弧长法在斜直井内管柱非线性屈曲分析中的应用

对于斜直井内底部一段管柱的后屈曲问题,基于受径向约束管柱的微分求积(DQ,Differential Quadrature)单元,构建了弧长迭代法.给出详细的迭代步骤和迭代初值的确定方法,对不同端部侧向约束条件下的管柱非线性屈曲进行迭代计算.并与现有文献中的近似解析解、实验结果和纯载荷增量迭代法的数值计算结果进行比较.结果显示,本文方法克服了有限单元法在处理管柱自重时的困难,同时能自动调节增量步长,跟踪管柱非线性后屈曲平衡路径的全过程.计算效率高、收敛性好、易于实施,可以用来分析斜直井内管柱的非线性屈曲问题.

Arc-length Method for Nonlinear Buckling Analysis of Tubular in Deviated Wells

Based on differential quadrature(DQ) element of tubular with a radial constraint,an arc-length incremental iteration method is established.It is used for the post-buckling analysis of tubular in a deviated well bottom.Detailed iteration steps and method of determining initial values of iteration are given.Iterative calculations are carried out for nonlinear buckling of tubular under various end lateral constraints in deviated wells.Numerical results are compared with approximate analytical solution,experimental data and numerical results obtained with purely incremental methods in literature.It shows that the developed method overcomes difficulties encountered in finite element method in dealing with tubular weight.At the same time,it is capable to adjust automatically increment step and trace complex path in the space load/displacement of tubular nonlinear post-buckling.The method is of high efficiency,good convergence,easy to implement.It can be used to analyze nonlinear buckling of tubular in deviated wells.