i\hlX. Timc: 3 hrs,

Dr. Babasaheb Ambedkar Technological University, Lonel'cScmcstcr Examination (Mlly2017j IC- b0 QVI Scmcstcr B, Tcch. (Mcchanical) ~'\ C __JSubjcct: Machinc Dcsign - II

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I!\'STRUCTIONS: l. Quc.! is COMPULSORY, Attempt any FIVE questions out ofthe remaining preferably in the order they are appearing.

2. Necessary data is given in the rcspective questions, If stich a data is not given, itmeans that the knowledge of the data is a part of the examination,

3. Make suitable assumptions if necessary and statc them clearly giving reasons.

Max. Marks: 70

Quc,!: Choose the appl'Oflriatc answcr for the fL)llowings: (10)/I) Cold lIorking ...I) increases l'lliguc strength 2) decreases f,Higue strength3) has nll influence on fatigue strength .+) nOllL'l,f the abol'c

number of teeth on gear = 70, center distance = 285 mm, normal module = 5 111m

bce width = 50 mill, n;,rmal pressurc angle = 20°, ultimate tensile strength = 600 N/mm'

surf'ICl' hardness = 300 BIIN, grade of machining = 6, service f'lctor = 1,25

Calculate i) helix anglc ii) the beam strength iii) the wear strength i,') the stalic load I)

the dynamic load by Buckingham's equation vi) the cfrective load vii) the eflcL'li\e I'lctor

of safety against bending I~,ilure viii) the effective factor of safL,ty against pilling Llilure,DATAThe error IL)rgrade 6 is given by e = 8.- o 63<1Jwhcre tlJ = m" ,. 0.2:' /;/I.ellis forlll f'lctor is givcn as bel(lII

, "io, of teelhy

~..:. A) What data is required fi,r selecting a flat belt from manuf'lcturer's cat,i1nguc'.'

B) A !lat open belt drive transmits 15 kW power. The driving and driven pulln mt"lL's at

1,140 rpm and 480 rpm respectively, The center distance bct\lt'en the pulleys is twicL' tile

d'al11':\':r 01' bigger pulley. Th~ belt should operate at :l velocity of 20 m/s appro.sill1'ltC!:,

and stress in thc helt should nut exceed 2.25 :'\/mm', The (knsitl of leather is O.l)S gm/cc( ,

"and the cocl1icient of friction is 0.3:'. The thic~ness "I' the belt is 5 mll1. calculate

b) The length and lI'idth oj tlw Iwll

C) Ir a ball bearing is coded by 6310 then, bore diamcter of bearing is ...I) 40 mm 2) 30 mm 3) 50 nlln 4) (,0 mm

4) crushing

.+)20

3) hL'nd ingE) Type of failure occur in ball bearing isI) shear 2) j~,tigue

F) The spur gear arc used f~)r thL' gc"r ratio up to1)6 2)2 3)10

D) A ball bearing sustain a radial load of 3(,72 1\. the diamcter of thL' hearing is60 nlln and its length is 90 mm, Diametral ckarancL' is 0.1 ll1ll1and shalt rotates at450 rpm. If oil vis;osity is 0.06 kg/m-s thel;. the value of Sommerfeld no is ..I) 17 X 106 2) 14.3 X 106 3) 15.3 xlO" 4) 16.3 x10"

B) ;"vlaximum strL'SS concentration f:'1Ctor for a rectangular plate with a IransvL'rsehole loaded in tension and compression is ..1)2 2)3 3)2:' .+) I

(OJ)

What is load correction factor IL)[ !lat belt?

OR

A) What is the flolygunal action in roller chain'.' 11011'will you reduce it'!

a) The diameters of the pulleys

c) The belt tensions

13) It is required to select a flat belt drive I('r a l"ln running al ~(,() rpll1 IIhicl] is dril'L'1l

bv 10 kW, 14.+0 rpm motor. The belt drivc is open type "nd spaeL' alailahk f,'l' a L'L'nlrc

distance of 2 m approximately, The belt \docity should be betvwcn 17.8 to 2) -') III s. lile'

power transmitting capacity of belt per mll1 \\'idth ply at IRO"arc oj contact and at hL'lt

velocitv of :'.OR m/scc is 0.0 J 1S kW. Th" load correction e"clo,' can hL' ta~L'n ,to 12.

Suggest preferred diameter of motuI' "nd fau pulleys and gill' completion spL'Ci fication "f I) Fabric belts arc used in industrial applications because ...I) may be cheap 2) thev can \\Ult at high tL'mpcrature3) they are unaffected by moisture and humidity 4) none of the ab'lI'e

G) Wear strength of gear can be improved byI) Increasing BHN 2) increasing endurance limit3) increasing S" 4) increasing compressive ,trcngth

bL'iting. (II7)

II) Which is positile drive')I) !lat belt drive 2) V belt drive 3) crossed helt dri,'c .+) limint( belt

&&&&&&&&&&&&%%%%%%%%%&&&&&&&&&&&&&& .I) Which is incorrect relationship lilr gears'.'

