In making tension tests, the slippage of the joints was noted at three points across each joint. In addition, stress strain curves were obtained for plain tension specimens, and a chemical analysis was made of the sheet

Rettew, H F

Thumin, G

English

NASA Technical Reports Server

..
l
. .
TE(H31iIWLNOTES
NATIONALADVTSORYCXXYMITTEEFORAERONAUTICS.
\
NO.165
,.
.
-—
TESTSONRIVETEDJOINTSIN SHEETDURALU’MIN.
By H. F. RettewandG. Thtiin,
MassachusettsInstituteof Technology.
Abstractedand revj.sedby J. G. Lee.
November,1923.
.
https://ntrs.nasa.gov/search.jsp?R=19930080960 2020-03-17T04:13:53+00:00Z
..
a NATIONALADVISORYCOMMITTEEFORAERONAUTICS.
TECHNICALNOTENO-165.
TESTSON RIVETEDJOINTSIN SHEETDURALUMIN.*
~ H. F.RettemandC. Thumin.
Introduction~
Thefollotvingnotes weretaken froma thesisby H. F.Rettew
andC. Thumin,presentedin June,1921,to theDepartmentof Mechan-
icalEngineering,of theMassachusettsInstituteof Technology.
.
Theoriginalthesisconsistedof twenty-sixtensiontestson
variousformsof single–rivetedlap-jpints.Threethicknessesof
duraluminsheetwereused:
. .02011and .040[1heat-treated,and .095tI
annealed.Thematerialwasfurnished,mostof therivetingwasdcne,
.
andadviceandassistancemerefreelygivenby theEngineeringDivis-,
icnof theArmyAir Service.Inmakingthe tests,theslippageofLo
thejointswasnotedat threepointsacrosseachjoin’t-Inaddition,
stress-straincurveswereobtainedforplaintensionspecimens,and
a chemicalanalysiswasmadeof the sheet.No analysiswasmadeof
therivetswhich,incidentally,wereannealeduraluminwithheads
formedbeforeriveting.
ResultsandCoi~clusions.
Themastsurprisingresultsof theworkweretheunusuallyhigh
. values.ofcrushingand shearfoundto exist. Thesevaluesarenearly
.m- doublewhatisordinarilyfoundin shearor compressiontests,and
* Abstractedandrevisedby J. G. Lee.
.-
*2-
4.
* areapparentlydue tothefrictionof therivetedplatesandthere-_
enforcementof therivetheads. Sincethisfrictionandreinforce-
* mentisnecessarilypresentin allgoodrivetedjoints>thehigh
strengthvaluesmayproperlybe usedindesign-
.
Followingarethevaluesforrivetedjointsinheat-treateddur-
aluminsheet:
suggested
Commercial T’,aluesfrom valuesfor
values Rettew& Thumin designof joints
lb/sq.in. lb/sq.in. lb/sq.in.
Tearing (ft) 55,000 54,000 50,000
Crushing(fc) 45,000 105,000 100,000
Shear (fs) 25,000 43,000 40,000
Therecommendedvaluesfortearingand shearfallbelowallof*
theindividualtestvaluesfound
, specimensof crushing,wherethe
muchas 5%belowtherecommended
‘-l
by RettewandThumin,butcertain
variationwasmuchlarger,fellas
valueof 100,000lb/sqtincNever-
theless,100,000lb/sq~in.appearstobe a reasonablysafeaverage
figure. “
Fromtherecommendedvaluesa charthasbeenplQtted(Fig<1)
.. basedon thefollowingformulasforrivetfailure:
Shearing
. F = nd2fs/4= 33.,400d2 forsingleshear
F= nd2f~/2= 62,800d2 fordoubleshear
Crushing
F = t~fc= 100,000td
.
Tearing
*- F = (p-d)tft = 50,000t(p-d)
.i -3-
+ Critical Rive%Diameter
100,000%d = 31,4~ da
DoubleShear d =
CriticalPitch
d=
t =
P=
d= 3.2t
1.6t
50,000t(p-d]= 100,000td, p = 3 d
Fordoubleri.ve~ing,50,000t(p-d)= Z(100,0OOt~),
P =5d
Fortripleriveting,similarly,p = 7 d
drivendiameterof r5vet
thicknessof plate
pitchof rivets,on centers
