Particles in new motor oils

Kjer, Torben

doi:10.1016/0043-1648(81)90329-x

Cited by 11 publications

(10 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The presence of particles in new lubricants was shown in references [43] and [44] with pictures and data about the particles found. Abrasive, metallic, and non-metallic debris were reported in those studies, usually at low concentrations, originating from air-borne contamination or contamination of the oil transportation cans during fabrication.…”

Section: Introductionmentioning

confidence: 99%

A mechanistic model of spherical particle entrapment in elliptical contacts

Nikas

2006

Proceedings of the Institution of Mechanical Engineers, Part J:

View full text Add to dashboard Cite

The dynamic interaction of solid, spherical particles with the counterfaces of concentrated, dry or lubricated, conforming or non-conforming, rolling -sliding elliptical contacts is mathematically analysed. Criteria for the entrapment or rejection of particles are postulated on the basis of the resolution of mechanical and fluid forces on a particle for given contact geometry and operating conditions. Three-dimensional maps of the various force components on a particle are presented for a typical application, together with the maps of the zones where a particle would be 'conditionally' entrapped, 'weakly' rejected, or 'unconditionally' rejected, where the previous terms are defined in a comprehensive evaluation system in the model to assess the risk of damage of the contact from the presence of contaminants. This study is concerned with the process of particle entrapment, meaning that a particle must be in contact with both the counterfaces of a concentrated contact, and not entrainment (particle wandering in the lubricant, which has been studied by the author (Nikas, 2002)). To the best of the author's knowledge, this is the first study explicitly dealing with the general case of elliptical contacts. Elliptical contacts cover circular contacts and, taken to the limit, can also simulate line contacts; thus, the model's applicability and validity as a design tool are generalized. In summary, the purpose of the article is to expand previous models developed for simpler geometries and to present an effective computational tool for the simulation of particle entry into elliptical contacts and the resulting risks of contact damage.

show abstract

Section: Introductionmentioning

confidence: 99%

A mechanistic model of spherical particle entrapment in elliptical contacts

Nikas

2006

Proceedings of the Institution of Mechanical Engineers, Part J:

View full text Add to dashboard Cite

show abstract

“…3,4 Debris originate from many sources including (a) internal sources, e.g. new oils (see the studies of Kjer, 5 Jones, 6 Leng and Davies, 7 and Stachowiak et al 8 and Figure 2 in the studies of Nikas 1,2 ); (b) wear processes [9][10][11][12] including abrasion, adhesion, erosion, contact fatigue, spalling and scuffing; (c) external, environmental sources such as air and water carrying sand, dust, swarf, grits from machining operations, glass fragments, etc., which usually contaminate mechanical systems due to insufficient sealing or are introduced during repair and maintenance such as lubricant changes, replacement of filters and seals, etc.…”

Section: Introductionmentioning

confidence: 99%

An experimentally validated numerical model of indentation and abrasion by debris particles in machine-element contacts considering micro-hardness effects

Nikas

2012

Proceedings of the Institution of Mechanical Engineers, Part J:

View full text Add to dashboard Cite

Indentation and abrasion of machine-element contacts by solid contamination particles is a major problem in many industries and manufacturing processes involving the automotive, aerospace, medical and electronics industries among others. Published theoretical studies on indentation and soft abrasion of surfaces by ductile debris particles other than those of the author are based on several major simplifications concerning material properties, hardness, plasticity modelling, interfacial friction, kinematic conditions, etc. None of the studies published in the literature to date (2011) have those simplifications concurrently relaxed.In view of the shortcomings of existing numerical models on debris particle indentation and abrasion, and given the importance of dent geometry and size on fatigue life of machine elements, a greatly improved numerical model has been developed based on the previous studies of the author. The new model deals with elastoplastic indentation and abrasion of rolling-sliding, dry and lubricated contacts by spherical particles of any hardness, from very soft (e.g. 40 HV) to very hard (e.g. over 1000 HV), including harder than the contact counterfaces. The model incorporates strain-hardening and strain-gradient or indentation-size micro-hardness effects with an expanding-cavity plasticity model, a localised treatment of friction, generalised boundary and kinematic conditions involving localised stick and slip of the particle, linear and nonlinear work-hardening models of the particle, a basic approach on pile-up/sink-in plasticity effects and several other improvements. The model has passed extensive validation tests and found to give realistic predictions that are quantitatively quite close to the experimental results published by independent researchers in the literature concerning dent dimensions and slope. Moreover, it has verified and explained theoretically for the first time the formation of dimples inside and outside dents experimentally observed in rolling and rolling-sliding contacts. This article presents the mathematics of the model, the validation procedure with several real cases from the experimental literature, and a parametric study to show the model's predictions on precise dent geometry in several realistic cases.

show abstract

“…The frictional force on the counter-surface (driven surface 2) is almost equal in magnitude and of opposite sign. This behaviour is controlled by the contact pressure distribution on the disc-transforming particle in conjunction with local kinematics (equations (2) and (10) to (12)). The damaging point is obviously the force spike exhibited at the entrance of the Hertzian zone.…”

Section: Parametric Study Definitions and An Examplementioning

confidence: 99%

“…Lubricant contamination is an omnipresent problem even with new lubricants. [1][2][3][4] Analysing the mechanical response of an EHD contact to a variety of potential contamination particles gives the technical expertise to make a factual selection of operational parameters that minimise damage risks.…”

Section: Introductionmentioning

confidence: 99%

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

Nikas¹

2017

Proceedings of the Institution of Mechanical Engineers, Part J:

View full text Add to dashboard Cite

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.

show abstract

Particles in new motor oils

Cited by 11 publications

References 3 publications

A mechanistic model of spherical particle entrapment in elliptical contacts

A mechanistic model of spherical particle entrapment in elliptical contacts

An experimentally validated numerical model of indentation and abrasion by debris particles in machine-element contacts considering micro-hardness effects

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

Contact Info

Product

Resources

About