薄壁圓管承受循環彎曲負載至塑性區域時，圓管斷面會呈現橢圓化的變化，而隨著彎矩或循環次數的增加，管面橢圓化也跟著增加，最後，當橢圓化達到某個臨界值時，薄壁圓管會產生皺曲損壞的現象。本文以有限元素分析軟體ABAQUS模擬316L不銹鋼薄壁圓管，在對稱曲度控制循環彎曲負載下所呈現的力學行為，該行為包含有：彎矩-曲度關係及橢圓化-曲度的關係。根據模擬分析結果顯示，由於有限元素ABAQUS中吾人使用的塑性模型使得彎矩-曲度曲線無法呈現循環硬化或軟化的現象，也就是第一個循環迴圈便是穩定的迴圈，至於橢圓化-曲度曲線則是隨循環次數呈棘齒狀的增加。最後，本文將316L不銹鋼薄壁圓管的實驗結果及內涵時間理論結合虛功原理的理論分析結果作比較發現，有限元素ABAQUS所分析的彎矩-曲度曲線雖然在第一圈加載時和內涵時間理論結合虛功原理的理論分析結果有些差異，但穩定的彎矩-曲度迴圈卻是非常相似。至於橢圓化-曲度及橢圓化-曲度的曲線和內涵時間理論結合虛功原理的理論所分析結果非常接近。

Thin-walled circular tubes subjected to cyclic bending into the plastic range leads to a progressive accumulation of ovalization of the tube cross-section. It has been found that the ovalization increases when the bending moment or the number of cycles increases. Finally, when the tube ovalizes to a critical value, it buckles. This thesis presents the simulation of the mechanical behavior of thin-walled 316L stainless-steel tubes subjected to curvature-symmetric cyclic bending by using the finite element software ABAQUS. The mechanical behavior includes the moment-curvature relationship and ovalization- curvature relationship. According to the analysis result, due to the plasticity model used in ABAQUS, there is no cyclic hardening or softening phenomenon of the moment-curvature curve. That is the first cyclic loop is the steady-state loop. As for the ovalization-curvature curve, the curve shows the gradual accumulation of ovalization in a ratcheting manner with the number of cycles. Finally, the experimental result and the endochronic theory combined with the principle of virtual work analysis are compared with the ABAQUS simulation results. It is demonstrated that the first loop of the moment-curvature curve simulated by ABAQUS has some difference with the simulation by the endochronic theory. However, the simulations by aforementioned two methods on the steady-state loop of the moment-curvature curve are very close. In addition, the simulations of the ovalization-curvature curve are very similar. Therefore, it can be concluded that the simulated result by ABAQUS agrees well with the prediction by the endochronic method.

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