航空紧固件应用详解外文资料Word文件下载.docx
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航空紧固件应用详解外文资料Word文件下载.docx
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∙Explainthedifferencesbetweendifferentnuttypes
∙Demonstrateanunderstandingofbasicsofaircraftnutinstallation
∙Demonstrateanunderstandingofaerospacerivettypes:
solidandblind
∙Explaintheaerospacefastenermaterialselectionandfactorsdefiningit
∙Demonstrateanunderstandingofaerospacefastenerstandardization
(Slide2)
FastenersinAviation
∙AerospaceFasteners&
theirSpecifications
oTypesofFastenersinAerospaceIndustryandtheirDistinguishingFeatures
▪AerospaceBolts
▪AerospaceRivets
▪AerospaceScrews&
Studs
oQualityAssuranceofAerospaceFasteners
▪MaterialSelection&
Testing
▪ScreeningInspectionsandTest
∙VisualInspection
∙TensileTesting
∙HardnessTesting
oNationalAerospaceStandards(NAS)onFasteners
▪NumericalListingforAerospacebolts,nuts,andwashers
(Slide3)
AerospaceFasteners
(Slide4)
AerospaceFasteners&
theirSpecifications
∙Onaverage,forexample,2.4million(2,400,000)fastenersareusedtoforassembleaBoeing787aircraft
∙22%arestructuralbolts(mostlytitanium)andtherestisrivets
∙TypesofFastenersinAerospaceIndustryandtheirDistinguishingFeatures:
oAerospaceBolts
oAerospaceNuts&
Washers
oAerospaceRivets
(Slide5)
AerospaceBolts
∙Boltsareusedinaircraftconstructioninareaswherehighstrengthisneeded.
∙Wherethisstrengthisnotnecessary,screwsaresubstituted.
∙Aircraftqualityboltsaremadefrom:
alloysteel,stainlessorcorrosionresistantsteel,aluminumalloysandtitanium.
(Slide6)
AerospaceBoltHeadTypes
∙Therearemanyheadtypesavailable,suchashex,slotted,12-point,spline,socket,Torx,andPhillips.
∙SinceIcan'
tcoverthemall,I'
llgiveoneimportantcaveat:
Mostspecifications,includingMILandNAS,DONOTgiveamaximumsocketheaddepth.Onlytheminimumdepthisgiven.Ifthesocketdepthgoesbelowtheundersideofthehead,theheadmaypopoffduringinstallationorduringnormaloperation.Therefore,oneshouldspecifyamaximumsocketdepthonyourfastenerpurchaseorder.
∙Thepointslistedbelowshouldthenbeconsideredbeforemakingafastenertypeandmaterialchoice:
oTrytopickafastenerthatisalreadydefinedbyaconsensusspecification.
oIfthefastenermustbecoated,thetemperaturelimitationwillusuallybedeterminedbythecoating(e.g.,cadmiumcansometimescausehydrogenembrittlementasitburnsoff.)
oJ-threadswithclass3fitsarethenormfortheaerospaceworld.
oItisnotdesirabletousefastenerswithlessthan10%elongation.
oAlthoughrivetsarestillbeingmadefrom5056aluminum,itisastresscorrosionsensitivematerial.Ipersonallydonotrecommendit.
oTitaniumfastenersareverygood,particularlyinamarineatmosphere.
oSuperalloyCRESfastenersareexcellent,ifyoucanaffordtheweightpenaltyofsteelandthecost.
(Slide7)
BoltMarkings
∙Aircraftboltswillalwayshaveamarkingontheirhead.
∙Donotuseboltswithoutmarkingontheirheadbecauseitisprobablyacommercialgradebolt.
∙Themarkingsonboltsvaryaccordingtothemanufacturer.
(Slide8Hidden)
(Slide9)
AerospaceBoltHeadMarkings
∙Mostly,theywillhavean"
X"
oranasteriskalongwithaname.Corrosionresistant(stainlesssteel)boltswillhaveoneraiseddashonitshead.Likewise,aluminumboltwillhavetworaiseddashesonitshead.Aluminumboltshavelimiteduse.Theyshouldnotbeusedintensionapplicationsorwheretheywillbecontinuouslyremovedformaintenanceorinspection.NASboltshaveahighertensilestrength(usuallyabout160,000psi)andcanbeidentifiedbyacuppedouthead.Closetoleranceboltsaremachinedmoreaccuratelythangeneralpurposeboltsandtheyareusedinapplicationsrequiringaverytightfit.ClosetoleranceboltscanbeeitherANorNASandtypicallyhaveaheadmarkingconsistingofaraisedorrecessedtriangle.
