点腐蚀损伤管道剩余强度的评价方法

Residual Strength Assessment Method of Pipeline Containing Damage of Pitting Corrosion

采用模拟多孔材料拉伸试验,建立了含孔洞型损伤管线钢的宏观力学性能退化规律模型。结果表明：管线钢的弹性模量和屈服强度随孔隙率的增大而显著降低,对于X70管线钢,当孔隙率达到50%时,材料表观弹性模量和屈服强度降为零。基于损伤理论,将用于评价体积型缺陷的API RP 579公式进行了改进,建立了点腐蚀损伤管道的剩余强度评价公式。算例分析结果表明：将点腐蚀缺陷简化为局部腐蚀缺陷,其保守程度随点腐蚀深度增加而增大,当最大点腐蚀深度小于t/10时,这种简化处理在工程上可以接受。

The mechanical property degradation rules of pipeline steel with damage have been established through tensile test of X70 steel specimens containing mechanical holes. Elastic modulus E and yielding strength as decreased observably with hole ratio when. The hole ratio was up to 50%, E and σs degrades to zero. Based on damage theory, residual strength assessment formula has been developed by modifying API RP 579 formula for volumetric flaw evaluation. The results of case analysis calculation indicated that the conservation extent of evaluation result of pitting defect would increase with pitting corrosion depth if it was simplified as a volumetric defect. If the maximum depth of pitting corrosion is less them t/10, this kind of engineering simplification method can be accepted.