4

B) Following data is given for full hydrodynamic bearing.

Que.2: A) What is Jaw cycle fatigue? Give practical example of low cycle fatigue~ (03)

B) Explain why surface finish factor decreases as ultimate strength of the component

the life of the shaft. (DATA: for given shaft-surface finish factor K, = 0.79, Size factor

Kb = 0.75, reliability factor Kc = 0.897) (07)

Que.3: A) Det~ne static and dynamic load carrying capacity of the roHer bearing. (02)

B) A baH bearing subjected to radial load of 5 kN, is expected to have a life of 8000 hI' at

1450 rpm with a reliability of 99%. Calculate the dynamic load capacity of the bearing.

so that it can be selected from the manufacturer's catalogue based on reliability of 90%.

(05)

C) A single row deep groove baH bearing is subjccted to radial force of 8 kN and thrust

force of 3 kN. The value of X and Y factors are 0.56 and 1.5 respectively. The shaft

rotates at 1200 rpm. The diameter of shaft'is 75 mm and bearing No. 6315 (C= 112000

N) is subjected for application.

i) Estimate life of bearing with 90% reliability.

ii) Estimate the reliability for 20,000 hI'Sof life. (05)

Que.4: A) State the function of bearings. Compare rolling and sliding contact bearings.

(05)

00-107

Journal speed = 900 rpm

Viscosity of lubricant = 20 cP

+35

-72

es

100H7

100e7

Radial load = 25 kN

Unit bearing pressure = 2.5 MPa

Class of fit = f-he7

The tolerances are as follows.

flows are given in following table.C) E: C~o) s </J (~y Cc~J (~) (p~JI

0 1.0 00 85 00 If 0 .0.1 0.9 1.33 79.5 26.4 3.37 o 150 0.5400.2 0.8 0.631 74.02 12.8 3.59 0.280 0.5290.4 0.6 0.264 63.10 5.79 3.99 0.497 0.484

I 0.6 0.4 0.121 50.58 3.22 4.33 0.680 0.4 I5,0.0446 36.24 1.70 4.62 0.842 0.3130.8 0.2

0.9 0.1 0.0188 26.45 1.05 4.74 0919 0.2470.97 0.03 0.00474 15.47 0.514 482 0973 0.1521.0 0 0 0 0 0 I 0

Calculate a) Coefficient of friction b) Minimum film thickness c) Requirement of oil

Where es and ej are upper and lower deviations in microns.

The dimensionless performance parameters for full journal bearing with side

flow ._ (07)

Que. 5: A)' What ~re effects of increasing or decreasing pressure angle in gear design? (02)

B) What is dynamic load? What are its causes in gear drive. (02)

C) It is required to design a pair of spur gears with 20° full depth involutes teeth based on

Lewis equation. The velocity factor is to be used to account for dynamic load. The pinion

shaft is to be connected to a 10 kW, 1440 rpm motor. The starting torque of motor is

150% of rated torque. The speed reduction is 4: 1. The pinion as weH as gear is made of

plain carbon steel 40C8 (Sut = 600 N/mm2). The factor of safety is 1.5. Design gear and

suggest suitable surface hardness for the gears. (08)

[NOTE: Minimum no. of teeth for 20° pressure angle is 18, Lewis form factor =0.3081.

Que.6: Following data is given for a pair of parallel helical gear made of steel: (12)

power transmitted = 20 kW, speed of pinion = 720 rpm, number of teeth on pinion = 35

(02)

t

2) Module = (PCD/No. ofteeths)4) Addendum ,,, 2.157 x module

Bearing length = 100 mm

.66

0.10.05

2.05

0.025

2.6

Journal diameter = 100 mm

I) Circular pitch x diamctral pitch = rr3) Dedendum = 1.157 x module

increases?

from the foHowing table values.

C) The section of shaft is shown in Fig. I. The shaft is machined by turning process. The

section XX is subjected to constant bending moment of 500 KN-nl. The shan material.

has ultimate tensile strength of 500 MN/m2, the yield point of 350 I'lilN/n/ and endurance

limit in bending for a 7.5 mm diameter specimen of 21 0 MN/m2 The notch sensitivity

factor can be taken as 0.8. The theoretical stress concentration factor can be interpolated~)(

(~ t ~~g,.,,,,_.1 _4SlJ "'", _ ~nn••••, .

.1-

l4 X F'9Lf~e."

Where '1'1" is fillet radius and 'd' is diameter of shaft. The reliability is 90%. Determine

. : •.•.•. 2 3