Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2018 Winter 5th Sem New 2152508 Design Of Machine Elements Previous Question Paper
1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?V (NEW) EXAMINATION ? WINTER 2018
Subject Code:2152508 Date:16/11/2018
Subject Name:Design of Machine Elements
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. PSG Design Data Book is permitted
MARKS
Q.1 (a) Explain following terms: 1) Notch sensitivity 2) Endurance limit 03
(b) Explain the term stress concentration. In design how the effect of stress
concentration is considered?
04
(c) A steel rod is to be subjected to reversed axial load of 150 KN. Find the
diameter of the rod for the factor of safety of 2. Neglect column action. The
material has an ultimate tensile strength as 1090 N/ ????
2
, Yield stress as 920
N/ ????
2
and Endurance limit as 540 N/ ????
2
. Other correction factors are:
Theoretical stress concentration factor: 2.5, Notch sensitivity: 0.8
07
Q.2 (a) Explain the term Wahl factor and its significance in helical spring design 03
(b) Define the following terms:
(i) Spring Rate (ii) Free Length (iii) Solid Length (iv) Spring Index,
04
(c) Prove that ?The bending stresses in full-length leaves are 50 % more than
those in graduated-length leaves.?
07
OR
(c) It is required to design a helical compression spring subjected to a maximum
force of 7.5 KN. The mean coil diameter should be 150 mm from space
consideration. The spring rate is 75 N/mm. the spring is made of oil-hardened
and tempered steel wire with ultimate tensile strength of 1250 N/ ????
2
. The
permissible shear stress for the spring wire is 30% of the ultimate tensile
strength take modulus of rigidity as 81370 N/????
2
. Calculate wire diameter
and number of active coils.
07
Q.3 (a) Compare Involute and Cycloidal tooth profile of gear. 03
(b) Derive an expression for Lewis equation to calculate the beam strength of the
Spur gear.
04
(c) Discuss causes of gear tooth failure. 07
OR
Q.3 (a) Explain the terms used in bevel gear, i) formative number of teeth ii) cone
radius.
03
(b) How worm gears are designated and explain the terms in it. 04
(c) A pair of spur gears with 20? full depth involute teeth consists of a 20 teeth
pinion meshing with a 41 teeth gear. The module is 3 mm while the face width
is 40 mm. The material for pinion as well as gear is steel with an ultimate
tensile strength of 600 N/ ????
2
. The gears are heat treated to a surface
hardness of 400 BHN. The pinion rotates at 1450 rpm and the service factor
for the application is 1.75. Assume that velocity factor accounts for dynamic
load and the factor of safety is 1.5
Determine the rated power that the gears can transmit.
Take Lewis Form factor = 0.32
07
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1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?V (NEW) EXAMINATION ? WINTER 2018
Subject Code:2152508 Date:16/11/2018
Subject Name:Design of Machine Elements
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. PSG Design Data Book is permitted
MARKS
Q.1 (a) Explain following terms: 1) Notch sensitivity 2) Endurance limit 03
(b) Explain the term stress concentration. In design how the effect of stress
concentration is considered?
04
(c) A steel rod is to be subjected to reversed axial load of 150 KN. Find the
diameter of the rod for the factor of safety of 2. Neglect column action. The
material has an ultimate tensile strength as 1090 N/ ????
2
, Yield stress as 920
N/ ????
2
and Endurance limit as 540 N/ ????
2
. Other correction factors are:
Theoretical stress concentration factor: 2.5, Notch sensitivity: 0.8
07
Q.2 (a) Explain the term Wahl factor and its significance in helical spring design 03
(b) Define the following terms:
(i) Spring Rate (ii) Free Length (iii) Solid Length (iv) Spring Index,
04
(c) Prove that ?The bending stresses in full-length leaves are 50 % more than
those in graduated-length leaves.?
07
OR
(c) It is required to design a helical compression spring subjected to a maximum
force of 7.5 KN. The mean coil diameter should be 150 mm from space
consideration. The spring rate is 75 N/mm. the spring is made of oil-hardened
and tempered steel wire with ultimate tensile strength of 1250 N/ ????
2
. The
permissible shear stress for the spring wire is 30% of the ultimate tensile
strength take modulus of rigidity as 81370 N/????
2
. Calculate wire diameter
and number of active coils.
07
Q.3 (a) Compare Involute and Cycloidal tooth profile of gear. 03
(b) Derive an expression for Lewis equation to calculate the beam strength of the
Spur gear.
04
(c) Discuss causes of gear tooth failure. 07
OR
Q.3 (a) Explain the terms used in bevel gear, i) formative number of teeth ii) cone
radius.
03
(b) How worm gears are designated and explain the terms in it. 04
(c) A pair of spur gears with 20? full depth involute teeth consists of a 20 teeth
pinion meshing with a 41 teeth gear. The module is 3 mm while the face width
is 40 mm. The material for pinion as well as gear is steel with an ultimate
tensile strength of 600 N/ ????
2
. The gears are heat treated to a surface
hardness of 400 BHN. The pinion rotates at 1450 rpm and the service factor
for the application is 1.75. Assume that velocity factor accounts for dynamic
load and the factor of safety is 1.5
Determine the rated power that the gears can transmit.
Take Lewis Form factor = 0.32
07
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2
Q.4 (a) Explain with the help of neat sketch the working principal of centrifugal
clutch.
03
(b) In brake design explain self-energizing and self-locking condition 04
(c) Figure below shows the arrangement of two brake shoes which act on the
internal surface of a cylindrical brake drum. The braking force F1 and F2 are
applied as shown and each shoe pivots on its fulcrum O1 and O2. The width
of the brake lining is 30 mm. The intensity of pressure at any point A is 0.4
sin? N/ ????
2
, where ? is measured as shown from either pivot. The coefficient
of friction is 0.4. Determine the braking torque and the magnitude of the
forces F1 and F2. All dimensions are in mm.
07
OR
Q.4 (a) Why flywheel is needed in an Engine? 03
(b) Explain coefficient of fluctuation of speed. 04
(c) A multi-cylinder engine is to run at a constant load at a speed of 600 r.p.m.
On drawing the crank effort diagram to a scale of 1 m = 250 N-m and 1 mm
= 3?, the areas in sqmm above and below the mean torque line are as follows:+
160, ? 172, + 168, ? 191, + 197, ? 162 sq mm The speed is to be kept within
?1% of the mean speed of the engine. Calculate the necessary moment of
inertia of the flywheel.
07
Q.5 (a) Clutches are usually designed on the basis of Uniform wear.
Justify the statement.
03
(b) In pressure vessel design, what is Autofrettage and explain its need. 04
(c) A shrink fit assembly, formed by shrinking one tube over another, is
subjected to an internal pressure of 60 N/ ????
2
. Before the fluid is admitted,
the internal and the external diameters of the assembly are 120 mm and 200
mm and the diameter at the junction is 160 mm. If after shrinking on, the
contact pressure at the junction is 8 N/ ?? ?? 2
, determine using Lame?s
equations, the stresses at the inner, mating and outer surfaces of the assembly
after the fluid has been admitted.
07
OR
Q.5 (a) Why is the efficiency of self-locking square threaded screw less
than 50%?
03
(b) Discuss types of pulleys for flat belts 04
(c) Explain step by step design procedure of screw jack. 07
*************
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This post was last modified on 20 February 2020