焊接结构疲劳评估教程(I)-聂春戈-100

TheMesh-InsensitiveStructuralStressMethodforFatigueEvaluationofWeldedStructures焊接结构疲劳评估的网格不敏感结构应力方法Dr.PingshaDong董平沙博士ProfessorandNorthropGrummanEndowedChair教授诺斯普·格鲁门荣誉主席Director,CenterforAdvancedMarineStructuresandFabrication(CAM-SF)先进船舶结构与工艺中心主任SchoolofNavalArchitectureandMarineEngineering海洋结构与船舶工程学院TheUniversityofNewOrleans新奥尔良大学TrainingCourse培训教程[e-mail]©2006-2009PingshaDongAllRightsReserved目录焊接疲劳基本相关术语和定义材料性能的影响残余应力的影响几何不连续性的影响传统方法描述结构应力方法（I）结构应力定义与数值实现焊缝的表示方法与其它方法（如ASME，IIW等）的比较和示例结构应力的度量方法与确认结构应力方法（II）一般的结构应力计算过程边界细节的处理计算实例多轴结构应力状态的特征点焊激光焊演示/工作流程——结构应力后处理器试用版主S-N曲线方法基于K的结构应力求解技巧与验证双态裂纹生长模型与验证等效结构应力幅参数与验证基于结构应力的寿命预测过程失效、焊线定义、焊缝表示方法等疲劳测试的含义寿命预测实例其它应用焊喉开裂多轴疲劳低周疲劳与热疲劳电子封装中的焊料疲劳8121631475763717587103115118130135140144158165174185216226234249254268282289MajorAwardsandRecognitionsRecentlyReceived最近获得的主要奖励与荣誉IIW2008PatonPrizeSNAME2007ElmerLHannAwardR&DMagazine’sR&D100Award(2006)TIMEMagazine2005MathInnovatorsAviationWeek&SpaceTechnology:Aerospace2004LaurelsAwardSAE2004WeldChallenge:BestLifePredictionWinnerAWS2004R.D.ThomasAwardSAE2003HenryFordIIDistinguishedAwardforExcellenceinAutomotiveEngineeringASME2002G.E.O.WideraLiteratureAward,…AnOverviewofAdvancedWeldModelingCapabilities:FusionWelding先进焊接建模能力概览：熔化焊AnOverviewofAdvancedWeldModelingCapabilities:SolidJoining先进焊接建模能力概览：固态连接FatigueofWeldments:SomeFundamentals焊件疲劳：基本知识Somerelevantterminologiesanddefinitions一些相关术语和定义What’sspecialaboutweldments?焊件有哪些特性、•Stressconcentration应力集中•Materialproperties材料属性•Residualstresses残余应力Whatdecadesofresearchsay?近几十年的研究对此的描述Limitationsofconventionalfatiguedesignmethods传统疲劳设计方法的局限Whatconstitutesagoodfatigueparameter?哪些物理量构成好的疲劳参数TerminologiesDescribingATypicalWeldedJoint描述一个典型焊接接头的术语Materialzonesinajoint接头材料区域Basemetal母材（BM）Heat-affectedzone热影响区（HAZ）Weldmetal焊材（WM）Geometriclocations几何位置Weldtoe焊趾Weldthroat/depth焊喉/焊深Weldroot焊根RelevantFatigueTerminologiesandDefinitions–I相关疲劳术语和定义-ICyclicloading循环载荷Nominalstressatafailurelocation,e.g.,weldcrackintobaseplate失效位置的名义应力，例如，侵入母材的焊接裂纹处F/（Wt）Mc/lNominalstressrange名义应力变化范围F/（Wt）Mc/lRelevantFatigueTerminologiesandDefinitions–II相关疲劳术语和定义-IIMaximumstress最大应力Minimumstress最小应力Stressrange应力变化范围（σ）Meanstress平均应力WhatsSpecialaboutWeldedJoints?