本研究是先以有限元素分析軟體ANSYS Workbench 15.0分析局部切痕6061-T6鋁合金管承受對稱曲度控制(最大及最小曲度量相等但符號相反)循環彎曲負載下的應力分佈。接著，再根據分析出的最大循環應力值及沈睿騰【9】實驗的循環至損壞圈數關係，提出適當的疲勞理論並求得相關的疲勞參數。本文所考慮的6061-T6鋁合金管尺寸為:外徑35 mm，壁厚為3 mm，循環彎曲控制的對稱曲度分佈為: 0.2 m-1 ~ 1.1 m-1，而切痕的深度為: 0.4、0.8、1.2、1.6和2.0 mm。
　　由有限元素ANSYS分析結果顯示，當切痕深度相同時，控制曲度越大時，應力值也就越大。此外，當考慮控制曲度相同時，隨著切痕深度越大，應力值也就越大。由於所考慮負載的曲度為對稱的情況，循環彎曲的最大及最小應力也呈現對稱的狀態，所以分析時不用考慮平均應力的影響。根據有限元素ANSYS求得的應力幅度及沈睿騰【9】實驗所求得的循環至損壞圈數在雙對數座標中可以用最小平方法近似出一條直線，則相關的疲勞理論可簡易的建立，且所對應的參數即可透過直線的斜率與截距求得。

In this study, the finite element method software - ANSYS Workbench 15.0 was used for analyzing the mechanical behavior of local-cut 6061-T6 aluminum alloy tubes under symmetrical curvature-controlled (maximum and minimum curvatures with equal amount and opposite sign) cyclic bending. Next, according the analysis amount of the cyclic maximum stress and the number of cycles required to failure tested by Shen【9】, an appropriate fatigue theory was proposed and the related fatigue parameters were determined. The 6061-T6 aluminum alloy tubes considered were 35 mm in outside diameter and 3 mm in wall thickness. The symmetrical controlled curvature of the cyclic bending was from ±0.2 m-1 to ±1.1 m-1. The different local-cut depths were 0.4, 0.8, 1.2, 1.6 and 2.0 mm.
According to the analysis results from ANSYS, for a constant cut depth, a higher controlled curvature leads to a higher amount of stress. In addition, for a constant controlled curvature, a higher cut depth leads to a higher value of stress. Due to symmetrical curvature-controlled loading, the maximum and minimum stresses of the cyclic bending were also symmetrical. Thus, the mean stress effect was not considered in this study. Finally, based on data of the stress amplitudes determined by ANSYS and the experimental number of cycles required to failure tested by Shen【9】on log-log scale, a straight line was determined by least-square method. Therefore, a simple fatigue theory was easily built and the related material parameters were determined from the slope and intercept of the line.

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