N9 001969
IB-JGT..J -NFA I MECHANICAL ENGINEERING
Paper I
ITime Allowed Three HoursI IMaximum Marks: 2001
INSTRUCTIONS
Candidates should attempt questions 1 and 5
which are compulsory, and any THREE ofthe
remaining questions selecting at least ONE
question from each Section.
If any data is considered insufficient,
assume suitable values and indicate the same
clearly.

All questions carry equal marks.
Marks carried by each sub-part ofthe question
is indicated at the end of the sub-part.

Answers must be written in ENGLISH only.
Unless otherwise indicated, symbols notations
have their usual meanings.

SECTION A
1. Answer any four of the following
What are the various types of dislocations Explain any two of them with the help of sketches. What is interstitial free steel and where is it used?
B-JGT-J-NFA 1 [Contd.l
Show that the cycloidal or the involute shape for profiles of wheel teeth satisfy the fundamental condition for the transmission
of uniform motion.
What are the principal advantages of the involute shape over cycloidal shape of gear tooth? 10
Two rigid bodies and turn about fixed parallel axes and drives by direct contact. Show that the ratio of angular velocity of B to that of A can only be constant, if contact surfaces are so shaped that the norma] at the point of contact intersects the line of centres at a fixed
point. 10
Cd) What is deep drawing process for sheet metal fanning? Explain the function of a blank holder. What is drawing ratio and how is the drawing ratio increased? 10
Construct Shear Force and Bending Moment diagrams for a beam as shown in Figure 1. The loading is shown in the diagram. 10
400 kN (at an angle tan-1


2m +2m m+1 2m +2m 1
Figure 1 (not to scale)
B-JGT-J-NFA 2 [Contd .l
2. In a compound helical spring the inner spring is
arranged within and concentric with the outer
one but is 15 mm shorter. The outer spring has
12 coils of mean diameter 30 mm and the
diameter of wire is 3 mm. Find the stiffness of
the inner spring if an axial load of 120 N causes
the outer one to compress 25 mm. If the vertical
clearance between the two springs is to be 2 mm,
find the diameter of the wire of the inner spring
when it has 8 coils. Take G =80 GPa for both
springs. 15
In two-dimensional stress system, normal
stresses of 30 MPa and 100 MPa act on two
mutually perpendicular planes 1ll conjunction
with shear stress of 40 MPa. The stress
intensity, judged by the distortion energy, 15
excessive. As it was found impossible to reduce
the applied stresses, the severity of the distortion
energy condition was reduced by increasing the
normal stress of 30 MPa to have higher value, S.
Find the value of S at which the distortion
energy is minimum. 15
A straight bar of alloy 1 m long and
12 mm x 6 nun in section is loaded as a column
till it buckles. Assuming Euler fonnula for
pinned-ends to apply, estimate the maXImum
central deflection before the material attains its
yield point, at 260 MPa. E =80 GN/m2 . 10

3. A 40 mm diameter shaft 2·5 m long has a mass of 1 kg/metre length. It is simply supported at the ends and carries three masses 90 kg, 140 kg and 60 kg at a distance of 1·7 1·0 and 0·5 m respectively from right support.
Taking E 200 GN/m2, find the frequency of transverse vibrations.
A revolving mass of a scooter engIne crank is 2 kg at a radius of 10 em. Determine the magnitude of balance mass at a radius of 100 mm in two planes 10 em apart. One of the planes is at a distance of 5 em from the plane of
the crank. These planes are
on same side of crank
on opposite sides of crank. 15
How do the following parameters affect the
pressure angle in a cam follower combination
Steepness of displacement diagram
Base circle radius
Follower displacement
Justify your answer. 10

