套管连接螺纹的受力分析与改善措施

The Load Analysis and Betterment of Casing Connections

套管在轴向拉力作用下,连接螺纹的各牙受力很不均匀,从而严重制约了套管接头的承载能力.针对套管螺纹的结构特点,建立了连接螺纹在轴向拉力作用下的力学模型,分析了各牙螺纹的受力和变形特点.在此基础上,给出了改善套管螺纹受力分布的具体方法,并从便于进行螺纹加工的角度出发,提出了外螺纹螺距不变,内螺纹变螺距的近似方案,最后用有限元法验证了这种方案的可行性.为改进套管螺纹设计,提高套管螺纹连接质量提供了依据.

For a common casing thread, the forces acting on each thread under tensile loads are not uniform, which decreases the load-bearing capacity of the casing connections notably. According to the structure character of casing connections, a mechanical model was developed to analyze the force and deformation on casing threads under tensile load. Then a method was presented for optimizing the load distribution on each casing thread. Moreover, concerning the feasibility of the thread processing, this paper also put forward an approximate method:the pitch of pin keeps unchanged, the pitch of box change slightly according to the calculation result. At last, a finite element model was founded to test the approximate method. The results show the approximate method is effective. Thus it can be taken as references in improving the design of casing thread so as to improve the quality of the connections.