Tribology of partial pad journal bearings with textured surfaces

Tribology of partial pad journal bearings with textured surface

Optical measurements of cavitation in tribological contacts

The paper describes the use of a white light interformeter to measure the cavitation bubble and oil film thickness in a tribological contact and compares the results to theory. It is found that oil film thickness is best predicted by the theory proposed by Coyne and Elrod.

A CFD study comparing surface texture features on stationary and entraining surfaces

A CFD study comparing surface texture features on stationary and entraining surface

An averaged approach to asperity contact interactions for non-gaussian lubricated surfaces

An averaged approach to asperity contact interactions for non-gaussian lubricated surface

Cavitation bubble measurement in tribological contacts using digital holographic microscopy

The use of advanced measurement techniques such as the digital holography method described in this paper improves the understanding of the cavitation phenomenon in tribological contacts such as the sliding contact of the piston ring–cylinder liner conjunction. The paper describes the use of digital holography measurement technique to measure cavitation bubble formation and thickness. The position of observed lubricant film rupture preceding the cavitation region is compared with some commonly predicted boundary often used with Reynolds equation. The experimental results indicate that the Reynolds and Elrod boundary conditions are the most suitable for the investigated sliding contact conditions

Cavitation bubble measurement in tribological contacts using digital holographic microscopy

The use of advanced measurement techniques such as the digital holography method described in this paper improves the understanding of the cavitation phenomenon in tribological contacts such as the sliding contact of the piston ring–cylinder liner conjunction. The paper describes the use of digital holography measurement technique to measure cavitation bubble formation and thickness. The position of observed lubricant film rupture preceding the cavitation region is compared with some commonly predicted boundary often used with Reynolds equation. The experimental results indicate that the Reynolds and Elrod boundary conditions are the most suitable for the investigated sliding contact conditions

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

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

The influence of large scale surface roughness on flow factors

The influence of large scale surface roughness on flow factor

Asperity contact modelling for measured surfaces

The analysis of surface roughness in contacts forms a major part of tribology in almost all application. In any contact in which asperity interactions occur their load carrying capacity must be considered however the separation at which asperity interaction first occurs and the load carrying capacity at that separation are due to the stochastic nature of the surface roughness of the two surfaces. A model that can accurately and quickly provide an estimation of the load carrying capacity as a function of surface separation is required for the specific surfaces used in such conjunctions from implementing surface data. The paper presented provides details of a procedure for modeling asperity interactions of rough surfaces from measured data. The model is validated against a deterministic approach before being applied to measured surfaces

Optimisation of piston compression ring for improved energy efficiency of high performance race engines

The primary function of the piston compression ring is to seal the combustion chamber from the bottom end of the engine. As a result its conformance to the cylinder liner surface is of prime importance. This close contact contiguity results in increased friction, making this contact conjunction responsible for a significant proportion of energy losses. The frictional losses can be as much of 2-6% of expended fuel energy, which is quite significant for such a diminutive contact. Under these conditions, geometrical profile, surface topography and inertial properties of the ring assume significant importance. The paper presents an integrated mixed-hydrodynamic analysis of the compression ring-cylinder liner contact with multi-parameter optimisation, based on the use of genetic algorithm. The multi-objective functionality includes minimisation of parasitic energy loss, reduction of incidence of asperity level interactions as well as minimisation of ring mass. Both cold and hot running engine conditions in line with the New European Drive Cycle have been considered. Hitherto, such an approach has not been reported in literature