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MIICHANICAL INGINIIIIIUNG 'iTtii1~;y;'ii1g f:;{Ji~l?::tri~l?::tri~l?::tri~l?::tri~.~~~;~'~i~~;~'~i~~;~'~i~~;~'~i~~;~~lit{~lit{~lit{~lit{~lit{~li{ltigfi;~gfi;~gfi;~gfi;~gif~r;;~'~r;;~'~r;;~'~r;;~'~r;;~;i:m:f~lf~i:f~lf~i:f~lf~i:f~li~'t~.:t:i·ttt·~~~J.~!t:r:w.:t:i·t~li1~;y;'ii1giriN~::!: !l

PAP~ft ..... U Time Allowed: 3 Hows MaxiltuunMarks: 300

Cl>ndzllalss shoold ansmpt quJlSiion.s 1md 5 wltidt on compulsory and my litre• of lit• remt1mi>1g tpMiions seloclio>u!tloo.st on• tpMiion sslsctmg at Is art on• qusstionfrom oodt S•ction. ~

!f my data is considored insujfidmt, assum• suitabl• •a/us. Jlkwton may bB con .. n..d to Iff using lit• equt1li '"'"'

2.

(1 kN) = 100 Iff, if found n•.,.,..,.

SEC110NA 0 Answer any three of the followmg ~

(a) The ball b eanngs are to be selected for an apphcatton tn whtch the tall o,ad 1 s 2 kN dwmg 9 0 per cent of the ttme and 8 kN dunng the remauung I 0 per cent • shaft 1 s to rotate at

(b)

150 rpm. Determine the minimum value of the basic dyn~ $ ing for 5 00 0 hours of operation with not more than I 0 per cent failures. , "-/

The figure given below shows the state of stre~oamely 30 N/mm2 tensile in~~ direction. 20 nlmm2 tensile in Y·direction and s tress of 50 N/mm2

. Find the location of the principal pi anes, princip a! stresse~ , e aximwn shear stress graphically or otherwise.

20

:!0 /rnm2

30 N/m 2 50 N/mm~

30 Nlm~~W::7f 1-+430 Nlmm•

0 + 50 1'1/Mm j 20 Nl mm2

(c) (i) formula for increase in volwne of a thin metallic sphere when it is subjected

(d)

(a)

em a! pressure p.

· A thin spherical shell of copper has a diameter of 4 00 mm and a wall thickness of 2

pwnped in to raise the inside pressure to 1.5 N/mm2. The modulus of elasticity for

copper is I x 10 N/mm2, K (Bulk Modulus) is 2.5 x 10 N/mm2 and Poisson's ratio is 0.25.

20

What are the defects developed by the components of steel of any machine during heat treatment operation? Give the causes for such defects and explain the remedies taken.

20

A machine of mass 6 8 kg is mounted on springs of combined stiffness k II 0 0 N/mm with an assumed damping factor of 0, 2. A piston within the machine of mass 2 kg has reciprocating motion with a stroke of75 mm and a speed of 3000 rpm. Assuming the motion of the piston to be simple harmonic, determine

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(i) the amplitude of vibration of the machine

(ii) the phase angle with respect to the existing force and

(iii) the transmissibility and the force transmitted to the foundation.

30

(b) A punching press is drived by a constant torque electric motor. The press is provided with a flywheel that rotates at a maximum speed of 2 25 rpm. Radius of gyration of the flywheel is 0.5 m. The press punches 70 holes per hour; each punching operation takes 2 seconds and requires 15 kN -m of energy. Find the power of the motor and the minimum weight of the flywheel if the speed of the same is not to fall below 2 00 rpm.

3. (a)

(b)

4. (a)

What are cerarni cs ? How are they classified?

(he Explain (a) Silicates (b) Vitreous structure

Sheet structure as applied to engineering materials.

(c) Explain the various alloys of copper giving the details of composition of each alloy.

SECnONB 5. Answer any three of the following:

20

20

(a) The assembly line for small tricycles has the following work elements identified and the sequence indicated

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(b)

Work element

A

B

c D

E

F

G

H

J

Immediate Predecessor of the work element

Nil

Nil

B

A,C

D

D

E, F

E, F

G,H

Work element lime (in minutes)

5

3

3

2

2

3

5

8

For the above ~ + (i) prep are the precedence diagram.

