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1、外文原文：FormingFormingcanbedefinedasaprocessinwhichthedesiredsizeandshapeareobtainedthroughtheplasticdeformationsofamaterial.Thestressesinducedduringtheprocessaregreaterthantheyieldstrength,butlessthanthefracturestrength,ofthematerial.Thetypeofloadingmaybetensile,compressive,bending,o
2、rshearing,oracombinationofthese・Thisisaveryeconomicalprocessasthedesiredshape,size,andfinishcanbeobtainedwithoutanysignificantlossofmaterial.Moreover,apartoftheinputenergyisfruitfullyutilizedinimprovingthestrengthoftheproductthroughstrainhardening.Theformingprocessescanbegroupedund
3、ertwobroadcategories,namely,coldforming,andhotforming.Iftheworkingtemperatureishigherthantherecrystallizationtemperatureofthematerial,thentheprocessiscalledhotforming.Otherwisetheprocessistermedascoldforming.Theflowstressbehaviorofamaterialisentirelydifferentaboveandbelowitsrecryst
4、allizationtemperature・Duringhotworking,alargeamountofplasticdeformationcanbeimpartedwithoutsignificantstrainhardening.Thisisimportantbecausealargeamountofstrainhardeningrendersthematerialbrittle.Thefrictionalcharacteristicsofthetwoformingprocessesarealsoentirelydifferent.Forexample
5、,thecoefficientoffrictionincoldformingisgenerallyoftheorderof0.1,whereasthatinhotformingcanbeashighas0.6・Further,hotfonninglowersdownthematerialstrengthsothatamachinewithareasonablecapacitycanbeusedevenforaproducthavinglargedimensions.Thetypicalfonningprocessesarerolling,forging,dr
6、awing,deepdrawing,bending,andextrusion.Forabetterunderstandingofthemechanicsofvariousformingoperations，weshallbrieflydiscusseachoftheseprocesses.RollingInthisprocess,thejobisdrawnbymeansoffrictionthrougharegulatedopeningbetvveentwopower-drivenroll.Theshapeandsizeoftheproductaredeci
7、dedbythegapbetweentherollsandtheircontours・Thisisaveryusefulprocessfortheproductionofsheetmetalandvariouscommonsections,e.g.,rail,channel,angle,andround.ForgingInforging,thematerialissqueezedbetweentwoormorediestoalteritsshapeandsize.Dependingonthesituation,thediesmaybeopenorclosed
8、.DrawingInthisprocess,thec
