The Effect of Slider Geometry on the Performance of a Powder Lubricated Bearing

Abstract

The experimental investigation was carried out for dry contact tribosystems to elucidate the ascertained, yet uncharacterized, relationship between the coefficient of friction, η and apparent contact geometry in sliders. This paper presents the results of various experimentally evaluated slider pad width to length ratios, B/L (L is signified with direction of motion), while maintaining the unit loading constant. The empirical data is intended to provide guidance in design and in theoretical prediction of optimum bearing geometry for solid/powder lubricated systems. In this experiment, a liquid lubricant, two different dry powders (MoS2 and TiO2), and four test specimens with B/L ratios ranging from 0.5 to 2.0 were used. An alternative experimental method has been used to simulate wear debris in the dry contact tribosystems, vis-à-vis dry powders, which were introduced into the interface gap to address the affinity of the wear process. Slider pads' performance characteristics as a function of the applied load (ranging from 34.5 to 345 kPa) and surface speed (0.004 to 4.5 m/sec) were determined at ambient condition. Experimental evidence shows that in the pre-hydrodynamic regime (low speed) the friction coefficient, η, decreases as B/L ratio increased from 0.5 to 1.5. Beyond a B/L ratio of 1.5, η increased with increasing B/L ratios. Optimum B/L ratio of 1 (based on measured minimum η) was identified for operation in the hydrodynamic regime. Overall reduction in η as a function of load was observed which is independent of B/L ratio and lubricant type. Also presented are the velocity effects on slider frictional performance.