Download PTU B.Tech 2020 March Aero 6th Sem ASPE 311 Vibration And Structural Dynamics Question Paper

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Roll No. ‘ ‘ ‘ ‘ ‘ ‘ ‘ ‘ ‘ Total No. of Pages : 02

Total No. of Questions : 09

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B.Tech.(Aerospace Engg.) (2012 Onwards) (Sem.-6)

VIBRATION AND STRUCTURAL DYNAMICS

Subject Code : ASPE-311

M.Code : 72456

Time : 3 Hrs. Max. Marks : 60

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INSTRUCTION TO CANDIDATES :

1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students have to attempt any TWO questions.

SECTION-A

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1. Distinguish between the following :
   1. Simple pendulum and compound pendulum
   2. Internal and external sources of excitation
   3. Discrete and continuous systems
   4. Damped and un-damped systems
   5. Single degree of freedom and two degree of freedom systems

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2. Derive the equivalent spring constant for two springs in series.
3. Over-damping and under-damping
4. Free and forced vibration
5. Principle modes and normal modes vibration

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6. Whirling of shaft with and without air damping

SECTION-B

1. What are vibration absorbers? Explain the working principle of a centrifugal pendulum vibration absorber with the help of a neat sketch.
2. For damped free vibration system, derive the equation for amplitude for over-damped and critically damped system.
3. An Instrument has a natural frequency of 15 Hz. It can stand a maximum acceleration of 10 m/s². Find the maximum displacement amplitude.

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4. A 25 kg mass is resting on a spring of 5 kN/m stiffness and a dashpot of 150 N-s/m damping coefficient in parallel. If a velocity of 0.1 m/s is given to the mass at rest position. What will be its displacement from the equilibrium position at the end of first second?
5. Add the following harmonic motions analytically :
   x1 =4 cos (?t + 15°); x2 = 6 sin (?t + 60°)

SECTION-C

1. A vibrating system having mass of 1 kg is suspended by a spring of stiffness 1100 N/m and it is put to harmonic excitation of 12 N. Assuming viscous damping, determine
   1. The resonant frequency

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   2. The phase angle at resonance
   3. The amplitude at resonance
   4. The frequency corresponding to the peak amplitude and
   5. Damping frequency. Take C = 40 N-sec/m.

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2. Write short notes-on the following :
   1. Holzer’s method.
   2. Euler’s equation for beams
   3. Vibration measuring instruments
3. A uniform string is tightly stretched between x = 0 and x = l and is plucked at x = l/4, through a distance / and then released from rest. Find its subsequent displacement.

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NOTE : Disclosure of identity by writing mobile number or making passing request on any page of Answer sheet will lead to UMC case against the Student.