Abdominal Biofidelity Assessment of 50th Percentile Male and 10‐Year‐Old ATD Responses Relative to a Recently Developed Belt‐Loading Corridor

Abstract

This study investigated the biofidelity of anthropomorphic test device (ATD) abdomens subjected to a belt loading test condition. A total of six ATD/abdomen insert combinations were subjected to belt loading using a seatbelt pull mechanism, with the ATDs seated upright in a free‐back configuration. Three 50th percentile male ATDs were tested, including THOR‐K, Hybrid III 50th percentile male with reusable rate‐sensitive abdomen (HIII‐50M RRSA), and Hybrid III 50th percentile male with standard abdominal insert (HIII‐50M). Additionally, three 10‐year‐old (10yo) size child ATDs including Large Omni‐directional Child (LODC), Q10, and HIII 10yo were tested and evaluated. Force‐penetration results of the 50 th percentile male ATDs were compared directly to a belt loading corridor derived from post‐mortem human subject (PMHS) testing in this test configuration, while 10yo ATD responses were compared to a scaled version of the corridor. Biofidelity of the ATD abdomen responses under free‐back seatbelt loading condition were quantified using the NHTSA Biofidelity Ranking System (BioRank). Among the adult ATDs, HIII‐50M, HIII‐50M RRSA and THOR‐K scored 1.99, 1.71 and 1.33 respectively, indicating that the THOR‐K has a response closest to PMHS. All three child ATDs displayed responses that were outside of the scaled PMHS corridor. The child ATDs showed surprisingly similar responses even though their abdominal area structures are quite different.

