机器设计-综合方法p1430.pdf

MACHINEDESIGN-AnIntegratedApproach,4thEd.14-30-1

PROBLEM14-30

Statement:Giventhefollowingdataforahelicaltorsionspring,loadedinfatigue,findthespringindex,

unloadedcoildiameter,minimumloadedcoildiameter,andsafetyfactorinfatigue.Stateall

assumptionsandsourcesofempiricaldataused.

6

Given:Minimumdeflectionθmin0.25revBendingmodulusE3010psi

1

umdeflectionθmax0.75revSpringratek60inlbfrev

NumberactivecoilsN20Wiredia.d0.192in

a

DesignChoices:

Useunpeenedmusicwirewith2-in-long,straightends.Thecoilisloadedtocloseit.

YieldstrengthfactorK0.80(fromTable14-13)

s

LengthofendsL2in1L2in2

MaterialstrengthfactorsA184.65ksib0.1625(ASTMA228wire)

WireendurancelimitS77.99ksi