涡动条件下钻柱的屈曲分析

A buckling analysis of the drillpipe in the condition of whirling

建立了涡动条件下钻柱屈曲的平衡方程。在弯曲挠度为小变形和钻柱中轴向力为0的条件下,采用理论方法分析了钻柱的弯曲挠度、屈曲应力随转盘转速变化的情况。当涡动速度增加导致钻柱的弯曲挠度增加和钻柱中存在轴向力时,钻柱的弯曲挠度以及交变应力的大小就需要通过非线性有限元来进行分析。使用非线性有限元方法求解了不同轴向拉力条件下钻柱的弯曲挠度、最大应力、最小应力和应力幅度。计算结果表明,不考虑轴向力时,理论分析结果与非线性有限元分析结果精度较高且具有一致性;当钻柱中轴向拉力大于200 kN时,由涡动引起的交变应力对钻柱的影响可以忽略;适当增大钻铤长度可以减轻钻柱的疲劳失效。

The equilibrium equation for drillpipe buckling in the condition of whirling was established.In the condition that the bending deflection was of small deformation and the axial force in the drillpipe was zero,the theoretical method was adopted to analyze the change of the drillpipe's bending deflection and buckling stress with the rotational speed of the rotary table.When the increase of whirling velocity caused the increase of bending deflection and the production of axial force in the drillpipe,the bending deflection and alternating stress of the drillpipe should be analyzed by the nonlinear finite element method.The method was used to solve the bending deflection,maximum stress,minimum stress and stress amplitude of the drillpipe in different axial tensions.The calculation result showed that,when the axial force was not considered,the theoretical analysis and the nonlinear finite element analysis were of high precision and consistent with each other;when the axial tension of the drillpipe was greater than 200 kN,the effect of the whirl-caused alternating stress on the drillpipe was negligible;a proper increase of the drill collar's length could reduce the fatigue failure of the drillpipe.