The Effect of Frictionally Generated Heat on Lubricant Transition

Ettles, C. M. McC.; Dinç, O. S.; Calabrese, S. J.

doi:10.1080/10402009408983312

Cited by 6 publications

(5 citation statements)

References 13 publications

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“…There is in fact a transition temperature, c , above which friction rises abruptly. 118 Thus, following Lai and Cheng, 119 the kinetic friction coefficients are linked to temperature as follows…”

Section: Particle Deformation and Discretisationmentioning

confidence: 99%

“…There is in fact a transition temperature, θ c , above which friction rises abruptly. 118 Thus, following Lai and Cheng, 119 the kinetic friction coefficients are linked to temperature θ as follows where μ- and μ+ are constants, and is the average temperature at the interface of the particle with each contact surface. For lubricating oils, usually θ c < 200 ℃, and more commonly, θ c < 150 ℃.…”

Section: Numerical Modelmentioning

confidence: 99%

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Debris particle indentation and abrasion of machine-element contacts: An experimentally validated, thermoelastoplastic numerical model with micro-hardness and frictional heating effects

Nikas

2012

Proceedings of the Institution of Mechanical Engineers, Part J:

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For a very long time, debris particles have been blamed to causing serious problems in machine-element contacts such as those of bearings and gears. This involves a huge number of mechanisms and machines worldwide. The financial cost associated with machinery failure under such circumstances is enormous. Past research has identified the main mechanisms governing damage from debris particles. A few theoretical models have been built on the experience accumulated on damage mechanics. The capabilities of said models vary a lot. The model originally developed by this author in the 1990s was recently expanded. The previous version of the model, which was published in this journal in May 2012, offered a number of innovative features to calculate spherical-particle indentation and soft abrasion in lubricated rolling-sliding contacts. It was experimentally validated following a rigorous programme. However, it neglected frictional heating from particle extrusion. This study significantly expands the previous model of the author by integrating thermal effects. It includes flash temperature calculations with moving sources of heat, dynamic heat partition, three-dimensional conduction and convection, and thermally anisotropic surfaces with temperature-dependent thermal and mechanical properties, all integrated in the elastoplastic model of indentation and abrasion. These are in addition to model features such as nonlinear strain hardening, strain-gradient plasticity, particle work hardening, generalised local kinematics, pile-up/sink-in plasticity effects and many more. The same rigorous experimental verification programme as in the previous model of the author is used here, too. It is shown that in some cases, the theoretical results on dent geometry are even closer to the experimental ones than with the isothermal model of the author. Furthermore, the thermal analysis reveals that extreme frictional heating can take place, often leading to melting wear in a fraction of a millisecond. The formation of dimples inside and outside main dents, which have been shown experimentally and verified theoretically by this author’s previous model, is revisited in light of frictional heating. A parametric study shows the effects of particle size and hardness, kinetic friction coefficients, and strain hardening on dent geometry and flash temperatures, including effects on particle and surface melting. Finally, the reality of flash temperatures is explored.

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Section: Particle Deformation and Discretisationmentioning

confidence: 99%

Section: Numerical Modelmentioning

confidence: 99%

Debris particle indentation and abrasion of machine-element contacts: An experimentally validated, thermoelastoplastic numerical model with micro-hardness and frictional heating effects

Nikas

2012

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…to provide for an abrupt increase in the friction coefficient from a to b at a transition temperature t associated with tribofilm rupture through desorption or melting 80 (usually, 150 4 t 4 200 C). Force balance in any particle block in the x-and yaxes ( Figure 1) yields the following differential equation, 51,56,[60][61][62] relating normal and interfacial shear stresses…”

Section: Mathematical Analysismentioning

confidence: 99%

Particle extrusion in elastohydrodynamic line contacts: Dynamic forces and energy consumption

Nikas¹

2017

Proceedings of the Institution of Mechanical Engineers, Part J:

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The author’s model of particle entrapment and thermoviscoplastic indentation built and experimentally validated in recent publications is utilised to calculate the contact forces on ductile, isolated interference particles passing through elastohydrodynamic, rolling–sliding, line contacts. The model is detailed and enriched by supplementary equations. A parametric study deals with the effects of particle size and cold hardness, kinetic friction coefficient, rolling velocity and slide-to-roll ratio of the contact on the particle contact forces, mean friction coefficient, temperature, plastic work and power required to deform a particle, as well as on dent volume and plastic strain rates of the indented contact surfaces. A factual selection of optimal conditions and parameter values that minimise the disruption of a contaminated contact is thus greatly facilitated.

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“…There is also provision for a local lubricant transition temperature (equation ( 9) in reference 71 ) in computing local tractions, which is in accordance with experimental findings. [93][94][95][96][97] At each time step, the contact mechanics analysis is accompanied by a thermal analysis. The thermal analysis involves the calculation of the thermal power frictionally generated at interfacial zones P 1 P 2 P 3 and P 7 P 6 P 5 .…”

Section: Nikasmentioning

confidence: 99%

Section: Numerical Modelmentioning

confidence: 99%

Strain-rate effects on the plastic indentation and abrasion of elastohydrodynamic contacts by debris particles

Nikas

2013

Proceedings of the Institution of Mechanical Engineers, Part J:

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A numerical model of plastic indentation and abrasion of elastohydrodynamic contacts by debris particles previously developed by the author is extended to include the dependence of material flow stress on strain rate. Using the JohnsonCook viscoplasticity model, the flow stress of all materials involved in the indentation process is expressed as a function of plastic strain, strain rate and temperature. This complements other elements of the model, including strain-gradient plasticity, work-hardening, frictional heating from particle extrusion, thermal softening, melting and material loss due to adhesion. Following a laborious programme of experimental validation and numerical comparisons, the predictions of the model are shown to be in excellent agreement with the experimental results on soft and hard particles in rolling and rolling-sliding elastohydrodynamic contacts. The incorporation of strain-rate effects further improved the agreement between theoretical and experimental results previously established with simpler versions of the model that ignored the strain-rate factor. Strain rate is also shown to affect several parameters in the process of surface damage, including the magnitude of contact stresses and flash temperatures, as well as the behaviour of a particle in a concentrated contact. It is also shown that for an optimum contact velocity linked to strain-rate effects and fluid film thickness in lubricated contacts, surface damage is minimised, particularly for large and hard particles.

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The Effect of Frictionally Generated Heat on Lubricant Transition

Cited by 6 publications

References 13 publications

Debris particle indentation and abrasion of machine-element contacts: An experimentally validated, thermoelastoplastic numerical model with micro-hardness and frictional heating effects

Debris particle indentation and abrasion of machine-element contacts: An experimentally validated, thermoelastoplastic numerical model with micro-hardness and frictional heating effects

Particle extrusion in elastohydrodynamic line contacts: Dynamic forces and energy consumption

Strain-rate effects on the plastic indentation and abrasion of elastohydrodynamic contacts by debris particles

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