公螺纹应力减轻槽效果分析

EFFECT ANALYSIS OF STRESS-RELIEF GROOVES ON THE PIN THREADS

陈勇 林元华 施太和 林凯 韩勇

Chen Yong Lin Yuanhua Shi Taihe Lin Kai Han Yong

西南石油学院油气藏地质及开发工程国家重点实验室, 四川成都 610500 石油管材研究所, 陕西西安 710065

在钻井过程中,钻具疲劳失效事故频繁发生,其失效部位主要集中在螺纹接头处,如何减轻集中在接头处的应力,国内外有关学者提出了在螺纹部位加工应力减轻槽以降低公扣最末完全扣和母扣根部的应力集中,该方法经现场应用后,效果显著。以?177.8mm钻铤公螺纹接头作为研究对象,用有限元方法对加工有不同应力减轻槽的钻铤公螺纹接头进行了分析计算,得出了4种不同公螺纹结构在相同的边界条件和载荷作用下最末完全扣处的应力集中情况。计算结果表明,带有应力减轻槽的公螺纹具有较小的应力集中,特别是API标准应力减轻槽的应力集中最小,因此抗疲劳性能最佳,建议采用这种应力减轻槽结构。

During drilling job, BHA failures take place frequently, which concentrate on the thread connection. So decreasing of the stress concentration on connection becomes very important. Machining stress-relief grooves on thread in order to decreasing the stress concentration is brought forward by researchers at home and abroad, which has excellent effect. Take pin threads of ?177.8 mm drill collar for instance, Finite Element Method is used to analyze the different stress-relief grooves of pin thread connection, so the stress concentration on the last engaged pin threads is gained. FEM Results showed that stress of the pin threads with stress-relief grooves is smaller than that of API standard connection without stress-relief grooves and the stress-relief grooves of API standard is best for resistance of fatigue.

10.3969/j.issn.1000-7393.2004.06.006