版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
12024/10/27
Thestrengththeorywhichhavecrackinbody22024/10/27GOAL:recountconventionalstrengththeoryofnonindividualbody.Fundamentalassumptionofelasticandplastictheory.Basicapproachandequationtosolvethestress.Descriptionandanalysisofonepoint’sstressstate.APPLY:strengthdesignCalculateexternalforce;Countonepoint’sstressstate(theoryofelasticityandplasticity);Verdictapoint’sstressiscriticalstate(yieldordestroy)ornotaccordingtothestrengthcondition.ATTENTION:Generallyusedforchecking.Briefsummaryoffirstfourchapters32024/10/27UncertaintiesduringstressanalysisIndeterminacyofexternalload.Indeterminacyduringstressanalysis.Indeterminacyofmaterialcharacteristics.Practicalapplication:Securitycoefficientwhichbiggerthanone.Design’sbasicideanonindividualbodyneverdamageProblemsandsolvesduringstrengthdesign
42024/10/27Realityofengineeringdamage52024/10/27Whoisresponsiblefortheaircrash?In1979,therewasalargestdisastereventinAmericanhistory,morethan270peopledied.Reason:Connectionwhichconnectenginesandwingshadfractured.ReviewofthehistoryRailway:England,
wheel、track、orbitalfractureBridge:Belgium,14accidentsin4yearsSteamship:WorldWarTwo,Americanfreighter、tanker,weldAirplane:British“comet”Missile:American“Polaris”Pressurevessel:Aerospaceplane、…Inthe1950s,
American“Polaris”solidfuelenginewasfracturedwhenlaunch.Thematerialwashigh-strengthsteel,yieldstrength
s=1400MPa,workingstress
900MPa。Accidentcase62024/10/27Whenitdamage,workingstressismuchlessthanmaterial’syieldlimit;Theprimarycauseofdamageisthatthereareallkindsofdefectsorcracksintheactualstructuralmaterials.Theexistenceofthesecrackssignificantlyreduceactualstrengthofstructuralmaterials.Theimportantreasonwhyitcausedamageisdefectsinthestructure.CommonfeaturesoftheaccidentsWheredocrackscomefrom?Materialdefect;Fatigueinitiation;Damagesinmachining、manufacture、assembleandsoon.72024/10/27After1950s,Crack-containingbodystrengththeorywasbeenresearchedanddeveloped
:FractureMechanicsHowtosolveit?Fissurecancauserupturefailure,howtoanalyseandcontrol?Ifyoudon’tknowhowtoanalyse,constructionalelementwillhavefissures,andthenuseless.82024/10/275.1Introduction5.2Thecrack-tip’sstress-strainfield5.3Stressintensityfactorandit’ssolution5.4Brittlerupture’sK-factors5.5Thepopularizationoflinearelasticfracturemechanicsinsmallscaleyielding5.6Elastic-plasticfracturemechanics5.7Fatiguecrackgrowthrate5.Crack-containingbodystrengththeory92024/10/275.1.1Developmentprocessoffracturemechanics5.1.2Researchcontentsoffracturemechanics5.1.3SeveralbasicconceptionoffracturemechanicsBrittleruptureandductilefractureTrans-granularfractureandinter-granularfractureThedivisionoflengthandbreakrelateddisciplines5.1.4FractureanalysisMacro-fractureanalysisMicro-fractureanalysis5.1
Introduction102024/10/2715century,Vinci:Ironwirebreakingloadandlengthareinreverseproportion.In1919,RussiaКолоcoB:Thestressconcentrationproblemwhentheinfinityplatecontainsanovalholestress.(stress)Conclusion:Elementswithcrackunableloadbearing.In1921,Griffithresearchbrittlematerial’sfractureproblem.(energy)AfterworldwarII,Irwin
andOrowansupplementedtheGriffiththeoryrespectivelyandindependently,sothatitcanbeapplicabletometallicmaterial.Linktheconceptofenergyreleaserateandstressintensityfactor.Laythefoundationsoflinearelasticfracturemechanics.5.1.1Developmentprocessoffracturemechanics112024/10/27In1958,Irwin,withamendmentstobroadenthescopeofapplicationoflinearelasticfracturemechanics;WellsproposeCOD;In1968,RiceandHutchinsonetal.work,providedatheoreticalbasisforj-integralmethod.
