本文主要研究不同方向局部尖銳凹槽SUS304不鏽鋼管在不同的曲度率循環彎曲負載下的力學行為與皺曲損壞。其中不同的曲度率分別為：0.35、0.035及0.0035 m-1s-1，而不同方向分別為0o、30o、60o及90o。從彎矩-曲度關係圖中顯示，當加載曲度率較快時，則彎矩-曲度之迴圈較大，反之，彎矩-曲度圖之迴圈則較小。而在同一曲度率下，凹槽的方向對彎矩-曲度的關係幾乎沒有影響。其次，當曲度率較快時，則橢圓化-曲度關係成長的速度較快，而當固定凹槽深度時，隨著角度的增加，橢圓化-曲度關係會從不對稱趨於對稱的趨勢。
最後，本文參考Kyriakides and Shaw【5】論文中所提出的控制曲度與循環至皺曲圈數之關係式，並根據實驗數據提出相關的理論來描述不同方向局部尖銳凹槽SUS 304不鏽鋼承受不同曲度率循環彎曲負載的控制曲度與循環至皺曲圈數關係。經與實驗比對驗證後發現，此理論方程式合理的描述出實驗結果。

關鍵字:局部尖銳凹槽、橢圓化、凹槽方向、循環彎曲、曲度率

This paper studies the mechanical behavior and buckling failure of local sharp-notched SUS304 stainless steel tubes for different notch directions under cyclic bending with different curvature-rates. Wherein the different curvature-rates were: 0.35, 0.035 and 0.0035 m-1s-1, respectively, and different directions were: 0o, 30o, 60o and 90o, respectively. From the moment-curvature relationship, a faster curvature-rate leads to a larger loop of the moment-curvature relationship, on the contrary, a lower curvature-rate leads to a smaller loop of the moment-curvature relationship. However, for a certain curvature-rate, the notch direction has almost no influence on the moment-curvature relationship. Next, the ovalization-curvature relationship increases faster for a higher curvature-rate. The ovalization-curvature relationship changes from unsymmetry to symmetry along with the increasing notch direction when a fixed notch depth is considered.
Finally, by referring to the paper from Kyriakides and Shaw【5】of the formulation between the controlled curvature and number of cycles to produce buckling and by the experimental data, a related formulation was proposed for simulating the relationship between the controlled curvature and number of cycles to produce buckling of local sharp-notched SUS304 stainless steel tubes for different notch directions under cyclic bending with different curvature-rates. By comparing with the experimental data, the theoretical formulation can properly describe the experimental result.

Key words: Local Sharp-notch, Ovalization, Notch Direction, Cyclic Bending, Curvature-Rate

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

3. 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.

4. Shaw, P. K. and Kyriakides, S., 1982, “Inelastic Analysis of Thin-Walled Tubes under Cyclic Bending,” International Journal of Solids and Structures, Vol. 18, pp. 957-973.

5. 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.

6. 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.
7. Corona, E. and Kyriakides, S., 1988, “On the Collapse of Inelastic Tubes under Combined Bending and Pressure,” International Journal of Solids and Structures, Vol. 24, pp. 505-535.

8. Corona, E. and Kyriakides, S., 1991, “An Experimental Investigation Degradation and Buckling of Circular Tubes under Cyclic Bending and External Pressure,” Thin-Walled Structures, Vol. 12, pp. 229-263.

9. 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.

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

11. 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.

12. 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.

13. 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.

14. 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.

15. Lee, K. L., Pan, W. F. and Hsu, C. M., 2004, “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.

16. 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 .

17. 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.

18. 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。

19. 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。

20. 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。

21. 潘文峰，2014， 「不同方向局部尖銳凹槽圓管承受循環彎曲負載下行為影響之實驗研究」，九十週年校慶基礎學術研討會會議論文。