Contact dynamics of starved elastohydrodynamic lubrication

In this paper, the, transient, pressure, film thickness and lubricant profile of a starved EHL contact, operating under sinusoidally varying loads, is presented. In a theoretical section, the dimensionless, quasi-static, dry contact solution is discussed. Subsequently, the equations for lubricated contacts will be stated, as well as the Jakobsson-Floberg-Olsson (JFO) relation for time-dependent, two-dimensional contacts. Numerical solutions are presented, which were obtained by a transient version of Elrod's algorithm. Apart from a brief discussion of the steady state results, the paper focuses on the transient solution. It is shown that the induced oscillatory motion of the rolling element, leads to film thickness modulations, which are similar to the modulations observed for free vibrations reported in [10]. These modulations propagate at the dimensionless speed of unity and their (dimensionless) wavelength will be shown to equal 2π/Ωe, where Ωe is the dimensionless excitation frequency. Furthermore, it is shown that lubricant layer modulations are induced in the wake. Initially, these modulations, deposited as a result of the squeeze motion, are concentric with the Hertzian contact region and, like the film thickness modulations, propagate at the dimensionless speed of unity. At later times, the film thickness modulations which have propagated through the contact, interfere with the lubricant layer modulations, giving rise to a particular lubricant profile in the wake. It is shown that the phenomena, as described by the JFO relation, indeed show in the numerical solution.