材料的动态行为_香港科技大学余同希讲座PPT

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1、CHAPTER3CHAPTER3.2012年DYNAMICBEHAVIOR10月25OFMATERIALS日材料的动态行为3.1Materials’BehavioratHighStrain-rates3.2DynamicExperimentalTechnique13.3ConstitutiveEquationsatHighStrain-rates3.1MATERIALS’BEHAVIORATHIGSAGHSTRAIN-RASATES材料在高应变率下的行为2STRAIN-RATEESTIMATIONDefinitionofstrainrate:d1,

2、(unit:s)dtCalculatethestrainratesExample1.Atensilespecimenwithlengthof10cmisextddtendediittnatestiingmachhiitneatliavelocittfyof11/m/s.ll00v1ms1,(unit:s)tlvlm0.100110sIfthetensilespeedis6mm/min,then3110s3STRAIN-RATEESTIMATION(CONT’D)CalculatethestrainratesEx

3、ample2.Acylindricalprojectileimpingingarigidtarget.Assumeththeprojjtildectiledecelerateslinearlltytorestthwhenththlelengthreducesto2.5cm(inshapeofatruncatedcone)l2.5sc2.5mlt5t022ss5v,t510stv2.54110s55510sForshockwavesproducedbynucleardetonation,theshockfrontthick

4、nessdecreaseswithincreasingpressure.Strain-ratehbtth891tilitmayreach10~10s,butthematerialresponseisnotknownIncreeptests,7110s4SCHEMATICCLASSIFICATIONOFTESTINGTECHNIQUESACCORDINGTOSTRAIN-RATEstrainrate,s-110-910-810-710-610-510-410-310-210-1100101102103104105106107erstnal

5、oineslic,uulicvenineslic,ues;ntereringbartestactpfoilseraactpivesHydraExplosCreeptesConventiscrew-dricityhydraticmachiplastomopkinsonyloranvill.plateimxplodingPulsedllplateimtingmachsevo-hydrasrotingmachscamxpandingEHacEatetecaTInNormHigh-veloorpneumCommonHighCreepandstressDynamic-D

6、ynamicQuasi-staticvelocitytestingrelaxationlow-highimpactmethodsTestswithconstantcross-headPlasticDynamicMechanicalVisco-plasticvelocityandstressbeingthewaveShockwaveconsideraresonanceresponseofmetalresponseofmetalsamesamethroughoutlengthofthroughoutlengthofpropa-propagationisimport

7、ant-tionsspecimengation5InertialforcesnegligibleInertialforcesimportantSTRAIN-RATEDEPENDENCE1905,B.Hopkinson’sexperimentsonsteel,showthedynamiticstrengthwastlatleasttittwiceashihihghasititslow-strain-ratestrength.AfterthatmanydynamicexperimentshaveshownAfterthat,manydynamicexperim

8、entshaveshownthatth