JNTU
JNTU B.Tech IV VIBRATION AND AERO-ELASTICITY Previous Question Paper (January/February - 2023 - R18)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
(25 Marks)
What do you mean by free vibration?
Answer
Free vibration occurs when a mechanical system is displaced from its equilibrium position and allowed to vibrate under the action of its own inherent elastic forces, without any external periodic excitation force.
List out different types of vibration? Explain in brief.
Answer
Vibrations are primarily classified as:
- Free Vibration: Occurs without external force after an initial disturbance.
- Forced Vibration: Occurs under the influence of an external periodic driving force.
- Damped Vibration: Energy is dissipated over time due to friction or resistance, reducing amplitude.
- Undamped Vibration: Motion continues indefinitely without energy loss.
What do you mean by logarithmic decrement?
Answer
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In how many ways can a system be damped? Explain at least two in brief.
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What is orthogonality principle?
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Explain the importance of influence coefficient in the vibrating system.
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Why vibration data acquisition system is needed?
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Explain in brief about the critical shaft speed.
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What do you mean by Aeroelasticity?
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What is Wing Divergence Speed? What are its effects?
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Part B
(50 Marks)
Explain in brief about the different types of damping with the help of suitable diagrams and expressions.
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Determine the frequency of oscillation as shown in figure 1. Also determine the time period if m= 4 kg and r = 80 mm.
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The column of the water tank shown in Figure 2 is 90 m high and is made of reinforced concrete with a tubular cross section of inner diameter 2.5 m and outer diameter 3.5 m. The tank weighs 2.6 × 106 N when filled with water. By neglecting the mass of the column and assuming the young’s modulus of reinforced concrete as 4 × 106 N/m2, determine the following: a) The natural frequency and time period of transverse vibration of the tank. b) The vibration response of the water tank due to an initial transverse displacement of 0.254 m. c) The maximum values of the velocity and acceleration experienced by the water tank.
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A damper offers resistance 0.05 N at constant velocity 0.04 m/sec. The damper is used with k= 9 N/m. Determine the damping and frequency of the system when the mass of the system is 0.10 kg.
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Derive an expression for the steady state amplitude for forced vibration with rotating and reciprocating unbalance.
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Prove that an undamped measuring instrument will show a true response for frequency ratio.
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Explain in brief about vibration absorber and vibration Isolator.
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Two pendulums of different lengths are free to rotate y-y axis and coupled together by a rubber hose of torsional stiffness 7.35 × 103 Nm/rad as shown in figure 3. Determine the natural frequencies of the system if masses m1 = 3kg, m2 = 4kg, L1 = 0.30 m, L2 = 0.35 m.
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Determine the pitch (angular motion) and bounce (up and down linear motion) frequencies and the location of oscillation centers (nodes) of an automobile (Figure 4) with the following data: Mass = 1000 kg, Radius of gyration = 0.9 m, Distance between front axle and C.G = 1.0 m, Distance between rear axle and CG = 1.5 m, front spring suspension = 18 kN/m and rear is 22 kN/m.
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What are the different methods to compute the frequency domain analysis? Explain in brief.
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Explain the procedure involved for computing the root cause analysis.
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Explain the difference between the trending analysis and signature analysis for the vibrating system.
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Explain in brief about the function of Accelerometers.
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Explain flutter behaviour from the consideration of extraction of energy from airstream.
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When the wing is said to be torsionally divergence? Justify your statement.
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What is meant by Aerodynamic coupling? Mention its types and explain each.
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