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1、南京航空航天大学硕士学位论文摘要超塑性胀形工艺具有设备简单、模具制造方便、成形精度高等特点,随着高应变速率材料的出现,加工时间大为缩短,在航空航天工业中越来越得到更广泛的应用,对于飞行器整流罩、发射或聚焦罩等类零件,都需要实现锥形的拉胀成形。超塑性胀形存在厚度分布不均的缺点,本文通过有限元软件MARC对方锥形件气压胀形成形过程的仿真模拟,重点研究了TC4钛合金材料胀形过程中,不同加载方式对板料成形壁厚分布的影响。比较获得了相对优化的P-T曲线,通过TC4方锥件胀形实验进一步分析验证了有限元软件的模拟结果。超塑性胀形存在空洞的缺陷,本文通过有限元软件MARC
2、对圆锥形件气压胀形成形过程的仿真模拟和实验,重点研究了Al5083铝合金材料在不同应变条件下,使用背压对板料内部孔洞缺陷和成形极限的影响。实验结果表明,在胀形过程中添加合适的背压不仅能够有效地抑制胀形件的孔洞缺陷,而且能够显著提高材料的成形极限,改善材料的成形性能,并且给出了普通胀形件和背压胀形件极点处孔洞体积分数随等效应变变化的曲线。关键词:超塑性,TC4,Al5083,应变速率,延伸率,敏感指数,有限元模拟,厚度分布,孔洞I锥形件成形工艺研究ABSTRACTSuperplasticequipment,convenientdieconstructiona
3、ndhighformingprecisionarethefeaturesofsuperplasticformingofbugling.Theproductionofhighstrainratematerialreducesprocesstimesothatitgainspopularimplicationintheindustryofaeronauticsandastronautics.Somepartssuchasaircraftrectifyingcover,launchingcoverandfocusingcoverneedtherealizatio
4、nofconeshapedorsimilar-to-cornshapeddrawing-buglingforming.Howeversuperplasticformingofbuglinghasthedisadvantageofuneventhicknessdistribution.Throughpressurebulgingsimulationofsquarecorn-shapedpartbyMARC,finiteelementsimulationsoftware,thisthesisattachesgreatimportancetoresearchth
5、einfluencesonthethicknessdistributioninsheetmaterialsbydifferentloadingmethodsduringthepressurebulgingofTC4titaniumalloy,acquiresrelativeoptimizedP-Tcurve.ThesimulatedresultsbyMARCarefurtherverifiedbybuglingexperiment.Accordingtothedisadvantageofcavityinsuperplasticformingofbuglin
6、g,thisthesisalsoexperimentspressurebulgingsimulationofcorn-shapedpartbyMARC,triestocomparetheinfluencesofbackpressurebuglingonAl5083undervariableconditions,suchasinnercavity,thicknessdistributionandforminglimitation.Theresultsofexperimentsindicatesthattheemploymentofsuitablebackpr
7、essurebuglingcaneffectivelyrestraincavity,improvetheforminglimitation,andbettertheformingcapability.Last,thisthesisprovidesthecurveofvariablecavityvolumefractionwiththechangeofequaleffectatthelimitationpointinnormalbuglingandbackpressurebugling.Keywords:superplastic,TC4,Al5083,str
8、ainrate,strainratesensitivity,elo