DESIGNANDDEVELOPMENTOFANECONOMICAL

TORSIONTESTINGMACHINEby

GlennVallee,Ph.D.,P.E.AndRobertShort

MechanicalEngineeringDepartmentWesternNewEnglandCollege聚劃算http:///ProjectObjectivesDesignandbuildatorsiontestingmachinecapableofperformingtheASTMTorsionTestMachinemustmeasurematerialpropertiestowithin5%ofpublisheddataMachinemustbeaffordableTorsionTestingApparatusExperimentallydeterminestorsionalshearpropertiesofmaterialsAcylindricaltestspecimenistwisteduntilfailureAppliedtorqueandangleoftwistarerecordedASTMStandardizedTestMethodUsed

-SpecifiesTestProcedure/SpecimenGeometryDesignConstraintsMachinemustbecapableoffracturingasteeltestspecimenSpecimendiametertobe3/8inchtoallowexaminationoffracturesurfaces

-ASTMthereforerequiresaspecimenlengthof

6inchestomeettheminlength/diameterratioTorqueandangleoftwistmeasuringdevicestobeeasilyaccessibletostudentsDesignConstraintsMachinemustproducemeasurementswithin5%ofpublishedASTMresultsBudgetallocationof$500ManyYearsofService!!!DeterminationofShearProperties

Elementarymechanicstheoryusedtorelate

appliedtorque,Ttoshearstress,τ

using

Eq.(1)whereρ=radiusofthespecimencrosssection

J=polarmomentofinertiaofcrosssection

Shearstrainγiscalculatedusing

Eq.(2)

γ

=ρθ/L

whereL=specimenlength

θ=angleoftwistDeterminationofShearPropertiesShearModulusGisdeterminedbyfindingtheslopeofthesheartress-straindiagramShearmodulusmayalsobecalculatedusingEq.(3)Design–TorqueandAngleofTwistRequirementsEquation(1)wasusedtoestimatethetorquerequiredtoyieldaC1018planecarbonsteeltestspecimenintorsion3000in-lbwouldberequiredtofailC1018materialatconstantrotationalvelocityExperimentswereperformedusingaluminumtofindrequiredangleoftwist(10revolutions)DesignLayoutDriveTrain

ADCmotorwithanintegralgearreductionandspeed

controllerwasusedAsprocketsethavinga6:1gearratiodevelopedrequired

torqueFrameDesignBaseFrame/MotorSubAssembly

Twoinchsquaresteelchannelwaswelded

togethertoformtheframeGagemountedona45°AngleTorqueGageMeasurementofTorque

Atorquegaugewasfittedtothe

fixedhubMeasurementofTorqueσ(kpsi)

(kpsi)σ2=σ1=2?

StrainGaugealignedwithdirectionofMaxPrinciple

Stress45°maxσ1σ2StateofPureShearMeasurementofAngleofTwistPotentiometerWeightWheelSprocket

Apotentiometerwasmountedtoawheel

whichcontactedtherotatinghub.ChuckAlignment

AT-slidewasusedtopreventdevelopment

ofaxialloadsandtoaidinalignmentTorqueCalibrationFabricatedTorqueWrenchGage

Aweightedleversystemwasusedtocalibrate

thetorquegaugeTorqueCalibrationCurveCompleteAssemblyPotentiometerLeadsMotorSpeedControlPowerSwitches/LEDsStrainGaugeLeadsPerformanceDataCollectionwithLabVIEWTestingof1018ColdDrawnSteelShearmodulusmeasuredas10.7Mpsi,3%lowerthanthepublishedvalueTestingof2014AluminumShearmodulusmeasuredas3.7Mpsi,5%lowerthanthepublishedvalueBudgetAnalysisItemDescriptionManufacturerMfg.#VendorVendor#QuantityCostEa.($)TotalCost($)

DCMotorDayton4Z530Grainger4Z5311258258DCSpeedControlDartControls125DV-C-KGrainger2M510177772inchSprocketUSTsubaki50B9FGrainger6L9271111112inchSprocketBrowning50Q60Grainger1L21319393Chain(10feet)USTsubaki50TW10Grainger2W09513434PotentiometerEITMW22B-10-2KNewarkInOne83H756811010DrillChuckJacobs30602McMaster3094A1721938NeonLampAssemblyRadioShack2720712RadioShack2720712144NeonLampAssemblyRadioShack2720708RadioShack2720708144DualBindingPostRadioShack2740718RadioShack2740718155

FinalCost($)534IntegrationIntotheMECurriculumTorsionmachinehasbeenintegratedintwoways

-ASTMtorsionexperimenthasbeen

includedinthejuniorlaboratorysequence

-designanduseofthetorsionmachineis

introducedinthesophomoreMechanicsof

MaterialscourseJuniorLaboratoryExperienceStudentsexaminethetorquecellandcalculateitslimitingtorsionalstrengthStudentscreatecalibrationcurvesforthetorquecellandrotationalpotentiometerSteelandaluminumspecimensaretestedofailureandtheresultsarecomparedtopublisheddataMechanicsofMaterialsCourseStudentsexaminethetorque