尖銳凹槽316L不鏽鋼管在純彎曲潛變及鬆弛負載下行為之實驗與理論研究

Experimental and Theoretical Analysis of the Response for 316L Stainless Steel Tubes under Pure Bending Creep and Relaxation

本文主要是實驗及理論研究尖銳凹槽 316L 不鏽鋼管承受純彎曲潛變及鬆弛負載下的行為。純彎曲潛變係指試件被彎曲至某個預設的彎矩後，並維持該彎矩一段時間，而純彎曲鬆弛係指試件被彎曲至某個預設的曲度後，並維持該曲度一段時間。由純彎曲潛變的實驗結果得知，曲度與橢圓化皆會隨著時間的增加而增加，直至皺曲毀損為止，且在較高的預設彎矩值，曲度與橢圓化值增加的較快。由純彎曲鬆弛的實驗結果得知，彎矩會隨著時間迅速的下降，之後漸漸趨近一穩定值，至於橢圓化量則會隨著時間些許的增加後也趨近一穩定值。由於純彎曲鬆弛係固定曲度量因此造成固定的橢圓化量，所以圓管不會發生皺曲損壞。最後，本文修改Lee 和Pan [1]所提出的方程式來描述尖銳凹槽316L 不鏽鋼管承受純彎曲潛變負載下的起始與第二階段潛變曲度–時間關係及純彎曲鬆弛負載下的鬆弛彎矩–時間關係。在與實驗值比較後發現，理論分析能合理的描述實驗結果。

In this study, the response sharp-notched 316L stainless steel tubessubjected to pure bending creep and relaxation is experimentally andtheoretically studied. Pure bending creep means to bend the specimen toa desired moment and hold that moment for a period of time; pure bendingrelaxation means to bend the specimen to a desired curvature and hold thatcurvature for a period of time. From the experimental result for purebending creep, the curvature and ovalization increase with time until thetube buckles. A higher desired moment leads to higher curvature andovalization. From the experimental result for pure bending relaxation, thebending moment rapidly decreases with time and becomes a steady valueafter all. As for the ovalization, the amount increases with time and graduallybecomes a steady value. Due to the constant ovalization caused bythe constant curvature under pure bending relaxation, the tube does notbuckle. Finally, the formulation proposed Lee and Pan [1] is modified forsimulating the initial and second stages of the creep curvature-time relationshipunder pure bending creep, and relaxation moment-time relationshipunder pure bending relaxation for sharp-notched 316L stainless steeltubes. Through comparing with the experimental finding, the theoreticalanalysis can reasonably describe the experimental result.