裂纹型缺陷对套管承载能力影响研究

Influence on Load-Bearing Capability of Oil Thimble by Crack Defect

套管裂纹缺陷中最危险的是表面裂纹,可分解成表面周向裂纹和表面轴向裂纹问题。采用能量差率方法,将裂纹的三维问题转化为二维问题,获得了关于裂纹张开位移的伯努利方程的简化封闭解,导出了空心圆管内、外表面的周向半椭圆表面裂纹在轴向拉伸载荷作用下的应力强度因子的封闭解,并在实例中用双边界元法证明了封闭解的正确性;对轴向裂纹的应力强度因子,比较了经验公式求解与双边界元计算的结果;分析了工程实例中裂纹缺陷对套管安全的影响。

The exterior surface crack is the most dangerous among crack defects of oil thimble. And it can be turned into surface circumferential crack and surface axial crack. In this paper, three dimensional crack problems can be transformed into two dimensional problems. Energy difference rate method is applied to obtain a simplified closed form solution of the Bernauli＇s equation about crack opening displacement. The closed form solution of stress intensity factors is ultimately deduced in the oil thimble with semi-ellipse outer surface crack or inner surface crack under the axial traction load. The analytical solution of stress intensity factors is proved right and effective by boundary element method. For the axial crack, stress intensity factor difference between experiential formula and boundary element method. Finally, influence on safety of oil thimble is analyzed by the size of crack in engineering application.