摘要:

The study of elastohydrodynamic (EHD) contacts is primarily concerned with the film thickness and the traction force developed between two, heavily loaded, solid surfaces in relative motion with each other. The aim of this paper is to calculate simultaneously film thickness, pressure, and shear stress distributions in isothermal EHD point contacts lubricated with a Ree–Eyring fluid under steady state conditions. A numerical method is developed to solve the EHD point contact problem for moderate and high loads. Theoretical results show that film thicknesses do not vary from those computed for a Newtonian fluid, except in the cases of very small values of the Eyring reference stress which lead to a significant reduction in film thickness. Calculated traction forces in rolling–sliding contacts are similar to those measured experimentally. The theory is compared with experiments made on a rolling–sliding point contact apparatus in which film thicknesses and traction forces are measured simultaneously. Good agreement is found.

ISSN:0148-6055    

DOI:10.1122/1.550140

出版商:The Society of Rheology    

年代:1990

数据来源: AIP

摘要:

A spinline viscometer was used to measure the apparent extensional viscosity of eight motor oils consisting of two SAE grades at two different temperatures. Oils corresponding to a 5W30 grade appeared to be slightly more elastic than 10W40 oils in extension. However, none of the oils was very elastic; measured Trouton ratios were less than 20 in each case. In fact, the 10W40 oils exhibited Newtonian behavior at low stretch rates. All the oils became slightly less elastic as the temperature of measurement was raised. In addition, an oil formulated using a synthetic base stock was found to behave differently from oils containing solvent extracted or hydrotreated base stocks.

ISSN:0148-6055    

DOI:10.1122/1.550091

出版商:The Society of Rheology    

年代:1990

数据来源: AIP

摘要:

High pressure lubrication, also called elastohydrodynamic lubrication (EHL) is a branch of tribology which has been considerably developed since 1960. Mechanisms running under this regime are characterized by high contact pressures (≳0.7 GPa) and very high values (up to 4 GPa) are now found. The advances have been realized in the fields of metallurgy, tooling, surface treatments and roughness control, lubricant elaboration, and fluid rheology. In most EHL problems, the main parameters governing the global contact behavior are the fluid film thickness which separates the solids and the dissipated shear energy which is usually expressed by the traction coefficient. Aside from solid properties, kinematic and geometric data, the lubricant high pressure rheology controls these important parameters. In this paper, we show how high pressure rheology can answer EHL problems. To illustrate this, we present experimental results on high pressure viscometry and high pressure rheometry. Simultaneously, we mention analytical and numerical work in which the EHD flow is modeled, showing the historical evolution of shear models, from Newtonian behavior to the Montroseetal. model. Other works related to EHL needs are presented, for instance, ultrasonic propagation in lubricants. The existence of phase transition effects in EHL is considered.

ISSN:0148-6055    

DOI:10.1122/1.550092

出版商:The Society of Rheology    

年代:1990

数据来源: AIP