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Sri Vidya College of Engineering and Technology

Virudhunagar – 626 005 Department of Mechanical Engineering

Question Paper for Internal Assessment Test II

Semester & Branch: III/ Mechanical Date: / 09 /2014

Subject Name : Strength of Materials Max. Marks: 50

Subject Code: CE6306 Max. Time: 90 mins

Part A

Answer all the questions (5 x 2 = 10)

1. Write down the equation of torsion showing the various terms involved in it.

2. Define torsion and give at least two practical example for it.

3. How do you classify a cylinder or a shell in to thick or thin?

4. Define circumferential and Hoop stress.

5. On what basis, a cylinder is considered as thin one?

PART – B (1 x 8 + 2 x 16 = 40)

6. Expression for central deflection of the closed coil spring.

(Or)

7. Expression for longitudinal stress.

8. A hollow shaft with diameter ratio 3/5 is required to transmit 450KW at 120 r.p.m. The shearing stress

in the shaft must not exceed 60 N/mm2 and the twist in a length of 2.5m is not to exceed 1o. Calculate

the minimum external diameter of the shaft. C = 80 KN/mm2.

(Or)

9. A closed coiled helical spring has stiffness of 10 N/mm; its length when fully compressed with adjacent

coils touching each other is 400mm; the modulus of rigidity of the material of the spring = 80GPa

a. Determine the wire diameter and mean coil diameter if their ratio is 1/10.

b. If the gap between any two adjacent coil is 2mm, what maximum load can be applied before the

spring becomes solid (ie) adjacent coils touch.

c. What is the corresponding maximum shear stress in the spring?

10. A cylindrical vessel whose ends are closed by means of rigid flange plated, is made steel plate 3mm

thick. The length and the internal diameter of the vessel are 50cm and 25cm respectively. Determine

the longitudinal and hoop stresses in the cylindrical vessel due to an internal fluid pressure of 3N/mm2.

Also calculate the increase in length, diameter and volume of the vessel. Take E=2x105 N/mm2 and μ =

0.3.

(Or)

11. A cylindrical shell 3 m long which is closed at the ends has an internal diameter 1m and a wall

thickness of 15 mm. Yong’s modulus 200GN/m2 and Poisson’s ratio = 0.3. Calculate the

circumferential and longitudinal stresses induced and also change in diameter and change in length of

the shell, if it is subjected to an internal pressure of 1.5 MN/m2.

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Answers

1. Torsion of circular shafts

Definition of Torsion: Consider a shaft rigidly clamped at one end and twisted at the other end by a torque

T = F.d applied in a plane perpendicular to the axis of the bar such a shaft is said to be in torsion.

2. Torsion

3. Thin cylinder and thick cylinder measuring

A cylinder with a diameter to thickness ratio of more than 20 is considered to be

thin. A ratio of less than 20 is considered to be thick.

4. Hoop stress

This is the stress which is set up in resisting the bursting effect of the applied pressure and can be most

conveniently treated by considering the equilibrium of the cylinder.

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5.

In the figure we have shown a one half of the cylinder. This cylinder is subjected to an internal

pressure p.

i.e. p = internal pressure

d = inside diametre

L = Length of the cylinder

t = thickness of the wall

5. cylinder is considered as thin one

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6. Expression for central deflection of the closed coil spring.

7. Expression for longitudinal stress.

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9.

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10.

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