本文利用彎管試驗機及曲度－橢圓化量測器來進行不同外徑/壁厚比（D/t比）316L不銹鋼管的循環彎曲負載至皺曲的實驗，四種不同D/t比分別為30、40、50、60，實驗將觀察316L不銹鋼管的彎曲力矩、彎曲曲度、管徑橢圓化及到達皺曲時循環圈數之間的相互關係。
　　由實驗結果顯示，在彎曲曲度與彎曲力矩的關係圖形中，316L不銹鋼管會隨著循環彎曲次數的增加而呈現循環硬化的現象，但最後會到達一穩定的迴圈。至於管徑橢圓化與彎曲曲度的關係圖形中，管徑橢圓化會呈現棘齒狀的變化，而隨著循環次數的增加管徑橢圓化也會漸漸的增加。此外，當D/t比越大時，以同樣的曲度進行循環彎曲所需要的彎曲力矩值的會越小，而橢圓化的累積速率會越快，使得皺曲發生所需的圈數會越少。最後，由控制曲度量與循環至皺曲圈數的對數關係圖中發現，四組D/t比分別對應出四條經由最小平方法所求得的直線幾乎平行。因此，本文引用Kyriakides　and　Shaw　[3]及Lee等人[10]所提出的理論進行描述，並將實驗和理論結果進行比較，結果顯示理論能合理的描述實驗結果。

This thesis uses the bending-tube device and curvature-ovalization measurement apparatus to test the 316L stainless steel tubes with different diameter/thickness ratios (D/t ratios) subjected to cyclic bending. Four different D/t ratios of the tubes are 30, 40, 50 and 60. The relationship among the bending moment, bending curvature, tube ovalization and number of cycles to produce buckling of the 316L stainless steel tubes will investigate.
It is shown from the experimental result that the 316L stainless steel tube exhibits cyclic hardening along with the bending cycle from the moment- curvature curve. But the moment-curvature loop gradually becomes steady after a few cycles. As for the relationship between the ovalization and curvature, the ovalization exhibits a ratcheting manner with the number of the bending cycles. However, when the bending cycle increases, the ovalization also gradually increases. In addition, when the D/t ratio is higher, the bending moment is lower for cyclic bending with a same amount of the controlled curvature. However, the accumulation speed of the tube ovalization is fast so that the number of cycles to produce buckling reduces. Finally, form the relationship between the controlled curvature and number of cycles to produce buckling in log-log scale, four straight lines (correspond to four different D/t ratios) determined by least square method, are almost parallel to each other. Therefore, the theoretical models proposed by Kyriakides and Shaw [3] and Lee et al. [10] are used in this simulation. Based on the comparison between the theoretical analysis and experimental results, it is shown that the theory can properly simulate the experimental finding.

1、S.Kyriakides and P.K.Shaw,“Response and Stability of Elastoplastic Circular Pipes Under Combined Bending and External Pressure”,International Journal of Solids and Structures, Vol. 18, pp.957-973 (1982)。
2、P.K.Shaw and S.Kyriakides,“Inelastic Analysis of Thin-Walled Tubes Under Cyclic Bending”,International Journal of Solids and Structures, Vol. 21, pp.1073-1100 (1985)。
3、S.Kyriakides and P.K.Shaw,“Inelastic Buckling of Tubes Under Cyclic Bending”,Journal of Pressure VesselTechnology, Vol.109,pp.169-178(1987)。
4、E.Corona and S.Kyriakides,“On the Collapse of Inelastic Tubes Under Combined Bending and Pressure”,Int. J. Solids Structures,Vol.24,No.5,pp.505-535(1988)。
5、E.Corona and S.Kyriakides,“An Experimental Investigation Degradation and Buckling of Circular Tubes Under Cyclic Bending and Buckling of Circular Tubes Under Cyclic Bending and External Pressure”, Thin-Walled Structures Vol.12, pp.229-263(1991)。
6、S.Kyriakides and G.T.Ju,“Bifurcation and Localization Instabilities in Cylindrical Shells Under Bending-Ⅰ. Experiments”,Int. J. Solids Structures,Vol.29,No.9, pp.1117-1142(1991)。
7、W.F.Pan and K.T.Leu, “Endochronic Analysis for Viscoplastic Collapse of a Thin-Walled Tube Under Combined Bending and External Pressure”, JSME International Journal, Series A, Vol. 40, pp189-199(1997)。
8、W.F.Pan, T.R.Wang and C.M.Hsu,“ A Curvature-ovalization Measurement Apparatus for Circular Tubes Under Cyclic Bending”,Experimental Mechanics Vol.38, No. 2, pp99-102 (1998)。
9、W.F.Pan and Y.S.Her,“Viscoplastic Collapse of Thin-Walled Tubes Under Cyclic Bending”,Journal of Engineering Materials and Technology,Vol.120,pp.287-290 (1998)。
10、李國龍, “圓管在不同外徑/壁厚比及不同曲度率循環彎曲負載下皺曲行為之研究“, 國立成功大學博士論文(2000)。
11、K.L.Lee, W.F.Pan and J.N.Kuo,“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 (2001)。
12、K.L.Lee and W.F.Pan, “Viscoplactic CollapseofTitanium Alloy Tubes Under Cyclic Bending“,Structural Engineering and Mechanics,Vol.11, No.3,pp.315-324 (2001)。
13、W.F.Pan and K.L.Lee,“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)。
14、李慶峰, “316L不銹鋼圓管在不同彎曲曲度率循環彎曲負載下對皺曲行為影響之實驗研究“ ,國立成功大學碩士論文(2003)。