Parallel Sliding Load Support in the Mixed Friction Regime. Part 2—Evaluation of the Mechanisms

When two parallel surfaces slide parallel to each other in the presence of a liquid, classical lubrication theory shows that no load carrying capacity should result. In Part 1 of this work the experimental data showing that such load support does occur are reviewed. In this paper several of the proposed mechanisms for parallel sliding load support are evaluated by combining the mechanism with a mixed friction model and comparing predictions to experimental results. Both water and oil type bearings are considered. While there are exceptions, it has been found that in general the thermal wedge, microasperity lubrication, microasperity collisions, and squeeze effects cannot account for the large apparent load support in the experimental cases studied. However, small deviations from parallel geometry have a strong effect and can easily account for the observed load support, but several questions remain. It is concluded that future investigations should be directed to developing a better understanding of how favorable macrogeometries might be developed and searching for other sources of pressure generation in parallel sliding.