本文主要探討不同切痕方向之6061-T6鋁合金管在循環彎曲負載下的力學行為及循環至損壞的影響。本文共分為實驗與理論分析兩部分進行，並比對兩部分的分析結果。
由實驗彎矩-曲度曲線中顯示，在曲度控制循環彎曲負載時，6061-T6管皆有少量的循環硬化的現象，而經過一些循環圈數後迴圈會呈現較為穩定的狀態，而切痕方向對彎矩－曲度關係幾乎沒有影響。其次，由實驗橢圓化－曲度曲線中發現，橢圓化值會隨著循環彎曲的圈數增加而呈棘齒狀的增加，且當橢圓化值增加到某一臨界值時，圓管便會發生損壞，而切痕方向對橢圓化－曲度關係有強烈的影響。此外，由實驗曲度－循環至損壞圈數關係中可看出，控制的曲度越大時，循環圈數就越少；而當角度越大，則循環圈數就越多。若將上述實驗值置於雙對數座標中可發現，四個不同方向的切痕試件其上述關係呈現四條近似平行的直線。最後，本文參考Shaw and Kyriakides【5】論文中所提出的理論方程式，並適當的導入角度因子而提出一個方程式可以用來描述不同方向的6061-T6鋁合金管在循環彎曲負載時控制曲度與循環至損壞圈數的關係。實驗與理論的比較結果顯示，理論方程式能合理的描述實驗結果。

In this thesis, the influence of different chopped directions on the mechanical behavior and fracture of chopped 6061-T6 aluminum alloy tubes subjected to cyclic bending are investigated. The material is divided into two parts, which includes experimental testing and theoretical analysis. And, the comparison between these two parts is also included.
From experimental moment-curvature curve, the 6061-T6 aluminum alloy tube shows a little bit cyclic hardening under curvature-controlled cyclic bending. After a few cycles, the loop becomes stable. The chopped direction has almost no influence on the moment-curvature relationship. Next, from the experimental ovalization- curvature curve, the ovalization increases in a ratcheting manner with the number of bending cycles. The tube will fracture when the ovalization reaches a critical value. The chopped direction has a strong influence on the ovalization-curvature relationship. In addition, from experimental controlled curvature-number of cycles to produce fracture curve, a higher controlled curvature leads to a lower number of cycles to produce fracture and a higher chopped direction leads to a higher number of cycles to produce fracture. If the aforementioned relationship is plotted on a log-log scale, four straight lines can be seen corresponding to four chopped directions. Finally, by referring the theoretical equation proposed by Shaw and Kyriakides [5] and importing the appropriate factor of the chopped direction, a theoretical formulation is proposed to simulate the relationship between the controlled curvature-number of cycles to produce fracture relationship for chopped circular tube subjected to cyclic bending. Through comparison with the experimental data, the theoretical equation can reasonably simulate the experimental results.

1. Brazier, L. G., 1927, “On the Flexure of Thin Cylindrical Shell and Other Thin Sections,” Proceedings of the Royal Society, Series A, Vol. 116, pp. 104-114.

2. Tuggu, P. and Schroeder, J., 1979, “Plastic Deformation and Stability of Pipes Exposed to External Couples,” International Journal of Solids and Structures, Vol. 15, Pp. 643-658.

3. Korol, R. M., 1979, “Critical Buckling Strains of Round Tubes In Flexure,” International Journal of Mechanics And Science, Vol. 21, pp719-730.

4. Shaw, P. K. and Kyriakides, S., 1985, “Inelastic Analysis of Thin-Walled Tubes under Cyclic Bending,” International Journal of Solids and Structures, Vol. 21, pp. 1073-1100.

5. Shaw, P. K. and Kyriakides, S. , 1987, “Inelastic Buckling of Tubes Under Cyclic Bending,” ASME, Journal of Pressure Vessel Technology, Vol. 109, pp. 169-178.

6. Ju, G. T. and Kyriakides, S., 1992, “Bifurcation Buckling Versus Limit Load Instabilities of Elastic-Plastic Tubes under Bending and External Pressure,” Journal of Offshore Mechanics and Arctic Engineering, Vol. 113, pp. 43-52.

7. Pan, W. F., Wang, T. R. and Hsu, C. M., 1998, “A Curvature- Ovalization Measurement Apparatus for Circular Tubes under Cyclic Bending,” Experimental Mechanics, Vol. 38, No.2, pp. 99-102.

8. Pan, W. F., and Her Y. S., 1998, “Viscoplastic Collapse of Thin-Walled Tubes under Cyclic Bending,” ASME Journal of Engineering Materials and Technology, Vol. 120, pp. 001-004.

9. Pan, W.F. and Fan, C.H.,1998,”An Experimental Study on the Effect of Curvature-Rate at Preloading Stage on Subsequent Creep on Relaxation of Thin-Walled Tubes under Pure Bending,”JSME International Journal, Series A, Vol.41, No.4,pp.525-531.

10. Lee, K. L., Pan, W. F. and Kuo, J. N., 2001, “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, pp. 2401-2413.

12. Lee, K. L. and Pan, W. F., 2002, “Pure Bending Creep of SUS 304 Stainless Steel Tuber,” Steel and Composite Structures - an International Journal, Vol. 2, No.6, pp. 461-474.

13. Lee, K. L., Shie, R. F. and Chang, K. H., 2005, “Experimental and
Theoretical Investigation of the Response and Collapse of 316L Stainless Steel Tubes Subjected to Cyclic Bending,” JSME International Journal, Series A, Vol. 48, No.3, pp. 155-162 .

14. Chang, K.H., Pan, W.F. and Lee, K.L., 2008, “Mean Moment Effect
on Circular Thin-walled Tubes under Cyclic Bending,” Structural
Engineering and Mechanics - an International Journal, Vol. 28, No.5,
pp. 495-514.

15. 廖信智，2009，「尖銳凹槽薄壁管在循環彎曲負載下黏塑性皺曲行為之研究」，國立成功大學工程科學研究所碩士論文。

16. 翁弘杰，2011，「尖銳凹槽圓管在循環彎曲負載下平均曲度對皺曲行為影響之實驗研究」，國立成功大學工程科學研究所碩士論文。

17. 張育生，2012， 「尖銳凹槽圓管在純彎曲負載下潛變行為之實驗研究」，國立成功大學工程科學研究所碩士論文。

18. 劉穎哲，2013， 「不同方向局部尖銳凹槽圓管在循環彎曲負載下行為之研究」，國立成功大學工程科學研究所碩士論文。