It is ~od practicetohavethelapfrom2.5 to 3d andthedis-
tancebetweenrowsindoubleriveting(staggered}fromI to1.5p.
In readingthechaztoneusually~tartswiththeplatethick-
-.
nessandfollowsthatlinealonguntilit intersectsoneor otherof
l
tine shearourves.Thisgivesthecriticalrivetdiazneter.Thenear–
estavailablerivetdiameteriS chosen(pre~erablylarger)andtine
strengthreadoffon thescaleof ordinatesat tineleft,tieofiinate...
of theplateth’iclmesslinebeingusedif therivetdiameteris above
thecriticalfigure,whiletheordinateof theshearparabolais chos-‘
en if’thediameterisbelowthecritioal.To findthepitch,read
downfromthechosendiameter,andtakethenearestconvenientpttch
(largerthanthatgivenby thegraph).
Thetensiletestsgavethefollowingaverageresults:
-4-
-
Thickness(inches)
Elongationin 8fi($)
Elongationin211(%)
Yieldpoint(lb/sq.in)
Tensilestrength(lb/sq.in)
Modulusof elasticity
Reductionof area(~) .
Ratioof Y-P.to T.S.
Heat-treated
b020 .040
12.67 -.19:53
14.83 24.25
27,800 26,100
56,530 56,625
~l,~lo,ooo11,020,000
15.33 19.97
.491 .456
Annealed
l095
12.55
17.75
13,750
31,750
9,773,000
34.48
.437
Therivetedjointsinthe .095”annealedsheetshowedthefol-
lowingvalues in lb/sq.in.:
ft= 32,700 fs = 42,800 fc= 62,300
All of thetensionfailuresbothin therivetedjointsandin
theplainspecimensoccurredas shearalonga 45°plane. Thecrush-
ingfailuresappearedtobe crushingof theplateand,notof the
‘*
rivets,althoughtheplate,beingheat-treated,hasthehigherth~-
reticalstren@hof thetwo. Theshearingfailureswereinstantan-
eouss,as opposedto thegradualdistortionwhichprecededa failure
by crushingor tearing.
Theonlynoteworthyresultof thetestsforslippageof the
jointsis thatin allcasesa redistributionf loadtakesplaceat
thelowerstresses,as is evidencedby thedifferentamountsof slip-
pageat differentpointsalongthejoint. In generaltheslippage
l is smallandunimportant.
d
-5-
Thechemicalanalysesof thethreethicknessesof sheetare
l givenbelow:
Thickness Cu.
.020~i ‘4.21
.040’1 4.04
.095’r 4.16
.
Fe. St. ?&l. Mg.
.41 .26 .40 .82
.38 .23 ‘ .38 .8?
.42 .26 l 39 .82
Remainder,aluminum,
~thods of Test.
Theplaintensilespecimenswere testedin theusualmanner.
Owingto thethir~essof thesheetandto theunevennessfoundin
thesmoothestof metal jaws it was necessarytouse thepeculiar
formof specimenshornin Fig.2. Thenotchescutat theendswere
to receiveplugsfittedintothe testingmachinejaws. Severalof
themorecommontypesof endsweretriedbut failuregenerallyoc-
.I
curredin thejamsuntiltheabovewasadopted.
‘m
Therivetedspecimensweremadewith5 half-inchboltholesin
theend(Fig.3)by whichtheywerecqed intoa pairof special
jawsmadewithoutserrations.Thesejaws,in turn,werefastened
intothetestingmachine.Slippageof thejointwas
/urlngthedist~ncebetweentwoscribedlinesundera
notedby meas–
magnifyinglens.
-a
id
r+
94
W
o
w
02000
g
;
-E
Ca
Mloc)o
o
0.5
1.0
1.5
7n
ft‘5moo lb/sq in f~=40000 l.b/sqin fc=100006lb/sqin
r I I Ii 1 I
— “--——~—i
t <t
---1--
a
.—
I
I
i ~~
I ~
i I‘1
1 .t
-.” 0 1/16 l~g 3/16 1/4 5i;16 3/8 7/16 3./2 9/16M
Drivendiameternf rivets.
Fig.1 Single-rivetedlap joints.
,l .
P
q
&
w
I
“it
u
=.
m=
1
\,
Tnicalrivetedsp~cim~n


Tests on riveted joints in sheet duralumin

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server