ansys分析随机振动

DynamicStructuresPSDVerificationRandomVibrationAnalysiswithANSYSandVerificationByYeZhouMay2002DynamicStructuresPSDVerification1595544930249Rev.17/23/202010:52:00PMp.2/14TableofContents1INTRODUCTIONTORANDOMVIBRATION..................................................................................................................31.1FailureModesinRandomVibration..............................................................................................................31.2RandomVibrationInputCurveandUnits......................................................................................................31.3NormalDistributionCurve.............................................................................................................................41.4PSDforFatigueCalculation..........................................................................................................................52FORMULATION..........................................................................................................................................................62.1Steinbergformulation[1.9.16]:.....................................................................................................................62.2Thomsonformulation[2.10.3]:......................................................................................................................72.3Newlandformulation[4.7]:...........................................................................................................................73ANSYSPROCEDURES...............................................................................................................................................84REFERENCES...........................................................................................................................................................105APPENDIX–ANSYSPSDINPUT/OUTPUTFILE......................................................................................................115.1InputFile......................................................................................................................................................115.2OutputFile....................................................................................................................................................13ListofFiguresFigure1Typicalwhitenoisecurvewithaconstantinputpowerspectraldensity(PSD)......................................4Figure2Sample1-DOFmodel..............................................................................................................................6Figure3ANSYScalculatedoutputPSD...............................................................................................................8ListofTablesTable1Typeofspectraldensities..........................................................................................................................4Table2Safetyindex/sigmavaluesusedinbuildingcodes....................................................................................6Table3ANSYSresultsverification.......................................................................................................................9Table4ANSYSPSDresultloadsteps..................................................................................................................9DynamicStructuresPSDVerification1595544930249Rev.17/23/202010:52:00PMp.3/141IntroductiontoRandomVibrationRandomvibrationisbeingspecifiedforacceptanceandqualificationtestsbymanyinstitutions,becauseithasbeenshownthatrandomvibrationmorecloselyrepresentsthetrueenvironmentsinwhichthestructuresandequipmentmustoperate.1.1FailureModesinRandomVibrationTherearefourbasicfailuremodesthatmustbeconsideredunderrandomvibration.Thesefailuresare:1.Highaccelerationlevels.2.Highstresslevels.3.Largedisplacementamplitudes.4.Electricalsignalsoutoftolerance(electricalcomponentonly).1.2RandomVibrationInputCurveandUnitsTherearemanydifferenttypesofcurvesthatcanbeusedtoshowtherandomvibrationinputrequirements.Themostcommoncurve,whichisalsothesimplest,isthewhite-noisecurveshowninFigure1.Randomvibrationinputandresponsecurvesaretypicallyplottedonlog-logpaper,withthepowerspectraldensityexpressedsquaredaccelerationunitsperHertz,suchasg2/Hz.ThepowerspectraldensityPisoftenreferredasthemeansquaredaccelerationdensity,anditisdefinedas:fGPf20limwhereGistherootmeansquare(RMS)oftheaccelerationexpressedingravityunits.Rootmeansquareaccelerationlevelsarerelatedtotheareaundertherandomvibrationcurve.TheinputRMSaccelerationlevelscanbeobtainedbyintegratingundertheinputrandomvibrationcurve,andtheoutput(orresponse)RMSaccelerationlevelscanbeobtainedbyintegratingundertheoutputorresponserandomvibrationcurve.ThesquarerootoftheareathendeterminedtheRMSaccelerationlevel,withunits:RMSGGHzHzGArea22Forexample,theinputRMSaccelerationlevelresultingfromthewhite-noiserandomvibrationinputspecificationshowninFigure1iscalculatedasfollows:0.3)10100(1.0fPGRMS(RMSinputaccelerationlevel)Randomvibra