局部尖銳凹槽SUS304不鏽鋼管在循環彎曲負載下之力學行為與皺曲損壞

Mechanical Behavior and Buckling Failure of Local Sharp-notched SUS304 Stainless Steel Tubes Subjected to Cyclic Bending

本文係針對局部尖銳凹槽深度為0.2、0.4、0.6、0.8、1mm的SUS304不鏽鋼管，進行曲度控制循環彎曲負載的實驗，以探討其相關的力學行為與皺曲損壞。由實驗彎矩－曲度的關係中發現，隨著循環圈數的增加彎矩值也漸漸的增加，並在經過一些循環曲圈數後該關係會呈現一穩定的迴圈，且凹槽的深度對彎矩－曲度關係幾乎沒有影響。至於橢圓化－曲度關係則隨著循環圈數的增加而呈現棘齒狀的成長，且凹槽的深度越深橢圓化－曲度關係就越不對稱，橢圓化增加也就越大。此外，雖然有五種局部尖銳凹槽的深度，但在雙對數座標的控制曲度－循環至皺曲圈數關係卻呈現五條幾乎平行的直線。最後，本文以有限元素ANSYS來模擬彎矩－曲度及橢圓化－曲度的關係，此外，本文也提出理論模式來描述控制曲度－循環至皺曲圈數的關係。在與實驗結果比較後發現，理論能夠合理描述實驗結果。

In this study, SUS304 stainless steel tubes with local sharp-notched depths of 0.2, 0.4, 0.6, 0.8 and 1 mm were subjected to cyclic bending for investigating relative mechanical behavior and buckling failure. From observing the experimental moment-curvature relationship, when the number of cycles increased, the bending moment also increased. The relationship became a steady loop after several bending cycles. In addition, the notch depth had no influence on the moment-curvature relationship. Regarding the ovalization-curvature relationship, when the number of cycles increased, it exhibited an increased and ratcheted manner. The greater the depth of the notch, the more unsymmetrical the ovalization-curvature relationship became, and the greater the increase of the ovalization. Furthermore, although five local sharp-notched depths were tested, only five nearly parallel lines were observed for the controlled curvature-number of cycles that produced a buckling relationship in the log-log scale. The finite element ANSYS software package was used to simulate the moment-curvature and ovalization-curvature relationships. In addition, this study proposes a theoretical model for simulating the controlled curvature-number of cycles to produce the buckling relationship. Through comparison of the experimental data, the theoretical model could appropriately simulate the experimental findings.