Full text

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AbstractThisstudyinvestigatedthebiofidelityofanthropomorphictestdevice(ATD)abdomenssubjected
toabeltloadingtestcondition.AtotalofsixATD/abdomeninsertcombinationsweresubjectedtobeltloading
usingaseatbeltpullmechanism,withtheATDsseateduprightinafree‐backconfiguration.Three50th
percentilemaleATDsweretested,includingTHOR‐K,HybridIII50thpercentilemalewithreusablerate‐sensitive
abdomen(HIII‐50MRRSA),andHybridIII50thpercentilemalewithstandardabdominalinsert(HIII‐50M).
Additionally,three10‐year‐old(10yo)sizechildATDsincludingLargeOmni‐directionalChild(LODC),Q10,and
HIII10yoweretestedandevaluated.Force‐penetrationresultsofthe50thpercentilemaleATDswerecompared
directlytoabeltloadingcorridorderivedfrompost‐mortemhumansubject(PMHS)testinginthistest
configuration,while10yoATDresponseswerecomparedtoascaledversionofthecorridor.Biofidelityofthe
ATDabdomenresponsesunderfree‐backseatbeltloadingconditionwerequantifiedusingtheNHTSABiofidelity
RankingSystem(BioRank).AmongtheadultATDs,HIII‐50M,HIII‐50MRRSAandTHOR‐Kscored1.99,1.71and
1.33respectively,indicatingthattheTHOR‐KhasaresponseclosesttoPMHS.AllthreechildATDsdisplayed
responsesthatwereoutsideofthescaledPMHScorridor.ThechildATDsshowedsurprisinglysimilarresponses
eventhoughtheirabdominalareastructuresarequitedifferent.
Keywordsabdomen,biofidelity,LODC,seatbelt,THOR.
I. INTRODUCTION
Abdominalinjuriescausedbybluntorpenetratingtraumasuchasthoseexperiencedinmotorvehiclecrashes
(MVCs)maybelifethreatening,especiallyduetothelackofearlysymptomswhichmayleadtoadiagnosisthat
istoolate.Forinstance,inaneventofblunttraumatotheabdomen,avascularinsufficiencyleadingtobowel
necrosismaynotmanifestuntilhoursaftertheevent.Duetotheconsiderableriskofabdominalinjuriestoboth
adultsandchildreninMVCsasshownbyvariousstudies[1‐4],itisdesirabletohaveananthropomorphictest
device(ATD)abdomenthatwouldevaluateinjuryriskinalltypesofcarcrashes.
MeasuringtheriskofabdominalinjurieswithATDsisachallengefrombothabiofidelityandinstrumentation
standpoint.Itisdifficulttoaccuratelyrepresenttheviscoelastic,heterogeneousnatureofthehumanabdomen
andorganmobilityinresponsetoloading.Itisalsoachallengetodevelopviableinstrumentationtomeasure
beltpenetrationinsuchasoftcomponent.Thelackofabiofidelicresponsemayleadtoinaccurateconclusions
whileevaluatingmotorvehiclesafetysystems.ToevaluateandimproveuponthebiofidelityofanATD
abdomen,datafromATDtestsshouldbecomparedtopublishedresponsecorridorsbasedonlaboratorytests
usingpost‐mortemhumansurrogates(PMHSs)underidenticaltestconditions.Additionally,anATDshouldbe
capableofmeasuringparametersthatarerelevanttopredictionofinjurywhensubjectedtocrashloads.
Severalstudieshaveinvestigatedvariousmetricsforbothinjuryandresponsepredictionthathaveledtothe
developmentofnewerabdomeninserts[5‐8].
TheabdominalinsertfortheHybridIII50thpercentilemale(HIII‐50M)ismadeofurethanefoamcovered
withvinylskinandfillsthespaceinthepelvis.Itissomewhatellipticalinshapeandhasnoinstrumentationto
measureabdominalinjuryinadditiontonothavingabiofidelicmechanicalresponse[9].Inorderto
demonstraterate‐sensitivityandgoodbiofidelityundervariousloadingconditions,[10]developedaReusable
Rate‐SensitiveAbdomen(RRSA)forusewithintheHIII‐50M.TheRRSAinsertcomprisesofabladdermadeof
R.RamachandraisaPhD(ramachandra.6@osu.edu/+16142924448),YS.KangandJH.BolteIVarePhDsattheInjuryBiomechanics
ResearchCenteratTheOhioStateUniversity,Columbus,OH,USA.J.StammenisaPhDatNationalHighwayTrafficSafety
Administration,VehicleResearch&TestCenter,U.S.DepartmentofTransportation,Washington,DC,USA. A.HagedornisaResearch
ScientistatTransportationResearchCenterInc.,EastLiberty,OH,USA.
AbdominalBiofidelityAssessmentof50thPercentileMaleand10‐Year‐OldATDResponsesRelativeto
aRecentlyDevelopedBelt‐LoadingCorridor
R.Ramachandra,Y‐S.Kang, A.Hagedorn,J.Stammen,J.BolteIV
