MPPSC AE 2017: State Engineering Service Examination, Mechanical Engineering Paper-I
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SEAL
RoU No.
Candidate should write his/her Roll No, here.
Total No. of Questions :7 No. of Printed Pages : 7
SEM-2017(03)-!
MECHANICAL ENGINEERING
Paper—^1
Time :3 Hours ] [ Total Marks: 300
Instructions to the candidates;
Please read each ofthefollowing instructions carefully before
attempting questions.
Candidates are required to attempt FIVE questions in all.
Question No. 1 is compulsory. The remaining FOUR questions are required to attempt by
selecting at least ONE question from each ofthe three Sections A, B and C.
All questions carry equal marks. The number of marks carried by a part ofa question is
indicated against it.
Answers must be written in ENGLISH only.
Unless otherwise mentioned, symbols and notations have their usual standard meanings.
Assume suitable data, if necessary and indicate the same clearly.
Neat sketch may be drawn wherever required.
All parts and sub-parts ofa question are to be attempted together in the answer book.
Any pages left blank in the answer book must be clearly struck out.
Use ofgeometrical instrument box is permitted.
SEM-2017/ME-1 [ P.T.O.
1V3S
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1. Answer the following questions : 6x10=60
(a) A hollow circular bar of outside diameter twice the inside diameter is used
as a beam. The bar is subjected to bending moment of 40 kN m. If the
allowable bending stress in the beam is to be limited to 100 MN/m^, find
the inside diameter of the bar. 6
(b) Make a list of six principal theories of failure. Explain major consideration
and application of maximum principal stress theory. 3+3=6
(c) A flat bar 32 mm wide and 12 mm thick is loaded by a steady tensile load of
85 kN. The material is mild steel with yield point stress of 315 N/mm^.
Find the factor of safety based on the yield point.
(d) Design the longitudinal joint for a T25 m diameter steam boiler carrying a
steam pressure of 5 N /mm^. The allowable stress of the plate material is
80 N/mm^ in tension. Length of the shell of boiler is 5 m. Take allowable
stress for shielded arc weld = 95 N / mm . 5
(e) Find the length of belt(open and cross) necessary to drive a pulley of 80 cm
diameter running parallel at a distance of 12 m from the driving pulley of
diameter 480 cm. 3+3=6
(f) Make a list of various types of gear trains. Derive an expression for velocity
ratio of a simple gear train. 2+4=6
(g) A uniform disc of diameter 30 cm and weighing 5 N is mounted on one end
of an arm of length 60 cm. The other end of the arm is free to rotate in a
universal bearing. If the disc rotates about the arm with a speed of
300 r.p.m. clockwise, looking from the front, with what speed will it precess
about the vertical axis? 6
(h) For what type of materials ultrasonic machining (USM) is best suitable
process of material removal? Make a sketch showing major parts of USM
setup. 2+4=6
(i) Classify comparators. Explain the working and constructional details of
any one comparator. 6
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(j) For a small project with five jobs, the following data is given
Job ■ Immediate Duration(days)
predecessors Mean Std. deviation
A —
10 2
B — 5 1
C A 16 2
D A 12 2
E B, C 15 1
(i) Draw the project network in activity on arc mode.
(ii) Under PERT assumptions, determine the distribution of project
duration.
Section—A
Attempt at least one question
2. (a) A short column of I-section 25 cm x20 cm has cross-section area of52 cm^
and maximum radius of gyration 10-7 cm. A vertical load ui kN acts
through the centrpid of the section together with a parallel load of u;/4 kN
acting through a point on the centreline of the web distant 6 cm from the
centroid. Calculate the greatest allowable value of w if the maximum stress
is not to exceed 65 MN/m^. What is then the minimum stress?
15+10=25
(b) A close-coiled helical spring is to have a stiffness of 900 N/m in
compression, with a maximum load of 45 N and a maximum shearing
stress of 120 N./mrn^. The solid length of the spring (i.e., coils touching) is
45 mm. Find the— .
(i) wire diameter;
(ii) mean coil radius;
(Hi) number of coils.
Take modulus of rigidity of material of the spring =0-4x10® N/mm^.
5+5+5=15
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(4)
(c) A simple band brake,is applied to a drum of 560 mm diameter which
rotates at 240 r.p.m. Angle of contact of the band is 270°. One end of the
band is fastened to a fix pin and the other end to the brake lever 140 mm
from the fixed pin. The brake lever is 800 mm long and is placed
perpendicular to the diameter that bisects the angle of contact. Assuming
the coefficient of friction as 0-3, determine the necessary pull at the end of
the lever to stop the drum if 40 kW of power is being absorbed. Also, find
the width of the band if its thickness is 3 mm and the maximum tensile
strength is limited to 40 N/mm 20
3. (a) A V-belt of 6-0 cm^ cross-section has a groove angle of 40° and an angle of
lap of 150°, |x =0-10. The mass of the belt per meter run is 1-2 kg. The
maximum allowable stress in the belt is 850 N/cm^. Calculate the horse
power that can be transmitted at a belt speed of 30 m/s. 20
(b) Derive an expression for maximum and minimum values of swaying
couple.
