本文利用彎管實驗機及曲度-橢圓化量測器，針對局部尖銳凹槽深度為0.2、0.4、0.6、0.8、1.0 mm的SUS304不鏽鋼管，進行對稱曲度控制循環彎曲負載的實驗，以探討其相關的力學行為與皺曲損壞。由實驗結果可知，局部尖銳凹槽圓管的彎矩-曲度關係隨循環圈數的增加，漸漸呈現一穩定的迴圈，且凹槽深度對彎矩-曲度關係幾乎沒有影響。至於橢圓化-曲度關係則隨著循環彎曲圈數的增加而呈現棘齒狀的成長，且凹槽深度越深，橢圓化-曲度關係就越不對稱，橢圓化增加就越大。此外，實驗結果也顯示，雖然實驗有五種局部尖銳凹槽的深度，但在雙對數座標的控制曲度-循環至皺曲圈數關係卻呈現五條幾乎平行的直線。最後，本文提出理論方程式來描述不同局部尖銳凹槽深度圓管在對稱曲度控制循環彎曲負載下控制曲度-循環至皺曲圈數的關係，在與實驗結果比較後發現，方程式能夠合理描述實驗結果。

In this study, the tube-bending machine and curvature-ovalization measurement apparatus are used to test SUS 304 stainless steel tubes with the local sharp-notched depths of 0.2, 0.4, 0.6, 0.8 and 1.0 mm under curvature-controlled symmetrical cyclic bending for investigating the relative mechanical behavior and buckling failure. From experimental result, when the number of cycles increases, the moment-curvature relationship becomes a steady loop for local sharp-notched circular tube. And, the notch depth does not have any influence on the moment-curvature relationship. As for the ovalization-curvature relationship, when the number of cycles increases, it exhibits an increasing and ratcheting manner. It can be seen that the greater the depth of the notch, the more unsymmetrical ovalization-curvature relationship and the greater the increase of the ovalization.
In addition, the experimental result shows that although five local sharp-notched depths are tested, but five almost parallel straight lines are found for the controlled curvature-number of cycles to produce buckling relationship in the log-log scale. Finally, the theoretical equation is proposed in this study for simulating the controlled curvature-number of cycles to produce buckling relationship for local sharp-notched circular tube subjected to curvature-controlled symmetrical cyclic bending. Through comparison with the experimental data, the equation can properly simulate the experimental finding.

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