Nonsteady oscillations of the roller contacting with rigid surface with lubrication layer

Analytical solution is obtained for the problem of non-steady hydrodynamic contact between roller and solid body in a presence of liquid lubrication material. This problem is very actual one because nonsteady regime is dominating during launching of spaceсrafts. Distribution of the pressure along the lubrication layer is obtained by integration of the Reynolds equation taking into account both the tangential and normal velocities of the roller. Normal oscillations of the roller contacting with lubrication layer is described by a stiff second order ordinary differential equation. Solution of this equation is presented as an asymptotic series expansion with respect to the singular small parameter. It was found that the relaxation process is characterized by two different time scales. The first one determines a steep growth of the pressure maximum just after the loading jump. The second one is related to a relatively slow process of the pressure relaxation to its stationary state corresponding to the enhanced loading value. The obtained results indicate clearly that simulation and analysis of nonsteady relaxations processes in bearing devices of flight vehicles is of great importance. In particular, in case of slow quasi-stationary increase of loading in 2 times the pressure maximum over the lubrication layer has approximately two-fold enhancement. However, similar in amplitude, but sudden jump of loading yields much stronger enhancement (more than in 10 times) of the pressure maximum over the lubrication layer during the time-relaxation process. Such strong and fast pressure jump in the lubrication layer can make a crucial influence on the operation resources of vehicles.