本文以實驗及理論的方式來探討五種不同材料圓管在循環彎曲負載下彈塑性力學行為及皺曲損壞之行為。實驗是以『彎管實驗機』及『曲度-橢圓化量測器』對圓管進行實驗，而理論則是採用內涵時間理論及虛功原理來分析圓管在循環彎曲負載時彎矩、曲度及橢圓化關係。從彎矩-曲度的實驗曲線中顯示，在對稱曲度循環彎曲負載時，本文所採用所有不同材料圓管皆呈現循環硬化的現象，而經過了一些循環圈數後迴圈會變的較穩定。而從橢圓化-曲度的實驗曲線中顯示，在對稱曲度循環彎曲負載時橢圓化會漸增且呈對稱棘齒的變化，橢圓化量會一直增加直到圓管發生皺曲。從控制曲度及循環至皺曲圈數的實驗曲線中顯示，控制循環曲度量越大時，循環至皺曲圈數就越少。最後，本文修改1987年Kyriakides與Shaw所提出的理論模式，使該理論架構可用來描述不同材料圓管在循環彎曲負載時控制曲度和循環彎曲至皺曲圈數的關係。理論分析和實驗結果進行比較後發現，理論能合理的描述實驗結果。

This paper discuss the thin and circular tubes of five kinds of different materials by the way of experiments and theories, including SUS 304 is managed with 316L stainless steel, 7005- T53 aluminum tube and C2700 copper tube and titanium alloy tube ,which were researched the mechanical behavior of the elasticity and plasticity, and buckling failure of circular tubes subjected to cyclic bending. The experiment of circular tubes subjected to cyclic bending is in charge of the experiment with the “tube bending machine” and “curvature-ovalization measurement apparatus.” The theory part is to adopt the endochronic theory for the basic theory of the deformation of the elasticity and plasticity, cooperate with the principle of virtual work to derive the essential balance equation. We also use one group of Fourier series to approximate to in charge of every some displacement on the section while being round to spread, trying to get the relationship of the moment, curvature and ovalization from the each other corresponding parameter. Shown by the experiment and theory result: Circular tubes of different materials subjected to symmetrical and cyclic bending, we will get the situation of the strain hardening. After the cyclic bending, the moment and the curvature will get the steady states gradually.The diameter of tube will present the behavior of ovalization , the ovalization of the tube cross-section increases in a ratcheting manner with the number of cycles.Owing to the progressive accumulation of the ovalization of the tube cross-section during cyclic bending.In addition as controlled curvature getting bigger, the number of cycles of buckling failure is getting less. Conversely, the controlled curvature getting less, the number of cycles of buckling failure is getting bigger.Finally, the relationship of the controlled curvature from the experiment and the number of cycles of buckling failure, we will use the theory which advanced by Kyriakides and Shaw in 1987, try to get the corresponding parameters.

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