Surface specific asperity model for prediction of friction in boundary and mixed regimes of lubrication

Abstract

Machine downsizing, increased loading and better sealing performance have progressively led to thinner lubricant films and an increased chance of direct surface interaction. Consequently, mixed and boundary regimes of lubrication are prevalent with ubiquitous asperity interactions, leading to increased parasitic losses and poor energy inefficiency. Surface topography has become an important consideration as it influences the prevailing regime of lubrication. As a result a plethora of machining processes and surface finishing techniques have emerged. The stochastic nature of the resulting topography determines the separation at which asperity interactions are initiated and ultimately affect the conjunctional load carrying capacity and operational efficiency. The paper presents a procedure for modelling of asperity interactions of real rough surfaces, from measured data, which do not conform to the usually assumed Gaussian distributions. The model is validated experimentally using a bench top reciprocating sliding test rig. The method demonstrates accurate determination of the onset of mixed regime of lubrication. In this manner, realistic predictions are made for load carrying and frictional performance in real applications where commonly used Gaussian distributions can lead to anomalous predictions.

Thermohydrodynamics of lubricant flow with carbon nanoparticles in tribological contacts

“…This term was originally developed for fairly smooth surfaces with a Gaussian distribution of asperity heights. Various rather laborious models exist which extend the application of the Greenwood and Tripp model for non-Gaussian surfaces such as those by Leighton et al [24,25] for elastic interaction of asperities, Kogut and Etsion [26] for elasto-plastic adhesive dry contact and Chong et al [27] for wet asperities subjected to elastic deformation and adhesion. Table 2 shows that roughness of the surfaces in the current study does not completely conform to a Gaussian distribution and hence ideally a more accurate model needs to be developed.…”

“…For further information on details of surface analysis the reader is referred to [24]. For a Gaussian distribution it is shown in [28] that a polynomial-fit function can be used to approximate the statistical integration as: (18) where, ≅ 3 is the critical value of film ratio, specifying the onset of mixed regime of lubrication.…”

Lubrication behaviors of PVA‐casted LSPEEK hydrogels in artificial cartilage repair

“…In general, a larger surface roughness means a larger coefficient of friction. Lower surface roughness and proper surface topography can enhance lubrication and extend wear life . It was found in subsequent experiments that their interaction with the friction pair would reduce friction of the sample surface.…”

Nano and microscale contact characteristics of tribofilms derived from fully formulated engine oil

“…A reciprocating sliding-strip tribometer, shown in Figure 2, is used to reproduce specific piston compression ring-liner contact conditions at top dead centre reversal in transition from compression to power stroke [37][38][39]. Generated friction is measured using a floating plate, mounted upon ultra-low friction bearings.…”