# Download GTU B.Tech 2020 Summer 5th Sem 2151907 Design Of Machine Elements Question Paper

Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Summer 5th Sem 2151907 Design Of Machine Elements Previous Question Paper

Seat No.: ________
Enrolment No.___________

GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER? V EXAMINATION ? SUMMER 2020
Subject Code: 2151907 Date:29/10/2020
Subject Name: DESIGN OF MACHINE ELEMENTS
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.

2. Make suitable assumptions wherever necessary.

3. Figures to the right indicate full marks.

Q.1 (a) Discuss the various alloying elements used in `alloy' steels and their effect 03
on properties of Alloy steels.

(b) A manufacturer is interested in starting a business with seven different 04
models of tractors ranging from 40 to 360 kW capacities. Specify power
capacities of the models.

07
Q.2 (a) Explain the Wahl's factor used in spring design in detail.
03

(b) Explain the buckling of helical compression spring. How will you prevent it? 04

(c) Design a helical compression spring made of cold drawn steel is subjected to 07
a fluctuating load from 500 N to 1000 N and during this, it deflects through
25 mm. The spring index is 8. The spring has square and grounded ends. There
should be a gap of 2 mm between adjacent coil when the spring is subjected
to maximum load of 1000 N. If the ultimate tensile stress for the spring
material is 1000 MPa and the permissible stress in shear is 50 % of the
ultimate tensile stress. For spring material, the modulus of rigidity is 81730
N/mm2. Find: 1. Size of the spring wire, 2. Diameters of the spring, 3. Number
of turns of the spring, and 4. Free length of the spring.

OR

(c) A semi-elliptic leaf spring used for automobile suspension consists of two 07
extra full-length leaves and 8 graduated-length leaves, including the master
leaf. The centre-to-centre distance between two eyes of the spring is 1 m. The
maximum force that can act on the spring is 30 kN. For each leaf, the ratio of
width to thickness is 2.3. The modulus of elasticity of the leaf
material is 207000 MPa. The leaves are pre-stressed so as to equalize the
stresses in all leaves under maximum load. The ultimate tensile stress for the
spring material is 1500 MPa and the factor of safety is 2. Determine (i) the
width and t
hickness of the leaves; (ii) the deflection at the end of the spring.
Q.3 (a) Distinguish between flat and V- belt drives.
03

(b) Explain the step by step procedure used for selection of chain drive.
04

(c) Two pulleys, one 450 mm diameter and the other 200 mm diameter, on 07
parallel shafts 1.95 m apart are connected by a crossed flat belt. Find the length
of the belt required and the angle of contact between the belt and each pulley.
What power can be transmitted by the belt when the larger pulley rotates at
200 rev/min, if the maximum permissible tension in the belt is 1000 N, and
the coefficient of friction between the belt and pulley is 0.25?

OR

Q.3 (a) State the advantage and disadvantage of the chain drive over belt and rope
03
drives.

(b) Explain the different types of stresses induced in a belt with neat sketch.
04
1

(c) V- belt drive is used to transmit 90 kW power from an electric motor running 07

at 750 rpm to compressor running at 250 rpm. The diameter of the pulley on
the compressor shaft must not be greater than 1 metre while the centre distance
between the pulleys is limited to 1.75 metre. The belt speed should not exceed
1600 m/min. Determine the number of V-belts required to transmit the power
if each belt has a cross-sectional area of 375 mm2, density 1000 kg/m3 and an
allowable tensile stress of 2.5 MPa. The groove angle of the pulleys is 35?.
The coefficient of friction between the belt and the pulley is 0.25.Calculate
also the length required of each belt.
Q.4 (a) Explain the wire wounding in pressure vessels.
03

(b) An air receiver consisting of 500 mm diameter cylinder closed by 04
hemispherical ends. The gas pressure is limited to 15 MPa. It is made of steel
FeE 200 (Syt = 200 N/mm2 and = 0.27) and the factor of safety is 2.5.
Calculate the cylinder wall thickness and the hemispherical ends. Neglect the
effects of welded joints. Consider the receiver as thin cylinder.

(c) Explain the different types of end closure for cylindrical pressure vessel with 07
neat sketch.

OR

Q.4 (a) Explain the pre-stressing in pressure vessels.
03

(b) Explain the different pressure vessels materials in detail.
04

(c) A high-pressure cylinder consists of an inner cylinder of inner and outer 07
diameters of 200 mm and 300 mm respectively. It is jacketed by an outer
steel tube, having an outer diameter of 400 mm. The difference between the
outer diameter and the inner diameter of the jacket before assembly is 0.25
mm. Calculate the shrinkage pressure and maximum tensile stress induced in
any of the cylinders. ( Take E = 207 kN/mm2 ).
03

(b) Explain the different parameters affecting endurance strength of the 04
components.

(c) A solid circular shaft mad of steel Fe 620 (Sut = 630 N/mm2 and Syt = 380 07
N/mm2) is subjected to a alternating torsional moment that varies from - 200
Nm to + 400 Nm. The factor of safety is 2 and the expected reliability is 90%.
The shaft is grounded. Neglecting the effect of stress concentration; determine
the diameter of the shaft for infinite life. Assume the distortion energy theory
of failure.

OR
Q.5 (a) Explain Stress Concentration in brief with neat sketches.
03
(b) Explain the design consideration of castings process with sketches.
04
(c) Explain the Soderberg, Gerber and Goodman criteria used in fatigue design 07
with the help of neat sketches (diagrams).

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