Sincethengraduallyestablishedasystemofmainparametersofelastic-plasticfracturemechanics;In1961,Parisproposedfamousformulathatistherelationshipbetweenstressintensityfactorandcrackgrowthrate;Studyonquantitativeanalysisofdynamicfractureisintheascendant……5.1.1Developmentprocessoffracturemechanics122024/10/27Researchthepowerandresistanceofmaterialorstructure’scrackgrowth(initiation).
Fracturecriterionanditsscopeofapplicationandapplicableconditions.Applytotheanalysisofmultiplestructure:Processofcrackfrominitiation,extendingtounstability.Estimationthelifeofstructurewithcracks:Fatigueproblems.Thegoaloffracturemechanicsisquantificationallyresearchontheconditionsoffracturewhichcausedbyhereasonthatthemaincrackinthesupportingbodyextend(includingstaticloadandtheexpansionunderfatigueload).5.1.2Researchcontentsoffracturemechanics132024/10/275.1.2ResearchcontentsoffracturemechanicsEngineeringapplicationUndertheactionofknownexternalload,howmuchisthecracklengthinthestructureallowing(i.e.criticalcracklength)?Whenstructureexist(orassumed)aninitialcracklength,howlongdoesitneedtoexpandtothecriticalcracklength(ornumberofloadcycles)?-----RemaininglifeWhatfunctionrelationsbetweenresidualstrengthsofstructureandcracklengths?142024/10/27IssuesrelatetomaterialselectWhatkindsofmaterialarenoteasygerminationcrack?Whatkindsofmaterialcanallowrelativelylongcrack’sexistbutnotbreak?Whatmaterialhavebetterperformanceinresistcrackgrowth?Howcanmelting,processingandtreatmentgetthebestresults?5.1.2Researchcontentsoffracturemechanics152024/10/27Fracturemechanicsinvolvemanyproblemsofmechanics,materialsscienceandengineeringapplication,itcanbeusedtoprocess:Whenstructurehasbeenset,crackingisknow,howaboutthisstructure’sbearingcapacity
(residualintensity)?Whenstructurehasbeenset,externalloadisknow,howmuchistheallowingmaximumcrack(Damagetolerance)?Knowingofdamagetoleranceandexternalloadofstructure,howtomakeeachcomponentofstructuremeetdimensionalrequirement(damagetolerancedesign)?Lifetimecalculation.(Fatiguecrackgrowth’slife)Selectingmaterial.5.1.2Researchcontentsoffracturemechanics162024/10/27BrittlefractureandductilefractureToughness:
Abilityofmaterialsabsorbenergyduringtheelastic-plasticdeformationwhichbeforematerialbreak.5.1.3Severalbasicconceptionoffracturemechanics172024/10/27Brittlefractureandductilefracture
Whenbreaking,thereisnotobviousplasticdeformation,itisasuddenbreakandwithoutwarningbeforebreaking;
Thefracturesurfaceisquitesmooth,anditisbasicallyperpendiculartotheaxial;
Thefractureisabreastandluminous,anditisperpendiculartothenormalstress.Onthefractureoftenfollowazig-zagorradiationpattern.
Therootofcutwhichbeforebreakingoccurplasticdeformation,andtheareaofsurplussectionwillreduce(i.e.necking);
Fracturemaybejagged;
Withtheobservationofnakedeyeandlowtimemicroscope,thefractureisdarkgreyandfibrous.Brittlefracture:DuctilefractureNotice:Therelativityofconcept(Influencebytemperature,stressandenvironment)5.1.3Severalbasicconceptionoffracturemechanics182024/10/27Trans-granularfractureandinter-granularfractureCleavageforms(Simpleabruptionofatomicbinding)BrittlefractureSlipandemptyaggregationDuctilefractureFracturearousebytemperbrittlenessorcrystalboundaryhasbrittlephase,hydrogenembrittlementandanyotherreasons,italwaysbelongstothebrittlefracture.5.1.3Severalbasicconceptionoffracturemechanics192024/10/27Thedivisionoflengthdimensionandbreakrelateddiscipline(Subject)5.1.3Severalbasicconceptionoffracturemechanics202024/10/27Thedivisionoflengthdimensionandbreakrelateddiscipline(Fissure)Staticcracking(Stressanalysis)Subcriticalcrackgrowth(fracturecriterion)
UnstableextensionsCrackarrest5.1.3Severalbasicconceptionoffracturemechanics212024/10/275.1.4Fractureanalysis(concept)Metalfracture:Aftermetalcomponentsbreak,thegeneraltermsofdamagedpart’soutwardappearance.Recordingtheprocessofcrack’sgeneration,propagationandfracture.Fractureanalysis:Usingmethodsofmacroscopeandmicroscopetoanalyseandresearchtofracturemorphology.
