Abstract: The existing problems of the original contact fractal model of friction pair faces of mechanical seals were analyzed, and the original model was modified.The relationship between bearing area ratio of asperity and face pressure on the friction pair faces was obtained.In the modified model, the effects of film pressure of fluid between the end faces of friction pair, the differences between real micro contact area and micro contact sectional area of asperity were taken into account.The relationship between elastic-plastic deforming asperity contact pressure and contact area was expressed by a cubic polynomial, which satisfied the continuous and smooth conditions of the transformation of asperity contact area and contact pressure at the critical point of transition of asperity distorting state.According to the modified model, the influence factors of asperity bearing area ratio of friction pair faces matched by cemented carbide YG8-carbon graphite M106K of partial balance mechanical seals were analyzed.The results showed that the asperity bearing area ratio increased approximately linearly with spring pressure, increased monotonously nonlinearly with fluid pressure, increased at first and then decreased with the increase of fractal dimension, and decreased with the increase of characteristic length scale.The real contact area accounts for only a small part of the nominal contact area under normal operating conditions.

Key words: mechanical seal, fractal model, asperity bearing area ratio, face pressure

摘要： 分析了原机械密封摩擦副端面接触分形模型存在的问题,并进行了修正,得到了摩擦副端面微凸体承载面积比与端面比压的关系式。修正模型考虑了摩擦副端面间流体膜压的作用、微凸体实际微接触面积与微接触截面积之间的区别,并通过采用一个三次多项式来表达弹塑性变形微凸体的接触压力与接触面积的关系,从而满足了接触微凸体在变形状态转变临界点处的接触面积与接触压力转化皆是连续和光滑的条件。依据修正后的接触分形模型对密封面配对材料为硬质合金YG8-碳石墨M106K的部分平衡型机械密封摩擦副端面微凸体承载面积比的影响因素进行了分析。结果表明,微凸体承载面积比随着弹簧比压的增大近似呈线性增大,随着密封流体压力的增大而非线性单调增大,随着端面分形维数的增大先增大后减小,随着端面特征尺度系数的增大而减小;在正常工作参数范围内,真实接触面积仅占名义接触面积的很小一部分。

关键词: 机械密封, 分形模型, 微凸体承载面积比, 端面比压