Ifa S 2CfD
81. No. B-JGT-K-NFA


:311
MECHANICAL ENGINEERING
Paper-I
ITime Allowed Three Hours Marks 200 I
INSTRUCTIONS
should attempt: Question .Nos. 1 and 5
which are compulsory, and any THREE of the
remaining questions, selecting at least
ONE question from each Section:

All questions carry equal marks.
Marks carried by parts of a question are indicated against each.
Answers must be written in ENGLISH only.
If any data is considered insufficient, assume suitable values and indicate the same clearly.
Unless otherwise indicated, symbols and notations have their usual meanings.
Section-A
..
1. fa) In reference to balancing of recipro­cating masses, define what is 1-Iammer Blow'.
If a mass B is kept at radius b in order to balance the reciprocating parts onlY1 what is the magnitude of the Hammer Blow? What is the effect of
/23 P.T.O.

Hammer Blow on rail wheels? Give the expression for the permissible angular speed so that the wheels will not lift from the rails. 10
A thick-walled steel cylinder having an inside diameter of 150 mm is to be subjected to an internal pressure of 40 NImm 2. Find to the nearest rom the
outside diameter requ.iTed, if the hoop stress in the cylinder wall is not to exceed 125 N /mm2 . 10
Distinguish -between radial follower and offset follower in reference to path of motion of a flat-faced follower-cam mechanism. Draw neat sketches for each of the two. 5
An infmitesimal e!ement of a body subjected to plane stress is found to have the state of stress as shown below:
10 MPa
1 t
Draw Mohr's circle for the above state of stress. What is this state of stress called? 5
What is coordination number? Explain with an example. 5
What is 'polymorphism'? What changes may take place during polymorphic change? 5
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2. Define the phenomenon of interfer-'
ence in mating gears. What is the
method of prevention of this?
A rack and pinion drive has the
following data .

Pinion:
Rack: What is
20 numbers of involute teeth, 120 mm pitch circle diameter and addendum of 6'25 rom
Addendum of 6·25 mm
the least pressure angle
which can be used to avoid interference? With this ·pressure angleJ fmd the minimum number of teeth in contact at a time. 15

Show the controlling force vs. radius of rotation graphs for Porter governor and iii) Spring-controUed governors, and discuss the stability considerations. 10


A machine part of mass 2 kg vibrates in a viscous medium. Determine the damping coefficient when a harmonic exciting force of 20 N results in a resonant amplitude of 12 nun with a period of 0·2 second. If the system is excited by a harmonic force of frequency 4 Hz, what will be the percentage increase in the amplitude of vibration when damper is removed as compared to that with damping? 10


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3. ra) A beam of I-section 300 mm depth with
flanges 150 mm wide and 20 mm thick,
and web 12 mm thick IS simply
supported over a span of 10 m. If the
maximum permissible bending stress is
75 MPa, what concentrated load can be
carried at a distance of 3 m from one of
the supports?

20
rb) Determine the ratio of the maximum shear stress in the hollow shaft to that in the solid shaft for the following data: The two shafts are constructed of the same material and have the same length, and same outside .radius r. The inside radius of the hollow shaft is O·6r. Assume that both shafts are subjected to the same torque. 10
(el Draw the Bending Moment and Shear Force Diagrams for a simply supported beam of span I and a uniformly distributed load of intensity w/unit length acting over the entire length of the span of the beam. 5
An axial tensile load of 100 kN is applied to a steel rod of 38 m.m diameter and 500 mm long. Calculate the change .. in volume of the rod, ifE 200 GPa and v =0-26. 5
4.. ra) What is the purpose of 'annealing' and
'tempering' steel? Explain with the help
of diagram or other diagrams the
cycles and the resultant properties
in steel. 20

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The following data are available in case of a V-belt drive connecting two shafts 1 m apart to transmit· 75 kW at 1200 r.p.m. of driver pulley
Effective diameter of driver pulley
300mm
Effective diameter of driven pulley 900mm Coefficient of friction between belt and pulley O'25 Density ofbelt materi8.1 kg/m3
I .
Angle of groove 40° .. Area of belt section 400
Permissible stress in belt· 2·46 MPa
How many belts are needed?
Can .the driven . be flat? Justify your answer. 10
A simply supported beam of span L
and rectangular cross-section x is loaded by uniformly distributed load of w N/unit .length. If cr max IS the maximum bending stress and A is the
.1, cross-sectional area, then show that the elastic strain energy due to bending of the be given by
cr x volume of the beam)
2E 45 .
Sketch the beam. 10
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Section-B

