机械密封用O形橡胶密封圈微动特性

Fretting Characteristics of the Rubber O-Ring for a Mechanical Seal

采用含高阶项的Mooney-Rivlin本构模型对机械密封用O形丁腈橡胶圈进行了轴对称有限元分析,重点考察了位移幅值、介质压力、压缩率及摩擦系数对其微动特性的影响.结果表明:随着位移幅值的增加,O形圈在微动界面上可呈现黏着、混合黏滑和完全滑移3种不同的接触状态;介质压力、压缩率及摩擦系数对O形圈的微动运行行为有重要影响;混合黏滑状态下O形圈密封界面摩擦力的显著波动会影响浮动环的浮动性;滑移状态下O形圈伴随着较高的Von Mises应力易导致其发生剪切破坏、表面磨损加剧;而在黏着状态下O形圈的综合性能最佳.因此,应避免O形圈运行于混合黏滑状态,压缩率取10%左右,并降低摩擦系数,以减缓其表面磨损和剪切破坏并满足补偿环浮动性和追随性.

The fretting characteristics of the nitrile rubber O-ring for a mechanical seal were successfully simulated by axisymmetric finite element analysis, using the Mooney-Rivlin model with high-order terms. The effects of the displacement amplitude, medium pressure, precompression ratio and friction coefficient were investigated. The results show that three contact states for the fretting characteristics of rubber O- ring can be determined, i.e. stick state, mixed stick slip state and slip state with the increase of the displacement amplitude. The fretting running behavior of rubber O-ring was strongly dependent upon the medium pressure, precompression ratio and friction coefficient. In mixed stick-slip state, the strong fluctuations of frictional force on the sealing interface would weaken the floatability of floating ring. In slip state, the high Von Mises stress may lead to shear failure and severe surface wear. However, O-ring possessed the optimum comprehensive performance when working in stick condition. In a word, to mitigate shear failure and surface wear of O-ring and meet the floatability and tracking property of the seal ring, the mixed stick-slip state should be avoided and a compression of appoximately 10% and a lower coefficient would be preferred.