Results of measured data from atomic force microscope on ring pack performance

Abstract

Frictional losses of an IC engine include 40-50% contribution due to piston assembly-liner conjunction. Reduction of friction would improve fuel efficiency and decrease harmful emissions. Therefore, it is important to accurately predict the frictional losses due to viscous shear of a thin lubricant film as well as boundary friction, generated by the direct contact of real rough contiguous surfaces. Greenwood and Tripp model is used to evaluate the contribution due to boundary friction. The model requires the determination of pressure coefficient of boundary shear strength of asperities, ς, which is analogous to the asperity coefficient of friction. This should be determined through measurement, using Atomic Force Microscopy (AFM) in Lateral Force Mode (LFM). The value of ς is dependent on the combination of surface and lubricant as a system. Boundary active lubricant additives adsorb or bond to the surface asperities and affect the value of ς. The value of this coefficient also alters with the evolution of interacting surfaces through the process of wear as well as any degradation of the lubricant. The approach can be used to create a database of such values for different lubricant-surface systems, in particular for piston-liner interactions.