4. IlComposite material is a generic term." 'Explain this statement. Explain also the tenns 'law of mixtures', and 'debonding' as applied to composite materials. What are the maln constituents of a grinding wheel?
B-JGT-J-NFA 4 [Contd.J
Distinguish between grain boundary movement during cooling and heating and grain distortion during metal deformation during extrusion. Give two products/examples where there are no grain boundaries and what properties are enhanced as a result of absence of grain boundaries.
SECTION B

5. Answer any four of the following:

What are codes and codes?
To make a 175 mm dia hole in a mild steel plate of thickness 5 mm, with the surface finish of the
finished hole to have a value of 20 microns,
choose suitable machine tools to operation. Give the process plan. carry out this 10
Two plates of aluminium and stainless steel are to be welded back to back to create a single plate of thickness equal to the sum of the thicknesses of the two plates. Suggest the suitable process and explain it in brief. 10
What IS the common composition of the electrolyte used in ECM process? What is the wear on the electrode for making a 5 mm dia 50 mm deep blind hole in a plate of stainless steel by EeM What will be the tool wear, if instead of EeM, we use EDM process? 10
How does Value Engineering differ from Value Analysis Define Ivalue'. Explain the different types of values with the help of suitable examples. 10
Define Material Requirement Planning (MRP). What are its objectives Explain the following terms associated with MRP
Dependent demand Lot size
Time phasing
Gross requirements Net requirements 10


6. With the help of Taylor's tool life equation,
deterniine the shape of the curve between
velocity of cutting and life of the tool. Assume an
HSS tool and mild steel as work material. 10
Where do you use gauges instead of micrometers
for the control of dimensions of machined parts
Set gauges for the shaft of size 100 ± 1 mm and a
bush with a hole size of 100 ± 1 mm. Can these
gauges be used if the tolerances are changed to
± 1·2 mm 10
Casting is a process which gives the products
with isotropic properties. Justify why the
castings are subjected to the forging process, and
the resulting change in some properties of the
product. Name these properties and gIve
examples of forgings where these properties are
absolutely essential. 20

7. What is sales forecasting? Explain why a sales
forecast is required.
The past data about the load on a machine centre
is as follows

Month
1
2 611
3 656
4 748
5 863
6 914
7 964


Compute the forecast of the load on the centre in the 8th month, using a five month moving average.


Compute a weighted three month moving 8th


average for the month, where the weights are 0,5 for the latest month, 0·3 and 0·2 for the other months, respectively. 10
A project consists of 7 jobs. Jobs A and F can be started and completed independently. Jobs B and C can start only after job A has been completed. Jobs E and G can start only after jobs and and and are completed, respectively. Time estimates of all the jobs are given in the following table
Job Time Estimates (Days)
Optimistic Pessimistic Mdst likely
A B C D E F G 3 7 4 4 4 5 2 7 11 18 . 12 8 19 6 5 9 14 8 6 12 4

Draw the network and determine the critical path, and its expected duration What is the
cprobability of completing the project in Te days Also, determine the total and free slacks of all the jobs. 15
8 lContd.l
What is a line balancing problem? Explain the following terms related with line balancing:
Minimum rational work element Total work content Workstation process time Cycle time Precedence diagram Balance delay 15
8. Draw a flow chart to find the diameter of a solid steel shaft, using language, to transmit a given power at a specified speed. The ultimate tensile strength of steel and factor of safety are also given. 15

What is a "transportation problem? Solve the following assignment problem, in which the figures in the matrix represent unit cost of production of each component. What is the minimum cost 15


Why and how is a queue formed? A store employs one cashier at its counter. On an average 10 customers arrive in 5 minutes while the cashier can serve 12 customers in the same


Component
1 2 3 4 5
A 11 17 8 16 20
B 9 7 12 6 15
Machine C 13 16 15 12 16
D 21 24 17 28 26
E 14 10 12 11 15


time. Assuming Poisson distribution for arrival and exponential distribution for service rate, find the average number of units in the system, the average length of the waiting line, expected time a customer spends in the system, expected time a customer spends in the queue.
B-JGT-J-NFA 10