学科分类
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33 个结果
  • 简介:Thispaperpresentsanextensionofadisplacementdiscontinuitymethodwithcracktipelements(aboundaryelementmethod)proposedbytheauthorforfatiguecrackgrowthanalysisinplaneelasticmediaundermixed-modeconditions.Theboundaryelementmethodconsistsofthenon-singulardisplacementdiscontinuityelementspresentedbyCrouchandStarfieldandthecrack-tipdisplacementdiscontinuityelementsduetotheauthor.Intheboundaryelementimplementationtheleftorrightcrack-tipelementisplacedlocallyatthecorrespondingleftorrightcracktipontopofthenon-singulardisplacementdiscontinuityelementsthatcovertheentirecracksurfaceandtheotherboundaries.Crackgrowthissimulatedwithanincrementalcrackextensionanalysisbasedonthemaximumcircumferentialstresscriterion.Inthenumericalsimulation,foreachincrementofcrackextension,remeshingofexistingboundariesisnotrequiredbecauseofanintrinsicfeatureofthenumericalapproach.Crackgrowthismodeledbyaddingnewboundaryelementsontheincrementalcrackextensiontothepreviouscrackboundaries.Atthesametime,theelementcharacteristicsofsomerelatedelementsareadjustedaccordingtothemannerinwhichtheboundaryelementmethodisimplemented.Asanexample,thefatiguegrowthprocessofcracksemanatingfromacircularholeinaplaneelasticplateissimulatedusingthenumericalsimulationapproach.

  • 标签: 疲劳生长模型 混合模式 疲劳裂纹 平面弹性介质
  • 简介:Fatiguecrackingtestsofasolderjointwerecarriedoutusingin-situscanningelectronmicroscopy(SEM)technologyundertensileandbendingcyclicloadings.Themethodforpredictingthefatiguelifeisprovidedbasedonthefatiguecrackgrowthrateofthesolderjoint.Theresultsshowthattheeffectoftheloadingtypeonthefatiguecrackgrowthbehaviorofasolderjointcannotbeignored.Inaddition,thefiniteelementanalysisresultshelpquantitativelyestimatetheresponserelationshipbetweensolderjointstructures.Thefatiguecrackinitiationlifeofasolderjointisingoodagreementwiththefatiguelife(N50%)ofatotallyelectronicboardwith36solderjoints.

  • 标签: 疲劳裂纹扩展速率 焊点 扩展行为 电子封装 类型 疲劳裂纹萌生寿命
  • 简介:Theconstitutiveequationunderthelow-cyclefatigue(LCF)wasdiscussed,andatwo-dimensional(2-D)modelforsimulatingfatiguecrackextensionwasputforwardinordertoproposeanewcyclicJ-integral.Thedefinition,primarycharacteristics,physicalinterpretationsandnumericalevaluationofthenewparameterwereinvestigatedindetail.Moreover,thenewcyclicJ-integralforLCFbehaviorswasvalidatedbythecompacttension(CT)specimens.ResultsshowthatthecalculatedvaluesofthenewparametercancorrelatewellwithLCFcrackgrowthrate,duringconstant-amplitudeloading.Inaddition,thephenomenonoffatigueretardationwasexplainedthroughtheviewpointofenergybasedontheconceptofthenewparameter.

  • 标签: 循环J积分 疲劳裂纹 低周期疲劳 构成方程 数字评估
  • 简介:Lowcyclefatiguecrackpropagation(FCP)behavioroftwoPC/ABSblendswithaweightra-tioofPCtoABSbeing80/20and60/40,respectively,isinvestigated.Experimentsarecarriedoutbyusingstandardcompacttension(CT)specimens.Thefracturesurfacesareexaminedwithascanningelectronmi-croscope(SEM).ItisshownthattheFCPresistanceofPC/ABSblendwith20%ABSparticlesishigherthanthatofPC/ABSblendwith40%ABSparticles.ItisfoundthatproperABSparticlecontentcanresultinthetougheningofPC/ABSblendsthroughparticlecavitationandshearyieldinginmatrix.

