Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2018 Winter 6th Sem New 2161901 Dynamics Of Machinery Previous Question Paper
1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VI (NEW) EXAMINATION ? WINTER 2018
Subject Code:2161901 Date:07/12/2018
Subject Name:Dynamics of Machinery
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.
MARKS
Q.1 (a) Define following term: (i) Degree of Freedom (ii) Damping (iii)
Resonance
03
(b) Explain the balancing of several masses rotating in same plane by
Graphical Method.
04
(c) Why is balancing of rotating parts necessary for high speed engines?
Explain clearly the terms static balancing and dynamic balancing. State
the necessary conditions to achieve them.
07
Q.2 (a) What is meant by critical speed of a shaft? Which are the factors
affecting it?
03
(b) How and why are reciprocating masses balanced in a piston-cylinder
assembly? Why reciprocating masses are partially balanced?
04
(c) The four masses A, B, C and D revolve at equal radii are equally spaces
along the shaft. The mass B is 7 kg and radii of C and D makes an angle
of 90? and 240? respectively (counterclockwise) with radius of B,
which is horizontal. Find the magnitude of A, C and D and angular
position of A so that the system may be completely balance. Solve
problem by analytically.
07
OR
(c) A single cylinder reciprocating engine has speed 240 rpm, stroke 300
mm, mass of reciprocating parts 50 kg, mass of revolving parts at 150
mm radius 30 kg. If all the mass of revolving parts and two-third of the
mass of reciprocating parts are to be balanced, find the balance mass
required at radius of 400 mm and the residual unbalanced force when
the crank has rotated 60? from IDC.
07
Q.3 (a) Explain briefly energy method to find out characteristic equation for
free vibration of single degree of freedom system.
03
(b) Explain and Derive an expression for critical speed of a shaft carrying
rotor and without damping.
04
(c) Discuss different cases showing the characteristics of the system
performance for a damped free vibration
07
OR
Q.3 (a) Write short note on ?Torsionally equivalent shaft? 03
(b) Define (1) Time Period (2) Stiffness of Spring (3) Periodic motion (4)
Equivalent Damper in series.
04
(c) A mass of 20kg is supported on two isolators as shown in fig. (a)
Determine the undamped and damped natural frequencies of the
system, neglecting the mass of the isolators.
07
Q.4 (a) Write a short notes on ?Frequency Response Curve? 03
(b) Define force transmissibility. Explain with neat sketch transmissibility
curves.
04
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1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VI (NEW) EXAMINATION ? WINTER 2018
Subject Code:2161901 Date:07/12/2018
Subject Name:Dynamics of Machinery
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.
MARKS
Q.1 (a) Define following term: (i) Degree of Freedom (ii) Damping (iii)
Resonance
03
(b) Explain the balancing of several masses rotating in same plane by
Graphical Method.
04
(c) Why is balancing of rotating parts necessary for high speed engines?
Explain clearly the terms static balancing and dynamic balancing. State
the necessary conditions to achieve them.
07
Q.2 (a) What is meant by critical speed of a shaft? Which are the factors
affecting it?
03
(b) How and why are reciprocating masses balanced in a piston-cylinder
assembly? Why reciprocating masses are partially balanced?
04
(c) The four masses A, B, C and D revolve at equal radii are equally spaces
along the shaft. The mass B is 7 kg and radii of C and D makes an angle
of 90? and 240? respectively (counterclockwise) with radius of B,
which is horizontal. Find the magnitude of A, C and D and angular
position of A so that the system may be completely balance. Solve
problem by analytically.
07
OR
(c) A single cylinder reciprocating engine has speed 240 rpm, stroke 300
mm, mass of reciprocating parts 50 kg, mass of revolving parts at 150
mm radius 30 kg. If all the mass of revolving parts and two-third of the
mass of reciprocating parts are to be balanced, find the balance mass
required at radius of 400 mm and the residual unbalanced force when
the crank has rotated 60? from IDC.
07
Q.3 (a) Explain briefly energy method to find out characteristic equation for
free vibration of single degree of freedom system.
03
(b) Explain and Derive an expression for critical speed of a shaft carrying
rotor and without damping.
04
(c) Discuss different cases showing the characteristics of the system
performance for a damped free vibration
07
OR
Q.3 (a) Write short note on ?Torsionally equivalent shaft? 03
(b) Define (1) Time Period (2) Stiffness of Spring (3) Periodic motion (4)
Equivalent Damper in series.
04
(c) A mass of 20kg is supported on two isolators as shown in fig. (a)
Determine the undamped and damped natural frequencies of the
system, neglecting the mass of the isolators.
07
Q.4 (a) Write a short notes on ?Frequency Response Curve? 03
(b) Define force transmissibility. Explain with neat sketch transmissibility
curves.
04
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2
(c) A 40 kg machine is supported by four springs each of stiffness 250
N/m. The rotor is unbalanced such that the unbalance effect is
equivalent to a mass of 5 kg located at 50mm from the axis of rotation.
Find the amplitude of vibration when the rotor rotates at 1000 rpm and
60 rpm. Assume damping coefficient to be 0.15
07
OR
Q.4 (a) Explain Vibration Isolation, What are the various materials used for
vibration isolation?
03
(b) What is damped vibration? What are the different types of damping
methods?
04
(c) Estimate the approximate fundamental natural frequency of the system
shown in Fig. (b) Using Rayleigh?s method. Take: m=1kg and K=1000
N/m.
07
Q.5 (a) What are the various sources of external excitations? 03
(b) Define logarithmic decrement and derive an expression for it? 04
(c) The damped vibration record of a spring-mass-dashpot system shows
the following data.
Amplitude on second cycle = 0.012m; Amplitude on third cycle =
0.0105m; Spring constant k = 7840 N/m; Mass m = 2kg. Determine the
damping constant, assuming it to be viscous.
07
OR
Q.5 (a) Define following terms: Zero frequency and Node point. 03
(b) Why the measurement of vibration is necessary? What do you mean
by vibration monitoring of machine? Enlist different vibration
measuring instruments.
04
(c) Explain Jump phenomenon and cross over shock in case of cam and
follower
07
*************
Fig (a ) ? Que : 3 C (OR)
Fig (b ) ? Que : 4 C (OR)
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This post was last modified on 20 February 2020