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简介：Carbon-manganesesteelisoftenappliedincomponentsofpipesinnuclearplant.Ultrasonicfatiguetestsfollowinglowcyclefatigue(LCF)cyclesdamagedareusedtostudythestrengthofveryhighcyclefatigure(VHCF).ThecomparisonoftestresultsofsimpleVHCFandcumulativefatigue(LCFplusVHCF)showsthatLCFloadinfluencesthefollowingVHCFstrength.ContinuumdamagemechanicsmodelisextendedtoVHCFregion.TheeffectofLCFloadonVHCFisstudiedbyanimprovedcumulativedamagemodel.

简介：Amodelisproposedtocorrelatethecrackgrowthrateandstressratiocontainingveryhighcyclefatigueregime.Themodelisverifiedbytheexperimentaldatainliterature.Thenaformulaisderivedfortheeffectofmeanstressonfatiguestrength,anditisusedtoestimatethefatiguestrengthofabearingsteelinveryhighcyclefatigueregimeatdifferentstressratios.TheestimatedresultsarealsocomparedwiththosebyGoodmanformula.

简介：Intheapplicationsofaircrafts,automobiles,railways,biomedicineandoff-shorestructures,manycomponentsmayexperiencecyclicloadingconditionsoveralongperiodoftime,runninguptoseveralhundredmillioncycles.1Determinationoflonglifefatiguebehaviorbecomesextremelyimportantforbetterunderstandinganddesignofcomponentsandstructures.

简介：Veryhighcyclefatiguebehaviorsoftwobainite/martensitedual-phasesteelswereinvestigated.Oneofthesteelswascyclicrapidheattreatedanditsmicrostructureswererefined.Fatiguestrengthofthesteelis225MPahigherthanthatwithoutrefining.Observationoffracturesurfacesshowthatthefatiguecracksinitiateatbainitesfornon-refinedsteelandatnon-metallicinclusionsfortherefinedsteel.Thesizeofinclusionsismuchsmallerthanthatofbainiteswhichresultsintheimprovementoffatiguestrength.

简介：Thefatiguelifeofnumerousaerospace,locomotive,automotiveandbiomedicalstructuresmaygobeyond10~8cycles.Determinationoflonglifefatiguebehaviorbecomesextremelyimportantforbetterunderstandinganddesignofthecomponentsandstructures.Initially,beforetheinventionofultrasonicfatiguetesting,mostoftheengineeringmaterialsweresupposedtoexhibitfatiguelifeupto10~7cyclesorless.Thispaperreviewscurrentunderstandingofsomefundamentalaspectsonthedevelopmentofacceleratedfatiguetestingmethodanditsapplicationinultra-highcyclefatigue,crackinitiationandgrowthmechanismsofinternalfracture,S-Ndiagram,fatiguelimitandlifeprediction,etc.

简介：Thedeterminationofstructuraldynamicstressspectrumdistributionisofgreatsignificanceinthestructuralfatiguestrengthevaluationaswellasreliabilitydesign.Inpreviousempiricaldataprocessingmethods,thedatagroupinganddistributionfittingwereexcessivelycoarseandcontaineddistinctivedefects.Thispaperproposedaneffectiveapproachtostatisticallygroupactualmeasureddynamicstressdataandvalidlyextrapolatethecombineddistributiontofitthedynamicstressspectrumdistribution.Thisapproachhasbeenverifieditseffectivenessthroughchi-squaretest,stressspectrumextrapolationanddamagecalculationindynamicstressstudy.

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简介：Thermalfatigue(TF)isoneofthemostimportantfactorsthatinfluenceturbine'slife.Thispaperestablishesa3Dsolid-fluidcouplingmodelforasteadytemperatureanalysisofahigh-pressureturbinenozzleatdifferentturbineinletgastotaltemperatures(TIGTTs).Thetemperatureanalysissuppliesthetemperatureloadforsubsequent3Dfiniteelementanalysistoobtainthestrainvalues.Followingthis,thepredictionoftheTFlifeismadeonthebasisofequivalentstrainrange.TheresultsshowthatthestrainincreaseswithTIGTT,andthepredictedTFlifedecreasescorrespondingly.ThislifepredictionwasconfirmedbyoneTFtest.