  • 标签: polymer BLEND POLYCARBONATE ACRYLONITRILE-BUTADIENE-STYRENE fatigue CRACK
  • 简介:Anapproachbasedoncontinuumdamagemechanicstofatiguelifepredictionforstructuresisproposed.Anewfatiguedamageevolutionequationisdeveloped,inwhichtheparametersareobtainedinasimplewaywithreferencetotheexperimentalresultsoffatiguetestsonstandardspecimens.WiththeutilizationofAPDLlanguageontheANSYSplatform,afiniteelementimplementationispresentedtoperformcouplingoperationondamageevolutionofmaterialandstressredistribution.ThefatiguelivesofsomenotchedspecimensandaPitch-change-linkarepredictedbyusingtheaboveapproach.Thecalculatedresultsarevalidatedwithexperimentaldata.

  • 标签: 疲劳寿命预测 连续损伤力学 损伤演化方程 应用 工程 APDL语言
  • 简介:Anumericalsimulationofstochasticdamaseevolutionprocessintheconditionoflowcyclefatigueloadingisdiscussed.Therelationsbetweendamagevariablesandmicro-cracksareob-tainedbymeansofthemicro-mechanicsmodeloftherepresentativevolumeelementproposedbyLemaitreandDufailiy.Thestochasticinitialdamagevaluesareintroducedinconsiderationoftheinherentmicro-defectsinmaterials.Themodelcombinedwithafiniteelementmethodisappliedtosimulatethedamageevolutionprocessunderlowcyclefatigueloading.Themicro-cracksonthesurfaceofaspecimenof19Mn6alloysteelaremeasuredwithareplicatechnique.Thenumericalresultsshowthatthenor.homogeneityofdamageandthelocalizationofthefatiguefailurearewellshownbytheproposedsimulations,andthefatiguelivesarereasonablypredicted.

  • 标签: STOCHASTIC DAMAGE MICRO-MECHANICS model low CYCLE
  • 简介:RandomfatigueofweldedK-typetubularjointssubjectedtoaxialorout-of-planebendingloadisanalyzed.Byconsideringthesizesofinitialsurfacecracksandmaterialconstantsasrandomvariableswithsomeprobabilisticdistributions,incorporatingtheeffectoftheweld,fivehundredrandomsamplesaregenerated.Statisticalcomputationalresultsoflifeofcrackpropagationandeffectofchangeofcrackshapearefinallyobtainedandcomparedwithexperimentaldataavailablebasedonaregressionanalysis.Meanwhile,crackpropagationbehaviorsarealsoinvestigated.

  • 标签: K-type TUBULAR joints RANDOM fatigue surface
  • 简介:基于镍的单个水晶superalloy与的低周期的疲劳(LCF)行为[001]取向在T0掳C的中间的温度和T0+的更高的温度被学习在10的经常的低紧张率下面的250掳C?3s?1在周围的空气。superalloy展出了依赖于温度并且使用紧张振幅的周期的紧张压缩不对称现象。破裂表面上的分析证明表面和表面下的扔micropores是主要裂缝开始地点。内部Ta富有的碳化物经常在所有标本被观察。骨折的二种不同类型被frac-togaphy建议。一种类型被模式描绘--我与一台用显微镜裂开在T0+的不平的表面250掳C。而在更低的温度T0C的另外的类型赞成了中的一个或几八面{111}飞机,与正常模式相对照--我生长模式典型地在低装载观察了频率(几Hz)。为二个裂开的模式的失败机制纬鈥?正在砍在T0+在矩阵和纬/纬鈥?接口在T0掳C和裂开的反对ned和矩阵猛抛250掳C。

  • 标签: 低循环疲劳 单晶 高温合金 温度条件
  • 简介:Veryhighcyclefatigue(VHCF)propertiesofalowtemperaturetemperingbearingsteelGCr15withsmoothandhole-defectspecimensarestudiedbyemployingarotarybendingtestmachinewithfrequencyof52.5Hz.Bothsmoothandhole-defectspecimensbreakinVHCFregimewithsomedifferenceinfatiguecrackinitiation.Forsmoothspecimens,afinegranulararea(FGA)isobservednearthegrainboundaryinthefracturesurfaceofthespecimensbrokenafter10~7cycles.ButnoFGAisobservedinthehole-defectspecimensbrokeninVHCFregime,andtheVHCFcrackdoesnotinitiatefromthesmallholeatthesurfaceasitdoesatloworhighcyclefatigueregime.InternalstressisemployedtoexplaintheVHCFbehaviorofthesetwotypesofspecimens.Atlast,anadvanceddislocationmodelbasedonTanakaandMuramodelisproposedtoillustratetheinternalstressprocessandtopredictfatiguecrackinitiationlifewithFGAobservedinthefractureregion.