5. -fa)· How do you define the cutting angles of a single-point tool in International and American system? Show them in the form of diagrams. 10

Which probability distribution is usually associated with PERT and why? Plot this distribution and indicate on it the relevant parameters of PERT. Which other distribution do you think may be appropriate for the purpose? 10


(ij Why does the tool wear during cutting? Enumerate the possible mechanism of tool .wear.

A topl lasted for 45 min before regrind in a milling operation. The cutting speed was recommended to be increased by but it was found that now the regrind was needed after every 20 min on an average. Can you define Taylor's equation valid for this operation, assuming that there is no other change in the system? 5+5


Draw a flow chart to find the torque to be transmitted by a solid steel shaft at a specified speed. Maximum shear stress is to be limited to a specified value. Factor of safety, tensile strength of steel and other parameters can be assumed to be given. 10


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6. Define 'angle of nip' and. 'angle of bite during rolling operation.,. 20

Calculate the neutral plane to roll 250 rnm wide annealed': copper strip from 2·5 mm to 2·0 mm thickness with 350 mm diameter steel rolls. Take

J.l 0·05 and 180 10


What instructions are necessary in typical part programming·for NC or CNC machine tool?


Differentiate between M andT functions.
With an· example, explain the differ.ence between word address format and f!Xed sequential fannat of instructions. 10
7. fa) A manufacturer of plastic parts. uses two machines M-l and M-2 such that each part is processed rust on machine M-l and then on M-2. The manufac­turer has currently 6 orders jobs on hand. The estimated processing times and due dates for these jobs are as given in the table below:

Job Processing time (in days) Due date from now
M-I
A B C D E F 5 4 7 8 12 9 9 6 10 8 9 6 37 41 38 47 52 39

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Determine the optimum sequence in which jobs can be processed to minimize make span. "
What is time? the value of make span
What is the average job tardiness resulting from optimum sequence obtained earlier?
the methodology/algorithm used to get optimum sequence in 10
Majestik Fumitures produces a type of desk that has bill of materials as given in the table below. The desk is made by assembling two two handles (one for each drawer), one drawer frame, and two legs into a drawer module. Then two drawer modules, a desk-back and a desk-top are assembled into the final product (desk)

Level Item description Quantity required Make/ Buy Lead time (in weeks)
00 01 01 01 02 02 02 02 Desk Desk-top Desk-back Leg/drawer module Drawer frame Desk-legs Drawers Handles 1 1 2 1 2 2 2 Make Buy Buy Make Buy Buy Buy Buy 1 2 1 1 1 1 2 2

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Construct the product structure tree for the product (desk).


Construct a production time chart.


For the following desk require­ments, construct the material requirements plan for the desk and each of its components using lot-far-lot procurement assuming no initial inventories

20

What is the difference between an X-chart and an R-chart? Why are they used together? 5


Briefly explain the following assump­tions of linear programming models 5


Proportionality


Certainty




Additivity
Divisibility
8. fa) Write a C program to get required
inputs from an organization to help
them in­
obtaining the break-even quantity for their product(s);
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obtaining profit in rupees from the sale of a specified quantity of product(s), there could also be a loss;
obtaining total revenue figures -at different quantities of sale of their 'product(s).
State the inputs that you would require. Draw a flow chart for the above program. Statements should accom­pany in your program to explain what is being done. ... 20
What is the measurement? measurement reference to method of use. standard of linear Differentiate between and gauging with the application and 10
Tourist vehicles arrive at the security check post at the entry of a wildlife park according to Poisson distribution with an average of 10 minutes between two successive vehicles. For security reasons, the time taken to complete the vehicle checking 8.f:ld issuing of vehicle pass is assumed to be exponentially distributed with mean of 9 vehicles per hour.
Detennine­
ti) the average number of vehicles waiting for the security pass;
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the average time spent by a vehicle in waiting before getting the entry pass;
the probability that a vehicle arriving at the security check post
will have to wait.
State the assumptions made in solving the above problem.

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