本文選用適當的應力－應變關係、元素、邊界及負載條件，有限元素分析 軟體ANSYS可用來描述圓管承受無或有外壓循環彎曲負載下的行為。本研究 中所考慮的負載的情況有：無或有外壓對稱循環彎曲負載及無或有外壓非對稱 循環彎曲負載。分析的結果將與Corona和Kyriakides [1]的1020碳鋼管實驗的 結果進行比較。實驗結果顯示，在非對稱循環彎曲負載時，橢圓化－曲率曲線 會偏向正曲率的方向，且在有外壓時橢圓化累積的速度比無外壓時快。經由相 互比較結果顯示，有限元素ANSYS分析能合理的描述實驗結果。

In this paper, by using an adequate stress-strain relationship, elements, boundary condition and loading condition, a finite element ANSYS analysis on the response of circular tubes subjected to cyclic bending with or without external pressure is discussed. Several loading cases were considered, which were symmetrical cyclic bending with or without external pressure and unsymmetrical cyclic bending with or without external pressure. Experimental data of 1020 carbon steel tubes tested by Corona and Kyriakides [1] were compared with the simulation. It has been shown from experimental data that the ovalization-curvature curve shows a bias along the positive curvature direction for unsymmetrical cyclic bending, and the speed of the accumulating ovalization with external pressure is faster than the speed without external pressure. Through comparison with the experimental data, the finite element ANSYS analysis can properly represent the experimental results.