基于高剪切率弹流摩擦特性试验的滚动轴承润滑脂流变特性及润滑机理的研究

Because the study on the elastohydrodynamic friction characteristics, rheological characteristics and lubrication mechanisms at the real operating conditions of a bearing is absent all over the world, we will carry out the friction tests of several kinds of lubricating greases, their base oils, their bleeding oils and the greases of different degradable degrees under fully flooded supply and limited supply on a self-made elastohydrodynamic friction test rig from pure rolling to slide-to-roll moving ,from slow rolling speeds to high rolling speeds and from light loads to high loads at high shear strain rates. Friction coefficient models of lubricating greases will be presented.Based on the elastohydrodynamic friction tests at high shear strain rates, the rheological characteristics and lubrication mechanisms of the lubricating greases at the real operating conditions of bearings are researched. Rheological models and the computation formulae for rheological parameters of lubricating greases at high shear rates will be derived.The discipline of the effect of the operating conditions, the type and viscosity of the base oil, the type and concentration of the soap, base oil-soap interaction and degradable degree on the friction characteristics,rheological characteristics and lubrication mechanisms will be found out. The gap on the study of the rheological characteristics of lubricating greases at high shear strain rates will be filled to a certain extent and the self-contradiction lubrication mechanism problems will be solved by the research results. The performance evaluation criterion on the lubricating greases at the real operating conditions of a bearing will be built.The research results may also provide theory guide to the choices of suitable lubricating grease for bearings , the improvement of the life of bearings and prescription of lubricating greases.They also may lay foundation for the development of lubrication and rheology theory.

针对国内外缺乏模拟轴承实际工况的润滑脂弹流摩擦特性、流变特性和润滑机理研究的现状，拟在自行研制的能模拟从纯滚到滑滚、从低速到高速，从低温到高温，从低载到高载的高剪切率弹流摩擦特性试验机上，对多种润滑脂及其基础油、析出油和不同衰减程度的润滑脂进行充分和限量供脂条件下摩擦特性测试，建立润滑脂的摩擦系数计算模型；基于高剪切率弹流摩擦特性试验，研究满足滚动轴承实际工况的润滑脂流变特性和润滑机理，建立高剪切率下润滑脂的流变模型和流变参数的计算公式，发现工况条件、基础油类型和粘度、稠化剂类型和稠度、基础油-稠化剂相互作用及衰减程度对摩擦特性、流变特性和润滑机理影响的规律。研究结果将填补高剪切率下润滑脂流变特性研究的空白，解决目前润滑机理自相矛盾的现状，建立润滑脂在实际滚动轴承中的性能评价标准，为轴承选择合适润滑脂、提高轴承寿命及为润滑脂的配方提供理论指导，为润滑理论和流变学的发展奠定基础。

当轴承被正确安装，没有结构和材料缺陷的情况下，脂润滑轴承的寿命主要由润滑脂的摩擦特性和流变特性来决定。目前我国在润滑脂摩擦特性和流变特性以及相应润滑机理的研究方面给出的均为非滚动轴承实际工况下的研究结果，使得长期以来我国生产的润滑脂在实际轴承中的性能得不到正确的评价，造成无法为轴承选择适合的润滑脂，脂润滑轴承达不到使用寿命，以及很多设备事故频发。所以，进行滚动轴承实际工况条件下润滑脂摩擦特性和流变特性以及相应润滑机理的研究非常急迫。. 首先研制了模拟滚动轴承宽工况范围的高剪切率弹流摩擦试验机，可模拟的工况范围如下：赫兹压力范围 0-2GPa， 温度范围-30℃-125℃，滚动速度1-50m/s，滑滚比s=-20%-20%. 对矿物油-锂基、PAO-锂基、多元醇酯-锂基、矿物油-聚脲、PAO-聚脲五种润滑脂进行了充分供脂条件下高剪切率弹流摩擦特性和润滑机理的研究。在给定载荷、滚速和温度条件下，测量润滑脂弹流摩擦系数随滑滚比变化的试验曲线。改变工况条件，可得到不同工况条件下润滑脂的摩擦特性曲线，并分析了工况条件、基础油类型、稠化剂类型、基础油粘度、稠化剂浓度、基础油-稠化剂配对及不同衰减程度对摩擦特性和润滑机理的影响。对五种润滑脂进行了限量供脂条件下高剪切率弹流摩擦特性和润滑机理的研究。在保证供脂量、滑滚比、滚动速度、载荷和温度不变的前提下，测量摩擦系数随时间变化的曲线图。分析了工况条件、基础油类型、稠化剂类型及不同衰减程度对摩擦特性的影响。通过分析不同工况条件和不同润滑脂特性下摩擦系数试验数据变化趋势，采用合适的数学模型建立摩擦系数与工况条件和润滑剂特性参数之间的关系式，建立了润滑脂摩擦系数计算公式。根据接触力学、弹流润滑理论、流变学理论建立了高剪切率下润滑脂流变特性曲线和润滑脂的流变模型。