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S/2020/6262
Total Pages : 2
Sixth Semester
Mechanical Engineering
Seventh Semester
PTDC Mech.
Scheme July 2008
DESIGN OF MACHINE ELEMENTS
Time : Three Hours
Note : i)
Maximum Marks : 100
Attempt any five questions.
{H$Ýht nm±M àíZm| H$mo hb H$s{OE&
ii) In case of any doubt or dispute, the English version question should be treated as final.
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1. a)
Explain in brief the general procedure in design of machine element.
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b)
Design a cottor joint to connect a piston rod to cross head for the maximum load on the piston rod 35kN.
Assuming all the parts are made of carbon steel having the following.
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Permissible stress. Tensile = 50 MPa;
Shear = 55 MPa; Crushing = 90 MPa
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^ma 35 {H$bmo ݶyQ>Z hmo& g^r Ad¶d H$m~©Z ñQ>rb Ho$ ~Zo h¢ {OZHo$ {b¶o gwa{jV à{V~b H$m ‘mZ {ZåZwgma h¢
VZZ = 50 ‘oJm nmñH$b; Anê$nU = 55 ‘oJm nmñH$b; H«$qeJ = 90 ‘oJm nmñH$b >
2. a)
Define the terms pitch; back pitch; diagonal pitch; and marginal pitch regarding riveted joints.
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b)
3. a)
Find the efficiency of the double riveted lap joint of 6mm thick plates with 20mm diameter rivets having a
pitch of 65mm. Assuming permissible tensile stress in plate = 120 MPa and permissible shearing and
crushing stress in rivets as 90 MPa and 180 MPa.
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6 {‘‘r. ‘moQ>mB© H$s ßboQ> ‘| 20 {‘‘r. S>m¶m‘rQ>a Ed§ 65 {‘‘r. {nM Ho$ [adoQ> H$m bon Omo‹S> H$s XjVm kmV H$s{O¶o
¶{X ßboQ> ‘| gwa{jV VZZ à{V~b = 120 ‘oJm nmñH$b VWm [adoQ> ‘| gwa{jV Anê$nU Ed§ H«$qeJ à{V~b H«$‘e…
90 ‘oJm nmñH$b Ed§ 180 ‘oJm nmñH$b hmo& >
Enlist the welding processes and write the advantages of welded joints compared to riveted joints.
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dopëS>¨J {d{Y¶m| H$s gyMr ~ZmB¶o Ed§ dopëS>¨J Omo‹S> Ho$ bm^ {b{I¶o&
b)
4. a)
A 12.5mm×50mm plate carries a static tensile load of 45kN. If it is welded by two parallel fillets of 25mm
each. Find the shear stress in the joint take factor of safety 1.5.
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12.5 {‘‘r. × 50 {‘‘r. H$s ßboQ> na ñW¡{VH$ VZZ ^ma 45 {H$bmo ݶyQ>Z h¡& Bg ßboQ> H$mo Xmo g‘mÝVa {’$boQ> doëS> go
à˶oH$ 25 {‘‘r. H$s bå~mB© Ûmam Omo‹S>m OmVm h¢& Omo‹S> H$m Anê$nU à{V~b kmV H$s{O¶o& gwajm JwUm§H$ H$m ‘mZ
1.5 h¢& >
Explain the function of key and give the classification of keys.
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Mm~r (H$s) H$m H$m¶© g‘PmB¶o Ed§ BgH$m dJuH$aU Xr{O¶o&
b)
Find the diameter of a solid shaft to transmit 20kW at 200 rpm. The ultimate shear stress for the steel may
be taken as 360 MPa and a factor of safety as 8.
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200 M³H$a à{V {‘ZQ> na 20 {H$bmodm°Q> e{³V g§MaU Ho$ {b¶o ñQ>rb emâQ> H$m ì¶mg kmV H$s{O¶o O~{H$ ñQ>rb H$s
ApëQ>‘oQ> H$V©Z à{V~b 360 MPa VWm BgHo$ {b¶o gwajm H$maH$ 8 hmo&
S/2020/6262
P.T.O.
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5. a)
Explain the working principle of any one type of clutch with the help of neat sketch.
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b)
For a single plate clutch both surfaces working have inner and outer radius 160 mm and 240 mm respectively.
Maximum pressure it can carry is 0.35N/mm2 and co-efficient of friction is 0.29 find the power transmitted by
the clutch at 1900 rpm.
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EH$ EH$b ßboQ> ³bM {OgH$s XmoZmo gVh {H«$¶merb h¢ H$s Am§V[aH$ Ed§ ~mhar {ÌÁ¶m H«$‘e… 160 {‘.‘r. Ed§ 240 {‘.‘r.
h¢& ¶h A{YH$V‘ 0.35 ݶy./{‘‘r2 Xm~ gh gH$Vr h¡ Ed§ BgH$m Kf©U JwUm§H$ 0.29 h¢& Vmo ³bM Ûmam 1900 M³H$a
à{V. {‘ZQ> na nmao{eV e{³V kmV H$amo&
6. a)
b)
Explain “Bearing characteristic Number” and its effect on performance of journal bearing.
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Select a single row, deep grove ball bearing for a radial load of 4200 N and axial load of 5000N. Operating
at 1550 rpm for an average life of 5 years at 8 hours per day. Assume uniform steady load.
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EH$b H$Vma Jham J«yd ~mb {~¶[a¨J H$m MwZmd H$s{O¶o ¶{X ao{S>¶b ^ma 4200 N Ed§ Ajr¶ ^ma 5000N h¢& ¶h EH$
g‘mZ ^ma na 1550 M³H$a à{V. {‘ZQ> na H$m¶© H$aVr h¢. BgH$s Am¡gV Am¶w 8 K§Q>m à{V{XZ H$s Xa go 5 df© h¢&
7. Write note on any four of the following :
a) Types of threads
b) Factors affecting selection of materials
c) Classification of clutch
d) Wahl’s factor
e) Bolt of uniform strength
4×5=20
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A) My{‹S>¶mo§ Ho$ àH$ma
~) nXmW© M¶Z H$mo à^m{dV H$aZo dmbo H$maH$
g) ³bM H$m dJuH$aU
X) dmëg ’o$³Q>a
B) g‘mZ gm‘϶© H$m ~moëQ>
Y
S/2020/6262