机械振动英文 参赛课件.ppt

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1、MechanicalVibrationsBMM3553Mohd.ShahrirbinMohd.SaniFacultyofMechanicalEngineeringLecture:1参赛选手：****Today’sObjectivesStudentswillbeableto:UnderstandthebasicconceptsofvibrationIdentifythedifferenttypesofmotionIdentifythedifferenttypesofvibrationIdentifytheDegreeofFreed

2、om.Inherentinthestudyofvibrationisoscillation.Electriccircuitscanhaveoscillatoryvoltagesorcurrentsbutthesearenotcalledvibratorysystemsandtheirstudyisnotcalledvibration.Airpressureoscillationiscalledsoundbutthestudyofsoundiscalledacousticsnotvibration.Vibrationisusual

3、lyusedtodescribethemotionofmechanicalobjectsthatoscillatesorhavethepotentialtooscillate7BasicConceptsofVibrationVibration=anymotionthatrepeatsitselfafteranintervaloftimeVibratorySystemconsistsof:1)springorelasticity2)massorinertia3)damperInvolvestransferofpotentialen

4、ergytokineticenergyandviceversaThedecomposedrotatingforcevectorissinusoidalThenaturalorfreemotionofanelasticbodyaboutequilibriumpositionissinusoidalCombinedtheycreateasinusoidalmotioncommonlyknownasVIBRATIONWhyissinefunctionoftenassociatedwithvibration?Rotatingforcev

5、ectorbecomessinusoidalforceintheverticaldirectionCompensatorSystem(plant)SensorOutputInputMechanicalSystemOutput(Oscillatory)InputControlsystemMechanicalVibrationsDifferencebetweenControlsystemandVibrationSystemClassificationofVibrationSimpleHarmonicMotionNaturalfreq

6、uency,characteristicfrequency,fundamentalfrequency,resonancefrequency,normalfrequencySimpleHarmonicMotionVibrationParameters:Displacement,VelocityandAccelerationDisplacementVelocityAccelerationPeriodicMotionRandomMotionMotionisnotdeterministic(i.e.Notrepeatable)Stat

7、isticofmotionhistorymaybewelldefined,butexactlocationasafunctionoftimeisnotobtainableVibrationsignalcontainsallfrequenciesinagivenband.OftengeneratedbymachineloosenessRandomMotionChaoticMotionCombinationofrandomandperiodicmotionRandomandrepeatablecharacteristicscombi

8、nedinanon-linearfashionVibrationsignalcontainsallfrequenciesinagivenbandbutnotisequalproportionsTransientMotionAnymotionotherthanth