焊接接头的特殊之处•PropertyHeterogeneity材料性质的多样性(母材BM,焊材WM,热影响区HAZ)•ResidualStresses残余应力•GeometricDiscontinuities几何不连续性PropertyVariationinWeldedJoints焊接接头材料性质的变化Process-inducedinducedpropertyheterogeneity焊接过程导致的材料性质的多样性WMstrengthmismatchbydesign焊材强度设计的不匹配HardenableSteel可硬化的钢材BM/WM/HAZPropertyHasLittleEffectonFatigueofWeldedJointsBM/WM/HAZ的性质对焊接接头疲劳影响很小ComparisonofFatigueStrengthbetweenPlainMetal,NotchBar,andWeldedSpecimens普通金属、带缺口金属条与焊接试件之间疲劳强度的比较Figure2:Influenceoftensilestrengthonthefatiguestrength图2：抗拉强度对疲劳强度的影响BMStrengthsvs.FatigueLife(Lewis,2001)母材强度与疲劳寿命(Lewis,2001)TRIPvCMn350–UnweldedSteelTRIPvsCMn350andMildSteel–WeldedSteel未焊接钢材焊接钢材WeldResidualStressEffectsonFatiguePerformance:WeldSequencing焊接残余应力对疲劳性能的影响——焊接顺序PassSequenceEffectsonTransverseResidualStresses焊道顺序对横向残余应力的影响TravelSpeed(LinearHeatInput)Effects–TransverseResidualStresses焊接速度(线性热输入)对横向残余应力的影响RestraintEffectsonTransverseResidaulStresses约束对横向残余应力的影响HighRestraintLowRestraint强约束弱约束ResidualStressDistributionsinSomeTypicalJointTypes一些典型焊接接头的残余应力分布Then,HowtoTreatResidualStressEffectsinFatigueDesigninPractice?在实际疲劳设计中应如何处理残余应力的影响？Conductcontrolledfatiguetesting采用控制疲劳测试Effectsonappliedmeanstresses对施加的平均应力的影响As-weldedversusstress-relieved焊态与应力释放Testspecimensmustcontainrepresentativeresidualstressstateinstructures试件必须包含结构中主要的残余应力状态Specimensizing试件尺寸Residualstressinducedtri-axialityversus“shake-down”Effects残余应力引起的三轴与失稳（？？？）的影响ModelorSpecimenSizeMustBeSufficientlyLargetoQuantifyResidualStressEffects模型或者试件的尺寸应该足够大以量化残余应力的影响AButtJoint对接接头Platejoints:w/t=6平板接头w/t=6ResidualStressandJointConstraintEffectsonLocalStress/StrainBehavior残余应力和接头约束对局部应力/应变行为的影响TestSpecimenSizeRequirementsforContainingWeldResidualStressEffects试件尺寸要求包含焊接残余应力效应AxialResidualStress轴向残余应力Tubegirthweldlength:~2.5sqrt(rt)圆管环焊缝长度:~2.5sqrt(rt)TubularGirthWeld管状环焊缝ResidualStressEffectsonFatigueBehaviorofWeldedJoints-ExperimentalEvidence残余应力对焊接接头疲劳行为的影响——试验验证•StressratioisNOTimportant应力比并不重要•Stressrangeisimportant应力幅是关键因素•Compressivecyclicloadingcanbeequallydamaging压缩循环载荷同样可以引起材料破坏RecentS-NDatafromHHI–MeanStressEffectsonS-NBehaviorHHI的最新S-N数据—平均应力对S-N行为的影响ComparisonofFatigueTestDatawithDifferentStressRatioorMeanStressEffects:As-Welded在不同应力比或平均应力效应下疲劳测试数据的比较——焊态ComparisonofFatigueTestDatawithDifferentStressRatioorMeanStressEffects:AsAs-WeldedvsStress-Relieved在不同应力比或平均应力效应下疲劳测试数据的比较——焊态与应力释放StressReliefPost-WeldHeatTreatment(PWHT)焊后热处理(PWHT)的应力释放UniformPWHT:CertainmagnitudeofresidualstressesstillretainedinidealPWHT整体热处理：理想的热处理下仍然存在一定的残余应力OthertreatmentssuchaslocalPWHT其它处理方式比如局部热处理higherresidualstressesretainedthanuniformPWHT比整体热处理方式存在更多的残余应力higherresidualstressesthanas-weldedconditionsmayresult可能比焊态条件下的残余应力水平更高Observations–ResidualStressEffectsonFatigue小结：残余