钻柱疲劳寿命预测研究

Research on Fatigue Life Prediction of Drill String

疲劳破坏是钻柱失效的主要形式,进行钻柱疲劳寿命预测可以为钻柱的使用和管理提供依据。建立了钻柱力学模型,对钻柱的受力进行了分析,尤其分析了交变弯曲应力,并用Forman模型预测了钻柱的疲劳寿命,使计算结果更加准确。还应用形状改变能判据对构件屈服区进行了渐进分析,扩展了线弹性断裂力学的应用范围。理论计算结果和现场统计数据的一致性证明了此模型的实用性。

Fatigue failure is a main type of drill string failure. The fatigue life prediction of drill string is a base for its application and management. The mechanical model of drill-string is established and the stress ( especially the alterative bending stress) of the drill string is analyzed in this paper. Moreover, Forman fatigue life prediction model is used to predict the drill string fatigue life, which makes the result better. At the crack tip, the plastic deformation and the plastic zone correction is taken into account to broaden the applied scope of the liner-elastic mechanics in this paper. According to the field application and the theoretical results, the model is considered to be reliable.