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1、http://www.paper.edu.cnJOURNALOFMATERIALSSCIENCE39(2004)365–367FatiguevoidsinstructuralAl-alloysunderhigh-frequencycyclicloadingQ.Y.WANGDepartmentofCivilEngineering&Mechanics,SichuanUniversity,Chengdu610065,People’sRepublicofChinaE-mail:wangqy@scu.edu.cnN.KAWAGOISHI,Q.CHENDepartmentofMechanicalEngin
2、eering,KagoshimaUniversity,Kagoshima890-0065,JapanAluminumalloysarewidelyusedforautomotiveandTwoaluminumalloys,7075/T6and6061/T6,wereaerospacestructuralapplications.Fatigueinducedfromselectedforthisstudy.Themechanicalpropertiesandvariousmechanicaloraeromechanicalsourcescanthechemicalcompositionaresh
3、owninTablesIandII,reachtheverylongliferegion(>107cycles)duetorespectively.highfrequencyvibrations.TherequireddesignlifetimeHourglass-shapedspecimensdesignedtoresonateofmanyengine,wheel,chassis,andbodycomponentslongitudinallyat19.5KHzweremachinedfromoftenexceeds109(giga-range)cycles[1,2].Inrecent6061
4、/T6and7075/T6alloys,bothsuppliedintheformyearstherehasbeenadevelopmentofinterestinveryof20mmdiameterbar.Allthespecimenshadagaugelonglifefatiguebetween107and1010cyclesforvariouslengthof27.1mm,agaugediameterof4.0mm,ahighstrengthsteels[2–6].Itiswellknownthatmanymaximumsectiondiameterof12.0mm,andacontin
5、-materials,includingaluminumalloys,donotexhibitauousradiusof25.0mm.ThetotalresonancelengthsconventionalendurancelimitinS-Ncurvesbetweenofthespecimenscalculatedusingananalyticalmethod106and107cycles[7].Fatiguefailurecouldoccurbe-[14]are67.0mmfor6061/T6alloyand69.1mmforyond107cycles.Itisthereforeimpor
6、tanttorealizethe7075/T6alloy.Adiagramofthespecimenisshowninriskofusinganarbitrarycut-offvalueof106(or107)Fig.1.Thespecimengaugesurfacesweremechanicallycyclestoestablishthefatiguelimit.However,onlylim-polishedwithemerypaperbeforetesting.itedstudiesofverylonglifefatigueandnearthresholdFatiguetestingwa
7、scarriedoutinapiezoelectricres-fatiguecrackgrowthbehaviorofaluminumalloyshaveonancesystemoperatingat19.5KHzwithzeromeanbeenperformedduetotestingtimelimitationswithstress(R=−1).Thetestingfacilityhasbee
