On the time-dependent, thermal and non-Newtonian elastohydrodynamic lubrication of line contacts subjected to normal and tangential vibrations

Abstract

Complete numerical solutions were obtained for the time-dependent thermal elastohydrodynamic lubrication (EHL) of line contacts under combined vertical and longitudinal vibrations. It was assumed that the contact was composed of two in®nitely long steel rollers. These rollers were then simpli®ed as an in®nite plane and an equivalent roller. The lubricant was assumed to be a Ree±Eyring non-Newtonian¯uid. The time-dependent numerical solutions were achieved instant after instant in each period of vibrations. The periodic error was checked at each end of the vibration period until the responses of pressure, ®lm thickness and temperature were all periodic functions with the frequency of the roller's vibrations. At each instant, the pressure ®eld was solved with a multi-grid method, the surface deformation was solved with a multi-level multi-integration technique, and the temperature ®eld was solved with a ®nite difference scheme through a sweeping process. It was shown that the normal vibration dominated the EHL characteristics and could be either strengthened or weakened slightly depending on the phase of the tangential vibration. It was also found that the vibration of the roller could produce transient surface dimples within the contact conjunction.

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

“…There are two sudden changes on the curve of h min for f = 2000 Hz, one starts at ωt = 0.8π, because of the jump of the location of h min from the exit region to the inlet region [16], the other starts at ωt = 1.322π, because of the quick movement and disappearance of the EHL exit constriction.…”

“…It is well accepted that vibrations are usually harmful because they can reduce both the accuracy and the durability of machine components. 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.…”

Effects of starvation and viscous shear heating in hydrodynamically lubricated rolling/sliding line contacts

“…The Legendre coefficients of temperatures T 0 , T 1 , T 2 , and T 3 are obtained by solving equations (19), (20) along with equations (15(a) and (b)). Thermal pressure is computed iteratively using equation (10) after incorporating thermal effects in viscosity. In computation, wherever reverse flow arises, upwind differencing (sweeping in the direction of flow) has been resorted.…”

Transient elastohydrodynamic analysis of elliptical contacts. Part 2: Thermal and Newtonian lubricant solution

“…It was assumed that d ¼ 2.5a in the calculations reported here. Such an assumption was considered to be sufficiently accurate, particularly under a relatively high speed adopted [14]. The steady state temperature field T steady corresponding to the initial pressure field p steady was used to provide the initial conditions for equations (3) to (5).…”

“…There are only a limited number of studies where both thermal and transient effects have been combined in EHL contacts and most have been for relatively simple line contact problems [9][10][11][12][13][14][15]. Transient thermal EHL solution for point contacts has been considered to be a huge task, because a transient solution needs to be obtained at a large number of steps.…”