本實驗是研究四種不同凹槽方向與五種不同凹槽深度的局部尖銳凹槽C2700黃銅圓管在循環彎曲負載下的力學行為與失效損壞，其中的四種凹槽方向分別為: 0°、30°、60°與90°，而五種不同的凹槽深度分別為: 0.2、0.4、0.6、0.8與1.0 mm，並根據實驗數據可得彎矩-曲率、橢圓化-曲率與控制曲率-循環至損壞圈數的關係圖。由實驗結果可發現，不同凹槽方向與凹槽深度對彎矩-曲率的關係影響不大，彎矩-曲率曲線皆形成一穩定的迴圈，而橢圓化-曲率關係圖均呈現棘齒與增長的趨勢，當凹槽深度越深時，正曲率的橢圓化就越高，但變化量不會太大。而當凹槽方向越大時，正曲率的橢圓化就越少，但變化量也不會太大。此外，由雙對數座標控制曲率-循環至損壞圈數的關係圖發現，在固定凹槽方向時，五種不同的凹槽深度呈現出五條不相交的直線。最後，本文採用2018年 Lee 等人所提出的不同凹槽方向與不同凹槽深度的局部尖銳凹槽SUS304不鏽鋼圓管於循環彎曲下控制曲率-循環至損壞圈數的關係式，此外，本文也提出並修改其中的材料參數，則該關係式可用來描述不同凹槽方向與不同凹槽深度的局部尖銳凹槽C2700黃銅圓管在循環彎曲下控制曲率-循環至損壞圈數的關係，在透過與實驗值比對後發現，理論能合理的描述實驗結果。

This experiment investigates the mechanical behavior and failure damage of local sharp-notched C2700 brass circular tubes under cyclic bending loads, considering four different notch orientations (0°, 30°, 60°, and 90°) and five different notch depths (0.2, 0.4, 0.6, 0.8, and 1.0 mm). The moment-curvature, ovalization-curvature, and controlled curvature-cycles to failure relationships are depicted based on experimental data. The results reveal that the notch orientation and depth have minimal impact on the moment-curvature relationship, forming stable loops. The ovalization-curvature graphs exhibit a trend of serration and growth, with deeper notch leading to higher ovalization for positive curvature, but the variation is not substantial. Additionally, larger notch orientations result in less ovalization for positive curvature, with similarly limited variation. Furthermore, the double logarithmic co-ordinates of controlled curvature-cycles to failure reveal five non-intersecting lines for different notch depths when the notch orientation is fixed. Finally, adopting the relationship proposed by Lee et al. in 2018 for local sharp-notched SUS304 stainless steel tubes under cyclic bending, this study modifies the material parameters. The modified relationship effectively describes the controlled curvature-cycles to failure for local sharp-notched C2700 brass circular tubes with different notch orientations and depths under cyclic bending, demonstrating reasonable agreement with experimental results.

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