316L 不銹鋼管在循環彎曲負載下行為之實驗分析

Experimental Analysis on the Behavior of 316L Stainless Steel Tubes Subjected to Cyclic Bending

本文目的是實驗研究316L 不銹鋼管在循環彎曲負載時的力學行為及皺曲損壞。力學行為包含有：彎矩─曲度的關係及橢圓化─曲度的關係，而皺曲損壞包含有：控制循環曲度─到達皺曲橢圓化的關係及控制循環曲度─循環至皺曲圈數的關係。本研究採用「彎管試驗機」及」曲度─橢圓化量測器」來進行測試316L不銹鋼管。從彎矩─曲度的實驗曲線中顯示，在對稱曲度循環彎曲負載時316L不銹鋼管有循環硬化的現象，而經過了一些循環圈數後迴圈會變的較穩定。從橢圓化─曲度的實驗曲線中顯示，在對稱曲度循環彎曲負載時橢圓化會漸增且呈對稱棘齒的變化，橢圓化會一直增加直到鋼管發生皺曲。從控制循環曲度及循環至皺曲圈數的實驗曲線中顯示，控制循環曲度量越大時，循環至皺曲圈數就越少。此外，雖然所有的測試鋼管有不同的控制的循環曲度量，但鋼管到達皺曲時的橢圓化量幾乎是個定值。

The purpose of this paper is to experimentally investigate themechanical behavior and buckling failure of 316L stainless steel tubessubjected to cyclic bending. The mechanical behavior measured includes:the relationship between the moment and curvature, and the relationshipbetween ovalization and curvature. The buckling failure measured includes:the relationship between controlled cyclic curvature and ovalization atbuckling, and the relationship between the controlled cyclic curvature andthe number of cycles to produce buckling. It is found from themoment-curvature curve that the 316L stainless steel tube hardenscyclically and becomes steady after a few cycles for symmetriccurvature-controlled bending. However, from the ovalization-curvaturecurve, the ovalization of the tube cross-section increases in a ratchetingmanner with the number of cycles. Owing to the progressive accumulationof the ovalization of the tube cross-section during cyclic bending, the tubesbuckle eventually. It is also found, from the controlled cycliccurvature-number of cycles to produce buckling curve, that the higher isthe controlled cyclic curvature, the fewer the number of cycles to producebuckling. In addition, although the magnitudes of the controlled cycliccurvature are different for all tested tubes, the ovalizations at buckling areapproximately the same.