1.3--2.3扭转与剪切--英文字幕

Hello boysand girlsoLasttime welearned aboutcompression test and bendingtestoThe testprocedure、characteristics andapplication of the twotests areunderstood2In thislesson wewill studytwo otherstatic loadbehaviors torsionandshearo3Lets startwith twistingoThecylindrical specimenis subjectedto torsional moment,and themechanicalproperties of the materialare analyzedby recordingtherelationship betweentorsionalmomentand torsionalAngleSample shape:its diametreequal toten millimeters,scale distanceequal tofiftyor onehundred millimeters.Longitudinal forceuniform;The transversesurface isthe largestand thecenteris

0.In theelastic deformationstage,the shear stress andshear strainon thecrosssection arelinearly distributedalong theradius directionAfterplastic deformationoccurs,the distributionof shearstrain remainslinear,but the shearstressdecreases dueto plasticdeformation andnolonger remaina lineardistributionThe Testin accordancewith GB10128Metallic materials-Test methodfortorsion atroom temperatureoTheperformance indexesof torsion test areShear modulus:G Yieldingstressin torsion:、Torsional strength:bT ST5Its featuresincludeFirstly,The torsionstress stateso代coefficient aequal to

0.8,larger thantensile,easy toshow the plastic behaviorofthemetalSecondly,When thecylindrical specimenis twisted,the plasticdeformationis uniformon thewhole length,and thereis noneckingphenomenon,which canrealize thetest underlarge plasticdeformationhigh temperaturetorsiontest.Thirdly,It canbe used to studyor testthe surfacequality ofthe workpiecebyheat treatmentand theeffect ofvarious surfacestrengtheningprocessesThe forth,It isthe mostreliable methodto determinethe cut-off strengthofmost metalmaterials usedin production.It canjudge whetherthe finalfracturemode isnormal orcut-off according to themacroscopiccharacteristics ofthe fracture6oNow letsanalyze thefractureThe fracturesurface oftheplasticmaterial isperpendicular tothe axisofthe sample,and thefracture issmoothThe oneof brittlematerial is45Angle withthe sampleaxis,which isaspiral fractureunder theaction ofnormal stressThere isanother typeoffracture:Woody fractureThereare morenon-metallic inclusionsor segregationin themetal,andmake itdistribute alongthe axialdirection inthe rollingprocess,whichreduces theaxial cuttingstrength ofthe sample7These threestatic loadtests aresummarized belowaccordingtoSoftcoefficient ofstress statecurves itsindex applications.Finally,we brieflyintroduce theshear test.Its procedure:Usually,various sheartest devicesand correspondingtestmethods areusedtosimulate theworking conditionsofthereal standardworkpiece.Shear forceis imposedon thesample untilfracture,so astodetermine itsshear strengthcan alsobe carriedout onthe universaltestingmachine,and thesample isplaced intheshearfixture.The sheartest includesSingle sheartest、Double sheartestandPunchingshear test.Well,Summarize brieflyThislesson introducesthe torsiontest itscharacteristic performanceandindexoThree fracturetypes arealso explained,Plastic materialsbrittle materials,woody fractureFinally,the shearingtest isbriefly introducedThatsall fornowBye。