Purpose:Analyzethematerialorganizationandthecharacteristicsandessenceofdefect,sothatitcanaccuratelydeterminesteelquanlity,improvementsmeltingandheattreatmenttechnology;Studingthemicro-mechanismofmetalfractureprocess,asthefoundationofexpositionfractureprocesselementarytheory;Explorationthecauseofaccident.Method:Macro-fractureanalysis,micro-fractureananlysis.222024/10/275.1.4Fractureanalysis(Macroscopic)Macro-fractureanalysisThroughmacroscopicfractureanalysis,wecandeterminethenatureofthemetalfracture(brittle,ductileor
fatigue);Cananalyzethecracksourcelocationandthedirectionofcrackpropagation;
Canjudgethequalityofthematerial.Distinguishbetweenthestaticloadfractureandfatiguefracture232024/10/275.1.4Fractureanalysis(Macroscopic)Staticloadfracture:threeelementsFiberareaRadiation
areaShearlipareaNon-gaptensilespecimenandimpacttestsamplefracturechart
242024/10/275.1.4Fractureanalysis(Macroscopic)RadiationareashapeCounterdirectional
cracksource252024/10/275.1.4Fractureanalysis(Macroscopic)Threeregionsofthefracturesurfaceexistornot,size,location,scaleandshape,etc.willhavegreatchangealongwiththedifferenceofmaterialintensitylevels,stressconditions,sizedimensions,geometricforms,insideandoutsideflawsandpositions,temperature,externalenvironmentandsoon.Thetoughnessofmaterialisgood,theareathattextilefiberareaoccupiesisbig,evenhasnotradiation
area,isfulloffiberareaandshearlip.Materialwithbigbrittleness,theradiationareaincreases,fiberareareduces,evenwillnothavefiberareaandshearlip,andthepatternofemissionareaisverytiny,becomeslessobviousandpresentsothercharacteristics.262024/10/275.1.4Fractureanalysis(Macroscopic)Fatiguefracture272024/10/275.1.4Fractureanalysis(Macroscopic)MacroscopicfractureanalysismethodObservingwhethertherehaveradiationpatternorherringbonepatternonfracturesurface,wecanfindthecracksourcepositionaccordingtothetrace;Meanwhile,accordingtotherelativescaleofradiation
areaandfiberareawecanroughlyestimatedfractureproperties.Thebiggertheproportionthattheradiationareaaccountsis,thenthebrittlenessisbigger.Observingwhetherthereisshellpatternonthefracturesurface,ifitis,itindicatesthatthecomponentisfatiguefracture,andwecanfindthefatigueinitiationaccordingtothetrace.
Observingtotheroughdegree,glossandcoloroffracture.Thefractureisrougher,thecolorisgloomier,indicatedthatinthefracturegrowthprocesstheplasticdeformationisbigger,thedegreeofductilefractureisbigger;Otherwise,fractureisthinandflat,multi-gloss,itmeansthattheproportionofbrittlefractureissignificant.282024/10/275.1.4Fractureanalysis(Microscopic)Micro-fractureanalysisInadditiontobeingabletounderstandthecauseofthefracture,butcanalsostudymechanismsoffractureoccurred.