简介：Twostochasticmodelsoffatiguecrackgrowthunderconstantamplitudecyclicloadingareproposedandstudiedbyusingthestochasticaveragingmethodandtotalprobabilitytheoremtoac-countforhighfrequencycomponentandlowfrequencycomponent,respectively,oftheirregularna-tureoffatiguecrackgrowthobservedinVirkler’sexperiment.Particularattentionispaidtothepredic-tionperformanceofthemodelsunderachangeintheinitialcracklength.Itisshownthatthemodelsproposedinthepresentpaperyieldsbetteragreementwithexperimentaldatathanothermodelsavail-ableinliterature.

简介：Acousticfatiguelifeevaluationisessentialforthermalprotectionstructuresduetotheseverethermo-acousticloadinservice.AstudyontemperaturedependenceofacousticfatiguelifeforaC/SiCpanelispresentedinthispaper.EffectsoftemperatureonboththestructuralresponsesandtheS–Ncurvesareinvestigated.TheDirlikmethodisadoptedtopredictthefatiguelifeofaC/SiCpanelatthreedifferenttemperaturesrespectively.Significantdifferencesareobservedfromtheresultsofnumericalsimulationsbetweenthefatiguelivesofthepanelinthethreecases.Thetemperature-dependenceofacousticfatiguelifeofaC/SiCpanelisverified,andfatiguetestofthematerialneedstobemoreattentivelyperformed.

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简介：制造在上的影响张力并且3种制造方法生产的铜电影的疲劳行为被调查。张力、高的周期疲劳测试用作者开发的测试机器被执行。幼仔的moduli(72，71和69GPa，分别地)比文学价值低(108鈥?45GPa)当收益力量象358，350和346MPa一样高时，分别地并且最终的力量作为462，456和446MPa分别地。在3种电影的张力的性质没有许多差别。在3种电影的疲劳性质有小差别，但是他们之一在低周期区域比其它在高周期区域和更长的疲劳生活比其它过更短的疲劳生活。

简介：Theaimofthisresearchistocharacterizethedevelopmentoffatiguedamagebymeansofstress-strainhysteresis.Experimentswereconductedon14specimensmadeofcold-finishedunannealedAISI1018steel.Resultsdemonstratethatthemechanicalhysteresisloopareas,whenplottedasafunctionofthenumberofloadingcycles,showsignificantvariationsanddemonstratethethreeprincipalstagesconcerningtheprogressofthefatiguefailure—initialaccommodation,accretionofdamageandterminalfailure.ThesethreestagesoffatiguearemarkedbythetransitionsatcyclesN2andN3.ExperimentalresultsshowthatalthoughfatiguelifeNfrangesfrom2644cyclesto108992cycles,theratiosofN2/NfandN3/Nftendtobestable:N2/Nf=10.7%,N3/Nf=91.3%.

简介：Aso-called“localprobabilisticParisrelationmethod”waspresentedformeasuringtherandomthresholdsoflongfatiguecrackpropagation.Acheckwasmadetotheconventionalmethod,inwhichthethresholdsweremeasuredstatisticallyanddirectlybythetestdata.Itwasrevealedthatthismethodwasnotreasonablebecausethetestdatahaveseldomaunifiedlevelofcrackgrowthrates.Differently,inthepresentedmethodtheParis-Erdoganequationwasappliedtomodelthelocaltestdataaroundthethresholds.Localprobabilisticrelationswithboththesurvivalprobabilityandtheconfidencewereestablishedonalognormaldistributionofthestressdensityfactors.Andthen,theprobabilisticthresholdswerederivedfromtheprobabilisticfactorswithagivencriticallevelofgrowthrate.AnanalysisonthetestdataofLZ50axlesteelfortheChineserailwayvehiclesverifiesthatthepresentmethodisfeasibleandavailable.

