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Seat No.: Enrolment No.
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GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER-VI (OLD) EXAMINATION - WINTER 2018
Subject Code:161901 Date: 07/12/2018
Subject Name: Dynamics Of Machinery
Time: 02:30 PM TO 05:00 PM Total Marks: 70
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Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
Q-1 A Define Static and Dynamic balancing with suitable example.
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B Explain Vibration isolation and transmissibility
Q-2 A Write down short note on Variation of Tractive Force, Swaying couple and Hammer Blow.
Explain concept of Direct and Reverse Crank.
OR
B Four masses m1, m2, m3 and m4 are 200 kg, 300 kg, 240 kg and 260 kg respectively. The corresponding radii of rotation are 0.2 m, 0.15 m, 0.25 m and 0.3 m respectively and the angles between successive masses are 45°, 75° and 135°. Find the position and magnitude of the balance mass required, if its radius of rotation is 0.2 m.
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Q-3 A Discuss different cases showing the characteristics of the system performance for a damped free vibration.
Describe Dunkerley’s method to find the natural frequency of a shaft carrying several loads.
OR
Explain Hozer’s method to determine natural frequencies of multi-rotor system.
What are various frequency measuring instruments? Explain any one in detail.
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Define logarithmic decrement and derive an expression for it.
Q-4 A, B, C and D are four masses carried by a rotating shaft at radii 100, 125, 200 and 150 mm respectively. The planes in which the masses revolve are spaced 600 mm apart and the mass of B, C and D are 10 kg, 5 kg, and 4 kg respectively. Find the required mass A and the relative angular settings of the four masses so that the shaft shall be in complete balance.
OR
A Explain an analytical method of balancing of several masses rotating in different planes.
Derive an expression for torsionally equivalent shaft system
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Explain the method to determine the critical speed of shaft carrying single rotor, considering damping.
B Explain with neat sketch why reciprocating masses are partially balanced?
Q-5
OR
A Define and only write the equation of the following terms;
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I) Natural Frequency, II) Logarithmic Decrement, III) Natural Frequency Of Damped Vibration, IV) Damping Factor, V) Dynamic Magnifier, VI) Displacement Transmissibility.
B A cantilever shaft 50 mm diameter and 300 mm long has a disc of mass 100 kg at its free end. The Young's modulus for the shaft material is 200 GN/m². Determine the Frequency of longitudinal and transverse vibrations of the shaft.
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