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siliconerubberfilledwithsiliconegelsiliconegelwithinathicksiliconeshellandthisinsertperformedwell
comparedtothePMHSabdomenresponsedataof[11]underrigid‐bar,seatbelt,andairbagloading.TheTHOR‐
Kabdominalinsertconsistsinasinglefoamblockwithinavinylskinlayerequippedwithbi‐lateralthree‐
dimensionalIR‐TRACC(InfraRedTelescopingRodforAssessmentofChestCompression)devicesmeasuring
deflectionandanglevariation[12].
Studiessuggestthatchildoccupantsinthe6‐12yearoldagegroupareespeciallysusceptibletolapbelt‐
inducedabdominalinjuriesiftheirstatureisnotappropriateforseatbelts[2][5].Thesestudiesalsoindicatethat
havingawaytomeasureriskofabdominalinjurywouldpreventchildoccupantsfromsubmariningunderthe
lapbelt.WhiletheHybridIII10‐year‐old(HIII10yo)doesnotdirectlymeasureabdominalloading,therehave
beendevelopmenteffortstoaddressthisnecessity.TheHIII10yoabdominalinsertisconstructedsimilartothe
HIII‐50Minsert.AsapartoftheEnablingProtectionforOlderChildren(EPOCh)project,AbdominalPressure
TwinSensors(APTSs)wereintroducedintotheQ‐seriesATDstomeasurerestraintloadingtotheabdomen[13‐
14].TheLargeOmniDirectionalChild(LODC)developedbyNHTSA/OSU/TRCissimilarinsizetotheHIII10yoand
Q10ATDsandalsousestheAPTS[15].
ThepurposeofthecurrentstudywastocomparetheresponsesofdifferentATDabdominalinsertsthatareat
variousstagesofdevelopmentorimplementation,totheresponsesfromPMHStestsunderidenticaltest
conditions[16].AdultsizeATDsevaluatedincludedtheHybridIII50thpercentilemale(HIII‐50M)withstandard
abdomen,HIII‐50MretrofittedwithRRSA,andTHOR‐K.ThechildATDsevaluatedwereHIII10yo,Q10,and
LODC.
II. METHODS
Theseatbeltloadingdevicedescribedin[16]wasusedtotesttheATDs.Thedeviceusedapneumaticpiston
topullaseatbeltintotheabdomenoftheATDsinacontrolled,dynamicscenario.Theinstrumentationusedfor
theATDtestswereidenticaltothePMHStests,exceptforthe3aω motionblocksconsistingofthreelinear
accelerometers(Endevco,CA,Model#7264c)andthreeangularratesensors(DTS,CA,Model#ARS8k/ARS‐PRO
18k)onthespineandpressuretransducerslocatedwithintheabdominalvasculature.Astringpotentiometer
(FirstMark,NC,Model#162‐3405)wasattachedtothelumbarspineoftheATDsusingawire‐tietomeasure
displacementoftheATDwithrespecttothetable.Toaccountforanydifferenceinpelvisstructurebetweenthe
HIII10yo,Q10andLODC,thebeltwaspositionedatthesameheightfromthetableforallthreeATDs.Likethe
PMHStests,anotherstringpotentiometer(Celesco,CA,Model#PT101)attachedtotheseatbeltwebbingin
frontofthespecimenattheleveloftheumbilicusmeasureddisplacementofthebeltwithrespecttothetable.
Lastly,alineardisplacementpotentiometer(PennyGiles,UK,Model#SLS190)mountedbetweenthemoving
ramanditsstationaryframemeasuredramdisplacement.Abdomenpenetrationwascalculated,asshownin
Equation1,bysubtractingthedisplacementofthelumbarspineatthelevelofthebeltfromthedisplacement
oftheseatbeltintotheabdomen.
(1)
where,δ
Abd=abdomenpenetration;δ
Lumbar=displacementofthelumbarspinerelativetoram;δ
Belt=
displacementofseatbeltrelativetotablefixture;andδRam=displacementofram.Abdomenpenetrationspeed
wasfoundbydifferentiatingabdomenpenetration.Seatbeltloadcells(Denton,Model#5755)wereaffixedto
thebeltontheleftandrightsidesoftheATDtomeasurebeltforces.Beltforcewascalculatedasthesumof
forcesobtainedfromthetwoseatbeltloadcells.
Fig.1showsthepre‐testpositionoftheHIII‐50Malongwiththeexternalinstrumentationused.Priorto
impact,thearmswereliftedtoshoulderleveltoensurethattheywouldnotinterferewiththemovementofthe
ATD.Thelegssplayedslightlyoutwardinanaturalseatedposition.Theseatbeltwaspositionedtowraparound
theanteriorandlateralaspectsoftheATDabdomenatthemid‐abdomenlevel.Theinitialbelttensionwas
adjustedsothateachbeltloadcellmeasured15‐20N,toensurerepeatableinitialpositionofthebeltwith
respecttoeachATDandremoveanyslack.Additionally,thisinitialbelttensionwassimilartothepre‐stiffening
