生物摩擦学BiotribologyGeneral教学课件

Definition the study of tribes?the study of hair as in Trichology?Try-biology?TribologyDefinitionTribology:Tribo-,Gr.Tribos-(is):rubbing;-logy:names of sciences or departments of study“The branch of science and technology concerned with interacting surfaces in relative motion and with associated matters(as friction,wear,lubrication,and the design of bearings).Oxford English Dictionary“The science and technology of interacting surfaces in relative motion and the practices related thereto”Jost Report(1966)Surfaces,friction,wear and lubrication Definitionshef.ac.uk/mecheng/mecheng_cms/tribology/DefinitionBiotribology:All aspects of tribology related to biological systems(Professor Duncan Dowosn and Professor Verna Wright,University of Leeds,1973)Dental,skin,clothes,hair,footwear,contact lens and eye,replacement heart valves,fracture repair,pleural and pericardium,and natural synovial joints and artificial replacements.SurfacesGod made materials but surfaces were the work of the Devil.Pauli,Nobel Prize for Physics,1945 maitrise-orthopDowson et al,J Arthroplasty,2019SurfacesAll surfaces are rough:Atomic diameters1 to 10 Irregularities on mica20 Quartz crystal100 Ceramic surfaces 0.005 m(50)Metallic surfaces0.005 to 0.01 m(100)1 angstrom()=10-10 m=10-4 mSurfacesSurfacesmaitrise-orthop/corpusmaitri/index_us.html,A Dambreville*,M Phillipe*,A Ray*,*Clinique St-Michel,29000 Quimper,*Hpital de Carpentras 4200 CARPENTRAS,*Clinque du Parc 69458 LYON CEDEX-France SurfacesProfilometry Non-contacting such as laser or white light Contacting such as stylus method Average roughness(Ra)LSurfacesSame Ra,but not same tribology and other roughness parameters are also required!Use of Ra with caution!FrictionFriction is loosely defined as the resistance to motion.Leonardo da Vinci(AD 1452 1519)FrictionAmontons,1699The force of friction(F)is directly proportional to the applied load(w)The force of friction(F)is independent of the apparent area of contact FrictionCoefficient of friction()FrictionTransporting an Egyptian colossus from the tomb of Tehuti-Hetep,El-Bersheh,(c.1880 B.C.)Dowson,History of tribology,2nd ed,2019Wet:0.2 Clean(and dry):0.25-0.5WearProgressive loss of substance from the operating surface of a body occurring as a result of relative motion at the surfaceSurface deformation,Pitting,Scratching,Burnishing,Polishing,Delamination,Fretting,Cracking,WearLaws of wear:lWear increases as the normal load(W)increaseslWear increases as the sliding distance(S)increaseslWear decreases as the hardness(H)of the softer sliding component increases K:wear factor,mm3/(Nm)WearWear testing:simple screeningUni-directional pin-on-discReciprocating pin-on-plateMulti-directional pin-on-plateWearWear testing:Leeds hip simulator+35 to-250 70 704.5 kN0.9 kN0.9 kNWearWear measurements:volume,penetration WearWear measurements:debris/particles Lubricationo Abrasive wear o Adhesive wearo Fatigue wear asperity contact lubricantLubrication refers to adding a lubricant between two bearing surfaces in order to control friction and wearLubricationWhere Where h hminmin:the average film thickness:the average film thicknessR Ra a:the composite surface roughness of two :the composite surface roughness of two bearing surfacesbearing surfaceshmin ratioLubricationo Fluid film lubrication 3o Mixed lubrication 3 1 o Boundary lubrication 1 Lubrication regimes and ratioLubricationhmin:minimum film thicknessR:equivalent radiusw:loadu:entraining velocity,=(uhead+ucup)/2E:equivalent elastic modulus,:viscosity Lubrication film thickness,hminHamrock and Dowson,1978LubricationRadiusRheadRadial clearance,cEquivalent radiusRcupSummaryFrictionWearLubricationBiotribology:ExamplesSkin frictionBiotribology:ExamplesLubrication in total artificial heartBiotribology:ExamplesWear of heart valvesBiotribology:ExamplesDental wearBiotribology:ExamplesFracture fixationFlow of Red Blood Cells:Disk-shapedBiconcaveAxisymmetricDiameter:8 mThickness:1 to 2.5 mCapillaries:5 to 10 mFlow of Red Blood Cells:LubricationCapillary hemodynamicsMass transfer and supply of oxygenResistance to shear damageCell motionElastic deformationElastohydrodynamic lubricationOcular System:EyeOcular System:CorneaTransparent tissue without blood vesselsApproximately spherical at the central portion with a radius about 8 mmThickness:0.52mm,increasing to 0.65mm at the limbusRefractive Index:1.3771Roughness of epithelial surface:0.5 m(microridges),covered with a mucus gel further decreasing surface roughnessOcular System:Tear filmsOutmost:lipid(fatty,oily):0.1 mMiddle:aqueous,low viscosity and 7 to 10 mInnermost:mucous(viscous)Ocular System:Tear filmsNon-newtonian shear thinningViscosity at high shear rates0.0013 PasOcular System:Function of tear filmsSmooth motion and optical qualityOxygen supply due to diffusion and pumping(hydrodynamic action)Comfort and eliminate debrisOcular System:BlinkingOnce every 5 s(2 to 10)and 12 per minDuring closure:upper eyelid moves down with an approximate speed of 15 cm/s(10 to 12 mm during 0.08s)During opening:0.17 sLoad between the eyelid and the globe is quite small,less than a few grams 0.2 to 0.25 N in the normal direction0.0004 to 0.0005 N in the tangential directionOcular System:Lubrication mechanismsBoundary,Ehlers(1965)Hydrodynamic,Holly(1970)*10 m tear film,the surface roughness*low coefficient of friction,0.005*high shear rate 15,000 1/s during blinking*low shear stress on the ocular surface*but sufficient high to remove the dead cells and mucous threads contaminated with lipid from the ocular surface in the aqueous layerOcular System:Dry eyeBoundary lubricationSurface roughness increased by 10 timesThinner tear films and increased shear stressesOcular System:Importance of lubricationNormal lubrication mechanismsDiseases such as dry eyeArtificial tear filmsFunction of contact lensSynovial Joints:Synovial jointsHipKneeAnkleShoulderElbowSynovial Joints:FunctionRelative motion between two surfaces with low friction and negligible wearTransmit high load(3 to 6 times bodyweight)without damaging any of its structural components.Synovial Joints:Synovial jointArticular cartilageSynovial fluidBoneSynovial Joints:Synovial jointJournal bearingFuture Developments:o Many more applications!o Unification of lubrication mechanisms in different biological systemso Tribological approach to understand the wear mechanism in different artificial hip jointso Promoting fluid film lubrication in artificial hip jointsxiexie!xiexie!谢谢！谢谢！xiexie!xiexie!谢谢！谢谢！