钻铤螺纹断裂失效分析及结构改进措施

Failure Analysis of Drill Collar Thread Fracture and Measures of Structural Improvement

钻铤螺纹断裂是钻铤失效的主要原因,在整个钻铤失效中占比较大,根据螺纹断口分析,疲劳是导致螺纹联接失效的主要原因。分析了螺纹轴向载荷分布,使用Solidworks软件建立了钻铤NC50螺纹联接模型,用有限元法分析了各螺纹的静应力分布。应力槽可以很好地解决螺纹应力集中的问题,但是会大幅度减少钻铤的使用寿命。通过改进应力槽的结构,并使用有限元分析了各螺纹的应力分布,有效地降低螺纹应力集中,且可以延长钻铤使用寿命。针对内螺纹后孔结构的缺陷,改进了后孔的尺寸,提高了螺纹联接的强度。结果表明,改进后的钻铤螺纹自使用以来没有出现断裂事故,成功解决了钻铤疲劳断裂的难题。

Drill collar thread fracture is the main factor of drill collar failure,which accounts for a large proportion of the total drill collar failure.According to the analysis of thread fracture,fatigue is the main cause of thread connection failure.The axial load distribution of thread was calculated,and the NC50 thread connection model was established by Solidworks software.The static stress distribution of each thread was analyzed by finite element method.The stress groove can solve the problem of thread stress concentration well,but it can greatly reduce the service life of drill collar.The structure of the stress groove was innovated and improved,and the stress distribution of each thread was analyzed by using finite element method,which can effectively reduce the stress concentration of the thread and prolong the service life of the drill collar.For the defects of internal thread back hole structure,the size of back hole was improved,and the strength of thread connection was increased.The results show that the improved drill collar thread has not broken since use,and the difficult problem of drill collar fatigue fracture has been solved successfully.