Fatigue Life Design of Mechanical Structure知到智慧樹期末考試答案題庫2024年秋北京理工大學

FatigueLifeDesignofMechanicalStructure知到智慧樹期末考試答案題庫2024年秋北京理工大學High-temperaturefatigueismainlyaconcernattemperatures（）

A:Morethan30or40percentoftheabsolutemeltingtemperatureB:Morethan

5or10percentoftheabsolutemeltingtemperatureC:Morethan

10or20percentoftheabsolutemeltingtemperatureD:Morethan

20or30percentoftheabsolutemeltingtemperature

答案:Morethan30or40percentoftheabsolutemeltingtemperatureTwofracturemodesareindependenton（）

A:LoadingB:MaterialC:EnvironmentD:Finalfracture

答案:FinalfractureTheelasticstressconcentrationfactorsareoftenobtainedby（）

A:FatiguetestB:Strain-lifeC:FiniteelementmethodD:Fracturesurfaceobservation

答案:C:FiniteelementmethodThefeatureofcorrosiongenerallydoesnotinclude（）

A:EnvironmentalassistedcrackingB:StresscorrosioncrackingC:ElevatedtemperatureD:Hydrogenembrittlement

答案:ElevatedtemperatureThecorrectstatementaboutGlinka’sruleis（）

A:Relatedstrain-stresscurveisahyperbolaB:Sincen<1,smallernotchstress/strainispredictedbyGlinkaC:UsuallyagreeswithmeasurementsinplanestrainsituationD:Agreeswithmeasurementsinplanestresssituation

答案:C:Usuallyagreeswithmeasurementsinplanestrainsituation.Thekeywordsoffatiguedonotinclude（）

A:CrackB:CyclicloadingC:ProgressiveD:Deformation

答案:DeformationWhichisnotthecharacteristicofrealfatigueLimit（）

A:HightemperatureB:FullyreverseduniaxialfatiguetestC:Standard,highlypolished,unnotchedspecimenD:Groupmethod

答案:Testingfrequencyislargerthan100HzAmeanstressmayrelaxfullyorpartiallydueto（）

A:PlasticdeformationB:ResidualstressC:SurfaceconditionD:Environment

答案:A:PlasticdeformationAlargerfractionoflifeforcracknucleationoccurs（）

A:AtlowerstresslevelsB:FinalfractureC:AthigherstresslevelsD:Loadingonset

答案:AtlowerstresslevelsAboutplanestrain,thecorrectstatementisasfollows（）

A:OnedimensionisverylargeB:TwodimensionisverylargeC:ThreedimensionisverylargeD:allprincipalstressesarezero

答案:OnedimensionisverylargeThepercentageofthecrosssectionwherethecrackgrewpriortofinalfractureisrelatedto（）

A:SurfaceconditionB:MachiningconditionC:FracturetoughnessD:Shearlip

答案:FracturetoughnessThehysteresisloopsathightemperaturesare（）

A:ConstantB:DiscontinuousC:RegularD:Easy

答案:DiscontinuousThenumberofbeachmarksisrelatedto（）

A:DefectB:EnvironmentC:SlipD:Surfacecondition

答案:EnvironmentThecorrectstatementisasfollows（）

A:LifecanbeignoredinunstablegrowthregionB:ParislawfornearthresholdregionC:CrackgrowthrateisfasterinnearthresholdregionD:largereffectinstablecrackgrowth

答案:OnedimensionisverylargeDamagetolerancedesignis（）

A:Anti-crackmeasuresB:NominalstressC:CrackcannotoccurD:Nominalstrain

答案:A:Anti-crackmeasuresThestraintestingmethodsusuallycontain（）

A:Incremental-steptestmethodB:ExtensometerC:Multiple-steptestmethodD:Companiontestmethod

答案:A,CTheS-Nbehaviorcanbeaffectedbymanyfactors（）

A:MicrostructureB:SurfaceconditionC:SizeeffectD:Frequency

答案:Surfacecondition###Microstructure###Frequency###SizeeffectThedescriptionofcrackgrowthatnotchiscorrectasfollows（）

A:PredictingcrackgrowthfromnotchesusingLEFMisproblematicB:Smallcrackclosure,largereffectiveK,higherrateC:Crackissmall(smalllocalplasticity),lessresidualplasticdeformationD:Theconsumedfatiguelifeofcrackgrowththroughanotchstress-strainfielddependsontheconditionsofthenotchstress-strainfield

答案:A,B,C,DSomenecessarypointsabouttheestimationofcrackgrowthlifewithmeanstressmustbeagainnoted（）

A:Whichcrackgrowthrateequationshouldbeused?B:WhatvalueofΔKwillcausefracture?C:Doescorrosionortemperatureplayanimportantrole?D:Howdoweintegratethisequation?

答案:A,B,CSeveralconceptsaboutS-Ndiagraminclude（）

A:EndurancelimitB:FatiguelimitC:FatiguestrengthD:Cracknucleationlife

答案:Fatiguelimit###Endurancelimit###FatiguestrengthThecharacteristicsoffatigueinclude（）

A:MonotonictensionB:ConstantorvariableamplitudeC:Cracknucleation/growthD:Repeatedloading

答案:B,C,DForInfinite-lifedesign,thecorrectstatementisasfollows（）

A:TheoldestcriterionB:Mason-CoffinmodelC:FatiguelimitisdifficulttodefineD:Especiallyfornotchedmembers

答案:A,CThestrain-temperature-timerelationshipcanbeclassifiedinto（）

A:HoldtimeB:In-phase(0°)C:Out-of-phase(180°)D:Axialloading

答案:A,B,CParametersinthenotcheffectshouldbeconsidered,asfollows（）

A:NucleationandgrowthofcracksB:FatiguelimitC:ConcentrationofstressandofstrainD:Meanstresseffectsandresidualstresses

答案:Nucleationandgrowthofcracks###Meanstresseffectsandresidualstresses###Concentrationofstressandofstrain###FatiguelimitAnalyticalmodelscontain（）

A:Neuber’sruleB:Glinka’sruleC:ParisruleD:Linearrule

答案:Linearrule###Neuber’srule###Glinka’sruleOnlytheplasticportionofthestrain-lifecurveismodifiedtoaccountforthesurfacefinisheffects.（）

A:錯B:對

答案:A:錯Themechanismofcrackinitiationintheveryhighcycleregionhasbeenroughlyunderstood.（）

A:錯B:對

答案:B:對Fatigueinducedmechanicalfailureisaveryimportantfactorintheengineeringdesign.（）

A:對B:錯

答案:對VHCFFailuremodesarerelatedtosurfaceconditions,environmentaleffects,materials,appliednumberofcycles,etc.（）

A:對B:錯

答案:對Planestrainfracturetoughnessis對materialpropertyandregardlessofthickness.（）

A:錯B:對

答案:B:對Localε-Nmodelisusedtoobtainthecracknucleationlife.（）

A:對B:錯

答案:B:錯Thenumberofbeachmarksisthesamefordifferentfracturesurfaces.（）

A:錯B:對

答案:錯Crackgrowthratesareinitiallyhighbutdecrease,withthedecreasingcracklength.（）

A:錯B:對

答案:錯Intensified