%0 Journal Article
%T Effect of an Improved Yasutomi Pressure-Viscosity Relationship on the Elastohydrodynamic Line Contact Problem
%A Vincenzo Petrone
%A Adolfo Senatore
%A Vincenzo D'Agostino
%J ISRN Tribology
%D 2013
%R 10.5402/2013/149451
%X This paper presents the application of an improved Yasutomi correlation for lubricant viscosity at high pressure in a Newtonian elastohydrodynamic line contact simulation. According to recent experimental studies using high pressure viscometers, the Yasutomi pressure-viscosity relationship derived from the free-volume model closely represents the real lubricant piezoviscous behavior for the high pressure typically encountered in elastohydrodynamic applications. However, the original Yasutomi correlation suffers from the appearance of a zero in the function describing the pressure dependence of the relative free volume thermal expansivity. In order to overcome this drawback, a new formulation of the Yasutomi relation was recently developed by Bair et al. This new function removes these concerns and provides improved precision without the need for an equation of state. Numerical simulations have been performed using the improved Yasutomi model to predict the lubricant pressure-viscosity, the pressure distribution, and the film thickness behavior in a Newtonian EHL simulation of a squalane-lubricated line contact. This work also shows that this model yields a higher viscosity at the low-pressure area, which results in a larger central film thickness compared with the previous piezoviscous relations. 1. Introduction Elastohydrodynamic lubrication (EHL) is the lubrication of contacts between nonconformal surfaces, that is, surfaces that do not fit each other well. EHL is found in most common machine elements such as rolling element bearings, gears, and cam mechanisms. It is characterized by concentrated forces, high contact pressures (1¨C3£¿GPa), thin lubricant films (1¨C2000£¿nm), and short durations. Due to the high pressure and the limited contact area, elastic deformation of the surfaces will occur and it is not negligible, and the pressure dependence of viscosity plays a crucial role in EHL simulation because the viscosity at the inlet has crucial influence on film formation [1¨C4]. An understanding of these films, in turn, makes it possible to predict the risk for fatigue and failure due to adhesive wear, which inevitably results in unwelcome disruptions due to machine breakdown and costly repairs. Viscosity and the viscosity-pressure-temperature relationship greatly influence film formation in EHL contacts and in the light of the above facts, when conducting an EHL simulation, the real pressure-viscosity behaviour of the lubricants should not be overlooked. However, it is very difficult to measure the viscosity of lubricants under EHL conditions (i.e.,
%U http://www.hindawi.com/journals/isrn.tribology/2013/149451/