  • 标签: GCR15轴承钢 光滑试样 标本 缺陷 高周疲劳 疲劳裂纹萌生寿命
  • 简介:Fatiguepropertiesofage-hardenedAlalloy2017-T4underultrasonicloadingfrequency(20kHz)wereinvestigatedandcomparedwiththeresultsunderconventionalloadingofrotatingbending(50Hz).Thegrowthofacrackretardedatabout500μminsurfacelengthunderultrasonicloading,whileatabout20μmunderrotatingbending.Althoughstriationsbeingatypicalfracturemechanismwereobservedunderconventionalloading,mostoffracturesurfacewascoveredwithmanyfacetsunderultrasonicloading.Thesefacetswerealsoobservedunderrotatingbendinginnitrogengas.Thedifferenceingrowthmechanismdependingontheloadingfrequencyandtheretardationofacrackgrowthunderultrasonicloadingmaybecausedbytheenvironmentatthecracktipduetohighcrackgrowthrateunderultrasonicloading.

  • 标签: 疲劳性能 超声波 铝合金 负荷 硬化 年龄
  • 简介:Cold-stretchedpressurevesselsfromausteniticstainlesssteels(ASS)arewidelyusedforstorageandtransportationofliquefiedgases,andhavesuchadvantagesasthinwallandlightweight.Fatigueisanimportantconcerninthesepressurevessels,whicharesubjectedtoalternativeloads.Eventhoughseveralcodesandstandardshaveguidelinesonthesepressurevessels,therearenorelevantdesignmethodsonfatiguefailure.TounderstandthefatiguepropertiesofASS1.4301(equivalentsincludeUNSS30400andAISI304)insolution-annealed(SA)andcold-stretchedconditions(9%strainlevel)andtheresponseoffatiguepropertiestocoldstretching(CS),low-cyclefatigue(LCF)testswereperformedatroomtemperature,withtotalstrainamplitudesrangingfrom-.4%to-.8%.Martensitetransformationsweremeasuredduringthetests.Comparisonsoncyclicstressresponse,cyclicstress-strainbehavior,andfatiguelifewerecarriedoutbetweenSAandCSmaterials.ResultsshowthatCSreducestheinitialhardeningstage,butprolongsthesofteningperiodinthecyclicstressresponse.Martensitetransformationhelpsformastableregimeandsubsequentsecondaryhardening.Thestressesofmonotonicandcyclicstress-straincurvesareimprovedbyCS,whichleadstoalowerplasticstrainandamuchhigherelasticstrain.ThefatigueresistanceoftheCSmaterialisbetterthanthatoftheSAmaterial,whichisapproximately1?03to2?04cycles.TheS-NcurveoftheASMEstandardforASSiscomparedwiththefatiguedataandisjustifiedtobesuitableforthefatiguedesignofcold-stretchedpressurevessels.However,consideringtheCSmaterialhasabetterfatigueresistance,theS-Ncurvewillbemoreconservative.ThepresentstudywouldbehelpfulinmakingfulluseoftheadvantagesofCStodevelopanewS-Ncurveforfatiguedesignofcold-stretchedpressurevessels.

  • 标签: 英文摘要 编辑工作 优秀论文 医学期刊
  • 简介:Toconsidertheanisotropicdamageinfatigue,animprovedboom-panelmodelispresentedtosimulatearepresentativevolumeelement(RVE)intheframeworkofcontinuumdamagemechanics.TheanisotropicdamagestateoftheRVEisdescribedbythecontinuityextentsofboomsandpanels,whosedamageevolutionsareassumedtobeisotropic.Thenumericalimplementationisproposedonthebasisofdamagemechanicsandthefiniteelementmethod.Finally,theapproachisappliedtothefatiguelifepredictionof2A12-T4aluminiumalloyspecimenundercyclicloadingoftension-torsion.Theresultsindicateagoodagreementwiththeexperimentaldata.

  • 标签: 吊杆面板模型 各向异性的损坏 疲劳 紧张扭转 生活预言