四種不同曲率比對應出四條相互平行的直線。最後，本文使用Lee等人[14]所提出理論來描述不同外徑/壁厚比與不同圓孔直徑的6061-T6鋁合金圓孔管在不同曲率比循環彎曲負載下曲率範圍-循環至損壞圈數的關係，在與實驗結果進行比較後發現，理論可合理的描述實驗結果。

SUMMARY
This paper mainly studies the response and failure of 6061-T6 aluminum alloy round-hole tubes with different diameter-to-thickness ratios and different hole diameters subjected to cyclic bending with different curvature ratios. The different diameter-to-thickness ratios are: 16.5, 31.0 and 60.0, the different hole diameters are: 2, 4, 6, 8 and 10 mm, and the different curvature ratios are: -1, -0.5, 0 and 0.5. According to the experimental results, different hole diameters have little effect on the relationship between moment and curvature, but they have a significant effect on the relationship between ovalization and curvature. When the curvature ratio is -1, from the first cycle, the moment-curvature relationship presents a stable loop. However, the ovalization-curvature relationship shows an asymmetrical, ratcheting, growing and bowtie trend. When the curvature ratio is -0.5, 0 or 0.5, since the curvature range becomes smaller, the moment-curvature relationship shows a linear elastic trend from the second cycle. As the number of cycles increases, the relationship depicts a little relax but quickly becomes a steady state. In addition, when the diameter-to-thickness ratio is fixed, the relationships between the curvature range and the number of cycles needed to initiate failure for each hole diameter in double logarithmic coordinates show four mutually parallel straight lines correspond to four different curvature ratios. Finally, this study employs the theory proposed by Lee et al. in 2021 to describe the aforementioned relationships. After comparing the theoretical analysis with the experimental result, it is found that the theory can reasonably describe the experimental result.

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