On The Pure Squeeze Elastohydrodynamic Lubrication In Elliptical Contacts

Elastohydrodynamic lubrication (EHL) under pure squeeze was studied mainly in this thesis. Three problems are included: one is the EHL numerical analysis for the sudden stop process of elliptical contact; the other is the pure squeeze EHL analysis of the elliptical contact subjected to transient stepwise load impulse; the last is the pure squeeze EHL analysis under different initial film.The first part of this thesis is about the EHL numerical analysis for the sudden stop process of elliptical contact. Transient analysis of the residential film after sudden stop is developed with neglecting the variation in the velocity and taking the steady EHL solution as the initial condition. So, the process is divided into two EHL states, i.e., the steady state and the pure squeeze state. The numerical results show that, after a sudden stop, the lubricant in the remained film will gradually be squeezed out from the conjunction, and the residual film, therefore, can maintain itself in only a very short period. A higher Hertzian contact pressure can prolong the life of the residual film through the increase in the lubricant viscosity, but the general changing rule of the residual film cannot be changed fundamentally either by the Hertzian contact pressure, nor by the direction of the entrainment speed.A mathematical model of pure squeeze EHL in elliptical contact has been established, and full numerical solution has been achieved subjected to stepwise load in the second part of the thesis. It has been found that, the central pressure peak varies with the Hertzian contact pressure versus time, and so does the occurring time of the central pressure peak; different Hertzian contact pressure makes the distribution of pressure and film thickness be different, and a higher Hertzian contact pressure can change the pressure distribution from a single central peak into a pair of symmetrical pressure peaks in the contact region; the number of times of the stepwise load can make the contact region larger; the amplitude of the stepwise load can influence the contact region as well, that is, the higher the amplitude, the wider the contact region. It has also been found that, along the major and the minor axes of the contact ellipse, the distributions of pressure and film thickness are different tremendously.In the third part of this thesis, an EHL model of pure squeeze with zero initial film thickness in the contact region subjected to a load impulse has been established, and the film characteristics with different oils have been achieved. Good agreement has been observed between the numerical results and the experimental results given by Sakamoto. Meanwhile, Ml numerical solutions with different initial film thickness h_oil have also been achieved. It is found that the distributions of pressure and film thickness differ much from different oils under the same load condition due to the variation in the viscosity and the viscosity-pressure coefficient; under different initial film thickness h_oil the distributions of pressure and film thickness vary a lot.