ABSTRACT
Vibration-andShock-InducedLoosening765
Nisthenumberofcyclestoloosen Cisaconstantdependentonboltdesignandmaterial.
ResearchersfromESNA(ElasticStopNutCorporationofAmerica)performedextensivedynamictestsofboltedassembliessubjectedtovibrationandshock,whicharedocumentedin reportsfromESNA(Baublesetal.,1966;Faroni,1967).Thistestingresultedinthefirsttheory onshock-inducedloosening,whichisbasedontheideathatshocksorimpactstoabolted assemblywillcausethecomponentstoresonateandloosen.Thiscanbedemonstratedusing theblockonaninclineanalogyasshowninFigure8.Ifstaticfictionexceedsthecomponent ofweightthattendstocausesliding,theblockremainsatrest.Iftheplaneisvibratedorif
fiGURE8Blockoninclineanalogyoflooseningduetoanappliedshockorimpact. (AdaptedfromFaroni,1967.)
mechanical shocks are applied to it, the effective coefficient of friction is reduced, and the weight can slide down the plane.
