There are many kinds of vibration forms of drillstring in petroleum drilling. Whirl is one of the main vibration modes when drilling tools are drilling, and it is also the main reason of fatigue failure of the drillstring. In this paper, the causes of drillstring whirl are analyzed. The results show that the speed of rotation (RPM) is a major factor that affects the severity of the whirl. The greater the speed of rotation, the more intense the whirl. The whirl of the drillstring will produce bending stress. The severity of the whirl of the drillstring is the main factor affecting the bending stress. The increase of RPM and weight on bit (WOB) will lead to the increase of bending stress. The RPM has a great influence on the bending stress. Given the complex stress condition of drillstring, the calculation model of safety factor is established. The bending stress and safety factor are calculated under the different WOB and RPM. The relationship between dynamic bending stress and the safety factor of drilling tools is analyzed. Bending stress has great influence on the safety factor of drillstring. The variation trend of safety factor is opposite to that of bending stress caused by whirl. It provides a theoretical reference for the optimization of drilling tools in drilling engineering construction.

中文翻译：

---

旋转对钻柱疲劳的影响分析

石油钻探中，钻柱有多种振动形式。旋转是钻具钻进时的主要振动模式之一，也是钻柱疲劳失效的主要原因。本文分析了钻柱旋转的原因。结果表明，旋转速度（RPM）是影响旋转严重程度的主要因素。旋转速度越大，旋转越强烈。钻柱的旋转会产生弯曲应力。钻柱旋转的严重程度是影响弯曲应力的主要因素。RPM和钻压（WOB）的增加将导致弯曲应力的增加。RPM对弯曲应力有很大的影响。针对复杂的钻柱应力条件，建立了安全系数计算模型。在不同的WOB和RPM下计算弯曲应力和安全系数。分析了动态弯曲应力与钻具安全系数之间的关系。弯曲应力对钻柱的安全系数影响很大。安全系数的变化趋势与旋转引起的弯曲应力的变化趋势相反。为优化钻井工程施工中的钻井工具提供了理论参考。