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Failure analysis of 18CrNi3MoA drilling tails

International Journal of Minerals,Metallurgy and Materials 2012年第5期19卷 421-427页

作者： Hong-wu Zhu Ya-zheng Liu Le-yu lhobl Lei-ying Wang Bin Huang School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Xining Special Steel Co. Ltd. Xining 810005 China

The fracture of a drilling tail made of 18CrNi3MoA steel in the exchanging water hole was analyzed in terms of inclusions, prior austenite grain size, carburized layers, and fatigue fracture morphology by means of optical microscopy, quantitative metallography, and scanning electron microscopy （SEM）. Fatigue crack initiation and propagation on the drilling tail were also studied. The results showed that the fracture on the drilling tail was not induced by inclusions and the distribution inhomogeneity of prior austenite grain size. Instead, be- cause the outside surface of the exchanging water hole was not continuously geometric, there was a great deal of stress concentration in those areas under continuous twisting, axial impact, and corrosion of mineral water. Thus three crack sources emerged in these areas. Initial cracks centered on these sources spread from the outside surface to the inside surface, and eventually the drilling tail ruptured. Furthermore, the fractograph of the region around the crack sources exhibited a typical ductile dimple fracture pattern, and cracks initiated on the outside sur- face of the carburized layers of the exchanging water hole. Three crack sources could be the sources of fatigue crack propagation. Based on the analysis of fatigue crack propagation, it was further demonstrated that fatigue damage originated from the outside surface of the ex- changing water hole.

关键词： drilling tools failure analysis crack initiation crack propagation

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An Improved Control Strategy for Directional drilling Attitude

An Improved Control Strategy for Directional Drilling Attitu...

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第37届中国控制会议

作者： Zhen Cai Xuzhi Lai Min Wu School of Automation China University of Geosciences Hubei Key Laboratory of Advanced Control and Intelligent Automation for Complex Systems

In the process of geological exploration, the development of automatic control is insufficient. The paper presents an improved strategy of attitude control for directional drilling tools used in the geological environment. The drilling kinematics model is linearized with the Taylor series, and the model linearization solves the nonlinear term of the azimuth *** PI controllers are used to control attitude inclination and azimuth, respectively. The results of the transient simulation are presented, and the control effect of improved performance are certificated.

关键词： Directional drilling drilling tools Attitude Control

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