简介:Inthispaperweinvestigatedhowtherunningspeedwouldaffectthedynamicsofbodypitching,andwhetherbodyinertiaisimportantforanimals.Passivetrottingofspring-massmodelandpassiveboundingofspring-beammodelwerestudiedatdifferentspeedsfordifferentsetsofbodyparametersrespectively.Furthermore,differentbodyinertiaswereusedinbounding.Wefoundthatrunningspeedexertseffectonlegperformancebymeansofcentrifugalforce.Thecentrifugalforcecanbeunderstoodasanenhancementtothenaturalfrequencyofthespring-masssystem.Thedisadvantageofbodypitchingmaybeoffsetbythegreatincreaseincentrifugalforceathighspeed.Theresultsalsorevealthatbodymassdistributionmightnotbethemainreasonforthedifferenceinmaximalrunningspeedsofdifferentanimals.
简介:SometribologicalbehaviorbetweenmatureGampsocleisgratiosafootpadsandverticalflatsofdifferentmaterialswerestudiedinthiswork.stereomieroscope(SMS)andscanningelectronmicroscope(SEM)wereusedtomeasurethemorphologyoftheGampsocleisgratiosafootpads.Anatomicforcemicroscope(AFM)wasusedtomeasurethemorphologiesofthesurfacesofglassandawalldopedwithcalciumcarbonatematerial.TheattachingbehaviorofGampsocleisgratiosafeetonthetwoverticalsurfaceswasobserved.Theattachingforce(perpendiculartotheverticalsurface)andthestaticfrictionalforce(alongthedirectionofgravitation)ofGampsocleisgratiosafootpadsonaverticalglassweremeasured.Itwasshownthattheaverageattachingforceis50.59mNandthestaticfrictionalforceis259.10mN.ThephysicalmodelsoftheattachinginterfacebetweenGampsocleisgratiosafootpadsandthetwoverticalsurfaceswereproposed.Itwasobservedthatthefootpadsaresmoothinmacroscale;however,thepadsurfaceiscomposedbyapproximatehexagonalunitswithsizesof3μmto7μminmicroscale;theadjacentunitsareseparatedbynanoscalegrooves.TheObservationsshowedthattheGampsocleisgratiosacannotclimbtheverticalcalciumcarbonatewall;incontrast,theycaneasilyclimbtheverticalglasssurface.Basedonthefeaturesofthegeometricalmorphologiesofthefootpadsandtheglasssurface,wespeculatethattheattachingforceandstrongstaticfrictionalforceareattributedtotheinterinlaysbetweenthedeformableGampsocleisgratiosafootpadsandthenanoscalesharptipsoftheglasssurface.
简介:ThespinesofpencilandlanceurchinsHeterocentrotusmammillatusandPhyllacanthusimperialiswerestudiedasamodeloflight-weightmaterialwithhighimpactresistance.Thecomplexandvariableskeletonconstruction("stereom")ofbodyandspinesofseaurchinsconsistsofhighlyporousMg-bearingcalciumcarbonate.Thisbasicallybrittlematerialwithpronouncedsingle-crystalcleavagedoesnotfracturebyspontaneouscatastrophicdevicefailurebutbygracefulfailureovertherangeoftensofmillimeterofbulkcompressioninstead.Thiswasobservedinbulkcompressiontestsandbluntindentationexperimentsonregular,infiltratedandlatexcoatedseaurchinspinesegments.MicrostructuralcharacterizationwascarriedoutusingX-raycomputertomography,opticalandscanningelectronmicroscopy.Thebehaviorisinterpretedtoresultfromthehierarchicstructureofseaurchinspinesfromthernacroscaledowntothenanoscale.Guidelinesderivedfromthisstudyseeceramicswithlayeredporosityasapossiblebiomimeticconstructionforappropriateapplications.
简介:UHMWPEcompositesreinforcedwithBovineBoneHydroxyapatite(BHA)indifferentcontentswerepreparedbyheatpressingformationmethod.AhipjointwearsimulatorwasusedtoinvestigatethebiotribologicalbehaviorofUHMWPE/BHAcompositeacetabularcupsagainstCoCrMoalloyfemoralheadsinbovinesynovialubricationat37±1℃.ItwasfoundthattheadditionofBHApowdertoUHMWPEcanimprovethehardnessandcreepmodulusofUHMWPE/BHAcomposites,anddecreasetheirwearratesunderbovinesynovialubrication.WhenthecontentofBHAfillerparticleswasupto30wt%,UHMWPE/BHAcompositesdemonstratedthewelldesignperformancesofthesurfaceandbiotribologicalproperties.Fatigue,ploughingandslightadhesivewearwerethemainwearmechanismsforUHMWPEanditscomposites.Inaddition,thesizesofwearparticlesbecamelargerwithanincreaseinBHApowderaddition.TheseresultssuggestthatBHAfillerisadesirablecomponenttoincreasethewearresistanceofUHMWPE/BHAcompositesforbiomedicalapplications.
简介:Seaurchinspineswerechosenasamodelsystemforbiomimeticceramicsobtainedusingstarch-blendedslipcasting.Porousaluminaceramicswithcap-shapedlayerswithdifferentalternatingporositieswerefoundtohavesuperiorfracturebehaviorunderbulkcompressioncomparedtoceramicswithuniformporosity.Theyfailinacascadingmanner,absorbinghighamountsofenergyduringextendedcompressionpaths.TheporosityvariationinanotherwisesinglephasematerialmimicksthearchitecturalmicrostructuredesignofseaurchinspinesofHeterocentrotusmammillatus,whicharepromisingmodelmaterialsforimpactprotection.
简介:Biomimeticsurfaceisaneffectivewaystopromotetheperformancegradeandappliedrangeofmaterialswithoutalteringtheirsubstrate.Manyimprovedpropertiessuchasresistingfatigue,enduringwear,etc,havebeenachievedbyapplyingbiomimeticmorphologyorstructuretosomeengineeringmaterialsurfaces.Inthispaper,aimingtorevealtherelationshipbetweenthermalcrackingbehaviorandmechanicalpropertiesofengineeringmaterialswithbiomimeticsurface,biomimeticspecimenswerefabricatedusinglasertechniquebyimitatingtheheterogeneousstructureonthesurfaceofplantleaves.TheeffectofthermalfatiguecyclingonthetensilepropertiesofH13diesteelspecimenswithdifferentsurfaces(severaltypesofbiomimeticsurfacesandasmoothsurface)wascomparedandinvestigated.Asaresult,duetothecouplingeffectsofthemorphologicalfeaturesonthesurfaceandthemicrostructurecharacteristicswithinunitzone,thesespecimenswithbiomimeticsurfaceexhibitremarkablyenhancedUltimateTensileStrength(UTS)and0.2%YieldStrength(YS)comparedwithreferencespecimenswhilecorrespondingductilityremainslargelyunaffectedevenheightened,whetherthethermalfatigueloadsornot.Therelativemechanismsleadingtotheseimprovementshavebeendiscussed.