钻柱接头扣型改进设计的有限元分析

螺纹根部应力集中是导致钻柱接头失效的主要原因之一。文中采用有限元方法分析多种针对NC46扣型的改进设计方案，包括扩大螺纹根部圆弧半径、公母扣大端切削以及改变公扣锥度。详细分析各种改进设计方案对螺纹根部应力集中的影响，以及螺齿上接触载荷的分布变化。研究结果表明，改变公扣锥度方案对降低公扣根部应力集中的效果最好，其次是对螺纹大端进行切削的方案和采用SST扣方案。

FINITE ELEMENT ANALYSIS OF IMPROVING DESIGNS FOR A DRILL STRING JOINT

Most drill string failures occur in the last-engaged threads of the pin and box. This type of failure is mainly caused by stress concentration at the root of the threads. Some improving design schemes to decrease stress concentration are proposed, which include using SST thread, cutting the last-engaged threads of pin and box and adjusting the taper of pin. Using the method of finite element contact analysis, the effect of each improving design scheme on the stress concentration at the root of last-engaged threads is studied and compared with that of the original NCA6 thread of the drill string joint. The results show that every improving design scheme can decrease stress concentration in the last-engaged threads, and the scheme of adjusting the taper of pin has the highest efficiency, and the scheme of cutting the last-engaged threads is better than the scheme of using SST thread.