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不飞则已,一飞冲天;不鸣则已,一鸣惊人。——《韩非子》
StressLimitsinDesign
Howlargecanwepermitthestressestobe?Orconversely:
Howlargemustapartbetowithstandagivensetofloadswhat
aretheoverallconditionsorlimitsthatwilldeterminethesize
andmaterialforapart?
Designlimitsarebasedonavoidingfailureofthepartto
performitsdesiredfunction.Becausedifferentpartsmustsatisfy
differentfunctionalrequirements,theconditionswhichlimit
load-carryingabilitymaybequitedifferentfordifferent
elements.Asanexample,comparethedesignlimitsforthefloor
ofahousewiththoseforthewingofanairplane.
Ifweweretodeterminethesizeofthewoodenbeamsina
homesuchthattheysimplydidnotbreak,wewouldnotbevery
happywiththem;theywouldbetoospringy‘’.Walkingacross
theroomwouldbelikewalkingoutonadivingboard.
Obviously,weshouldbeconcernedwiththemaximum
deflection‘’thatwe,asindividuals,findacceptable.Thislevel
willberathersubjective,anddifferentpeoplewillgivedifferent
answers.Infact,thesamepeoplemaygivedifferentanswers
dependingonwhethertheyarepayingforthefloorornot!
Anairplanewingstructureisclearlydifferent.Ifyoulook
outanairplanewindowandwatchthewingduringturbulent
不飞则已,一飞冲天;不鸣则已,一鸣惊人。——《韩非子》
weather,youwillseelargedeflections;infactyoumaywish
thattheyweresmaller.However,youknowthattheimportant
issueisthatofstructuralintegrity‘’,notdeflection.
Wewantt