loadappliedtotheabdomeninthePMHSstudy.
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Fig.1.Pre‐testpositioningofHIII‐50MRRSAontheseatbelttestdevice(A:Linearpotentiometeronram;B:
Forcetransduceronram;C:Seatbeltloadcell;D:Stringpotentiometerattachedtolumbarspine;andE:String
potentiometerattachedtoseatbelt).
ForalltheATDtests,thechestjacketwasusedforaccurateATDrepresentationandtotakeintoaccountthe
influenceofouterflesh/skinontheabdominalresponse.Intermsofinput,allsixATDsweretestedusingan
accumulatorpressureof620kPa,whichisthesamepressureasTestConditionAforthePMHStestsin[16].Fig.
2showsthepre‐testpositionsoftheHIII‐50M,THOR‐K,HIII10yo,Q10,andLODConthetestapparatus.
Fig.2.Pre‐testpositionsofHIII‐50M(topleft),THOR‐K(topright),HIII10yo(bottomleft),Q10(bottomcenter),
andLODC(bottomright).
Datawereacquiredatasamplingfrequencyof20,000Hzandinthelaboratorycoordinatesystem(LCS),with
thepositivex‐axisdirectedfromposteriortoanterior,positivey‐axisdirectedfromlefttoright,andpositivez‐
axisdirectedfromsuperiortoinferior,perstandardSAE‐J211.Timechannelswerezeroedwhentheram
accelerationreached0.5g.Theforce‐penetrationresponsesfromalltheadultATDtestswerecomparedtothe
PMHScorridorshowninFig.33.
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Fig.3:Force‐penetrationcorridorsdevelopedinthePMHSstudy[2].
InordertoquantitativelyassessthesimilarityoftheadultATDresponsestothePMHS‐basedcorridor,an
objectivebiofidelityrankingscorewascalculatedusingthemethodologydescribedby[17].Theforceand
penetrationchannelswerefirstbroughttoacommontimebasisacrossthePMHSandATDtests.Thetimezero
wasestablishedasthefirst0.5gaccelerationofthepneumaticram.Thecalculationincludedthemiddle80%of
theeventconsideringthepeakforceandpeakpenetrationforeachtest.Equation2showsthecalculationused
forgeneratingabiofidelityscore.The√RvaluecorrespondstotheraoofcumulavevariancebetweentheATD
responseandmeanPMHSresponseoverthecumulativevariancebetweenthemeanPMHSresponseandmean
plusonestandarddeviation.AlowervalueoftheBiofidelityRank(BR)representsbetterbiofidelity.
(2)
whereR=responsemeasurementcomparisonvalue, ,i=bodyregion,j=testcondition,k=response
measurement,l=numberofbodyregions=1(abdomen),m=numberoftestconditions=1(seatbeltloading),
andn=numberofresponsemeasurementspertestcondition=2(forceandpenetration).TheBioRank
calculationsweredoneusingforce‐timeandpenetration‐timehistories,andnotusingforce‐penetration.
ScalingNormalisedAdultPMHSDatato10YearOld
Thenormalisedabdomenforce‐penetrationdataobtainedfromthePMHSstudyonsevendifferentPMHSs
(Fig.4)werescaledsothatthechildATDresponsesmaybecomparedqualitativelytotheestimatedabdominal
responseofa10yo.BiofidelityrankingscoreswerenotcalculatedforthechildATDsgivenuncertaintyofhow
appropriatethechosenscalingmethodisforthisfreebackabdominalbeltloadingcondition.
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Fig.4.AdultPMHSabdomendatafrom[16]
Reference[17]adaptedthescalingapproachintroducedby[18]toderiveresponsecharacteristicsfora10yo
byscalingelasticmodulusbyage.Thiswasusedforscalingtheabdominalresponseinthisstudy(TableI).In
TableI,mistheratioof10yomasstotheadultPMHSmass,vistheinputvelocityscalefactor(PMHSand10yo
ATDsweretestedatthesameinputrampressure),Listheratioof10yotoPMHSseatedabdominaldepth,Eis
theelasticmodulusscalefactorreportedfora10yo[19],Kisthestiffnessscalefactorcalculatedasaproduct
ofelasticmodulusandseateddepthratios,andtisthetimescalefactor.Theapproximateresponseofa10yo
wascalculatedbymultiplyingtheadultPMHSforce,penetrationandtimedatashowninFig.4byRf,Rp,
andtrespectively.Theaverageresponsewascalculatedfromthescaledforce,penetrationandtimedatafrom
thesevenPMHSstocomparewiththeHIII10yo,Q10,andLODCresponses.
TABLEI
SCALINGFACTORSUSINGEPPINGER/MERTZMETHOD
Parameters10yoPMHS1PMHS2PMHS3PMHS4PMHS5PMHS6PMHS7
M 33.456647086507467