(ii) using He! geson and Birnie or any other heurisrm~ show a feasible grouping of the work elements and number of worfl>kta · o~ng that the cycle time of one assembly is 8 minutes.

(iii) cal cui ate the balance-delay for your · m .

20

e and f shown in the typical spec· atiot · lustration given below represent?

flj 20

;f! : ·:· Also i~:!alues of surface roughness represented by the following triangles

20

p1 ess was set to produce rivets of I 0 mm length. The first 3 2 pieces made by the process wer e found to have the following lengths (in mm)

9.9, 10.0, 10.0, 9.9, 9.9, 9.9, 10.0, 10.0, 10.1, 101, 10.0, 10.0, 9.9, 101, 10.1, 9.9, 9.9, 10.1, 10.0, 10.1, 10.0, 9.9, 9.9, 9.9, 101, 10.0, 10.0, 10.1, 10.0, 10.0, 10.0,

(i) PI ot X and R control chart for the process, taking data for A2, D3 and D, from the following table

No. of observation! in the sample 2 3 4 5 6

A. '

l.BS 1.023 0.729 o.sn 0.'183

Da 0 0 0 Q 0

D4 3.276 2.575 2.282 2.115 2.~

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7.

8.

(d)

(a)

(b)

(a)

(ii) If the process is not under statistical control, discuss what steps should be taken to make the control chart viable?

20

A ball at the end of a very long pendulum can be assumed to move linearly between two metallic plates at a fixed distance apart. The inner distance between the plates is slightly more than the diameter of the pendulum bob which is spherical leaving clearance on the left or on the right. If the pi ates move in simple harmonic motion, the amplitude being very small, the bob may touch the left or the right side plate or it may not touch any, at any instant. If the bob touches the left pi ate, equation A is governed while if it touches the right plate, equ~· B is

Write a flow chart in FORTRAN for the motion of the bob. governed. If there is no contact by the bob on any of the plates, then equation~ c· s <! ve · . d.

20

(i) What are the advantages of laser beam machining in respect of the~g at erial removal mechanism, energy source, Energy transfer media, llutl':~~nt, power, gap and applications.

15

(ii) What is high energy rate forming? Discuss the the~Jtenergy metal fanning.

how nine degrees of these freedoms can be r~ · e the help of 6 pins. How are the remaining three degrees of freedom res~~ h iling the work -piece for machining?

3 0

In a stop watch time study, the actu~ad1 in minutes recorded for an element are

0.05. 0.06. 0.05. 0.05. 0 0~~ 0 0.06. 0.05.

0.06. 0.06. 0.06. 0.06. ~ 05. 0.06. and 0.05.

(i) Have sufficien~um o adings been taken for 95% confidence level and± 5% accuracy?

(u) If the ra~20K', at would be the normal time for the element?

(111) What w ~11th~ standard ttme for the element tf the personal needs allowance, fatigue a! ~e and contingency allowance are 5% 6% and 5% resp ectl vely?

(tv)~ts th4 purpose of provtding contingency allowance? Gtve two examples

30

(b)~ d or a newly mtroduced luxury car has been shown below The experts forecasted . s . of roo cars for the month of March. Wtth a smoothmg constant of 0.15 and ustng first

ponential smoothing what is the forecast for the month of August? Also cal cui ate D and Bias and give your comments on the same:

(a)

Month Actual Demand

March 150

April 200

May 100

June 50

July 150

30

Distinguish between the situations where transportation models and assignment models may be used.

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(iii) Net brake load applied at brake wheel having an effective circumference of 3. 86 m is 126 0 N at average speed of 2 27 r. p.m.

(iv) Number of explosions/minute= 77.

