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1、IRECHAlUCSOFMATERIALSELSEVIERMechanicsofMaterials27(1998)1-12DeterminationoftemperatureriseduringhighstrainratedeformationRajeevKapoor,SiaNemat-Nasser*CenterofExcellenceforAdvancedMaterials,DepartmentofAppliedMechanicsandEngineeringScience,UniversityofCal
2、iforniaSanDiego,LaJolla,CA92093-0416,USAReceived21July1997AbstractTheenergyconvertedtoheatduringhighstrainrateplasticdeformationismeasureddirectlyusinganinfra-redmethodforTa-2.5%Walloyand,indirectly,usingUCSD'srecoveryHopkinsonbartechniqueforthesamealloy,
3、aswellasforcommerciallypureTi,1018steel,6061A1andOFHCCu.Theinfra-redmeasurementyieldsa70%conversionofworktoheatforTa-2.5%Wandgenerallyunderestimatesthisfactorforalltestedmaterials.Thefinaltemperatureatagivenstraincanbedeterminedindirectly,basedonthecalcul
4、atedplasticwork.Forthis,threeseparatemeasurementsaremade:First,asampleisdeformedatahighstrainratetoatotalstrainof,say,60%;thisisessentiallyanadiabatictest.Thenasecondsampleisdeformedatthesamestrainratetoabout30%strain;thisshouldreproducethefirsthalfofthep
5、reviousadiabaticstress-straincurveandinourtestitdoes.Thissampleisthenallowedtocooldowntotheinitialroomtemperature.Thissamplemaythenbeheatedtothetemperatureaswasmeasuredbytheinfra-reddetectorsandthendeformedatthesamestrainratetocheckiftheadiabaticcurveistr
6、aced.Itisobservedthatonlywhenthesampletemperatureisincreasedbasedon100%conversionoftheplasticworktoheat,thattheoriginaladiabaticstress-straincurveistraced.Itisthusconcludedthattheinfra-reddetectionsystemrecordsalower(surface)temperaturethantheactualtemper
7、atureofthesample.©1998ElsevierScienceLtd.Keywords.Thermomechanicalprocesses;Infra-redsignal;Impacttesting;Kolskybar;Metallicmaterials1.Introductiondependsontheamountofdefectsandalsooftheirarrangementwithinthematerial.Thusrandomlydis-Plasticdeformationsgen
8、erateheat.Theplastictributeddislocationshavedifferentenergythandis-workperunitvolumeinauniaxialdeformationlocationswhicharepiledupagainstbarriers.Strohequalstheareaunderthetruestress-straincurve.(1953)andMooreandKuh