m =

M1 /Mre
f

0.600.520.480.390.670.450.50

v =

V1 /

Vre
f

1111111
L 186358311300300200265265

L =

L1 /Lre
f

0.520.600.620.620.930.700.70

e 10.8540.8540.8540.8540.8540.8540.854

K
=

E
*

L

0.440.510.530.530.790.600.60

t =

E
-1/2 *

m1/3

0.910.870.850.790.950.830.86
R
f
=

v * (

m *

K
)1/2 0.510.520.500.450.730.520.55
R
p
=

v * (

m /

K
)1/2 1.161.010.950.860.920.870.91
III. RESULTS
AtotalofsixATDsweretestedincludingtheHIII‐50M,HIII‐50MretrofittedwithRRSA,THOR‐K,HIII10yo,
Q10andLODC.Alltestswereconductedatthebaselineaccumulatorpressureof620kPatobeconsistentwith
theinputusedtodevelopthePMHScorridor.
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Fig. 5showstheresponsesofthethree50thpercentileATDstestedincomparisonwiththePMHScorridor.
TableIIcataloguesthepeakforce,penetrationandcompressionresultsfortheadultATDs.
Fig.5.Comparisonoftheforce‐penetrationresponsesofHIII‐50M,HIII‐50MRRSAandTHOR‐KtothePMHS
corridor.
TABLEII
SUMMARYOFVALUESRECORDEDANDCALCULATEDFROMTHEADULTATDTESTS
Fig.A1intheAppendixshowstheadultATDresponsescomparedtoPMHSbiofidelitytargets.TableIII
showsthattheBiofidelityRankofTHOR‐KabdomenisbetterthantheotherATDstestedundersimilarinput
conditions.AllthreeabdomensdemonstratedoverallBRunder2.0,suggestingabiofidelicresponse[20].Witha
differenceinBiofidelityRankofover0.2betweeneachother,thethreeATDabdomensareconsidered
significantlydifferentfromeachotherwithrespecttobiofidelity[17].Overall,theTHOR‐Kabdomenhadthe
lowest√Rindicangthemostbiofidelicresponseinthisparculartestconfiguraon.
TABLEIII
BIOFIDELITYRANKSFORATDS
MeasurementHIII‐50MHIII‐50MRRSATHOR‐K
Force‐Time1.291.071.18
Penetration‐Time2.692.361.48
Overall1.991.711.33
Fig.6showstheforce‐penetrationresponsesfromthe10yochildATDsincomparisontothescaledcorridor.
TestIDPeakForce
(kN)
PeakPenetration
(mm)
Compression
(%)
HIII‐50M5.257028
HIII‐50MRRSA3.429337
THOR‐K5.0210040
PMHS[12]2.90‐4.80110‐17745‐59
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Fig.A2intheAppendixshowsthechildATDresponseswiththeMertzscaled/normalisedlargechildbiofidelity
targets.TableIVcataloguesthepeakforce,penetrationandcompressionforthechildATDs.
Fig.6.Comparisonoftheforce‐penetrationresponsesofHIII10yo,Q10andLODCtotheaverage+/‐1SDscaled
responsefromPMHStests.
TABLEIV
SUMMARYOFVALUESRECORDEDANDCALCULATEDFROMTHECHILDATDTESTS
IV. DISCUSSION
Inthisstudy,adultPMHSabdominalresponsedatawerecomparedtoadultATDresponsedatainorderto
evaluatethebiofidelityoftheHIII‐50M,HIII‐50MRRSA,andTHOR‐Kabdomen.Secondly,theadultPMHSdata
werescaledtoestimatea10yearoldabdominaltargetresponseandthatscaledresponsewasthencompared
withHIII10yo,Q10andLODC.
ForthepurposesofATDevaluation,itisimportantthatabiofidelitytestconditionhaveaconsistentinput.
Thetest‐setupusedinthisstudyachievesthisobjectiveasitisamorerepeatable,better‐definedtestcondition
thanpreviouslypublishedcorridors[11][21]andthereforemoreappropriateforATDdevelopmentand
evaluationpurposes.Whiletheabdomenofthesubjectmayinfluencetheoverallstrokeoftheram,sucha
responseisidenticaltoallothercomponent‐levelbiofidelitytestswhereaknowninputvelocityisappliedbut
oncecontactwiththespecimenorATDismade,theimpactorisaffectedbywhatitcontacts.
TheinitialstiffnessoftheHIII‐50MwithRRSAwashigherwhencomparedtothePMHStests(seeFig.5).Itis
likelythattheshiftingoforgansandcontentsintheabdominalcompartmentupondistributedloadingisnot
capturedintheRRSA,inturnresultinginahigherinitialstiffnessresponseoftheabdomen.Whenseated,the
abdominalcontentsofthePMHS,likeinlivinghumans,arebroughtdownwards,especiallywhenthelungsare
filledduringadeepinhaleandtheorgansareallowedtomovefreelyawayfromthebeltloadingpath.However,