(Slide10)
AerospaceBoltHeadMarkings
•ANStandardsteelboltonaLycomingIO-320engine
•Imageontherightisazoom-inofleftimage
•Notethe“S”,“N”,and“M”onthebolthead
(Slide11)
•ANStandardsteelbolt
•Becauseoftheboltheadmarking:
“S”,“N”,and“M”onthebolthead
(Slide12)
BoltStandardization
∙ThestandardboltsusedinaircraftconstructionareAN3throughAN20.
∙Eachbolttypicallyhasahexagonshapedheadandashankthatfitsintothehole.
∙Theshankisthreadedontheend
∙theunthreadedportionoftheboltistermedthegrip.
∙Thediameterofaboltisthewidthofthegrip.
∙Theshankofaboltwillbeeitherdrilledtoacceptacotterpinorundrilled.Anotheroptionistopurchaseaboltthathastheheaddrilledforthepurposeofacceptingsafetywire.Clevisboltsaremanufacturedwithaslottedheadandareusedforcontrolcableapplications.
(Slide13)
ANNumberBreakdown
∙Thesize,material,etc.ofaboltisidentifiedbyanANnumber.AbreakdownofatypicalboltANnumberfollows:
AN4-8A
∙ANmeanstheboltismanufacturedaccordingtoAirForce-Navyspecs.
∙4identifiesthediameteroftheboltshankin1/16"
increments
∙8identifiesthelengthoftheshankin1/8"
∙Ameanstheshankoftheboltisundrilled(noletterheremeansadrilledshank)
∙So,thisparticularboltisa1/4inchdiameterANboltthatis1/2inchlongmeasuredfromjustundertheheadtothetipoftheshank.Theboltalsohasanundrilledshankwhichmeansitcannotacceptacotterpin.Also,boltlengthmayvaryby+1/32"
to-1/64"
.Iftheletter"
C"
followstheANdesignation(ANC)thatidentifiesastainlesssteelbolt.Theletter"
H"
afterAN(ANH)identifiesadrilledheadbolt.
(Slide14)
ANNumberExample
•Imageisoftwobinsofsimilaraircraftbolts,withslightlydifferentpartnumbers
•Whatdothepartnumberstellusaboutthesebolts?
•Whatisthedifferencebetweenthesebolts?
•Whichwouldyouselectifyouneeda1.5inchbolt?
Answer:
AN4-12A
•AN=manufacturedtoAirForce–Navyspecs
•4=diameteroftheboltshankin1/16"
increments,so4/16=¼
inchdiameter
•-12=thelengthoftheshankin1/8"
increments,so12/8=1.5inchlength
•Ameanstheshankoftheboltisundrilled(noletterheremeansadrilledshank)
(Slide15)
BoltSizing
∙
Thisisthegriplengthoftheboltanditismeasuredfromtheunderneathportionoftheheadtothebeginningofthethreads(seeFigure3below).
(Slide16)
∙Thegriplengthshouldbeequaltothematerialthicknessthatisbeingheldbytheboltorslightlylonger.
∙Awashermaybeusediftheboltisslightlylonger.
∙Apieceofweldingrodorsafetywirecanbeusedtomeasurethelengthofthehole
(Slide17)
Torque–BoltInstallation
∙Itisimportanttonot"
overtighten"
or"
undertighten"
aboltorthenutattachedtoabolt.“Undertorque”or“undertightening”resultsinexcessivewearofthehardwareaswellasthepartsbeingheld.
∙Overtighteningmaycausetoomuchstressontheboltornut.
(Slide18)
∙Thebestwaytoavoidthisistouseatorquewrench(Imageoftorquewrench)
∙AC43-13presentsatableoftorquevaluesfornutsandbolts.Itshowsfinethreadandcoarsethreadserieswithaminimumandmaximumtorquelimitininchpounds.
∙Imageisofatorquewrench
(Slide19)
BoltInstallationSummary
∙Certainacceptedpracticesprevailconcerningtheinstallationofhardware.Afewoftheseregardingboltinstallationsfollow:
1.Indeterminingproperboltlength-nomorethanonethreadshouldbehiddeninsidethebolthole.
2.Wheneverpossible,boltsshouldbeinstalledpointingaftandtothecenterofanairplane.
3.Useatorquewrenchwheneverpossibleanddeterminetorquevaluesbasedonthesizeofbolt.
4.Besureboltandnutthreadsarecleananddry.
5.Usesmooth,evenpullswhentightening.
6.Tightenthenutfirst-wheneverpossible.
7.Atypicalinstallationincludesabolt,onewasherandanut.
8.Iftheboltistoolong,amaximumofthreewashersmaybeused.
(Slide20)
9.Ifmorethanthreethreadsareprotrudingfromthenut,theboltmaybetoolon
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