Transient elastohydrodynamic analysis of elliptical contacts. Part 3: Non-Newtonian lubricant solution under isothermal and thermal conditions

Abstract

Transient non-Newtonian elastohydrodynamic lubrication (EHL) of elliptical point contacts was investigated numerically under both thermal and isothermal conditions. The multi-level technique used in Parts 1 and 2 of this series of papers for determining pressure and film thickness and the column-by-column relaxation technique used in Part 2 for temperature calculation were used again in this study. However, both Newtonian and non-Newtonian lubricant properties were considered, with the Ree -Eyring model being adopted in the latter case. The entrainment direction was assumed to be along the minor axis of the contact ellipse. A simplified numerical scheme for the evaluation of the equivalent shear stress and viscosity of the non-Newtonian lubricant was proposed and verified by comparing the steady-state thermal solutions without the simplification. The computing time required for a transient thermal and non-Newtonian case was typically 14 h on a personal computer with a 2.8 GHz central processing unit. For a steel -steel contact, the responses of the EHL films to a transient load impulse were determined for the non-Newtonian lubricant under both isothermal and thermal conditions. The isothermal non-Newtonian results were compared with those in Part 1, and the thermal results were compared with those presented in Part 2. A similar investigation for a glass -steel contact is also reported.

A theoretical study on the response of a point elasto-hydrodynamic lubrication contact to a normal harmonic vibration under thermal and non-Newtonian conditions

“…It was assumed that d = 2.5a, which was considered to be large enough to represent infinity in the numerical analysis [14,15].…”

“…Unlike that in reference [15], the problem in this paper does not require any initial condition, but needs to satisfy the cyclic requirement, that is, all variables such as pressure, film thickness, and temperature of the convergent solution, need to be periodic functions of time with the same frequency of the vibration.…”

“…When such a scheme was used, the computing time for a non-Newtonian solution was about five times that for the corresponding Newtonian solution. In order to reduce the computing time to an acceptable level, a simplified scheme for the calculation of the equivalent viscosity was developed by Cui et al [15], so that the computing time for a non-Newtonian solution was reduced to about 1.8 times that for the corresponding Newtonian solution. All cases solved in this study are for elliptical contact with a large slide-roll ratio and the entrainment is along the minor axis of the contact ellipse.…”

“…They investigated the thermal and non-Newtonian effects in the process of an asperity on the fast surface passing an asperity on the slow surface in a rolling/sliding circular point contact. Very recently, the numerical techniques reported in reference [13] have been simplified by Yang et al [14] and Cui et al [15], and the transient effects of a load impulse have been investigated under thermal conditions for both the Newtonian and non-Newtonian lubricants in elliptical point contacts.…”

“…Yang et al [16] have investigated the influence of the normal and tangential vibrations on the EHL behaviour for line contacts through a time-dependent thermal and non-Newtonian procedure, yet a similar procedure for point contacts remains to be developed. The main purpose of this study was to extend the transient EHL analysis under a load impulse considered in reference [15] to a complete time-dependent numerical solution associated with a normal vibration under thermal and non-Newtonian conditions with acceptable time of computation. Because harmonic oscillation is the basic form of the vibration phenomena, as a preliminary work, in the current paper the elliptical point contact is idealized as composed of a spherical roller and an infinite plane, and, it is further assumed that the roller is oscillating harmonically in the normal direction against the infinite plane, when both surfaces are running with a certain slide-roll ratio.…”