ANALYSIS OF THE BOUNDARY FILM SLIPPAGE EFFECT IN A MICRO CONTACT: INFLUENCES OF THE MICRO CONTACT WIDTH AND SURFACE ROUGHNESS

The influences of micro contact width and surface roughness on the boundary film slippage effect in a micro contact are analytically studied. The micro contact is a mixed contact and composed of the boundary film area and continuum fluid film area. When the film thickness is relatively high, the boundary film here can be regarded as the nanometer-scale thin film. The boundary film slippage is caused by the large pressure gradient in the boundary film area under relatively heavy loads, and it occurs simultaneously at both of the contact surfaces. The obtained results show that the boundary film slippage effect is strengthened with the increase of the micro contact width, while the increase of the surface roughness reduces and even vanishes the boundary film slippage. The influence of the boundary film slippage on the performance of the micro contact is that the boundary film slippage significantly increases the mass flow through the micro contact, reduces the load-carrying capacity of the micro contact, and drops the local pressure in the micro contact. When the boundary film thickness is on the scale of 1nm, the analysis of the performance of the micro contact should incorporate the boundary film slippage effect, since in this case the boundary film slippage effect can significantly reduce the local pressure in the micro contact and this pressure reduction can significantly change the local contact surface elastic deformations and then further influence the local film thickness in the micro contact, by considering the elasticity of the actual contact surfaces.