Method:transmissionelectronmicroscope(TEM)andscanningelectronmicroscopeMicrofracturemorphology:CleavagefractureToughnessnestfractureFatiguefracture292024/10/275.1.4Fractureanalysis(Microscopic)Cleavagefractureisakindoftransgranularfracture,onaspecificcrystalsurface,occurduetothesimplebreakdownofatomickeyfracture.Withinagrain,cleavagecrackhasrelativelyflat.Itmustchangedirectionatthegrainboundary,socleavagefractureiscomposedofmanysmallsmoothplaneswhichorientationisslightlydifferent,eachgroupofsmallplanerepresentsagrain;Themostimportantcharacterofcleavagefractureis"riverspattern"。Cleavagefracture:Akindofthecrispestfractureformwhichoccursinthecrystallizationmaterial.302024/10/275.1.4Fractureanalysis(Microscopic)Toughnessnestfracture:Toughnessnestfractureisamaintypeofductilefracture,italsobelongstotransgranularfracture;Thechieffeatureofthefracturesurfaceoftoughnessnestfractureistohavedimple;
Accordingtothedifferentforce,itwillformdifferentshapesofdimple,thereareisometrictoughnessnest,parabolictoughnessnestandelongationtoughnessnestandsoon.Fracturesurfacepresentsroughandirregularshape.312024/10/275.1.4Fractureanalysis(Microscopic)IsometrictoughnessnestParabolictoughnessnestElongationtoughnessnest322024/10/275.1.4Fractureanalysis(Microscopic)Fatiguefracture
Thechieffeatureoffatiguefractureisthereisshellpattern(ornamesbeachpattern,tree-ringpattern)inthefatiguezones(fracturegrowtharea).Sometimesitisunclearwiththeobservationofmacroscopicmethod,andpresentsclearwiththemicroapproach.Shellpattern’sstripesarebasicparallel,butslightlycurved,presentwave-shaped;Stripelineisperpendiculartothecrackdehiscencedirection;Eachstriperepresentsaloadprocess,stripetotalnumberisthenumberofvaryingload;Thetraceoftopandbottomfracturecorrespondcompletely.
332024/10/275.2Thecrack-tip’sstressanddisplacementfieldCrackBasictypesofcrackThestressfieldanddisplacementfieldnearbycrack-tip342024/10/275.2Thecrack-tip’sstressanddisplacementfieldCrackTheactualcomponentdefects:Entrappedslagandblowholegenerateinsmeltingproduce;Toolmarksandnotchgroovecauseduringmachining;Crack,notpenetration,blowhole,undercut,overburningandinclusionproduceduringwelding;Theshrinkholeandlooseincasting;Thecorrosioncrackandfatiguecrackproducewhenstructureareusedindifferentenvironment.352024/10/275.2.1Basictypesofcrack
Accordingtothelocationofcrack:Through-wallcrackSurfacecrackHiddencrackAccordingtocrackstresssituation:openingmode(I)Slidingmode(Ⅱ)Tearingmode(Ⅲ)5.2.1Basictypesofcrack
ModeI(openingmode):Bearwithcracksurfaceverticalnormalstress
,cracksurfacedisplacementalongtheYdirection,crackopening.
,裂纹张开。ModeII(slidingmode):Bearwithshearingstrength
ofplaneXY,cracksurfacedisplacementalongtheXdirection,andcracksurfaceslidesinXdirection.ModeIII(tearingmode):Bearwithshearingstrength
ofplaneYZ,,cracksurfacedisplacementalongtheZdirection,andcracksurfacetearsinZdirection.372024/10/275.2.2Thestressfieldanddisplacementfieldnearbycrack-tip
Analyticalmethod:Accordingtoelastictheory;Analysingtheboundaryconditions;Solvethestressfieldanddisplacementfield382024/10/27Stressanddisplacementnearbyopeningmode’scrack-tip.5.2.2Thestressfieldanddisplacementfieldnearbycrack-tip
ThemostcommonandharmfulcrackinengineeringismodeIcrack.
Tomakecrackgrowth,must
>0.
