Abstract: Ratcheting effect experiments of 90° elbow pipes under internal pressure and in-plane bending were carried out for nuclear power plants herein, and then the limit load, shakedown load and ratcheting boundary of 90°elbow pipes were studied by numerical method. First, based on twice elastic slope criterion and tangent intersection criterion, limit load of 90° elbow pipes under internal pressure or in-plane bending was determined by ideal elastic-plastic finite element analysis. Meanwhile, limit load and shakedown load of 90°elbow pipes under internal pressure alone or in-plane bending alone and the interaction between them were determined by LMM. Again, ratcheting boundary of 90°elbow pipes was determined by Ohno-Wang model combining with C-TDF and LMM. Finally, ratcheting boundaries of 90°elbow pipes determined by two methods were compared. The results indicate that the errors of limit load determined by twice elastic slope criterion, tangent intersection criterion and LMM are as 10.78%. It is also showed the efficiency and rapidity of LMM. The ratcheting boundary determined by both methods were compared, the results are well consistent when internal pressures are in the range of 20 MPa and 35 MPa, the trends of predicted results of both methods are different when internal pressures are less than 20 MPa.

Key words: 90°, elbow pipe, elastic-plastic finite element analysis, linear matching method(LMM), limit load, ratcheting boundary

摘要： 进行了核电站90°弯管在内压和面内弯曲载荷作用下的棘轮效应试验，并采用数值方法研究了90°弯管的极限载荷、安定载荷和棘轮边界。利用理想弹塑性有限元分析，基于两倍弹性斜率准则和切线相交准则分别确定了90°弯管单独承受内压和弯曲载荷的极限载荷；利用线性匹配方法确定了90°弯管在单独内压和弯曲载荷以及两者共同作用下的极限载荷和安定载荷；利用Ohno-Wang模型，结合C-TDF弹塑性有限元分析方法和线性匹配方法分别确定了90°弯管的棘轮边界；最后，对弹塑性有限元方法和线性匹配法确定的棘轮边界进行了比较。结果表明：两倍弹性斜率准则、切线相交准则和线性匹配方法确定的极限载荷误差为10.78%，其中弹性迭代的线性匹配法能高效、快速地进行计算。比较C-TDF法和线性匹配法确定的棘轮边界，结果发现：当内压在20~35 MPa之间时，两种方法确定的棘轮边界吻合很好；当内压小于20 MPa时，两种方法的预测结果呈现不同的趋势。

关键词: 90°, 弯管, 弹塑性有限元分析, 线性匹配法, 极限载荷, 棘轮边界