套管开窗万向节力学行为仿真及结构改进

Simulation of Mechanical Behavior of Universal Joint for Casing Window and Structural Improvement

针对水力径向喷射增产技术中的套管开窗工艺,利用有限元方法研究了万向节与导向器之间,以及万向节自身接触应力及摩擦力分布,并对现有的开窗工具进行了结构改进。在研究万向节与导向器内轨迹壁接触应力时,忽略万向节叉耳朵及中间外圆端面处倒角,不关注钻头与套管的相互作用,钻头前端简化成圆锥形状。分析结果表明,万向节在正常工作时,应力主要集中在万向节叉中间端面以及万向节叉耳朵位置;十字轴轴颈和两轴相贯的地方有应力集中现象,通过加大轴颈半径及改变两轴相交位置形状可有效降低应力集中,提高十字轴使用可靠性;合理设计万向节叉和导向器几何尺寸可以有效减小摩擦力与接触应力。

In light of casing window technology in hydraulic radial jet simulation technology, the finite element method was used to study the distribution of contact stress and friction force between universal joint and guide and the joint itself. The structure of window cutting tool available was modified. In studying the trajectory wall contact stress within universal joint and guide, the chamfer of the joint fork ear and the middle external end face was neglected, without caring about the interaction between drilling bit and casing. The front end of drilling bit was simpli- fied as the conical shape. The analysis shows that stress mainly concentrates on the fork middle end and the fork ear when universal joint works properly. Stress also concentrates on the cross journal as well as the intersection of two crosses. The stress concentration can be reduced effectively through increase of journal radius and change of the intersection form of two crosses, improving the service reliability of cross. The rational design of universal joint fork and geometric dimensions of guide can effectively reduce friction force and contact stress.