简介:Inthispaperwedevelopanelasto-dynamicmodelofthehumanarmforuseinneuro-muscularcontrolanddynamicinteractionstudies.Themotivationforthisworkistopresentacasefordevelopingandusingnon-quasistaticmodelsofhumanmusculo-skeletalbiomechanics.Themodelisbasedonhybridparametermultiplebodysystem(HPMBS)variationalprojectionprinciples.Inthispaper,wepresentanoverviewoftheHPMBSvariationalprincipleappliedtothefullelasto-dynamicmodelofthearm.Thegeneralityofthemodelallowsonetoincorporatemuscleeffectsaseitherloadstransmittedthroughthetendonatpointsoforiginandinsertionorasaneffectivetorqueatajoint.Thoughthetechniqueissuitablefordetailedboneandjointmodeling,wepresentinthisinitialeffortonlysimplegeometrywiththebonesdiscretizedasRayleighbeamswithelongation,whileallowingforlargedeflections.Simulationsdemonstratetheviabilityofthemcthodforuseinthecompanionpaperandinfuturestudies.
简介:Inthispaperwedevelopanelasto-dynamicmodelofthehumanarmthatincludeseffectsofneuro-muscularcontroluponelasticdeformationinthelimb.Theelasto-dynamicmodelofthearmisbasedonhybridparametermultiplebodysystemvariationalprojectionprinciplespresentedinthecompanionpaper.Thoughthetechniqueissuitablefordetailedboneandjointmodeling,wepresentsimulationsforsimplifiedgeometryofthebones,discretizedasRayleighbeamswithelongation,whileallowingforlargedeflections.MotionoftheupperextremityissimulatedbyincorporatingmuscleforcesderivedfromaHill-typemodelofmusculotendondynamics.Theeffectsofmuscleforcearemodeledintwoways.Inoneapproach,aneffectivejointtorqueiscalculatedbymultiplyingthemuscleforcebyajointmomentann.Asecondapproachmodelsthemuscleasactingalongastraightlinebetweentheoriginandinsertionsitesofthetendon.Simplearmmotionissimulatedbyutilizingneuralfeedbackandfeedforwardcontrol.Simulationsillustratethecombinedeffectsofneuralcontrolstrategies,modelsofmuscleforceinclusion,andelasticassumptionsonjointtrajectoriesandstressandstraindevelopmentintheboneandtendon.
简介:ThespinesofpencilandlanceurchinsHeterocentrotusmammillatusandPhyllacanthusimperialiswerestudiedasamodeloflight-weightmaterialwithhighimpactresistance.Thecomplexandvariableskeletonconstruction("stereom")ofbodyandspinesofseaurchinsconsistsofhighlyporousMg-bearingcalciumcarbonate.Thisbasicallybrittlematerialwithpronouncedsingle-crystalcleavagedoesnotfracturebyspontaneouscatastrophicdevicefailurebutbygracefulfailureovertherangeoftensofmillimeterofbulkcompressioninstead.Thiswasobservedinbulkcompressiontestsandbluntindentationexperimentsonregular,infiltratedandlatexcoatedseaurchinspinesegments.MicrostructuralcharacterizationwascarriedoutusingX-raycomputertomography,opticalandscanningelectronmicroscopy.Thebehaviorisinterpretedtoresultfromthehierarchicstructureofseaurchinspinesfromthernacroscaledowntothenanoscale.Guidelinesderivedfromthisstudyseeceramicswithlayeredporosityasapossiblebiomimeticconstructionforappropriateapplications.
简介:Seaurchinspineswerechosenasamodelsystemforbiomimeticceramicsobtainedusingstarch-blendedslipcasting.Porousaluminaceramicswithcap-shapedlayerswithdifferentalternatingporositieswerefoundtohavesuperiorfracturebehaviorunderbulkcompressioncomparedtoceramicswithuniformporosity.Theyfailinacascadingmanner,absorbinghighamountsofenergyduringextendedcompressionpaths.TheporosityvariationinanotherwisesinglephasematerialmimicksthearchitecturalmicrostructuredesignofseaurchinspinesofHeterocentrotusmammillatus,whicharepromisingmodelmaterialsforimpactprotection.