Dench J, Morgan N, Wong J S S
1Department of Mechanical Engineering, Imperial College London, London, SW7 2AZ UK.
Shell Global Solutions (UK) Ltd, Brabazon House, Threapwood Road, Manchester, M22 0RR UK.
Tribol Lett. 2017;65(1):25. doi: 10.1007/s11249-016-0807-3. Epub 2016 Dec 30.
Lubricant viscosity is a key driver in both the tribological performance and energy efficiency of a lubricated contact. Elastohydrodynamic (EHD) lubrication produces very high pressures and shear rates, conditions hard to replicate using conventional rheometry. In situ rheological measurements within a typical contact are therefore important to investigate how a fluid behaves under such conditions. Molecular rotors provide such an opportunity to extract the local viscosity of a fluid under EHD lubrication. The validity of such an application is shown by comparing local viscosity measurements obtained using molecular rotors and fluorescence lifetime measurements, in a model EHD lubricant, with reference measurements using conventional rheometry techniques. The appropriateness of standard methods used in tribology for high-pressure rheometry (combining friction and film thickness measurements) has been verified when the flow of EHD lubricant is homogeneous and linear. A simple procedure for calibrating the fluorescence lifetime of molecular rotors at elevated pressure for viscosity measurements is proposed.
润滑剂粘度是润滑接触的摩擦学性能和能量效率的关键驱动因素。弹流润滑（EHD）会产生非常高的压力和剪切速率，这些条件很难用传统流变学方法复制。因此，在典型接触中进行原位流变测量对于研究流体在这些条件下的行为非常重要。分子转子提供了一个机会来提取弹流润滑下流体的局部粘度。通过将在模型弹流润滑剂中使用分子转子获得的局部粘度测量值和荧光寿命测量值与使用传统流变学技术的参考测量值进行比较，证明了这种应用的有效性。当弹流润滑剂的流动是均匀且线性时，已验证了摩擦学中用于高压流变测量（结合摩擦和膜厚测量）的标准方法的适用性。提出了一种在高压下校准分子转子荧光寿命以进行粘度测量的简单程序。
