本研究使用適當的應力-應變關係、網格元素、邊界條件及負載條件，則有限元素分析軟體 ANSYS WORKBENCH 16.0 可分析不同尺寸及不同深度的圓形凹痕6061-T6鋁合金圓管承受對稱曲度循環彎曲負載下的相關力學行為(彎矩、曲度、應力及應變等) ，其中所考慮的圓管尺寸有三種，分別為外徑= 33 mm及壁厚= 2 mm、外徑= 31 mm及壁厚= 1 mm與外徑= 30 mm及壁厚= 0.5mm，而個別尺寸的凹痕深度分別為0、0.3、0.6、0.9及1.2 mm。接著，根據最大及最小應力、應變所求得的應力及應變幅度，分別與吳政昌【27】及王建竣【28】實驗所求得之疲勞損毀圈數，標示於雙對數座標中。由於雙對數座標應變幅度與疲勞損毀圈數幾乎分佈於一條直線上，因此本文運用簡易的疲勞理論，並以最小平方法將上述關係近似出一條直線，則所對應之疲勞參數可透過直線斜率及截距求得。

In this study, using the appropriate stress-strain relation, mesh elements, boundary conditions and load conditions, the finite element analysis software ANSYS WORKBENCH 16.0 was employed to analyze round-dented 6061-T6 aluminum alloy circular tubes with different sizes and different dent depths under the cyclic bending. Three kinds of tube’s sizes were considered including outer diameter = 33 mm and wall thickness = 2 mm, outer diameter = 31 mm and wall thickness = 1 mm and outer diameter = 30 mm and wall thickness = 0.5 mm. Different dent depths for each size of tubes were 0, 0.3, 0.6, 0.9 and 1.2 mm, respectively. Then, the relationship of stress or strain amplitudes obtained by the maximum and minimum stress or strain from ANSYS analysis and the number of fatigue cycles obtained by Wu [27] and Wang [28] were shown in a log-log scale. Since the relationships between strain amplitude and the number of fatigue cycles were almost distributed on a straight line. Therefore, a simple fatigue theory was used to approximate the above relationship. The corresponding fatigue parameters were determined through the slope and intercept of the straight line.

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