中文摘要：

基于统一强度理论,考虑中间主应力效应及拉压不等特性,对受内压作用的压力弯管进行塑性极限载荷分析,建立了等壁厚、变壁厚及局部减薄压力弯管的极限内压统一解,分析了统一强度理论参数、拉压比、弯曲系数和弯管壁厚对统一解的影响特性.并将计算结果与文献试验数据进行比较,结果吻合较好.所得统一解具有通用性,可退化为已有成果.研究结果表明：弯曲系数、强度理论参数等因素对极限内压曲线的影响显著,考虑中间主应力效应能充分发挥材料的强度潜能.该结果为压力弯管的设计及工程应用提供一定的参考.

英文摘要：

The plastic limit pressure formula for pipe elbows subjected to internal pressure was derived based on the unified strength theory with consideration of the intermediate principal stress and different strength in tension and compression. The unified solutions were obtained surrounding elbows with equal wall thickness, variable wall thickness and local thinning. Parametric studies were carried out to investigate the influence of the unified strength theory parameter, tension-compression ratio, bending coefficient and wall thickness. Good agreement can be found from the comparison of the calculation results and experimental data. The unified solutions obtained in this paper have a wide applicability, which can be naturally degraded to many existing results. The results demonstrate that the latent potentialities of pipe elbows are fully achieved due to considering the effect of intermediate principal stress. The limit internal pressure distribution is significantly influenced by the bending coefficient, unified strength theory parameter and other factors. The unified solutions have an important practical value for the engineering application of pressure pipe elbows.