Effect of surface roughness on hydrodynamic lubrication of slider bearings

The effect of surface roughness on the performance of hydrodynamic slider bearings is studied. A generalized form of surface roughness characterized by a stochastic random variable with non-zero mean, variance and skewness is assumed to define the bearing surface tomography. Various film shapes such as: plane slider, exponential, secant and hyperbolic are considered. The results are obtained for the general lubricant film shape in integral form which are numerically computed for the shapes under consideration. The results are presented both graphically as well as in tabular form. The performance of a rough heaving can be considered in terms of an identical smooth bearing with an equivalent film thickness. It is observed, for the lubricant film shapes under consideration, that the increasing positive values of alpha, sigma and epsilon decrease the load carrying capacity, frictional force and temperature rise while it increases the coefficient of friction. Increasing positive values of sigma and epsilon shift the center of pressure towards the outlet edge. For negative values of alpha, the increasing value reverses the trend of the effect on performance characteristics which is in conformity with the physical aspects of the problem. A similar trend is observed in case of the effect of negative values of epsilon. Thus, a negatively skewed surface roughness modifies the performance of a bearing suffers on account of positively skewed surface roughness. Moreover, it is noticed that in the case of exponential and hyperbolic slider bearings the effect of increasing values of sigma is more pronounced whereas in case of plant slider and secant shaped slider this effect is marginal.