简介：Inordertoreducehighcalibrationpressureinhydroformingofcomponentswithtoosmallradii,amethodwasproposedtomanufactureautomotivehollowcomponentswithrectangularshapebyrelativelylowerpressure.Theprocessissimulatedandanalyzed.Itisthoughtthatthefrictionforcebetweenthediesurfaceandtubeisamainreasonthathighpressureisneededtoformsmallradii.Usingthemethodproposedinthispaper,apetal-likesectionshapeisfirstpreformedsothatthecentralzonesofthefoursidesofthepreformsectiondonotcontactwiththediesides,thusthetubemetaliseasytoflowintothetransitionradiiareaincalibrationstage.Moreover,apositiveforcealongthesidesisproducedbytheinternalpressure,whichisbeneficialtoovercomethefrictionforceandpushthematerialintotheradii.Therefore,thepressureforformingthetransitionradiiisgreatlyreducedandthecomponentswithsmallradiicanbeformedwithrelativelylowerpressure.Fortheexperimentalcaseconductedinthispaper,theformingpressureisreducedbyabout28.6%thantheestimatedformingpressure.

简介：Atfirst,aseriesoffiniteelementmethod(FEM)simulationtestswereusedtofindthecriticalformingconditionsofhot-galvanizedsheetsteelduringtherectangularboxdrawingprocessingwhenconstantblankholderforceswereapplied.Accordingthetestresults,thereasonablealterationscopeofinitialvariableblankholderforce(VBHF)wasas1.9～2.3T.Then,basedonthetestproductionsofblankholderforce,12typicalVBHFcurveswereappliedtoperformthesimulationtestsbythesimulationsoftwareofDYNAFORM.ThesimulationtestresultsshowedthatVBHFhadgreateffectsondrawingformabilityofhot-galvanizedsheetsteelduringtherectangularboxdrawing.However,thedifferentVBHFcurveswereappliedtocontrolthewholedrawinganditwouldgetgreatdifferenteffects.Atthesametine,theVBHFhadgreateffectsonthemaximumthickthinningratio,buthadlittleeffectonthemaximumthickincrassationratio.So,reasonableapplicationoftheVBHFwouldgreatlydecreasethefractures.WhentheVBHFprofileistakenascurveL,thebesteffectofdrawingformabilitycouldbeobtained.WhencurveIisused,contraryeffectcouldbegotten.TheothertypesofcurveswouldcauseeffectsbetweenabovetwotypesofVBHFcurves.Finally,theactualtestswereappliedtocheckthevalidityoftheFEMsimulationtests.TheresultsshowthattheFEMsimulationtestsaregoodwaysforpredictingandoptimizingtheVBHF.