【摘要】 分析了立井钻机中心管含表面裂纹的断裂状况；探讨了在亚临界扩展阶段波劳断裂的发展趋势；导出了中心管断裂时的断裂条叮及裂纹扩展时极阳尺寸的计算公式．更多还原

【Abstract】 This paper analyses the break of the centre tube containing fare crackle of well drill, inqures into the tendency of fahgue break under suberihcal spread stage and obtain the break condition of the centre tube as well as the calculating formulas of entreme size on crackle spread.更多还原