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针对丝扣粘扣中接触压力过大引发的塑性变形的问题,基于双台肩钻杆接头的三维有限元分析,分析了上扣扭矩、轴向拉力、旋转扭矩作用下的钻杆接头接触压力分布规律和Mises应力分布规律。研究结果表明:当轴向拉力达到2500kN时,主台肩上的接触压力降为零,这将使得载荷主要由螺纹牙来承担,增加丝扣粘扣的风险。当旋转扭矩超过24000N m时,一方面提高了副台肩上的接触压力,增加了副台肩失效的风险;另一方面大幅提高了螺纹牙的承载比例,增加了丝扣粘扣的风险。适当增大副台肩间隙和副台肩处的接触面积可以降低大位移井中副台肩失效的风险。适当增大主台肩、副台肩的接触面积可以降低超深直井中丝扣粘扣的风险。本文计算的三种工况条件下,最大Mises应力同样均位于公扣大端第一个螺纹牙处,说明该处是最易发生粘扣的部位,在螺纹结构的优化设计中应予以重点考虑。
Aiming at the problem of plastic deformation caused by excessive contact pressure in threaded fastener, based on the three-dimensional finite element analysis of double shoulder drill fitting, the contact pressure of drill pipe joint under twisting torque, axial pulling force and rotating torque Distribution law and Mises stress distribution law. The results show that when the axial tensile force reaches 2500kN, the contact pressure on the main shoulder drops to zero, which will make the load mainly by the thread teeth and increase the risk of thread tripping. When the rotational torque exceeds 24000Nm, on the one hand, the contact pressure on the sub-shoulder is increased, which increases the risk of failure of the sub-shoulder; on the other hand, the bearing ratio of the thread teeth is greatly increased, which increases the risk of the threaded fastener. Properly increasing the contact area between the sub-shoulder clearance and the sub-shoulder can reduce the risk of sub-shoulders failure in the large-displacement well. Properly increasing the contact area of the main shoulder and the sub-shoulder can reduce the risk of thread buckles in ultra-deep vertical wells. Under the three working conditions calculated in this paper, the maximum Mises stress is also located in the first large end of the male thread, indicating that the place is the most prone to trimming. In the optimal design of the thread structure, the emphasis should be given .