本次實驗是研究四種不同圓孔方向與五種不同圓孔直徑的C2700黃銅圓孔管在循環彎曲負載下的力學行為以及失效損壞，其中不同的圓孔方向分別有:0、30、60與90，而不同的圓孔直徑分別有:2、4、6、8與10 mm，並根據實驗收集到的數據繪出: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。實驗結果發現，不同圓孔方向與圓孔直徑對彎矩-曲率的關係幾乎沒有太大的影響，但對橢圓化-曲率的關係則有強烈的影響。當圓孔方向固定時，隨著圓孔直徑越大，橢圓化-曲率的關係呈現由棘齒狀的增長模式，變成半蝴蝶狀的增長模式，到蝴蝶狀的增長模式。當圓孔直徑固定時，隨著圓孔方向越大，橢圓化-曲率的關係呈現由蝴蝶狀的增長模式、變成半蝴蝶狀的增長模式，到棘齒狀的增長模式。此外，在雙對數座標控制曲率-循環至損壞圈數的關係呈現斜率相近的直線，所以本文使用2019 年Lee 等人所提出的不同圓孔方向與不同圓孔直徑 6061-T6鋁合金圓孔管在循環彎曲下控制曲率-循環至損壞圈數的關係式，來描述不同圓孔方向與不同圓孔直徑的C2700黃銅圓孔管在循環彎曲下控制曲率-循環至損壞圈數的關係，在與實驗值進行比對後發現，理論能合理的描述實驗結果。

This experiment is to study the behavior and failure of C2700 brass round hole tubes with four different hole directions and five different hole diameters subjected to cyclic bending. The different hole directions are 0  , 30  , 60  and 90  , and the different hole diameters are 2, 4, 6, 8 and 10 mm. The experimental results show t hat different hole directions and hole diameters have little effect on the moment curvature relationship but they have a strong influence on the ovalization curvature relationship. When the hole direction is fixed, as the hole diameter increases, the relationship between ovalization and curvature changes from a ratchet shaped growth pattern to a butterfly shaped growth pattern. When the hole diameter is fixed, as the hole direction increases, the relationship between ovalization and curvature changes from a butterfly shaped growth pattern to a ratchet shaped growth pattern. In addition, in double logarithmic coordinates, the relationship s between curvature and the number of cycles needed to initiate failure present straight line s with a similar slope Therefore, this study uses the theory proposed by Lee et al. in 2019 to describe the relationship s between curvature and the number of cycles needed to initiate failure for C2700 brass round hole tube s with different hole directions and different hole diameters under cyclic bending. After comparing with the experimental data , it is found that the theory can reasonably describe the experimental results.This experiment is to study the behavior and failure of C2700 brass round hole tubes with four different hole directions and five different hole diameters subjected to cyclic bending. The different hole directions are 0  , 30  , 60  and 90  , and the different hole diameters are 2, 4, 6, 8 and 10 mm. The experimental results show t hat different hole directions and hole diameters have little effect on the moment curvature relationship but they have a strong influence on the ovalization curvature relationship. When the hole direction is fixed, as the hole diameter increases, the relationship between ovalization and curvature changes from a ratchet shaped growth pattern to a butterfly shaped growth pattern. When the hole diameter is fixed, as the hole direction increases, the relationship between ovalization and curvature changes from a butterfly shaped growth pattern to a ratchet shaped growth pattern. In addition, in double logarithmic coordinates, the relationship between curvature and the number of cycles needed to initiate failure present straight line s with a similar slope Therefore, this study uses the theory proposed by Lee et al. in 2019 to describe the relationships between curvature and the number of cycles needed to initiate failure for C2700 brass round hole tubes with different hole directions and different hole diameters under cyclic bending. After comparing with the experimental data , it is found that the theory can reasonably describe the experimental results.

1. Shaw, P. K. and Kyriakides, “Inelastic analysis of thin-walled tubes under cyclic bending”, International Journal of Solids and Structures, Vol. 21, No. 11, pp. 1073-1100 (1985).
2. Kyriakides, S. and Shaw, P. K., “Inelastic buckling of tubes under cyclic bending,” Journal of Pressure Vessel and Technology, Vol. 109, No. 2, pp. 169-178 (1987).
3. Pan, W. F., Wang, T. R. and Hsu, C. M, “A curvature-ovalization measurement apparatus for circular tubes under cyclic bending”, Experimental Mechanics, Vol. 38, No. 2, pp. 99-102 (1998).
4. Pan, W. F. and Her, Y. S., “Viscoplastic collapse of thin-walled tubes under cyclic bending”, ASME Journal of Engineering Materials and Technology, Vol. 120, No. 4, pp. 287-290 (1998).
5. Lee, K. L., Pan, W. F. and Kuo, J. N., “The influence of the diameter-to-thickness ratio on the stability of circular tubes under cyclic bending”, International Journal of Solids and Structures, Vol. 38, No. 14, pp. 2401-2413 (2001).
6. Lee, K. L. and Pan, W. F. “The effect of mean curvature on the response and collapse of thin-walled tubes under cyclic bending”, JSME International Journal, Series A, Vol. 45, No. 2, pp. 309-318 (2002).