astudyconductedby[22]usingafixed‐backconfigurationwiththePMHSininvertedpositionsimilarto[23]
suggestedthattheinitialpositionofabdominalorgans,especiallytheliver,withrespecttotheimpactorplays
animportantroleintheinternalorgankinematicsandoverallresponse.
Ontheotherhand,theTHOR‐Kabdomenexhibitedaninitialresponsethatissimilartotheresponse
recordedinPMHStests.Therewasanevidentsoftbehaviouruntilapproximately45mm,whichissimilartothe
PMHSresponseinthecurrentstudy,afterwhichthereisanincreaseinstiffnessuntilreachingapeakforceof5
kNandpenetrationof100mm.AdditionaltestswiththeTHOR‐Kabdomenundervariousloadingratesmay
provideinformationaboutviscousanddampingcharacteristics.Whileitmaybearguedthatthepre‐stiffening
TestIDPeakForce
(kN)
PeakPenetration
(mm)
Compression
(%)
HIII10yo3.4713170
Q103.1014475
LODC3.408245
PMHSScaled1.60‐2.15105‐14057‐76
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loadof15‐20Nappliedonthebeltmaypossiblyconfoundthetoeregionofforce‐penetration,itisunlikelythat
thebiofidelitywasaffectedsincetherewaslittletonoinitialpenetrationduetothebeltpre‐load.
ThesuddendipinforceofHIII‐50MRRSAaround40mmpenetrationwascausedbythebeltslidingoffinto
thegapbetweenthechestjacketandpelvisandcontinuingtoloadtheabdomendirectly.Thisphenomenonis
highlightedinFig.7thatshowsthepost‐testpositionofbelttrappedunderthepelvisskinandincontact
directlywiththeabdomen.WhentheHIII‐50Mhousedthestandardabdominalinsert,therewasverylittlegap
betweenthepelvicrimandthejacketlipasthetorsoflexesforwardslightlywiththeoriginallumbarspine
assembly.However,theinitialgapwasmorepronouncedwiththeRRSAasitusesamodifiedlumbarspine
assemblythatextendsthetorsoslightlyandabeltslippagemaybeexpectedinanactualfull‐scalevehicleor
sledtesting.Althoughtherewasaslippage,thebeltcontinuedtoloadtheabdomenafteritwentbetweenthe
pelvisandchestjacket,whichmaybeconsideredaresponsecharacteristicoftheabdomen.Further
investigationisnecessarytoidentifythevariationinBRSwithouttheslippage.InorderfortheRRSAabdomen
todrivetheoverallforce‐penetrationresponseandminimizetheriskofthisslippageoccurringinasledor
vehicletest,itmaybenecessarytoremovetheanteriorpelvisskinsimilartohowtheabdomenisconfiguredin
theLODCandQ10.
Fig.7.InitialplacementofseatbeltontheHybridIIIwithRRSA(left);finalpositionofseatbelttrappedbetween
thechestjacketandpelvis(right)
ToprovideamoredirectcomparisonforthechildATDabdominalresponses,thescalingapproachsuggested
by[18]wasappliedtotheadultPMHSdata.Thescalefactorsreducedtheforcebyalmosthalfwhileonly
slightlyreducingthepenetration(Rfaverage=0.54,Rpaverage=0.95).AllthreechildATDsdisplayedresponses
thatwereoutsideofthescaledPMHScorridor.ThechildATDsshowedsurprisinglysimilarresponseseven
thoughtheirabdominalareastructuresarequitedifferent.ThissimilarityislikelyduetothechildATDsbeing
lighterthanbothadultPMHSandATDs,whichindicatesthattheinertialeffect(childATDsaresimilarinmassto
oneanother)isdominatingtheresponseinthefreebackcondition,whereasinthefixedbackcondition,the
abdomenstiffnessisdominant.Moreinvestigationisneededtodevelopanappropriatepulseforevaluatingthe
biofidelityofchildATDsinthefreebackcondition,giventheapparentlackofresponsesensitivitytoabdominal
designs.
Inaddition,thefreebackconditionislikelyinfluencedmorebypre‐testATDpositioningthanthefixedback
case.AllthreechildATDshavingdifferentpelvicstructures,alongwithdifferencesintheabdomenconstruction.
TheQ‐seriesATDshaveamoreroundedabdomenandexhibitamoreflexedposture[24]comparedtoHIII10yo
andLODC.TheQ10inthecurrentstudystartsoutmuchmoreuprightwhenseatedcomparedtotheHIII10yo
