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

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