本研究主要探討不同內、外直徑對於薄壁圓管在循環彎曲負載下的力學行為與結構穩定性的影響。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。
實驗方面：本文使用三種不同內、外直徑的SUS 304無縫不銹鋼管，並將圓管的外直徑加以車削以達一特定的外直徑/壁厚比，再運用彎管試驗機及曲度-橢圓化量測器來進行不同的曲率控制循環彎曲負載至皺曲的實驗。實驗結果顯示SUS 304不銹鋼圓管在承受對稱循環彎曲作用下，會出現材料硬化現象，而控制曲率愈大，圓管彎曲達控制曲率所需力矩也愈大，且橢圓化累積速度也會愈快，使得彎曲達皺曲破壞所需循環圈數愈少。
理論方面：本文利用Kyriakides與Shaw【4】控制曲率和循環彎曲負載至皺曲次數的理論模式，並修改Lee、Pan與Kuo【11】所提出的外直徑/壁厚比的相關參數後，本文所提出的理論架構可用來描述不同內、外直徑的SUS 304圓管的控制曲率和循環彎曲負載至皺曲次數關係。理論分析的結果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 thesis presents the results on the influence of the different inside and outside diameters to the response and stability of circular tubes subjected to symmetrical cyclic bending. The research is divided into two parts, which includes experimental testing and theoretical analysis.
For experimental aspect, there are three different inside, outside diameters of SUS 304 stainless steel circular tubes. For obtaining the desired outside-diameter/wall-thickness ratio, the outside diameter of the tube is machined. The “bending testing machine” and the “curvature-ovalization measurement apparatus” are used to test the behavior of circular tubes under cyclic bending. The experiment is a curvature-controlled cyclic bending test. It can be observed from experiment data that the SUS 304 stainless steel circular tube under cyclic bending show a hardening phenomenon. It can be also observed that the higher the control curvature, the higher is the required moment of circular tubes to bend. Due to the increasing of the accumulating speed of the tube ovalization, the number of cycles to produce buckling decreases.
For theoretical aspect, the controlled curvature and the number of cycles to produce buckling model proposed by Kyriakides and Shaw【4】is used in this study. By modifying the related parameter of the outside-diameter/ wall-thickness ratio proposed by Lee、Pan and Kuo【11】, the new theoretical structure is used to simulate the relationship between the controlled curvature and the number of cycles to produce buckling for different inside and outside diameters of the SUS 304 stainless steel circular tubes under cyclic bending. By comparing the theoretical analysis result with the experimental result, it is shown that the theory can properly simulate the experimental data.

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