高速列车用7×××系高强铝合金焊接接头的疲劳行为分析

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1、RESEACHONFATIGUEPROPERTYOFA7N01WELDINGJIONTUSEDINHIGHSPEEDTRAINABSTRACTTheA7N01aluminumalloywithgoodpropertywhichbeongtothe7×××aluminumalloyiswidelyusedinhighspeedtrainandthestudyonthefatiguepropertyisofgreatsignificancetomakethehighspeedtrainsafer.Thro

2、ughthefatigueteststotheA7N01aluminumalloyweldedjointandtheobserviationofmicrostructureandthefatiguefractureandmorphologyofthefatiguedamageonsurface,wecansummarizethefollowingconclusions:TheratcheteffectisgeneratedduringthefatigueprocessintheA7N01aluminu

3、malloyweldedjoint.Resultsshowsthattheratchetingeffectisobviousatthefirststage,theplasticdeformationismoreobviousespeciallyinthefirstcycle.Atthesteadystatestage,theratchetingstrainrateisalmostconstant(about0)andtheratchetingstrainremainlow.Atthetertiarys

4、tage,asthematerialdeformationresistancedecline,cavitygrowthandthestressconcentrationinthematerial,leadtotheratchetingstrainincreasingsharplyandgreatplasticdeformationandultimatefractureofthesamples.TheA7N01aluminumalloyweldedjointmainlyshowscyclicsoften

5、ingduringthefatiguetest.Theproportionofcyclicsofteningonthewholefatigueprocessisdifferentwhenthetressisdifferent.Thecycletothestablestageislesswhenthestressisless.Whenthestressissmallerthan150MPa,thewholeprocesskeepcyclicsoftening.Whenthestressisbiggert

6、han220MPa,thereiscyclicsofteninginthewholeprocessinsteadofthecyclichardeningintheearlystage.ThefatigueplasticdeformationoftheA7N01aluminumalloyweldedjointmainlyoccurredintheweldzonewhosefatiguedamageismainlyslipbandcracking.Fatiguedamageontheheataffecte

7、dzoneisthefatiguemicrocrackgeneratedbythehardcompoundwithmuchelementofFeandSi,whichcanbeeasilyseparatedwiththematrixunderthefatiguestress.Whenthestressishigh,thelargeplasticdeformationintheweldzoneandthestressconcentrationinthefusionzoneandthehardcompou

8、ndintheheataffectedzonecanallleadtothefailureofthesample.Whenthestressislow,thehardcompoundintheheataffectedzoneisrelativelythegreatestdamagetothesampleandtheII万方数据samplesgenerallyfractureintheheataffectedzone.Owingtotheheatingcy