GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER-V (NEW) EXAMINATION - SUMMER 2019
--- Content provided by FirstRanker.com ---
Subject Code: 2152508 Date: 31/05/2019Subject Name: Design of Machine Elements
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
--- Content provided by FirstRanker.com ---
2. Make suitable assumptions wherever necessary.3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Explain the term: Fatigue failure, Fatigue life 03
(b) What is the difference between the Gerber curve and Soderberg and 04
--- Content provided by FirstRanker.com ---
Goodman lines?(c) What are the methods of reducing Stress concentration? Explain details. 07
Q.2 (a) What is the difference between clutch and flange coupling? 03
(b) A car engine develops maximum power of 15 kW at 1000 rpm. The clutch 04
used is single plate clutch both side effective having external diameter 1.25
--- Content provided by FirstRanker.com ---
times internal diameter p = 0.3. Mean axial pressure is not to exceed 0.085N/mm². Determine the dimension of the friction surface and the force
necessary to engage the plates. Assume uniform pressure condition.
(c) A single block brake with a torque capacity of 15 N-m is shown in Fig. The 07
coefficient of friction is 0.3 and the maximum pressure on the brake lining
--- Content provided by FirstRanker.com ---
is 1 N/mm². The width of the block is equal to its length.Calculate
(i) the actuating force;
(ii) the dimensions of the block;
(iii) the resultant hinge-pin reaction; and
--- Content provided by FirstRanker.com ---
(iv) the rate of heat generated, if the brake drum rotates at 50 rpm.OR
A machine component is subjected to Fluctuating stress that varies from 40 07
to 100 N/mm². The corrected endurance limit stress for the machine
component is 270 N/mm². The ultimate tensile strength and yield strength
--- Content provided by FirstRanker.com ---
of material are 600 and 450 N/mm² respectively.Find factor of safety using
I Gerber Theory
II Soderberg Theory
III Goodman Theory
--- Content provided by FirstRanker.com ---
Also find the factor of safety against static failure.
Q.3 (a) What is cooling stress in case of Flywheel? 03
(b) What is the coefficient of fluctuation of energy? 04
(c) It is required to design a V-belt drive to connect a 7.5 kW, 1440 rpm 07
induction motor to a fan, running at approximately 480 rpm, for a service
--- Content provided by FirstRanker.com ---
day. Fa = 1.3, PCD of Smaller pulley = 200 mm, pitch length L = 3200 mm,Correction factor Fc = 1.08, Power rating Pr = 6.36kW.
OR
Q.3 (a) Explain the Law of Belting. 03
(b) What is creep in belts? 04
--- Content provided by FirstRanker.com ---
(c) A pair of spur gears with 20° pressure angle consists of a 25 teeth pinion 07meshing with a 60 teeth gear. The module is 5 mm, while the face width is
45 mm. The pinion rotates at 500 rpm and the gears are made up on steel
with surface hardness of 220 BHN and ultimate tensile strength of 600
MPa. Take service factor 1.75 and factor of safety 2. Assume that the
--- Content provided by FirstRanker.com ---
dynamic load is accounted by means of velocity factor method. Determinerated power that can be transmitted by gears. Take Y= 0.32
Q.4 (a) What is the minimum number of teeth on the spur gear? why? 03
(b) Explain the concept of Interference and Undercutting. 04
(c) A pair of helical gears consists of a 25 teeth pinion meshing with a 50 teeth 07
--- Content provided by FirstRanker.com ---
gear. The normal module is 4 mm. Find the required value of the helixangle, if the centre distance is exactly 165 mm.
OR
Q.4 (a) What are the drawbacks of worm gear drives? 03
(b) Derive the Lame’s equation to determine wall thickness. 04
--- Content provided by FirstRanker.com ---
(c) The piston rod of hydraulic cylinder exerts an operating force of 10 kN. 07The friction due to piston packing and stuffing box is equivalent to 10% of
operating force. The pressure in the cylinder is 10 MPa. The cylinder is
made of cast iron FG200 and factor of safety is 5. Determine the diameter
and thickness of the cylinder.
--- Content provided by FirstRanker.com ---
Q.5 (a) What is the criterion to distinguish between thick and thin cylinder? 03
(b) Explain the terminology of power screw. 04
(c) It is required to design a helical compression spring subjected to a 07
maximum force of 7.5 kN. The mean coil-diameter should be 150 mm from
space consideration. The spring rate is75 N/mm. The spring is made of oil-
--- Content provided by FirstRanker.com ---
hardened and tempered steel wire with ultimate tensile strength of 1250N/mm². The permissible shearstress for the spring wire is 30% of the
ultimate tensile strength (G'=81 370 N/mm²). Calculate
(i) wire diameter; and
(ii) number of active coils.
--- Content provided by FirstRanker.com ---
OR
Q.5 (a) What is concentric spring? 03
(b) What is the nip of leaf spring? What is the objective of nipping? 04
(c) In a machine tool application, the tool holder is pulled by means of an 07
operating nut mounted on a screw. The tool holder travels at a speed of 5
--- Content provided by FirstRanker.com ---
m/min. The screw has single-start square threads of 48 mm nominaldiameter and 8 mm pitch. The operating nut exerts a force of 500 N to
drive the tool holder. The mean radius of the friction collar is 40 mm. The
coefficient of friction at thread and collar surfaces is 0.15. Calculate power
required to drive the screw and the efficiency of the mechanism.
--- Content provided by FirstRanker.com ---
This download link is referred from the post: GTU BE 2019 Summer Question Papers || Gujarat Technological University
--- Content provided by FirstRanker.com ---