andLODCduetodifferencesintheconstructionofthespine.ComparedtotheHIII10yoandLODC,theQ10
exhibitedagreaterpenetrationandareducedbeltforce,whichmaybeduetothehigherflexibilityofthetorso
leadingtothesofterabdominalresponseinadditiontothedifferentstartingpositions(Fig.8).TheQ10
responsehaddropinforce,liketheRRSA,buttherewasnobeltslip.However,intheQ10tests,thebeltwas
trappedbetweentheribcageandthepelvisuponforwardflexion.Sucharesponsemaybesimilartowhatmay
beseeninasledtest.However,itmustbenotedthatthisforwardflexionoccurredverylateintheevent,after
maximumpenetrationhadbeenreached.Althoughtherewasforwardflexion,suchaswhatmaybeseenina
sledtest,theauthorsareconfidentthattheabdomenresponsewasnotinfluencedbydummyflexionorpelvis
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movementoverthefirst80msec.
Fig.8.Q10(top)andLODC(bottom)inthestartingposition(left)andatpeakpenetration(right)
TheLODContheotherhanddoesnotexhibitasmuchflexionwhichmaybeattributedtotheabdominal
stiffnessasthebeltbeginstodisengagefromtheabdomenmuchsoonerthantheQ10andtheLODCbeginsto
translaterearward.TheHIII10yoalsohadasimilarabdomen‐beltinteractionsuchastheLODC,althoughthe
rearwardtranslationoccurredsoonerindicatingastifferabdomencharacteristicoftheHIII10yo.Differencesin
pre‐testpositioningmaybecompensatingfordifferencesinabdomenresponseamongthechildATDs.Further
quantitativeanalysisofthechangeintorsoanglethroughtheeventisrequiredtoevaluatethedifferencesin
abdominalresponsesofQ10andLODC.
Whilethefixedbacksetupprovidesaneffectivecharacterisationofisolatedabdominalresponseintermsof
biofidelity,oneofthekeybenefitsofafree‐backbeltloadingsetupisthatforagiveninputofthepneumatic
ram,thefreebacksetupallowstherestoftheATDtocontributetotheabdominalresponsebynotconstraining
thedummyinanyway,therebyprovidingamoreaccuraterepresentationofhowthedummywouldbeloaded
inacrashevent.WhileaTeflonskidwasusedtominimisefrictionaleffectsinbothPMHSandATDtests,itis
unclearhowmuchthepelvisandlegcontactwiththetablethroughouttheeventcontributedtodifferences
betweenPMHSandATD.Withlowerfriction,theATDmaybeallowedtoslidebackmorefreelyratherthan
allowingtheabdomentoabsorbmuchoftheenergy.However,thiseffectisassumedtobenegligiblebasedon
theinvestigationusinghigh‐speedvideosandtheslipperynatureoftheTeflonskid.
References[6][25]developedalowerabdomenbiofidelitytargetusingaseriesoffixedbacksupinetestson
porcinespecimensdevelopmentallymatchedtohumanpaediatricages.Thesetargetshoweverarenot
appropriateinthecurrentstudyduetothedissimilartestsetups,althoughtheKentstudyoffersthemostdirect
paediatricdatacomparisondatafortheHIII10yo,Q10andLODC.Reference[15]evaluatedtheHIII10yoand
LODCabdomendynamicresponsesemployingafixed‐backsetupsimilartobutnotidenticalto[6].Itwas
determinedthattheLODCresponsewasmoreconsistentwiththebiofidelitytargetthantheHIII10yobasedon
BioRankscores(0.66vs.1.61).
OneofthepossiblereasonsforthedifferencebetweenhowtheLODCabdomen,whichisstillundergoing
development,scoredinthefixedbackconditionandtheresponsewithrespecttothescaledcorridorinthefree
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backconditionmaybethedependencyofthisscalingapproachonthepublishedelasticmodulusscalefactor
derivedusinghardtissuesuchasthecranialboneratherthansoftviscerasuchasintheabdomen.Whilethis
approachprovidedareasonablecomparisonfortheupperthoracicresponseinthe[26]study,thetechnique
maynotbeabestpossiblerepresentationofthepaediatricpopulationwhileexaminingsofttissueresponses.
Additionally,intheabsenceofacomparisonbetweensofttissuestiffnessinadultversuschildspecimensinthe
sametestconfigurationintheliterature,theapproachusedinthisstudyassumesthatage‐relateddifferencesin
