DYNAMICS OF MACHINERY ME2302 NOV/DEC 2010 ANNA UNIVERSITY PREVIOUS YEAR QUESTION PAPER
ME 2302 — DYNAMICS OF MACHINERY
Time : Three hours Maximum : 100 Marks
Answer ALL questions
PART A — (10 × 2 = 20 Marks)
2. Define co-efficient of fluctuation of energy.
3. When is a system said to be completely balanced?
4. Name the efforts caused by the unbalanced primary force acting along the line of stroke due to partial balancing of locomotives.
5. Name the types of motion exhibited by critically damped or over damped vibrating systems.
6. Define logarithmic decrement.
7. Define transmissible.
8. When does resonance take place in a system?
9. When is a governor said to be Isochronous?
10. When is a governor said to be stable?
PART B — (5 × 16 = 80 Marks)
11. (a) The lengths of crank and connecting rod of horizontal steam engine are 300 mm and 1.2 m respectively. When the crank has moved 30° from the inner dead center, the acceleration of piston is 35 m/s2. The average frictional resistance to the motion of piston is equivalent to a force of 550 N and net effective steam pressure on piston is 500 kN/m2. The diameter of piston is 0.3 m and mass of reciprocating parts is 160 kg. Determine (i) Reaction on the cross-head guides; (ii) Thrust on the crankshaft bearings; and (iii) Torque on the crank shaft. [Marks 16]
12. (a) A shaft carries four rotating masses A, B, C and D in this order along its axis. The mass of B, C and D are 30 kg, 50 kg and 40 kg respectively. The planes containing B and C are 30 cm apart. The angular spacing of the planes containing C and D are 90° and 210° respectively relative to B measured in the same sense. If the shaft and masses are to be in complete dynamic balance, find (i) the mass and the angular position of mass A; and (ii) the position of planes A and D. [Marks 16]
13. (a) Determine: (i) the critical damping co-efficient, (ii) the damping factor, (iii) the natural frequency of damped vibrations, (iv) the logarithmic decrement and (v) the ratio of two consecutive amplitudes of a vibrating system which consists of a mass of 25 kg, a spring of stiffness 15 kN/m and a damper. The damping provided is only 15% of the critical value. [Marks 16]
14. (a) A body having a mass of 15 kg is suspended from a spring which deflects 12 mm under weight of the mass. Determine the frequency of the free vibrations. What is the viscous damping force needed to make the motion a periodic at a speed of 1 mm/s? If, when damped to this extent, disturbing force having a maximum value of 100 N and vibrating at 6 Hz is made to act on the body, determine the
amplitude of the ultimate motion. [Marks 16]
force transmitted to the foundation is 1/20th of the impressed force. The machine crankshaft rotates at 800 rpm. If, under actual working conditions, the damping reduces the amplitudes of successive vibrations by 30%, find: (i) the force transmitted to the foundation at 800 rpm, and (ii) the force transmitted to the foundation at resonance. [Marks 16]
15. (a) The turbine rotor of a ship has a mass of 2.2 tonnes and rotates at 1800 rpm clockwise when viewed from the aft. The radius of gyration of the rotor is 320 mm. Determine the gyroscopic couple and its effect when (i) The ship turns right at a radius of 250 m with a speed of 25 km/h., (ii) The ship pitches with the bow rising at an angular velocity of 0.8 rad/s., and (iii) The ship rolls at an angular velocity of 0.1 rad/s. [Marks 16]