Abstract This paper is dedicated to providing a detailed limit load analysis for 180° pipe bends under bending moment using three dimensional finite element (FE) method considering geometric nonlinearity. Results show that FE results for 180° pipe bends are all lower compared to those for 90° pipe bends, especially for pipe bends with thin wall and small bend radius (R/r = 1.5, r/t = 50). However, for pipe bends with thick wall and large bend radius (R/r = 4, r/t = 5), results seem very close. New predicted equations are proposed based on the FE results. If the geometric nonlinearity effect is considered, when the material parameters of yield strain es = 0, results still obey the estimating solutions without geometric nonlinearity considered. But the geometry change should have some significant influence on the failure with the material's behavior changing. With the applied bending load increasing, the ovalization parameter C will also continue to increase. The change of the parameter C is significant for the thin pipe bends (r/t = 50), while is not obvious for thick pipe bends (r/t = 5). The influence of the bend radius on the parameter C is not significant. Geometric effect is significant for a high yield strain value that the pipes will have enough ability to be deformed.

中文翻译：

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考虑几何非线性的面内弯矩作用下180°弯管的极限载荷

摘要 本文致力于使用考虑几何非线性的三维有限元（FE）方法对弯矩作用下的180°弯管进行详细的极限载荷分析。结果表明，180°弯管的有限元结果均低于90°弯管，尤其是壁薄、弯曲半径小的弯管（R/r=1.5，r/t=50）。然而，对于厚壁和大弯曲半径的弯管（R/r = 4，r/t = 5），结果似乎非常接近。根据有限元结果提出了新的预测方程。如果考虑几何非线性效应，当屈服应变的材料参数 es = 0 时，结果仍然服从不考虑几何非线性的估计解。但是几何形状的变化应该对材料的失效有一些重大影响' s 行为改变。随着施加的弯曲载荷的增加，椭圆化参数 C 也将继续增加。参数 C 的变化对于细管弯头 (r/t = 50) 是显着的，而对于粗管弯头 (r/t = 5) 则不明显。弯曲半径对参数 C 的影响不显着。几何效应对于高屈服应变值是显着的，管道将具有足够的变形能力。