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ID:40552603
大小:1.03 MB
页数:24页
时间:2019-08-04
《1 - Introduction to Mechanical Vibrations书》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、IntroductiontoMechanicalVibrations1.1IntroductionAllmechanicalsystemscomposedofmass,stiffnessanddampingelementsexhibitvibratoryresponsewhensubjecttotime-varyingdisturbances.Thepredictionandcontrolofthesedisturbancesisfundamentaltothedesignandoperationofmechanicalequipmen
2、t.Inparticular,theuseofsecondary,activeinputstothesysteminordertomodifythesystemresponseinacontrollablewayisthetopicofthisbook.Theanalysisofcontrolledsystemsisfoundedonthesameanalyticalapproachesusedtostudythevibrationsofelasticstructures.Abriefreviewofthemainconceptsofv
3、ibrationanalysisandtheassociatedtechniquesofsolutionisnecessarytosetthefoundationforthefollowingchapters.Inthischapterwebeginbydefiningterminologyandthemathematicalmethodsfordescribingthelinearresponseofvibratingsystems.Theequationsofmotionandlinearbehaviourofsingle-degr
4、ee-of-freedomsystemsareoutlinedforbothfreeandforcedresponse.TheuseoftheLaplacetransformtosolvefortransientresponseisreviewed.Theextensiontomulti-degree-of-freedomsystemsandthentheuseoffiniteelementanalysisarebrieflyintroduced.Theseapproachesarevalidforlightlydampedstruct
5、uresorelementsthataresmallrelativetothewavelengthofmotion.FormoredetailthereaderisreferredtothetextsofThomson(1993),Meirovitch(1967)andInman(1994).1.2TerminologyThefollowingisabrieflistofthemainterminologyanddefinitionsusedinanalysingthevibratoryresponseofmechanicalsyste
6、ms.Mechanicalsystem.Amechanicalsystemiscomposedofdistributedelementswhichexhibitcharacteristicsofmass,elasticityanddamping.Degreesoffreedom.Thenumberofdegreesoffreedomofasystemisequaltothenumberofindependentcoordinatepositionsrequiredtocompletelydescribethemotionofthesys
7、tem.Systemresponse.Allmechanicalsystemsexhibitsomeformofvibratoryresponsewhenexcitedbyeitherinternalorexternalforces.Thismotionmaybeirregularormayrepeatitselfatregularintervals,inwhichcaseitiscalledperiodicmotion.Period.TheperiodTisthetimetakenforonecompletecycleofmotion
8、.2ACTIVECONTROLOFVIBRATIONHarmonicmotionisthesimplestformofperiodicmotionwherebytheactualorobservedmoti
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