Friction · Wear · Lubrication

Tribology

The study of friction, wear and lubrication between interacting surfaces. This is the domain the whole reference is built on — from the Stribeck curve and lubrication regimes to real failure analyses where judgement, not a formula, decides the diagnosis.

Where a calculator gives a number, tribology often gives a diagnosis: whether a worn surface failed by adhesion, abrasion or fatigue; whether a lubricant film broke down; whether the design question was even the right one. That judgement is the scarce part, and it is what the failure-analysis material here tries to capture.

A camshaft surface showing pitting and spalling, with the affected area marked by an arrow — Camshaft pitting and spalling — surface fatigue under combined rolling and sliding.

A rail head with a chipped, spalled section from a fatigue crack — Rolling-contact fatigue fracture in a rail.

A rocker arm bearing pin showing scoring marks from scuffing — Scuffing on a rocker-arm bearing — traced by oil analysis to an EP-additive shortage.

A gear tooth flank showing scuffing damage — grooving and displaced material near the tip and root — Scuffing on a gear tooth flank — the protective lubricant film broke down under a momentary overload.

A camshaft lobe surface with material displaced toward the edges, forming a burr — Plastic deformation on a camshaft lobe — surface hardness measured well below spec, likely from over-grinding during a rebuild.

A cam follower's hardened surface showing micro-pitting on the left and progressed pitting (spalling) on the right — Micro-pitting and spalling on a sliding cam follower — surface fatigue from repeated rolling-sliding contact.

A mechanical seal face ring with radial thermal cracks — Thermal cracking on a mechanical seal face — high contact temperatures fracturing a brittle silicon-carbide ring.

Articles & failure analyses

Adhesion in dry rubbing metal–metal contactsMeasured friction and wear for dry metal pairs against bearing steel, and why high-shear materials give the highest friction.Aquaplaning as full hydrodynamic lubricationAquaplaning explained as a case of full-film hydrodynamic lubrication between tyre and road.Calculation of wear rateA common used equation to compute the wear rate is (Archard,1953)...Combustion engine lubrication system.The lubrication of the cylinder liner, the piston, the piston rings, the cams / camshaft and the rod bearing.Formula one racing — why are the tyres so wide?FORMULA ONE RACING The first classical law of friction states: “The size of the contact surface does not influence the friction”. Why, then, are tires for the Formula 1 racing…Formula one racing — carbon-fibre composite brake disksFORMULA ONE RACING Braking is one of the biggest strengths of a Formula One car. The brake disks of Formula 1 cars are made of a composite material reinforced with carbon fibre.…Grease lubricationHow grease lubricates, when to prefer it over oil, and the basics of grease selection.High performance Polymers / engineering polymers.Physical properties of hard wearing low friction polymers.History of science frictionLeonardo Da Vinci (1452-1519), Guillaume Amontons (1663-1705), Charles August Coulomb (1736-1806)How to measure the coefficient of frictionPractical methods and pitfalls in measuring the coefficient of friction between surfaces.Oil=Oil?Industrial oils / Engine oils / additives and specialty oils.Pin-on-ring test rig.The standard configuration for tribology research on materials, coatings and lubricants.Screw lubricationLubricant selection for screw drives and screw joints, lubselect Solid lubricantsSolid lubricants — graphite, MoS₂, PTFE and coatings — and where each is used.The Stribeck curve vs the transition diagramThe Stribeck curve and how it relates to the lubrication regimes and the transition diagram.Viscosity classificationsISO VG, SAE and other viscosity classifications for lubricants, and how they relate.Cone-on-plate viscometer spindle range (Brookfield)Cone angle, spindle radius and viscosity measurement range for the six spindles of the Brookfield Cap 1000/2000 cone-on-plate viscometer.Cylinder viscometer spindle dimensions (Brookfield)Disc and cylindrical spindle dimensions (C, D) for the Brookfield cylinder viscometer, with the LV spindle speed range.Lubricant selectionWhat's the best lubricant? A checklist of the factors that actually decide it — lubrication regime, viscosity index, boundary lubricity, oxidation stability and more.Machine lubrication — an integrated approachWhy lubricant selection depends on the lubrication regime, changing environmental and performance requirements, and a coherent maintenance plan — not the lubricant alone.Failure analysis: rail contactRolling-contact fatigue and wear at the wheel–rail interface, read from the damaged surface.How toFrequently Asked Questions in Machine design ISO failure mode classification for bearing damageThe ISO classification of rolling-bearing damage modes, with the visual signatures of each.ISO failure mode classification for gears (ISO 10825)Gear failure modes per ISO 10825 — pitting, wear, scuffing and fracture — and how to tell them apart.