NamelyonlythetensilestresscancausecracksopenextensionsDiscussingtothesituationthatainfiniteplatewhichhavea2a-longpenetratingcrack,anditstwoendssubjecttotensilestress
thatisperpendiculartothecrack.392024/10/27
Whatwediscussistheplaneproblem,so
yz=
zx=0;
Forplanarstressstate,
z=0。
Ifitisplanestrainstate,then
z=
(
x+
y)。ssxy2adxdyrqsysxtxyssqyar=+221cos[qq232sinsin]tsqqqxyar=22232sincoscosssqxar=-221cos[qq232sinsin]Attheplacethatisapartfromcrack-tipr,withtheXaxisanglefor
,pickupamicro-surfacewhosesizeisdx、dy;Usingmethodsofelasticmechanics,wecanobtainanypoint’s(r,
)normalstress
x
yandshearstress
xynearbythecrack-tip,thatis:5.2.2Thestressfieldanddisplacementfieldnearbycrack-tip
(5-1)402024/10/27Whatfracturemechanicscareforisthestressfieldnearbycrack-tip.Theaboveequationisthedominanttermofcrack-tip’sstressfield,alsohaver0steptermetc.
0,stress
ijtendtobeinfinityatr-1/2step,existingsingularity;Andthenr0stepbecomesubordinate,itcanbeignored.(5-1)theaboveequationmaywriteas:spfqijijKr=12()Ka1=sp式中:r
,
ijapproachtozero;Butobviously,when
=0,ontheXaxis,farawayfromthecrack,itmaybe
y=
,anddoesn’tinfluencebyr.Thereforethistimeweshouldtaketheafterr0stepasthedominantterm.ssxy2adxdyrqsysxtxy5.2.2Thestressfieldanddisplacementfieldnearbycrack-tip
412024/10/27Kreflectthestrengthofcrack-tipstressfield;Thesubscript1meansitismold1.If
ijisbigger,thenKisbigger;Cracksizeaisbigger,thenKisbigger.TheKdimensionis[stress][lengh]1/2,incommonuseMPamCrack-tip’sstressintensityfactorK1:
f(a,W,...)isgeometriccorrectionfunction,itcanbecheckedthroughhandbook.Particularly,whena<<wora/w
0,i.e.
Fortheinfinitewidth
centercrackedplatewhichbearingstretch,f=1;
Fortheinfinitewidthunilateralcrackplate,f=1.12.5.2.2Thestressfieldanddisplacementfieldnearbycrack-tip
Formula(5-1)isthesolutionofcenterthroughcrackinfiniteplane.
FracturemechanicsresearchindicatethatK1canmoregenerallywriteas:KafaW1=sp(,,...)422024/10/275.2.2Thestressfieldanddisplacementfieldnearbycrack-tip
Thestressanddisplacementnearthecrack-tipofslidingmodecrack.432024/10/275.2.2Thestressfieldanddisplacementfieldnearbycrack-tip
Thestressanddisplacementnearthecrack-tipoftearingmodecrack442024/10/275.3Stressintensityfactorandit’ssolutionThegeneralformulaofcrack-tip’sstressfieldanddisplacementfield:Analysisofstressfield:Thestressdistributionofcrack-tipnearbyregionisthefunctionofpositiondata,hasnothingtodowiththestresssizeandcracklengthofinfinitedistantplace;Thestresspresentssingularpointinthecrack-trip;
Atthecrack-tip,stressintensityfactorisafinitequantity;
Conclusion:Thestressisnotsuitableasestablishingthephysicalparameterofstrengthcondition.452024/10/275.3Stressintensityfactorandit’ssolutionThecharacterofSIF:TheSIFismeasurementofcrack-tipstress-strainfieldintensity;TheSIFismeasurementofcrack-tipstress-strainfieldwhohassingularity;ThemarginalvalueofSIFismaterial'sinherentattribute.Conclusion:EstablishesfailureconditiontobesuitablebyusingtheSIF.462024/10/275.3Stressintensityfactorandit’ssolutionGeneralformulaofSIFCalculationmethodofSIFMethodofcalculationMethodoflook-uptableMethodofsuperposition472024/10/275.3Stressintensityfactorandit’ssolutionThesuperpositionprincipleofsoughtofSIFThedecompositionandsuperpositionofstressStructureandforcedecompositionandsuperpositionatthesametimeInviewofdifferentkindsofcrack,consideringcomplexcriteria.482024/10/275.3Stressintensityfactorandit’ssolutionThesuperpositionofSIF492024/10/275.4TheKcriterionofbrittlefracture5.4.1StrainenergyreleaserateandGcriterion5.4.2TherelationshipbetweenSIFandstrainenergyreleaserate.5.4.3TheKcriterionofbrittlefracture5.4.4TheengineeringapplicationofKcriterion5.4.5Mixedmodefracturecriterion
502024/10/275.4.1StrainenergyreleaserateandGcriterionAnalysisprinciple:EnergymethodStrainenergyreleaserateEnergyratethatfracturegrowthneedstoabsorbExpandStabilizeCriticalCrackcriticalcondition:Gcriterion512024/10/275.4.1StrainenergyreleaserateandGcriterionExampleofinfiniteplatesubjectedtotensileinstanceCriticalconditionCriticalstressCriticalcracklength522024/10/275.4.1StrainenergyreleaserateandGcriterionDiscussionGicismaterialconstant,representtheabilityofmaterialresistofcrackgrowth,itwillbedeterminedbyexperiment.
