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n NATIONIT, U}TIVERSITYOFSINGAFORE
ME2II4 _ MECH.ANICSOF MATERIALS tr
(S€me$erII: AY2005-2006) TitDcAllos€d: 2 Hours
INSTRUCTIONSTt) CANDIDATES: l.
This €xaminationpapcrcontairsFOIrR (,1)questids atd cllnpris€sSX (6) priniad p6ges-
2.
Answrr all FOI,R (4) qu6tids.
3.
All quGtionscary cqld |rla*s.
4.
This is a CLOSEDE(X)X EXAMINATION.
Prgc 2
ME2l 14
ForEulre Th€follo*ing formula€witten usingslandardrDtationsmaybeus€d. Yield Crirerir: (l)
Tr€scaYield Critorion
'* =tG*-".")=? l _
@
Von MiscsCriterion -
/jk",
-",f * (", - o3f* (o3- o,f ]=o"
Strrir GDcrgreq!.tiorri Axial loading:
u=tI1o* 2EA 6
Bending:
u=t!4a, 62Er
Torsion:
L12 U= 'o2CJ l-:-d(
CoDstitotiv. rchtioD! for itoiropic cb.tic m.ted.b3
"-=+G-!o,
-*-)
",=iG, -u"-) ' . = j ( o . - n o , -.,--) ' t n = IE r n , f o = le r , ,
e=--!-
2Q+v)
l
r-=6r.
Page3
ME2l14
OuestionI A cylindricalprcssurevessel250mm irmerdiameterand5 mm wall thicknessis subjectedto an internalpressueof2.5 MPa.Thecylinder,which is cquippedwith two rigid endplates,is andthe weldedseamsare inclin€dat 125"to rhe longitudinal butt-weldedcircumferEntially axis asshownin Figurc l. Ifan axial comprcssivcloadof50 kN is appliedto ih€ endplates, usinstheMohr's circledetermine (a)
the str€sses at the weld.Indicateyoor resultson a sketchshowingbothdirectionalld magnitudeofthe slesses,and (15nark)
(b)
tbemaximumin-plarcshea.ingsf€ssin rhecylind€r.
(1 nmrks)
wouldyou expectthe maximumin-planesherring loadis increased, Ifthe axial compressiv€ or decrease? Explainrfiy. stressin the cylinderto incr€rse (6 narks)
Rigid endplates
Wddlines Figrre I
ME2lt4
Pagc4
Ou€stiotr2 Figure2 showsa pin-connect€d steelfame madeup of circularcross-section memberswhich havea feld stressin compression of200 MPa.MembenAC andBD ar€of30 mm diameter andmembersAB andCD areof25 mm diameter.Whenihe tumbucklesare tightened,the diagonalsAD andBC arein tension. (a)
If memberBD is loadedby a verticalforceof500 N, andassuminga factorofsaf€ty of 1.5,determinethe maximumallowabletensionthatcanb€appliedto diagonalBC. AssumeE=200GPa(15narks.l
o)
Ifa largehorizontalforceF (indicaredby the dottedline) is alsoappliedon member AB in the direcrionshown,would it resuhin rhe bucklingof memb€rAB? Explain why. 6 narks)
(c)
Stalelhe assumptiorsmadein the derivationofthe Eulerformula(you do not needto derivethe Eulerformulaused). (5 narks)
500N
J E
<....--..-. F
Tumbuckle
4.5
c
D
#,
77 3.05|n Figure2
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