The failure statistics of drill stem indicated that drill pipe failure accounted for 50 % ~ 60 % in total ones which failure mode is tube piercement and the main failure cause is corrosion fatigue .

钻柱失效案例统计表明钻杆失效事故占钻柱 总 失效 事故的50%～60%，主要 失效 形式是管体刺穿，主要失效原因是腐蚀疲劳；

Vertical short cracks on surfaces resume propagating till 70-80 percent of the total RCF failure lives and then are accelerated to propagate almost synchronously the two types of short cracks resume growing with a turned mode in subsurface .

在疲劳 失效寿命的 70%-80%时，垂直短裂纹恢复扩展，并随即加速长大.几乎同时，两种短裂纹在亚表层以转折的 方式重新扩展。