【摘要】 在钻井过程中,经常发生下部钻具组合断裂失效事故,其主要失效部位是在钻铤薄弱部位——螺纹连接处,由于螺纹类型复杂,过渡部位易发生应力集中,造成钻具疲劳断裂破坏。针对钻铤断裂事故,建立了常规钻铤螺纹连接部位3种螺纹类型的有限元模型,并采用线弹性有限元方法分析了不同模型在不同钻压条件下的应力分布情况,同时对使用API标准应力减轻槽的钻铤螺纹连接部位进行了结构优化设计。在设计中以螺纹连接处两个过渡圆角半径R1、R2为设计变量,分析了在一定条件下不同尺寸的R1、R2所对应的螺纹连接处应力分布情况。对比分析可知,在满足钻铤强度条件下,改进的螺纹应力减轻槽可有效降低螺纹连接处的应力集中水平,从理论上说明该方法是可行的。更多还原

【Abstract】 Failures of drilling tools are common during drilling.The main failure parts are threads connection parts.Because of the complicity of the type of thread,stress concentration is easier to occur in the transitional parts to cause tool fatigue failure.The finite element models for collar’s thread connection part with 3 types of thread were created.The stress distribution was analyzed in different drill bit pressure using linear elasticity finite element method.Thread connection parts were optimized in structure for collars using API standard stress relief groove.Using the R1 and R2,the radius of the transition fillets as two design parameters,the stress distribution were analyzed in the thread connection part in different R1 and R2 under certain conditions.The comparisons indicate that the improved thread stress relief groove can reduce the stress concentration when the collar strength is satisfied,and this shows that this method is reasonable.更多还原