Tribological investigation of organic and inorganic friction modifiers with varying quantities of dispersants [Abstract]

Tribological investigation of organic and inorganic friction modifiers with varying quantities of dispersants [Abstract

Characterisation of automotive bore material and coatings using atomic force microscopy [Abstract]

Characterisation of automotive bore material and coatings using atomic force microscopy [Abstract

Lubricant-surface system mitigating in-cylinder friction

Lubricant-surface system mitigating in-cylinder frictio

Asperity level tribological investigation of automotive bore material and coatings

Choosing in-cylinder surfaces is complex. A well-chosen surface has low friction and wear. Conversely, poor oversight often leads to premature failure through wear and scuffing. Typically cylinder bore surfaces are selected experientially. This paper demonstrates the use of Atomic Force Microscopy in LFM mode, characterising typical cylinder bore materials and coatings. The approach uses integrated LFM with continuum contact mechanics. It evaluates the real contact area and effective elastic modulus of the surface, including the effect of any reactive surface film. Surface energy and shear strength, as well as the coefficient of friction in nanoscale interactions are also determined. These properties are measured for 6 cylinder bore materials, including for composite Nickel-Silicon Carbide and DLC, used for high performance engines

A multiscale, integrated experimental–analytical approach to mitigate boundary friction using lubricant–surface system perspective

A multiscale, integrated experimental–analytical approach to mitigate boundary friction using lubricant–surface system perspectiv

Interaction of dispersants with anti-wear and friction modifiers in contacts representative of piston-ring liner interface [Abstract]

Interaction of dispersants with anti-wear and friction modifiers in contacts representative of piston-ring liner interface [Abstract

Thermal activation Eyring energy approach to characterise the dependence of nanoscale friction on the surface roughness

Atomic Force Microscope (AFM) is used to characterise the frictional response of surfaces with varying roughness parameters in dry and in the presence of fully formulated lubricants. The surface roughness has shown to affect nanoscale friction. The characteristics involved the investigation of roughness, small-scale adhesive forces and nanoscale friction using AFM in lateral force mode. The fluid-cell Lateral Force Microscopy (LFM) results were used to model thermal activation Eyring energy components in conjunction with the relevant continuum contact mechanics model. The paper shows that a combination of LFM, for dry and fluid-cell LFM and thermal activation Eyring energy barrier approach is a useful tool to explain the effect of surface roughness on nanoscale friction.<br

Tribological enhancement of piston skirt conjunction using graphene-based coatings

Piston skirt to cylinder liner conjunctions are amongst the major contributors to frictional power losses of Internal Combustion Engines (ICEs). Efforts have been made to mitigate the frictional losses of these conjunctions by incorporating different technologies such as texturing and application of novel coatings. Any potential technology needs to provide adequate wear resistance as well as frictional reduction in order to be practically applicable. In this paper, the piston skirt of a gasoline engine is deposited by three different variants of Graphene Oxide (GO) coatings deposited using an Electro-Phoretic Deposition (EPD) method. Their tribological performance is benchmarked against uncoated steel and graphite coated aluminium skirts. These coatings are experimentally characterised in terms of asperity level friction, topography and wear resistance. The conjunction and system level performance of these coatings considering both boundary and viscous friction and system dynamics are then evaluated using a multi-physics tribo-dynamic model. Results show that by incorporating an appropriate GO coating, the frictional power loss of the piston skirt to cylinder liner conjunction can be improved by up to 14% whilst maintaining the wear resistance of the coating at the level of an uncoated steel surface

Asperity level characterization of abrasive wear using atomic force microscopy

Using an atomic force microscope, a nanoscale wear characterization method has been applied to a commercial steel substrate AISI 52100, a common bearing material. Two wear mechanisms were observed by the presented method: atom attrition and elastoplastic ploughing. It is shown that not only friction can be used to classify the difference between these two mechanisms, but also the ‘degree of wear’. Archard's Law of adhesion shows good conformity to experimental data at the nanoscale for the elastoplastic ploughing mechanism. However, there is a distinct discontinuity between the two identified mechanisms of wear and their relation to the load and the removed volume. The length-scale effect of the material's hardness property plays an integral role in the relationship between the ‘degree of wear’ and load. The transition between wear mechanisms is hardness-dependent, as below a load threshold limited plastic deformation in the form of pile up is exhibited. It is revealed that the presented method can be used as a rapid wear characterization technique, but additional work is necessary to project individual asperity interaction observations to macroscale contacts.<br