Combined numerical and experimental investigation of the micro-hydrodynamics of chevron-based textured patterns influencing conjunctional friction of sliding contacts

Morris, Nicholas J.; Leighton, Michael; Cruz, Miguel De la; Rahmani, Ramin; Rahnejat, Homer; Howell-Smith, S.J.

doi:10.1177/1350650114559996

Cited by 81 publications

(80 citation statements)

References 50 publications

(122 reference statements)

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“…It is hypothesised that flow into the textures would be affected by recirculation and back-flow if the textures are introduced prior to or within the recirculation region. This would affect the effective pressure perturbations, usually induced by the textures as described in [11]. It is clear that in the cases where the abscissa value is negative, in fact a loss in load carrying capacity with respect to the equivalent un-textured ring surface of the same geometry is observed.…”

Section: Results For Generic Sliding Contactmentioning

confidence: 99%

“…The underlying reason for this is the retention of pockets of lubricant as reservoirs within the formed textures. This leads to pressure perturbations within the ring-liner sliding contact, a phenomenon known as micro-hydrodynamics [11]. However, despite the accrued benefits in reducing friction, and the emerging fundamental understanding of the underlying mechanisms, optimal performance of textured patterns remains somewhat illusive.…”

Section: Introductionmentioning

confidence: 99%

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A hydrodynamic flow analysis for optimal positioning of surface textures

Morris

Rahmani

Rahnejat

2017

Proceedings of the Institution of Mechanical Engineers, Part J:

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The current study uses Reynolds equation and the cross-film flow velocity profile to analytically determine pertinent locations for texture feature positioning in sliding hydrodynamic contacts. The position of textures is shown to have a significant effect on the lubricant film thickness, thus the load carrying capacity and generated friction and power loss. It is shown that textures, residing after the inlet lubricant recirculation boundary and prior to the position of maximum contact pressure enhance film thickness and reduce friction in the contact of real rough sliding surfaces. The methodology is applied to partial surface texturing of a thin compression ring of a high performance race engine, with the predicted results confirming the utility of the expounded analytical technique and its conformance to the findings of others reported in literature. The time-efficient analytical and fundamental approach constitutes the main contribution of the paper to furtherance of knowledge.

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Section: Results For Generic Sliding Contactmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A hydrodynamic flow analysis for optimal positioning of surface textures

Morris

Rahmani

Rahnejat

2017

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…A typical transmission fluid is used, the rheological data for which is provided in table 2. [18]. However, in the case of grooved brake friction discs the main purpose is to transfer the heat away from the contact by facilitating lubricant flow.…”

Section: Resultsmentioning

confidence: 99%

Efficiency of disengaged wet brake packs

Leighton

Morris

Trimmer

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part D:

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Key objectives in off-highway vehicular powertrain development are fuel efficiency and environmental protection. As a result palliative measures are made to reduce parasitic frictional losses, whilst sustaining machine operational performance and reliability. A potential key contributor to the overall power loss is the rotation of disengaged wet multi-plate pack brake friction. Despite the numerous advantages of wet brake pack design, during high speed manoeuvre in highway travel or at start-up conditions significant frictional power losses occur.The addition of recessed grooves on the brake friction lining is used to dissipate heat during engagement. These complicate the prediction of performance of the system, particularly when disengaged. To characterise the losses produced by these components, a combined numerical and experimental approach is required. This paper presents a Reynolds-based numerical model including the effect of fluid inertia and squeeze film transience for prediction of performance of wet brake systems. Model predictions are compared with very detailed combined Navier-Stokes and Raleigh-Plesset fluid dynamics analysis to ascertain its degree of conformity to representative physical operating conditions, as well the use of a developed experimental rig. The combined numerical and experimental approach is used to predict significant losses produced during various operating conditions. It is shown that cavitation becomes significant at low temperatures due to micro-hydrodynamic action, enhanced by high fluid viscosity. The magnitude of the losses for these components under various operating conditions is presented.The combined numerical-experimental study of wet multi-plate brakes of off-highway vehicles with cavitation flow dynamics has not hitherto been reported in literature.2

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“…Mixed or boundary regimes of lubrication would be expected under these conditions. Further details about the slider rig and its operation are provided in Morris et al [24]. Relatively low load and large apparent contact area, A (contacting face of the strip) yields insufficient lubricant pressures to cause any elasto-hydrodynamic deformation of the surfaces.…”

Section: Sliding Tribometermentioning

confidence: 99%

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

et al. 2016

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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.

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Combined numerical and experimental investigation of the micro-hydrodynamics of chevron-based textured patterns influencing conjunctional friction of sliding contacts

Cited by 81 publications

References 50 publications

A hydrodynamic flow analysis for optimal positioning of surface textures

A hydrodynamic flow analysis for optimal positioning of surface textures

Efficiency of disengaged wet brake packs

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

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