(v) Gas used/mt at 771 mm of mercury and 15 °C = 0. 217 cum

(vi) Lower calorific value of gas at NTP 49350 kJ/m3

(vii) Mean effective pressure from indicator card = 7. 5 bar

(viii) Weight of Jacket cooling water/mt = II kg

(ix) Temperature rise of cooling water= 34.2 °C

(x) Specific heat of water= 4.2 kJ/kg °C

4. (a)

5

(b) How do

(u)

(iii) Show that total head pressure

30

Po, [ u( C2, G1 -Po-, = I+ r,>.....l:~~;.t&":o;;~--~~~

The notae,nhe usual meanmg

+ SECnONB Answer~ e follo1Mng parts (Answer to each part should not exceed 200 words)

(a) ~e rms capacity rat1o, effectiveness and number of transfer uruts Denve an x e s1on for effectiveness for a parallel flow concentnc heat exchanger m terms of cap ac1ty

Njo d number of transfer un1ts

20

What are the harmful environmental effects of conventional refrigerants? Name any one eco­friendly refrigerant wh1ch 1s bemg commercially used and discuss 1ts Important characteristics

20

(c) With reference to air-conditioning practice, explain the difference between human comforts and industrial air-conditioning pointing out the various parameters in each of these applications. Give suitable examples. Sketch and discuss a comfort chart.

20

(d) Explain the essential distinguishing and relative merits and demerits of Boiling Reactor and Pressurized Water Reactor used in nuclear power plants. How is nuclear waste disposed off?

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6. (a)

(b)

(c)

7. (a)

(c)

20

A mixture of air and water vapour at 1.01325 bar. l6°C has dew point of 5°C. Calculate the relative humidity and specific humidity.

20

A refrigerating plant of I 0 kW capacities operates in the quasideal vapour compression cycle. The refrigerant is R 134 a The saturation temperatures in the evaporator and condenser are respectively -20°C and 40°C. The plant includes a heat exchanger in which the saturated liquid leaving the condenser is sub cooled to 3 0°C by the saturated vapour leaving the evaporator. The sub cooled liquid is then throttled to -20 °C before entering the e and the vapour leaving the heat exchanger is compressed isentropi cally to th pressure. Sketch the schematic diagram and the cycle on p-h and T-s diagr · the important point. Cal cui ate the mass flow rate of the refrigerant and p oV!.rP to to the compressor. The mechanical efficiency of the compressor may be compressor used by the plant is a single-stage single-acting recipro catin stroke-diameter ratio of 1.2 and a speed of 240 rev/mm. Asswnin com efficiency to be 8 0% determine the di arneter and stroke of the com pre 1or.

Properties of refrigerant maybe obtained from table below:

t 1',

-:10 1.32611

40 11).165

Enthalpy

kJ/kg Enlwopy kJ/kg-K

m'!loa . L~i<l I VaP"ur Ltq~~!d i i

0.14141ll:UI2 \3116..66 O.Ol~9 ;256.SS; 419~

: ;

•

o.aos.

1-12

35

A ~••• "'""'.''~'...~ bo im<ollod • Dolhl 00< "'"" m offi~ bWldiog dwing the swnmer seas . av :.ra;,out 0 f the plant and explain the various processes on a skeleton psychometri

In a concentric , ""· exchanger, cold water is heated by the heat released by the ste~ condens~ti . n. ~enters the tube at 10°C and leaves at 50°C. The steam pressure is maintained I. Ql.32 5 bar (atmospheric). If the I ength of the tube is increased to 3 times, wha~. w e the outlet temperature of water? Asswne overall heat transfer coefficient re "" onstant for both the cases. Specific heat for water may be asswned to be 4187

J <1-

15

respectively. The rod has the perimeter P and its cross-sectional area A. The rod loses heat to the environment at temperature, t,. The convection coefficient of heat transfer between the rod and the environment is h. Assuming the thermal conductivity of the materia! of the rod to be constant k, derive an expression for (i) the temperature distribution in the rod and (ii) the heat transfer from the rod to the environment.

15

The total emissivity of clean chromi wn as a function of temperature T K is approximately gtven as

C= 038(1-2:

3)

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Obtain an expression for the absorptivity of solar radiation as a function of surface temperature. The intensity of solar radiation at earth's surface may be calculated from the following data:

Diameter of sun 1.39 x I 06 km

Surface temperature of sun= 60 0 K.

Distance between sun and earth= 14 9 x I 06 km