本文研究相同截面上不同方向的多餘圓孔對6061-T6鋁合金圓孔管在循環彎曲負載下行為及損壞的影響，其中多餘圓孔與圓孔管的圓孔直徑皆為6 mm，而五種不同角度的多餘圓孔方向分別為:45°、67.5°、90°、135°及180°。根據實驗彎矩-曲率關係曲線發現，從第一循環圈數開始該曲線即呈現一穩定迴圈，而實驗橢圓化-曲率關係曲線則呈現棘齒狀的形式成長。根據實驗控制曲率-循環至損壞圈數關係曲線中發現，不同角度的多餘圓孔會影響循環至損壞圈數，至於實驗臨界橢圓化-控制曲率關係曲線中發現，控制曲率越大時臨界橢圓化就越大。最後，本文提出了理論來描述控制曲率-循環至損壞圈數與臨界橢圓化-控制曲率的關係，在與實驗結果做比較後可發現，理論能合理的描述實驗結果。

This paper is mainly to study the response and failure of 6061-T6 aluminum alloy round-hole tubes with a redundant round hole on the same cross-section and five different hole directions of 45°, 67.5°, 90°, 135°, and 180° under cycling bending. The diameters of the round hole and redundant hole are 6 mm. The experimental data include: moment-curvature curves, ovalization-curvature curves, controlled curvature- number of bending cycles required to ignite failure curves and critical ovalization- controlled curvature curves. The moment-curvature curve exhibits a stable loop from the first bending cycle. From Experimental ovalization-curvature curves, the ovalization of the tubes increases in asymmetrical and ratcheting manner. From the controlled curvature-number of bending cycles required to ignite failure curves, the number of bending cycles required to ignite failure is affected by different redundant hole directions. From the critical ovalization-controlled curvature curves, the larger controlled curvature leads the larger critical ovalization. Finally, theoretical formulations were proposed in this study to simulate the controlled curvature-number of bending cycles required to ignite failure and critical ovalization-controlled curvature relationships. By comparing the theoretical analysis with the experimental data, theoretical formulations properly simulate the experimental results.

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