本論文以具有0.2 mm深度尖銳凹槽之SUS304不鏽鋼管，進行不同平均彎矩循環彎曲負載的實驗。實驗以曲度－橢圓化量測器收集曲度、橢圓化及循環至皺曲圈數之實驗數據；再利用數據深入探討五種不同彎矩比r = −1、−0.75、−0.5、−0.25及0在不同彎矩範圍之條件下，求得彎矩-曲度、彎矩-橢圓化以及彎矩範圍-循環至皺曲圈數之關係。
實驗結果顯示，當對稱彎矩控制循環彎曲負載時，彎矩-曲度迴圈會向內縮，且迴圈呈現由大變小，並在一些循環數圈後便呈現穩定現象。當不對稱彎矩控制循環彎曲負載時，彎矩-曲度迴圈呈現循環棘齒狀往正方向移動，且在一些循環數圈後也呈現穩定現象。由彎矩範圍與循環至皺曲圈數之關係圖可發現，彎矩-橢圓化關係越對稱，越不容易發生皺曲，圓管壽命也越長；而彎矩與橢圓化關係越不對稱，越容易發生皺曲，圓管壽命也越短。最後，本論文提出ㄧ方程式來描述彎矩範圍與循環至皺曲圈數的關係，理論分析和實驗結果比較後發現，理論能合理的描述實驗結果。

This thesis investigates the buckling of 0.2-mm-sharp-notched circular tubes with different mean moment under cyclic bending. In this experiment, the curvature-ovalization measurement apparatus is used to collect the curvature, ovalization and number of cycles to produce buckling. Five different moment ratios r = -1, -0.75, -0.5, -0.25 and 0 under different curvature ranges are investigated. The relationships of moment-curvature, moment-ovalization and moment range-number of cycles to produce buckling can be found.
It is shown from experimental data that the moment-curvature loop shrinks for symmetric moment-controlled cyclic bending. The loop exhibits from large to small shape and becomes steady after a few cycles. It is shown that the moment-curvature loop demonstrates the ratcheting and moving to the right for unsymmetric moment-controlled cyclic bending. The loop also becomes steady after a few cycles. It can be seen from the relationship between the moment range and number of cycles to produce buckling that the tube’s life is longer if the moment-ovalization relationship is more symmetric. However, the tube’s life is shorter if the moment-ovalization relationship is more unsymmetric. Finally, an equation is proposed in this thesis for simulating the relationship between the moment range and number of cycles to produce buckling. It can be observed from the comparison between the experimental and theoretical data that the theory can properly simulate the experimental finding.

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