vdi2230

OverviewofVDI2230AnIntroductiontotheCalculationMethodforDeterminingtheStressinaBoltedJointImportantNoteThissummaryoftheVDI2230Standardisintendedtoprovideabasicunderstandingofthemethod.Readerswhowishtoputthestandardtouseareurgedtorefertothecompletestandardthatcontainsallinformation,figures,etc.Definitions•Covershigh-dutyboltedjointswithconstantoralternatingloads•Boltedjointsareseparablejointsbetweentwoormorecomponentsusingoneormorebolts•JointmustfulfillitsfunctionandwithstandworkingloadAimofCalculationDetermineboltdimensionallowingfor:•Strengthgradeofthebolt•Reductionofpreloadbyworkingload•Reductionofpreloadbyembedding•Scatterofpreloadduringtightening•Fatiguestrengthunderanalternatingload•Compressivestressonclampedparts1.RangeofValidity•SteelBolts•M4toM39•RoomTemperature2.ChoiceofCalculationApproach•Dependentupongeometry–Cylindricalsingleboltedjoint–Beamconnection–Circularplate–Rotationofflanges–FlangedjointwithplanebearingfaceCylindricalSingleBoltedJoint•Axialforce,FA•Transverseforce,FQ•Bendingmoment,MBBeamGeometry,Ex.1•Axialforce,FA•Transverseforce,FQ•Momentoftheplaneofthebeam,MZBeamGeometry,Ex.2•Axialforce,FA•Transverseforce,FQ•Momentoftheplaneofthebeam,MZRotationofFlanges•Axialforce,FA(pipeforce)•Bendingmoment,MB•Internalpressure,pFlangedJointwithPlaneBearingFace,Ex.1•Axialforce,FA(pipeforce)•Torsionalmoment,MT•Moment,MBFlangedJointwithPlaneBearingFace,Ex.2•Axialforce,FA(pipeforce)•Transverseforce,FQ•Torsionalmoment,MT•Moment,MBFlangedJointwithPlaneBearingFace,Ex.3•Axialforce,FA(pipeforce)•Transverseforce,FQ•Torsionalmoment,MT•Moment,MB3.AnalysisofForceandDeformation•Optimizedbymeansofthoroughandexactconsiderationofforcesanddeformationsincluding:–Elasticresilienceofboltandparts–Loadanddeformationratioforpartsinassembledstateandoperatingstate4.CalculationSteps•Beginswithexternalworkingload,FB•Workingloadandelasticdeformationsmaycause:–Axialforce,FA–Transverseforce,FQ–BendingMoment,MB–Torquemoment,MTDeterminingBoltDimensions•Onceworkingloadconditionsareknownallowfor:–Lossofpreloadtoembedding–Assemblypreloadreducedbyproportionofaxialboltforce–Necessaryminimumclamploadinthejoint–PreloadscatterduetoassemblymethodCalculationStepR1•Estimationofboltdiameter,d•Estimationofclampinglengthratio,lK/d•Estimationofmeansurfacepressureunderboltheadornutarea,pG•IfpGisexceeded,jointmustbemodifiedandlK/dre-determinedCalculationStepR2•Determinationoftighteningfactor,aA,allowingfor:–Assemblymethod–Stateoflubrication–SurfaceconditionCalculationStepR3•Determinationofrequiredaverageclampingload,Fkerf,aseither:–Clampingforceontheopeningedgewitheccentricallyactingaxialforce,FAOr–ClampingforcetoabsorbmomentMTortransverseforcecomponent,FQCalculationStepR4•Determinationofloadfactor,F,including:–Determinationofelasticresilienceofbolt,dS–Evaluationofthepositionofloadintroduction,n*lK–Determinationofelasticresilienceofclampedparts,dP–Calculationofrequiredsubstitutionalcross-section,AersCalculationStepR5•Determinationoflossofpreload,FZ,duetoembedding•DeterminationoftotalembeddingCalculationStepR6•Determinationofboltsizeandgrade–Fortighteningwithintheelasticrange,selectboltforwhichinitialclampingloadisequaltoorgreaterthanmaximuminitialclampingloadduetoscatterinassemblyprocess–Fortighteningtoyield,selectboltforwhich90%ofinitialclampingloadisequaltoorgreaterthanminimuminitialclampingloadduetoscatterinassemblyprocessCalculationStepR7•Ifchangesinboltorclampinglengthratio,lK/d,arenecessary,repeatStepsR4throughR6CalculationStepR8•CheckthatmaximumpermissibleboltforceisnotexceededCalculationStepR9•Determinealternatingstressenduranceofbolt•Allowforbendingstressineccentricloadapplications•Obtainapproximatevalueforpermissiblestressdeviationfromtables•Ifnotsatisfactory,useboltwithlargerdiameterorgreaterendurancelimit•ConsiderbendingstressforeccentricloadingCalculationStepR10•Checksurfacepressureunderboltheadandnutbearingarea•Allowforchamferingofholeindeterminingbearingarea•Tablesproviderecommendationsformaximumallowablesurfacepressure•Ifusingtighteningtoorbeyondyield,modifycalculation5.InfluencingFactors•Allowforfactorsdependingupon:–Materialandsurfacedesignofclampedparts–Shapeofselectedboltsandnuts–AssemblyconditionsStrengthoftheBolt•Stresscausedby:–Torsionalandaxialstressesduringtightening–Workingload•ShouldnotexceedyieldloadMinimumThreadEngagement•Dependsupon:–Threadform,pitch,tolerance,anddiameter–Formofthenut(wrenchingwidth)–Bolthole–Strengthandductilityofboltandnutmaterials–Typeofstress(tensile,torsional,bending)–Frictioncoefficients–NumberoftighteningsThreadShearStrength•Bolt-NutStrengthMatching•NumberforstrengthgradeofnutisequivalenttofirstnumberofstrengthgradeofboltCalculationofRequiredNutHeight•Allowsforgeometryandmechanicalpropertiesofjointelements•Predictstypeoffailurecausedbyoverloading•Considers:–Dimensionalvalues(tensilecross-sectionofboltthread,threadengagementlength,etc.)–Threadform&nutform–BoltclearanceholeBoltHeadHeight•Ensuresthatfailurewilloccurinfreeloadedthreadsectionorintheshank•HighesttensilestressinthreadHighesttensilestres