一种新型钻铤接头应力减轻结构的效果分析

摘要

石油钻铤失效事故大多发生在外螺纹接头靠近台肩处的最末啮合扣位置,而疲劳断裂与断裂处的应力水平有很大关系,应力水平越高,越容易发生疲劳断裂.因此,如何减小钴铤接头的局部应力集中、改善应力分布,一直是研究的热点问题.在API应力减轻结构的基础上,设计了一种新型应力减轻结构,并进行了实际应用.在考虑摩擦因数的前提下,利用有限元方法,对该新型结构进行了详细分析,对比了API接头、API应力减轻结构和该新型结构的效果,分析了3种结构在台肩面、螺纹牙上的应力分布以及台肩面上的接触力分布.结果表明,该新型结构可以有效地减小钻铤接头局部应力峰值,改善接头的应力分布,从而为改进钻铤接头设计、提高钻铤寿命提供了参考.%It has been a hot issue of reducing the local stress concentration on the drill collar joint to improve the stress distribution.For the oil-drill collar, thc failure often occurred at the root of the last engaged tooth in the pin near the shoulder, and the fatigue fracture was much related to the stress level. The larger the stress, the more easily fatigue fracture occurs. The new designed structure has accessed to the application, which was designed on the base of the stress-reducing structure of API. Detailed analysis was carried out on the new structure using finite element method. Thc stress distribution on the thread teeth and the contact normal force on the shoulder surface were compared among the API joint, the stress relief structure of API and the new structure. The results indicated that the new structure can effectively reduce the local stress peaks of the drill collar joints and improve the stress distribution, so it could provide reference of designing new drill collar joints and improving drill collar lifetime.