softandhardtissuepropertiesaresimilar,whichmayormaynotbethecase.Acomprehensivestudyofspinal
kinematicswithfocusonspinalrotationsthatmayleadtodifferencesinabdominalresponseisalsowarranted.
Itispossiblethatboththeforceanddeflectionbehaviorofeachabdomencouldbeinfluencedbythe
instrumentation(suchaspressuresensorsorIR‐TRACC)selected.Whilefurtherworkcouldinvestigatethe
influenceofdifferenttypesofinstrumentationwithinagivenabdomen,itisimportantthattheabdomen
containsomesensorforthepurposesofmeasuringdirectloadingtotheabdomen.
Alimitationofthisstudyistheuseofthesameaccumulatorpressuretodrivethebeltintotheabdomenin
boththeadultandchildATDtests.Itmaybearguedthattheinputneedstobescaleddownwhenconductinga
similartestbetweenadultandchild.However,therelationshipbetweenaccumulatorpressureandpenetration
velocityishighlydependentontheabdomencharacteristics(stiffnessanddamping).Therefore,ifthe
penetrationvelocityisconsideredtheinputtotheATD,itisdifficulttodeterminetheappropriatescalefactor
foraccumulatorpressure.FurtherworkisrequiredtobetterunderstandtheinputscalingrequiredforchildATD
biofidelityassessmentinthefreebackcondition.
Anotherlimitationrelatestotheuncertaintyinscalingtheabdominalforceandpenetrationresponsesin
bothfixedandfreebacksetups.However,whenevaluatingtheresponsesofthechildATDs,unlikethe
availabilityofadirectcomparisontopediatricdata[6][25]inafixedbacksetup,thereisnotadirectcomparison
inthefreebacksetup,makingthedatafromcurrentstudyheavilyrelyonscalingtechniques.
Insummary,thisstudyprovidesanassessmentofabdominalresponsebiofidelitybetweenPMHSandATDs
underidenticalloadingconditions.Thisevaluationisaimedatguidingdesignimprovementsforfutureversions
oftheseATDsandtheirabdominalinserts,aswellasmodelsthatsimulatethephysicalcounterparts.
V. CONCLUSIONS
ThisstudyinvestigatedtheresponseofATDabdomenssubjectedtoseatbeltloadingusingthesametest
apparatusasPMHStestsunderidenticalloading.ResultsfromtheseATDswerecomparedtoforce‐penetration
corridorsdevelopedin[16].Themainoutcomesareasfollows:
Usingthequantitativebiofidelityrankingsystem,theTHOR‐KresultedinthelowestBRoftheadultATDs
indicatingaresponseclosesttothetargetcorridorfromPMHSstudy.
AllthreechildATDsdisplayedresponsesthatwereoutsideofthescaledPMHScorridor.ThechildATDs
showedsurprisinglysimilarresponseseventhoughtheirabdominalareastructuresarequitedifferent.
ScalingofadultPMHSdatatoachild‐appropriateresponseinthefreebackconditionischallenginggiven
sensitivityoftheresponsetonon‐abdominalfactorssuchaspre‐testpositioning,frictionalandinertial
considerations,anddifferentmaterialproperty‐basedscalefactorsofskeletalandorganstructures
withinthelowertorsoregion.
Whilethefixedbacksetupprovidesaneffectivecharacterisationofisolatedabdominalresponseinterms
ofbiofidelity,thefree‐backbeltloadingprovidesamoreaccurateassessmentofhowmultiple
componentsincludingtheabdomencontributetotheoverallATDlowertorsoresponse.
Acknowledgement
ThisresearchwassupportedbytheNationalHighwayTrafficSafetyAdministration(NHTSA),USA.The
authorswouldliketothankKevinMoorhouse(NHTSA‐VRTC)fortechnicalguidance, andthestaffandstudents
ofInjuryBiomechanicsResearchCenteratTheOhioStateUniversity,USA,forassistinginthetests.
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VII. APPENDIX
Fig.A1.AdultATDsabdomenpenetrationvs.time(top)andbeltforcevs.time(bottom)responsescompared
withPMHSbiofidelitytargets
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Fig.A2.ChildATDsabdomenpenetrationvs.time(top)andbeltforcevs.time(bottom)responsescompared
withMertzscaled/normalisedPMHSbiofidelitytargets
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