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连续管道弯头应力增大系数修正计算及实验研究
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Abstract:
为探索管道弯头在二次应力校核中的应力增大效应，本文以工程中常用的U型弯管结构为研究对象，建立了管道弯头应力实验平台，测得了弯头应力最大值随外载荷变化规律并与有限元及ASME B31.3规范结果进行了对比分析，在此基础上提出了适用于工程应用的修正弯头应力增大系数(Stress In-tensification Factor, SIF)计算公式，进而研究了不同径厚比和相对管径对弯头应力分布的影响规律。研究结果表明，在弹性阶段弯头应力最大值出现在弯头内弧中心点附近，且随着外荷载的增加，弯头应力近似呈线性增长；壳单元有限元模型仿真结果与实验值基本一致，U型弯管中各个弯头应力分布规律受外弯矩作用影响较显著，具体表现为外弯矩越大，弯头应力值越高；基于实验及有限元计算结果，综合考虑弯矩对弯头应力增大效应的影响，本文提出的应力增大系数修正公式与原ASME B31.3规范公式相比，其计算结果更接近实验值，计算精度提升了16.77%；同时，在相同外荷载作用下，弯头应力随径厚比的增加而减小，随相对管径的增加而增大，径厚比大小对弯头应力分布作用较为显著，相对管径的改变对弯头应力计算影响较小。
In order to study the stress intensification effect of pipe elbow in the secondary stress check, the U-shaped pipeline commonly used in engineering was taken as the research object. The experiment platform for analyzing pipe elbow stress was established, and the maximum stress with the external load was measured and compared with the results of the Finite Element Analysis (FEA) results and ASME B31.3 Code. On this basis, a correction formula calculating the Stress Intensification Factor (SIF) of elbows was proposed, and the influence of the ratio of pipe diameter to wall thickness and the relative diameter on the elbow stress distribution was studied. The results showed that the maximum stress of the elbow appeared near the center point of the intrados of the elbow, and the stress of the elbow increased approximately linearly with the increase of the external load in the elastic stage. The simulation results of the shell element finite element model are basically consistent with the experimental values. The stress distribution law of each elbow in the U-shaped pipeline was significantly affected by the external bending moment, and the greater the external bending moment, the higher the elbow stress values. Based on the experimental and finite element calculation results and considering the influence of bending moment on the stress intensification effect of elbow, the calculation results of the SIF correction formula is closer to the experimental values compared with the ASME B31.3 code, and the computational accuracy was improved by 16.77%. Under the same external load, the elbow stress decreased with the increase of the ratio of pipe diameter to wall thickness and increased with the increase of the relative diameter. The ratio of pipe diameter to wall thickness had a significant effect on the elbow stress distribution, and the change of the relative diameter had little effect on the elbow stress calculation.
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