A Critical Analysis of Viscosity Measurements Made on an Impact Viscometer.
FRAMAN DISTRIBUTORS LTD WARFORD (ENGLAND)*
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Previous studies have generated a considerable amount of viscometric data on several lubricants which shows that the phenomenon of viscosity saturation found in earlier tests at lower pressures appears to be general. Providing a high enough pressure is applied and the time scale of the measurements is short enough, it is probably true that all lubricants will reach a limiting viscosity as measured on the dropping ball viscometer. Recent viscosity measurements on a long time scale by other workers have detected no evidence of this phenomenon on one of the test fluids. The task of the authors research was therefore to consider whether the dropping ball data could be consistently in error, or whether there was a general physical explanation, for viscosity reaching a limit. Presented is a critical examination of the experimental errors and the assumptions involved in calculating viscosity from the entrapment data. Following this, four possible physical models are considered which have met with some success in predicting another aspect of high pressure fluid properties on short time scales - traction in elastohydrodynamic rollingsliding contacts.
- Physical Chemistry
- Lubricants and Hydraulic Fluids