(c) A V-twin engine has the cylinder axis at right angles and the connecting
rods operate a common crank. The reciprocating mass per cylinder is
1-5 kg and the crank radius 75 mm. The length of the connecting rod is
0-3 m. Show that the engine may be balanced for primary forces by means
of a revolving balance mass. If the engine speed is 500 r.p.m., what is the
value of the maximum resultant .secondary force? 30
Section—B
Attempt at least one question
4. (a) Design the rectangular key for a shaft of 50 mm diameter. The shearing
and crushing stresses for the key material are 42 MPa and 70 MPa, take
u;= 16 mm and t = 10 mm,where w = width and t = thickness of the key. 15
(b) Design a cast iron protective type flange coupling to transmit 15 kW at
900 r.p.m. from an electric motor to a compressor. The service factor may
be assumed as 1*35. The following permissible stresses may be used : 30
Shear stress for shaft, bolt and key material =40 MPa
Crushing stress for bolt and key = 80 MPa
Shear stress for cast iron = 8 MPa
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(c) The following data relate to a shaft held in long bearings :
Length of the shaft = 1 • 2 m
Diameter of the shaft = 14 mm
Mass of a rotor at midpoint =16 kg
Eccentricity of centre of mass of rotor from centre of rotor = 0-4 mm
Modulus of elasticity of the shaft material = 200 GN/m^
Permissible stress in the shaft material = 70 x 10® N/m^
Determine the critical speed of the shaft. 15
5. (a) A steel rod is turned with a single-point cutting tool having rake angle 10°.
The chip thickness was measured as 1-5 mm. The dynamometer gave
indication of cutting forces as 980 N for tangential component and 440 N
for thrust component, compute friction force at chip tool interface and
shear strength of the material (assume uncut chip thickness as 0-6 mm
and uncut width of chip as 1-8 mm). 20
(b) During straight turning of 25 mm diameter steel bar at 300 r.p.m. with
HSS tool, a tool life of 10 minutes was obtained. When the same bar was
turned at 250 r.p.m., the tool life increased to 52-5 minutes. What will be
the tool life at a speed of 275 r.p.m? 10
(c) Comment on the following statements related to electrochemical machining
(ECM) ; 20
(i) "ECM is reverse of electroplating."
(U) "AC power supply cannot be used in ECM."
(Hi) "Tool wear in ECM does not involve material loss."
(iv) "ECM is a hi^ly predictive process of material removal."
(d) Write any five differences between traditional and non-traditional
machining processes. 10
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(6)
Section—C
Attempt at least one question
6. (a) A company uses the purchased item continuously in the manufacturing of
a large number of products. The item has the following characteristics :
Demand/year = 8000 Pc
Purchase price =f 100/Pc
Safely stock = 1 • 6 x lead time demand
Lead time from order to delivery =4 weeks
Purchasing quantity = 1000 Pc
Inventory carrying cost/year = 20% of the item value
A reorder point system that continuously reviews stock on hand is used to
generate purchase orders. The product is produced and in demand in all
52 weeks of the year :
(i) Determine the reorder point, the average tied-up capital in inbound
stock, the inventory turnover rate in the stock, the average run-out
time in the stock and the annual inventory carrying cost for the item.
(n) As the company buys several items from the same supplier it is
considering changing its review principle from continuous review to
periodic review stock on hand of all purchased items every second
week. By doing this, it is thought that it will be possible to coordinate
deliveries of several items from this supplier. How will the answer in
(i) change if a switch is made to periodic review? 10+10=20
(b) A company makes two types of leather belts, A and B. Belt A is high quality
belt and belt B is of lower quality. The respective profits are f 4 and f 3
per belt. Each belt of type A requires twice as much time as belt of type B,
and if all the belts were of type B, the company could make 1000 per day.
The supply of leather is sufficient for only 800 belts per day (both A and B
combined). Belt A requires a fancy buckle and only 400 per day are
available.
There are only 700 buckles a day available for belt B. What should be the
daily production of each type of belt? Formulate as a linear programming
problem (solution not required). 20
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(c) The following table shows the jobs of a network along with their time
estimates (in days) :
Job 1-2 1-6,. 2-3 2-4 3-5 4-5 5-8 6-7 7-8
to 3 2 6 2 5 3 1 3 4
t-m 6 5 12 5 11 6 4 9 19
tp 15 14 30 8 17 15 7 27 28
(i) Draw network diagram.
(ii) Find critical path. Also, find the expected duration of the project.
(Hi) Calculate the standard deviation of the project length.
(iv) Find the probability that the project is completed in 31 days. 5x4=20
7. (a) Calculate the fundamental deviation and tolerances and hence the limits of
size for the shaft and hole for the following fit : 20
60 mm Hg-fy
The diameter steps are 50 mm and 80 mm.
(b) A television repairman finds that the time spent on his jobs has an
exponential distribution with a mean of 30 minutes. If he repairs sets in
the order in which they came in, and if the arrival of sets follows a
Poisspn's distribution approximately with an average rate of 10 per 8-hour
day, what is the repairman's expected idle time each day? How many jobs
are ahead of the average set just brought in? . 20
(c) A cantilever member 0-1 m long having cross-section of 0-05 mxO-25 m
supports a load of 27-5 kN. What is the maximum shear stress and where
does it occur? 20
*★ ★
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Source: Madhya Pradesh Public Service Commission. Question paper published by Madhya Pradesh Public Service Commission.