Infuence of the boundary film shear elastic modulus on the performance of a micro contact

A contact model is developed to theoretically analyze the influence of shear elastic modulus of the boundary film on the performance of a micro contact. The contact is one-dimensional and formed by two sliding parallel planes. The upper contact surface is rough with rectangular micro projections, while the lower contact surface is smooth. Both of the contact surfaces are treated as rigid. The micro contact is filled with fluid. It consists of two sub-zones. In the outlet zone, the micro contact is distributed with boundary film because of the nanometer-scale contact separation, while in the inlet zone, the micro contact is distributed with fluid film because of the relatively high contact separation. The performance of the micro contact is determined by the behaviors of the boundary film and the fluid film. When the film thickness is relatively high, the boundary film here can be considered as the nanometer-scale thin film. Because of the limited shear stress capacity at the upper contact surface, the boundary film can slip at the upper contact surface. It is assumed that the shear stress capacity at the lower contact surface is high enough so that the boundary film can not slip at the lower contact surface. Because of the interaction between the boundary film and the contact surface, the viscosity, density and shear elastic modulus of the boundary film are all varied across the film thickness; their equivalent values, which are dependent on the boundary film thickness, are used in theoretical analysis. The analytical approach proposed by the author and his colleagues is used for analyzing the boundary film behavior. The fluid film is assumed not to slip at both of the contact surfaces. The effect of the shear elastic modulus of the fluid film is neglected in the analysis. The conventional approach is used for analyzing the fluid film behavior. The present paper gives the theoretical analysis and some of the computational results for different operating conditions.