Theaboveexampleofengineeringapplicationisapplicabletobrittlematerial.FortheGcriterionofmetalmaterialwhohassomeplasticity:Strainenergyreleaserate=Energythatformanewsurfaceneeds+Plasticdeformationenergythatcrackgrowthneeds532024/10/275.4.2TherelationshipbetweenSIFandstrainenergyreleaserateWhendiscussinglinearelasticfractureproblems,applyingGandKastheparameterisequal.542024/10/275.4.3TheKcriterionofbrittlefractureK
criterion:ThephysicalsignificanceofKiandKIcKI
:SIF,ObtainingthroughcalculationKIc
:Fracturetoughness:Abilityofmaterialresistbrittlefracture.TheexperimentobtainofKIcFracturetoughnessofplanestrain552024/10/275.4.4TheengineeringapplicationofKcriterionK
criterion:CriticalstressCriticalcracklength562024/10/275.4.4TheengineeringapplicationofKcriterionApplyingsituation:Knownstress,soughtthecriticalcracklength;Knowncracklength,soughtcriticalstress(residualintensity).Applicationsteps:Throughnon-destructivetesting,determinethelengthandpositionofcracka;Ananalysisofthedefects,calculateofchecktabletoobtaintheexpressionofSIFK;Throughexperimentorchecktable,determinematerialplanestrainfracturetoughnessKic;AccordingtoKcriterion,analysisoffracturemechanics,determinethecriticalcracklengthacorcriticalstress(residualstrength).572024/10/27Solution:1)Donotconsiderthedefects,consideronitstraditionalstrengthdesign.
Whenchoosethetwomaterials,thesafetycoefficientis:
Material1:n
1=
ys1/
=1800/1000=1.8Material2:n
2=
ys2/
=1400/1000=1.4excellentqualified5.4.4TheengineeringapplicationofKcriterion2)Consideringthedefects,accordingtocrackdesignconsideration.Because“a”isverysmall,forunilateralthroughcrack,itwillbeCase1:Somecomponenthasaunilateralthroughcrack,itslonga=1mm,sufferfromtensilestress
=1000MPa.Trytochoosematerial.
Material1:
ys1=1800MPa,K1C1=50MPam1/2
;Material2:
ys2=1400MPa,K1C2=75MPam1/2.582024/10/27Selectingmaterial1,low-stressbrittlefracturewillhappen;Selectingmaterial2,meetthestrengthconditionsandtherequestofanti-break.Selectingmaterial1:
1c=50/[1.12(3.14
0.001)1/2]=796MPa<
Selectingmaterial2:
2c=75/[1.12(3.14
0.001)1/2]=1195MPa>
rupturesafeAttention,a0issmaller,K1Cbecomesbigger,criticalrupturestress
cisbigger.So,enhanceK1C,managea0,canhelppreventlow-stressfracture.5.4.4TheengineeringapplicationofKcriterionMaterialrupturestressisMaterialrupturestressis:592024/10/275.4.4TheengineeringapplicationofKcriterion(Case1)
Whenamissileengineshellhavingthehydrostatictest,ithasaexplosion.KnowntheshellmaterialisD6GChigh-strengthsteel,~,traditionalexaminationisqualified,whencontinuethehydrostatictest,ithasaexplosion,thebreakdownstressis
.Thematerialfracturetoughnessis~,trytoanalysisthereasonsoflow-stressbrittlefracture.
