Rajasthan Technical University 2010 B.Tech Mechanical Engineering Noise, Vibration and Harshness - Question Paper
RTU Noise, Vibration and Harshness
Rajasthan tech. University
B.tech six sem (Main/back)
Year June 2010
K(MI No. (Total No, of Page*: ta
6K3052
B.Tech. Vllh Semester (Main/Back) Examination, June - 2010 Mechanical Engineering Noise, Vibration and Harshness
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Maximum Marks: 80 Min. Passing Marks : 24
Time: 3 Hours
Instructions to Candidates'.
Attempt any Jive questions selecting one question from each unit. All questions carry equal marks. (Schematic diagrams must be shown wherever necessary. Any data you feel missing may suitably be assumed and stated clearly. Units of quantities used/calculated must be stated clearly.)
Unit-I
1. a) Write a detailed note on subjective response of humans to sound, explaining
frequency dependent and sound pressure dependent human response. (8) b) What is inverse square law? Deduce a relationship between sound power level and sound intensity level. (8)
OR
2. What are the major industrial noise sources? Explain various strategies used to control the industrial noise. (16)
Unit -II
3. a) A helical spring ofstifTnessk is cut into two halves and a man mis connected
to the two halves as shown in figure (j) The natural time period of this system is found to be 0.5 Sec. If an identical spring is cut so that one part is one-fourth and the other part three-fourth of the original length, and the man m is connected to the two parts as shown in figure (ii) What would be the natural period of the system? (8)
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b) Describe ihc principle of conservation of energy and O Alembcrts principle.
Derive the equation of motion of spring*man system using both of these principles. (8)
OR
4. a) Explain thesalientcharaclcristicsofacoulambdanipcdsystem. (8) b) A vibrating system is defined by the following parameters.
M - 3kg. k 100 N/m. C - 3N sec/m Determine:
i) the damping factor / ratio.
I
ii) the natural frequency of damped vibrations.
iii) logarithmic decrement.
iv) the number of cycles after which the original amplitude is reduced to 20%
(8)
Unit-III
5. a) Derive the expression of displacement transmissibility for a single dcgrecof
freedom spring-man-dashpot system. Subjected to a harmonic excitation of the base. Plot the displacement transmissibility ratio for different amounts of damping against the frequency ratio. (8)
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b) A spring-man-damp system is subjected to a harmonic force. The amplitude is found to be 20 mm at resonance and ! 0 mm at a frequency 0.75 times the resonant frequency. Find the damping ratio of the system. (8)
OR
6. a) Wrileishortnoteon\ariousmateriaisusedin vibration isolation. (8)
b) Consider a spring-man-damper sys;em with k = 4000 N/m, m * 10 kg. and c-40N-Sec/m. Find the steady state and total response of the system under the harmonic force F(/)-200 cos 20f and the iniiial conditions *0.1 mand dx/dt * 0. (8)
Unit - IV
7. a) Explain the principle and working of centrifugal pendulum absorber.
b) For the following system derive and determine the equation of motion, natural frequencies of vibration and mode shapes. (8)
(8)
OK
8. a) Draw the free* body diagram of the following many degrees of freedom system and derive the differentia! equation governing the motion of the system using Newton's law of motion. Also arrange these equation in matrix form. (8)
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b) A mass less string is strcichcd with tension T has three mass points attached at equal intervals as shown in figure. Kind the natural frequency and mode shapes of the system. (8)
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9. a) Write a short note on I folzcr's method and point out advantage and limitations of this method. (8)
b) Find the lowest natural frequency of the following system using Stodola's method. (8)
OR
10. Derive the equationgoveming the transverse vibrations of atighily stretched suing. Also find the first four natural frequencies and corresponding mode-shapes for the fixed - fixed end conditions. (16)
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| Earning: Approval pending. |