7. Lee, K. L., Pan, W. F. and Hsu, C. M. “Experimental and theoretical evaluations of the effect between diameter-to-thickness ratio and curvature-rate on the stability of circular tubes under cyclic bending, JSME International Journal, Series A, Vol. 47, No. 2, pp. 212-222 (2004).
8. Chang, K. H., Hsu, C. M., Sheu, S. R. and Pan, W. F. “Viscoplastic response and collapse of 316L stainless steel under cyclic bending”, Steel and Composite Structures, Vol. 5, No. 5, pp. 359-374 (2005).
9. Chang, K. H., Pan, W. F. and Lee, K. L., “Endochronic simulation for the response of 1020 carbon steel tubes under symmetric and unsymmetric cyclic bending with or without external pressure”, Steel and Composite Structures, Vol. 8, No. 2, pp. 99-114 (2008).
10. CoronaCorona, , E. and KyriakidesE. and Kyriakides, , S., “An experimental invS., “An experimental investigation of the degradation estigation of the degradation and buckling of circular tubes under cyclic bending and external pressure”, Thinand buckling of circular tubes under cyclic bending and external pressure”, Thin--Walled Structures, Vol. 12, No. 3, pp. 229Walled Structures, Vol. 12, No. 3, pp. 229--263 (1991)263 (1991).
11. Chang, K. H., Pan, W. F. and Lee, K. L. “Mean moment effect on circular thin-walled tubes under cyclic bending”, Structural Engineering and Mechanics, Vol. 28, No. 5, pp. 495-514 (2008).
12. Lee, K. L., Hung, C. Y. and Pan, W. F., “Variation of ovalization for sharp-notched circular tubes under cyclic bending”, Journal of Mechanics, Vol. 26, No. 3, pp. 403- 411 (2010).
13. Lee, K. L., Pan, W. F. and Hsu, C. M. “The influence of diameter-to-thickness ratios on the response and collapse of sharp-notched circular tubes under cyclic bending”, Journal of Mechanics, Vol. 28, No. 3, pp. 461-468 (2012).
14. Lee, K. L., Pan, W. F. and Hsu, C. M. “Viscoplastic collapse of sharp-notched circular tubes under cyclic bending”, Acta Mechanica Solida Sinica, Vol. 26, No. 6, pp. 629- 641 (2013).
15. Lee, K. L., Chung, C. C., and Pan, W. F., “Growing and critical ovalization for sharp-notched 6061-T6 aluminum alloy tubes under cyclic bending” Journal of Chinese Institute of Engineers, Vol. 39, No. 8, pp. 926-935 (2016).
16. ChungChung, , C. C., C. C., Lee, Lee, K. L. and K. L. and Pan, Pan, W. FW. F.., “, “Collapse of sharpCollapse of sharp--notched 6061notched 6061--T6 T6 aluminum alloy tubes under cyclic bending”aluminum alloy tubes under cyclic bending”,, International Journal of Structural Stability and Dynamics, Vol. 16, No. 7, 1550035 [24 pages] (2016), Vol. 16, No. 7, 1550035 [24 pages] (2016).
17. LeLee, e, K. L., K. L., Chang, Chang, K. H. and K. H. and Pan, Pan, W. F., “Effect of notch depth and direction on W. F., “Effect of notch depth and direction on stability of local sharpstability of local sharp--notnotched circular tubes subjected to cyclic bending”, ched circular tubes subjected to cyclic bending”, International Journal of Structural Stability and Dynamics, Vol. 18, No. 7, 1850090 International Journal of Structural Stability and Dynamics, Vol. 18, No. 7, 1850090 [23 pages] (2018)[23 pages] (2018).
18. LeLee, e, K. L., K. L., Weng, MWeng, M. . LL. and . and Pan, Pan, W. F.,W. F., “On the failure of round“On the failure of round--hole tubes under hole tubes under cyclic bending”, Journal of Chinese Society of Mechanical Engineering, Vol.cyclic bending”, Journal of Chinese Society of Mechanical Engineering, Vol. 40, 40, No. 6No. 6, , pp. 663pp. 663--673 (2019).673 (2019).
19. LeLee, e, K. L., K. L., LLiu, H. Y., iu, H. Y., and and Pan, Pan, W. F.,W. F., “Response of round“Response of round--hole tubes submitted to hole tubes submitted to pure bending creep and pure bending creep and pure bending relaxation”, Advances in Mechanical pure bending relaxation”, Advances in Mechanical Engineering, Vol. Engineering, Vol. 13, No. 13, No. 9, pp. 19, pp. 1--17 (2021).17 (2021).
20. LeLee, e, K. L., K. L., Hsu, C. M., Hsu, C. M., and and Pan, Pan, W. F.W. F., “Response of sharp, “Response of sharp--notched circular tubes notched circular tubes under bending creep and relaxation”,under bending creep and relaxation”, Mechanical Engineering JournalMechanical Engineering Journal, Vol. , Vol. 11, No. , No. 2, pp. 12, pp. 1--14 (2014).14 (2014).