简介：Veryhighcyclefatigue(VHCF)behaviorsofbridgesteel(Q345)weldedjointswereinvestigatedusinganultrasonicfatiguetestsystematroomtemperaturewithastressratioR=-1.Theresultsshowthatthefatiguestrengthofweldedjointsisdroppedbyanaverageof60%comparingtothebasemetalandthefatiguefailurestilloccurredbeyond10~7cycles.Thefatiguefractureofweldedjointsinthelowcycleregimegenerallyoccurredatthesolderwhileattheheat-affectedzone(HAZ)intheveryhighcycleregime.Thefatiguefracturesurfacewasanalyzedwithscanningelectronmicroscopy(SEM),showingweldingdefectssuchaspore,micro-crackandinclusionwerethemainfactorsondecreasingthefatiguepropertiesofweldedjoints.Theeffectofweldingdefectsonthefatiguebehaviorsofweldedjointswasdiscussedintermsofexperimentalresultsandfiniteelementsimulations.

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简介：Thefatiguebehaviorofahighstrengthsteel300Minthegigacycleregimewasinvestigated.Fullyreversedtension-compressionfatiguetestsatambienttemperaturewereperformedusinganultrasonicfatiguesystemoperatingat20kHz.Thestaircasetestmethodwasemployedtoobtainaccuratevaluesofthemeanfatiguestrengthcorrespondingtofixednumbersofcyclesupto10~9.Theseresultswerecomparedtothecurvewhichisestimatedbythedatatestedinthemid-longliferegimeonconventionalservohydraulictestmachineat20Hz.Resultsindicatethatthefatiguestrengthdeterminedfromultrasonicfatiguetestingislightlyhigherthanconventionaltestingintherangeof10~6-10~7cycles.Itisobviousthatnucleationsoffracturestendtooccurbelowthesurface,iffractureshappenaftermorethan10~7cycles.AllthefracturedspecimensfailsfrominternalSiO_2inclusionsorsmallercarbidesandcarbideclusters.

简介：TheeffectoffrequencyandsampleshapeonfatiguebehaviorsofDZ125superalloyaresystematicallystudied.Theresultsshowthatfatiguefracturestilloccursabovethecycleof10~8fortestscarriedoutatthefrequencyoff=20kHzandstressratioR=-1,sothetraditionalfatiguelimitatcycleof10~7isnotappropriateforfatiguedesign.Fatiguefracturesurfacesareperpendiculartostressaxisforcylindricalandplatespecimens,andthefatiguecracksoriginatefromtheextrasurfaceofthespecimens.Fatiguecrackisapttopropagatefromcuttingdirectiontoforwarddirection,whichoccursmainlyinthesecondpropagationstageathigherstressamplitude.ThereisanobviousfrequencyeffectforDZ125superalloy.Thehigherthetestfrequencyis,themoreserioustheeffectoffrequencyonfatiguebehaviorsofthealloy.Afterthefrequencycorrection,theultra-highcyclefatigueS-NcurvewellcoincidewiththetraditionalfatigueS-Ncurve.

简介：在合金泡沫逐渐地由压缩疲劳导致了的铝(艾尔)的永久剩余紧张与装载周期的增加的数字增加。因而，Al合金泡沫的进步弄短降级由在泡沫的多房间的失败和ratcheting的动态材料表演。在这份报纸，压缩疲劳损坏的Al合金泡沫的动态性质被学习。有各种各样的剩余紧张的横梁标本被周期的压缩压缩应力做。动态弯曲模量和损失因素被使用一个横梁转移功能方法评估。作为结果，当因为击碎在泡沫的弄短的过程期间形成的房间墙的如此的因素的增加的精力驱散，损失因素被改进时，Al合金泡沫的动态弯曲僵硬结果由于损坏被减少。损失因素在疲劳剩余紧张上显示出明白依赖。