Learn / Contact Mechanics
Contact Mechanics
Contact, friction, wear,
and the numbers we
pull from them.
How surfaces touch, how they slide and wear, and what an indent or a scratch really measures.
Start here
New to Contact? Read these first.
StoryThe Mountain Range You Cannot See
A scrolling illustrated story about tribology: zoom into a contact until the real touching area appears, follow one…
GuideAsperities & the Real Area of ContactInteractive contact mechanics: single-asperity Hertz geometries, elastic to fully plastic transition,…
GuideHow a Hardness Number Gets MadeWhere hardness and modulus actually come from: fit the unloading curve yourself, watch S, hc and the contact area move,…
All topics
Surfaces & contact3 pages
GuideAsperities & the Real Area of ContactInteractive contact mechanics: single-asperity Hertz geometries, elastic to fully plastic transition,…Foundation · 10 minLabSubsurface Contact StressesPress a ball or roller on a flat and see the Hertz stress below the surface: where shear peaks, how friction…Foundation · 12 minLabSurface Roughness ParametersSee why the same Ra can hide very different surfaces. Move a live profile to read Rz, Rsk, Rku, the bearing…Foundation · 12 min
Friction & lubrication6 pages
LabTribofilms & Third BodiesWatch debris get trapped in a sliding contact, a ZDDP antiwear film grow on steel with heat and pressure, and…Advanced · 12 minLabAtomic-Scale FrictionDrag an AFM tip over atoms and watch stick-slip friction: the Prandtl-Tomlinson model, the effect of speed…Advanced · 12 minLabRolling Contact & TractionDrive or brake a wheel on a rail and watch the stick and slip zones, the creepage and the traction curve,…Advanced · 12 minLabLubrication Regimes & Stribeck CurveMove speed, viscosity and load along a Stribeck curve, compute EHL film thickness with Hamrock-Dowson and the…Foundation · 15 minLabFlash TemperatureSlide a ball or pin over a flat and see the flash temperature from Archard and Blok, asperity flashes against…Advanced · 15 minLabWhy Friction Is Not a Material ConstantChange junction shear strength and hardness (Bowden-Tabor), plough a groove with a cone or sphere, run a…Foundation · 15 min
Wear6 pages
GuideHow to Measure WearWhat wear rate, specific wear rate and the wear coefficient K each mean, how Archard's equation links them,…Foundation · 10 minToolWear Rate CalculatorTurn what you measured into every wear rate at once: a profile area, a mass loss, a ball scar diameter or a…Foundation · 7 minLabMicrostructure Under a Sliding ContactSee how sliding changes the metal under the surface: the dislocation trace line in copper, graded…Advanced · 12 minLabFretting & Partial SlipWatch a ball on a flat shake back and forth: the stuck centre, the slipping ring, the fretting loop, and a…Advanced · 12 minLabRunning-in & Wear Scar GrowthWatch a ball wear a flat scar: the scar grows, the contact pressure falls, and running-in makes one wear rate…Foundation · 12 minLabTribocorrosionWatch a sliding ball strip the passive film off stainless steel and titanium, see the current jump, and split…Advanced · 12 min
Indentation9 pages
GuideHow a Hardness Number Gets MadeWhere hardness and modulus actually come from: fit the unloading curve yourself, watch S, hc and the contact…Foundation · 12 minGuideWhen Your Hardness Number LiesIndentation size effect or a blunt tip? Pile-up wrecking the contact area? Substrate showing through a thin…Advanced · 12 minGuideWhat Indentation Tells You Beyond HardnessSpherical indentation stress–strain curves and the effective zero point, pop-in statistics against the…Advanced · 12 minGuideHow to Decide a Loading ModeEight indentation loading schedules side by side: what each one looks like in load–time, what curve it gives…Advanced · 10 minGuideWhen Does Oliver-Pharr Fail?Ten ways an Oliver-Pharr hardness goes wrong, run on one synthetic indent where the true answer is known: the…Advanced · 12 minLabNanoindentation MappingPlace a grid of nanoindents on a two-phase microstructure, see plastic zones, blurred maps and mixed indents,…Advanced · 12 minLabHardness Scales & ConversionsPress Vickers, Knoop, Berkovich, Brinell and Rockwell indenters into one metal, compare the numbers, and see…Foundation · 12 minLabResidual Stress from IndentationSee how in-plane residual stress shifts a nanoindentation curve and apparent hardness, then estimate the…Advanced · 12 minLabIndentation & Grain OrientationClick grains on an EBSD map to see how the indentation modulus, hardness and pile-up change with crystal…Advanced · 12 min
Scratch & adhesion2 pages
GuideWhat a Scratch Test's Critical Loads MeanLc1, Lc2 and Lc3 from a progressive-load scratch test, built from the contact mechanics up: Hertzian and…Foundation · 10 minGuideScratch vs. Indentation HardnessScratch hardness from the groove width, why four defensible width conventions give four different answers,…Advanced · 10 min
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Other chapters: TEM · EBSD · APT · Structure & Transformations · Mechanical Behavior · In-situ Testing.