G105钻杆的拉伸和扭转失效研究

钻杆是石油天然气勘探开发过程中的重要结构件，其服役环境恶劣，易发生失效。基于弹塑性力学中的形变理论建立了纯扭矩作用下钻杆抗扭强度计算的力学模型，根据该模型可以计算钻杆在弹塑性阶段的扭矩。同时，用G105实物钻杆分别进行了轴向载荷下的抗拉测试和纯扭矩下的抗扭测试，抗拉实验得到了钻杆的屈服强度和抗拉强度及断裂时的轴向载荷，抗扭实验得到了钻杆的弹性和塑性极限扭矩。抗扭实验结果和模型的计算结果一致。研究结果为钻柱疲劳、断裂失效机理的进一步研究提供了理论依据，为钻柱强度设计提供了新思路。

Research of G105 drill pipe failure under loads of pure tension and pure twisting

Oil drill pipe is one of most important components for oil and natural gas exploration and development, which is liable to failure because of the poor service environment. In order to avoid the drill string failure, it is necessary to study the failure mechanism of drill string. So, based on the deformation theory of plastic mechanics, the mechanical model which can calculate the twisting strength of drill pipe has been established in this paper. According to this model, the torque of drill pipe can also be calculated in the elastic and plastic stage. Simultaneous, the full-scale tensile and torsion test of G105 drill pipe were conducted. The yield strength and tensile strength were obtained through the tensile test. The elastic and plastic limit torque were obtained through the torsion test. The results of torsion test are in excellent agreement with the calculation results. The research results can provide powerful new thoughts and some theoretical basis for the strength design and the further development of the study on the failure mechanism of fatigue for drill pipe respectively.