包装技术基础(双语教学)14.ppt

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1、Lesson14TestMethodforProductFragility第14课产品脆值试验方法TestMethodforProductFragilityAshockmachineisusedtogenerateadamageboundarycurveAvibrationsystemisusedtomapoutthenaturalfrequenciesofaproduct.Shock:DamageBoundaryShockdamagetoproductsresultsfromexcessiveinternalstressinduced

2、byinertiaforces-SinceF=ma,shockfragilityischaracterizedbythemaximumtolerableaccelerationlevel,i.e,howmanyg’stheitemcanwithstand.-Whydamaged?-Howtoreduceg’s?Thepackagingmaterialchangestheshockpulsedeliveredtotheproductsothatthemaximumaccelerationisgreatlyreduced(andthepul

3、sedurationismanytimeslonger).-Thepackagedesigner’sgoal:Tobesurethattheg-leveltransmittedtotheitembythecushionislessthattheg-levelwhichwillcausetheitemtofail.Shock:DamageBoundaryThedamageboundarytheoryisusedtodeterminewhichshockinputswillcausedamagetoaproductandwhichwilln

4、ot.-Twopartsofashockcancausedamage:1.theaccelerationlevelA2.thevelocitychange∆V(theareaundertheacceleration-timehistoryoftheshock,thoughtastheenergycontainedinashock)-Thecriticalvelocitychange(∆Vc):aminimumvelocitychangewhichmustbeachievedbeforedamagetotheproductcanoccur

5、.1.Below∆Vc,nodamageoccursregardlessoftheinputA2.Exceeding∆Vc,doesnotnecessarilyimplythatdamageresults.a.If∆Voccursinamannerwhichadministersacceptabledosesofaccelerationtotheproduct,thevelocitychangecanbeverylargewithoutcausingdamage.b.If∆VcandAcarebothexceeded,damageocc

6、urs.Figure14.1:TypicaldamageboundarycurveShock:DamageBoundaryImplicationsofFig.14.1:a.iftheinput∆V

7、elerationleveloftheevent,onlytheenergyinput.b.iftheinput∆V>theproduct’s∆Vc,However,theonlywaytoavoiddamageistolimittheinputA

8、nertoloweraccelerationeventsexperiencedinsideattheunit.Shock:DamageBoundaryFigure14.1Typicaldamagebound