Circular Bar Torsion Test 圆柱扭转试验 实验报告 英语

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CircularBarTorsionTest

Thepurposes.

Measuretheshearingyieldlimitτsandtheshearingstrengthlimitτboflowcarbonsteelandmeasuretheshearingstrengthlimitτbofcastiron.

Learnthestructure,theoperationoftorsiontestmachine.Andlearntheproceduresoftorsiontest.

Comparethedeformationandthefractureoflowcarbonsteelandcastiron.Analysisthereason.

Theinstruments.

electronictorsiontestmachine,slidecaliperrule.

Specimen.

Takethestandardcylinderspecimen.d0=10mm.Thebothtwoendsarerectangular.

Thetheories.

Lowcarbonsteeltorsiontest.

Castirontorsiontest.

Theprocedures.

Measurethediameterdoofthespecimenatthebothtwoendandthemiddle.

Installthespecimen.

Drawastraightlinealongtheaxisofthespecimentoobservethedeformation.Maketherevofmotorat3~30°/min.ObservetheT-φcurve.Recordtheminimumyieldtorqueτsandtheultimatetorqueτb.Forcast-irontestonlygettheultimatetorqueτb.

Uninstallthespecimen,andcleanuptheinstruments.

Dataprocessing.

Theanti-torsioncrosssectioncoefficient:Wn=πd3/16

Shearingyieldlimit:τs=Ts/Wn

Shearingultimatestrength:τb=3Tb/(4Wn)

Forlowcarbonsteel:

d=10mmTs=36.37NmTb=97.00Nm

Theanti-torsioncrosssectioncoefficient:

Wn=πd3/16=1.964x10-7m3

Shearingyieldlimit:

τs=Ts/Wn=36.37Nm/(1.964x10-7m3)=185.2MPa

Shearingultimatestrength:

τb=3Tb/(4Wn)=3x97.00Nm/(4x1.964x10-7m3)=370.4MPa

Forcastiron:

Tb‘=45.75Nm

τb’=3Tb’/(4Wn)=3x45.75Nm/(4x1.964x10-7m3)=174.7MPa

Questions:

Lowcarbonsteelisductilematerial.Intheprocessoftorsion,itdoesthesameasinthetensiletest.Ithasthreestages:elasticstage,yieldstageandstrengthenstage.Thefractureisalmostflatandtheedgeofthefractureisdestroyedmost.

Castironisbrittlematerial.Thespecimenfracturedquicklyafterwetorsionit.Andthefractureisa45°helixlinetotheaxisofthisspecimen.

Comparewiththetensiletestandcompressiontest