602024/10/275.4.4EngineeringapplicationofK(Example1)stressanalysiscircumferentialstressandaxialstress612024/10/275.4.4EngineeringapplicationofK(Example1)ConventionalintensityanalysisIfitdoesn'texceedthepermissiblestress,thestrengthisqualified.fractureanalysisWhenthecriticalcracklengthis0.36mm,missingdetectioniseasy.improvementmeasuresChoosingthematerialthatKrcishighcanimprovethecriticalcracklengthtoensurethedetectionrate.622024/10/275.4.4EngineeringapplicationofK(Example2)Baosteel'sreductionboxfractographicanalysisstressanalysisbasicassumptionfractureanalysislifecalculation632024/10/27lowstressfracture:fractureundertheconditionsofenoughstaticstrengthresidualintensity:reducedstrengthundertheinfluenceofcrackmodeI(openingmode)isthemostcommonandharmfulintheengineering.normalstressσx,σyandshearstressτxyofanarbitrarypoint(r,θ)nearthecracktipcanbeobtainedbyelasticmechanicsmethod:spfqijijKr=12()Ka1=spsummaryThestressintensityfactorKreflectsthestrengthofstressfieldatcracktip;ThedimensionofKis[stress][length]1/2,alwaysMPa
642024/10/27Duringthestructurefacturedesign,threekeyfactorsmustbetakenintoaccount:workstress、defectsizeandfracturetoughness.
Fracturemechanicsshowthemathematicalrelationshipbetweenthesequantities.Onlyknowtwootherscanwecalculatethethirdquantity.summaryFracturedesignshouldbebasedontheavailabledata,suchasmaterialproperties,
workingenvironmentandstructuralload.IfK1Cisavailableanddesignstressislow,linearelasticfracturemechanicsisappropriate.652024/10/27Thestressintensityfactorofcracktipcanbemoregenerallywrittenas:KafaW1=sp(,,...)infinitelywidecenter-crackedplateunderstretching,f=1;infinitelywidesingle-edge-crackedplate,f=1.12
crack
lengthandshapeworkstressfracturetoughnessK1C
threeelementsoffractureorK
K1CKfaWa=(,)Lsp£Kc1fracturecriterion:resistanceactingsummary662024/10/27Question:MWMTMWMTI、I+III裂纹表面裂纹前缘IIIIII+III+II+III5.4.5Mixed-modefracturecriterionlargerotatingcomponent(suchasgeneratorshaft,etc),modeIcrackandmodeIIcrackcoexist.672024/10/27裂纹表面裂纹前缘IIIII5.4.5Mixed-modefracturecriterionThebackgroundofmixedmodecrack'sformationofplanebendingstructure.Themaindifferenc
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 2024年铌酸锂、钽酸锂单晶项目发展计划
- 幼儿园后勤工作计划
- 2024年重组人胰岛素合作协议书
- 2024年工业自动调节仪表与控制系统项目发展计划
- 承包土地合作经营协议书范本
- 2024年CCD光电荷耦合二极管及其组件项目建议书
- 2024年铁氧体粘结永磁磁粉项目建议书
- 金融投资居间服务补充协议
- 2024版合同范本120救护车驾驶员协议书
- 2024版杭州市农副产品购销合同
- 德国WMF压力锅使用手册
- S775(二)-重力式无阀滤池(共21页)
- 科技创新答辩PPT.ppt
- 国有企业共青团创新工作方法研究
- 浅谈英语课前三分钟演讲
- 湖北省中小学教师职务任职资格评审表
- 子宫下段剖宫产围手术期中医护理方案
- 集装箱设计PPT课件
- 马铃薯恒温贮藏库建设项目可行研究报告
- 第5讲 同余的概念和性质
- 四种客户类型(老鹰型、孔雀型、鸽子型、猫头鹰型)
评论
0/150
提交评论