关键词: 气体钻井,    , 钻柱,    , 本构关系,    , 损伤度,    , 损伤演化,   , 疲劳寿命

Abstract: Based on the modern damage mechanics research，aiming at the gas drilling string frequent fracture failure，the drill string damage evolution process was analyzed. The gas drilling damage fatigue life prediction model of the drill string was established. The gas drill string damage fatigue life model was the main factors influencing the fatigue life of drill string. And damage gradient was introduced to explore the relationship among axial load, injury tolerance and strain. According to the theory and case analysis, the relationship between injury tolerance and strain is going through a change from space period to quasi periodic with the axial load increasing. Meanwhile, damage localization occurs that lead to drill string fatigue failure. 

Key words: Gas drilling,    ,  String,    ,  Constitutive relation,    , Damage degree,    , Damage evolution,    ,  Fatigue life