本文係實驗研究平均曲率對6061-T6圓孔管在循環彎曲負載下的力學行為(彎矩－曲率與橢圓化－曲率的關係)與失效損壞(曲率－循環至損壞的關係)的影響，至於平均曲率的影響則是考慮四種不同曲率比r (最小曲率/最大曲率)，分別為-1、-0.5、0與0.5，而圓孔管的圓孔直徑則分別為:2、4、6、8與10 mm。根據實驗的結果顯示，在固定r時，圓孔直徑對彎矩－曲率的關係幾乎沒有影響，但圓孔直徑對橢圓化－曲率的關係則有劇烈的影響，且圓孔直徑越大時橢圓化增加就越快。當r = -1時，彎矩－曲率的關係從第一圈開始即呈現出一個彈-塑性且穩定的迴圈，至於橢圓化－曲率的關係則呈現不對稱、蝴蝶結狀且增加的趨勢。而當r = -0.5、 0與0.5時，由於曲率範圍縮小的緣故，使得彎矩－曲率的關係從第二圈開始即呈現出一個彈性的線性路徑，且隨著循環圈數的增加，線性路徑會有些許鬆弛後即呈現一穩定的線性路徑，由於變形皆在彈性的範圍內，也因此橢圓化呈現非常緩慢的增加趨勢。
而在固定圓孔直徑時，四種不同r的曲率-循環至損壞圈數雙對數座標關係呈現幾乎相互平行的直線。最後，本文提出理論來描述6061-T6圓孔管在不同r循環彎曲負載下的曲率-循環至損壞圈數關係，在與實驗結果相互比較後發現，此理論可合理的描述實驗結果。

This study experimentally investigated the behavior and failure of 6061-T6 aluminum alloy round-hole tubes with different hole diameters under cyclic bending at and different curvature ratios. Five different hole diameters of 2, 4, 6, 8 and 10 mm, and the four different curvature ratio (r) of -1, -0.5, 0 and 0.5 are considered. From the experimental results, for a fixed r, hole diameter has almost no influence on the moment-curvature relationship. But, hole diameter has a strong influence on the ovalization-curvature relationship. When r = -1, moment-curvature relationship shows a stable loop from the first cycle. The ovalization-curvature relationship shows an increasing, asymmetrical, and bow-shape trend. When r = -0.5, 0 and 0.5, because the range of controlled curvature is reduced, the moment-curvature relationship shows an elastic loop from the second cycle. And with the increase of the number of cycles, the linear path gradually shows a stable linear path after a little relaxation. Since the deformation is within the elastic range, the ovalization shows a very slow increasing trend.
When the diameter of the round hole is fixed, the controlled curvature-number of cycles required to ignite failure relationships with different r in double logarithmic coordinates present almost parallel straight lines for each hole diameter. Finally, this research proposes a theory to describe the aforementioned relationship. After comparing with the experimental results, it is found that this theory can reasonably describe the experimental results.

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