内压作用下等壁厚过渡及等圆角过渡三通塑性极限分析

Plastic Limit Analysis of Tees by Various Transition Methods of Christmas Tree under Loads of Internal Pressure

为了保证采油树的安全运行,采用弹塑性有限元方法,对采油树结构中常用的管件三通的极限载荷开展研究。国产采油树三通的相贯区域均有一定的壁厚加厚现象,通过采用两种过渡方法(等壁厚过渡和等圆角过渡)分析壁厚的影响。研究内容如下:分析了三通的失效形式,并确定了不同影响因素包括两种圆角过渡方法、主管径厚比及铸造圆角值对三通极限载荷均有一定程度的影响;建立了覆盖常用主管径厚比、铸造圆角及两种铸造方法的极限内压数据库;确定了两种过渡方法的优劣性及最佳铸造圆角值,得到了三通的影响因素曲线及工程估算公式;最后,通过试验验证了仿真的合理性。该研究结果可为三通的结构选型及设计优化提供参考依据。

In order to ensure the safe operation of the Christmas tree,the plastic limit load of the Tees commonly used in the structure of Christmas tree was analyzed by the elasto-plastic finite element method.Due to certain thickening of wall thickness in the intersecting area of the domestic tees of Christmas tree,two transition methods(equal-thickness transition and equal-fillet transition)were adopted to analyze the influence of wall thickness.The failure modes of the tees were analyzed,and different influencing factors were determined,including two fillet transition methods,the diameter-to-thickness ratio and cast fillet values,which have certain influence on the limit loads of the Tees.The limit internal pressure database covering common diameter-to-thickness ratio,cast fillet value and two casting methods was established.The merits and demerits of the two transition methods and the best cast fillet value were determined,and the influencing curve and engineering estimation formula of the Tees were obtained by analyzing and fitting the data.Finally,the rationality of the simulation was verified by tests.The study results can provide a reference for the structural type selection and design optimization of the Tees.