螺杆钻具壳体连接螺纹结构性能分析与优化

Performance analysis and optimization of connecting thread structure of screw drilling tool shell

考虑螺纹牙和基体的弹性变形,根据受力平衡方程和变形协调方程,构造线性方程组,建立了连接螺纹接头载荷分布特性的理论计算方法。采用迭代的方法,完成了全尺寸连接螺纹螺距P的优化,结果表明,针对连接螺纹螺距的优化极大地改善了螺纹牙载荷分布极度不均的现象,实现了螺纹牙均匀承载的变螺距结构设计。应用有限元分析方法分析了上扣扭矩状态下参数影响,结果表明,螺距P、牙高h等牙型参数全尺寸变化对提高强度性能效果不大,而降低前端几扣高度可以小幅提高连接螺纹接头的强度,但发生粘扣的风险却成倍增加。分析了外螺纹剪应力槽结构对连接螺纹性能的影响,并完成了相应参数优化。扭弯复合载荷作用下的连接螺纹接头应力分析表明,在产生弯矩的载荷作用下外螺纹受拉侧应力升高、受压侧应力降低,内螺纹则相反,环向Mises应力呈余弦函数分布。

The equations of stress distribution and stress distribution of thread are established. The results show that the load distribution of each screw thread is extremely uneven, which is a quasi-hyperbolic function distribution. Results show that the optimization of thread pitch P can greatly improve the uneven load distribution of thread teeth and realize the design of variable pitch structure with uniform load. In this paper, the finite element analysis method is used to analyze the effect of full-size change of thread pitch P, tooth height h on improving the strength performance under the condition of make-up torque, while the height of several threads at the end slightly improves the strength of the joint, but the risk of thread sticking is doubled. Influence of the structure of stress relief groove on the performance of connecting thread is analyzed, and the corresponding results are completed. Results show that the structural performance of the joint is improved effectively. The stress analysis of the threaded joint under the combined torsion and bending loads shows that the stress on the tension side of the external thread increases and the stress on the compression side decreases under the action of the bending moment, while the stress of the internal thread is on the contrary, and the circumferential Mises stress distribution is cosine function.