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Machine Dynamics Practice Test: Torsional Vibrations
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Torsional Vibrations topics include: Torsional vibrations of single, two and three rotor systems, torsionally equivalent shaft, isolation and transmissibility and geared system torsinal vibrations. Torsional vibration is a type of vibration that involves the angular vibration of an object, usually a shaft, along its axis of rotation. It can be caused by time-alternating torques that are superimposed on the steady running speed of a rotating shaft.  Torsional vibration can be measured by measuring the RPM of a shaft with a high number of pulses per revolution (PPR).  It can be measured... Show more
Machine Dynamics Practice Test: Torsional Vibrations
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25 Questions

1. Which of the following systems produce a vibration in the foundation?
2. If radius of gyration increases then the torsional free vibration increases.
3. From the following data, calculate the equivalent length of shaft in m.
l1=0.6m, l2=0.5m, l3=0.4m
d1=0.095m, d2=0.06m, d3=0.05m
4. Calculate the Polar moment of inertia in m4 of a single motor system from the following data:
C = 8 GN/m2, L=9m, I = 600 Kg-m2, f=10 Hz
5. In a three rotor system, free torsional vibration cannot occur if there is only one node.
6. From the following data, calculate the location of node from the left end of shaft (l1).
l1=0.6m, l2=0.5m, l3=0.4m
d1=0.095m, d2=0.06m, d3=0.05m
Ma = 900 Kg, Mb = 700 Kg
ka = 0.85m, kb = 0.55m
7. Keeping the mass moment of inertia of left end and the right end shafts in a three rotor system same, if the length of one shaft is doubled what should be the effect on the length of other shaft?
8. A geared system possessed a kinetic energy if 200kJ, later it was converted into a two-rotor system connected by a shaft. The kinetic energy of the equivalent system will be_____
9. When inertia of gearing is taken into consideration, then which of the following should be taken into account.
10. Which of the following is correct regarding isolation factor?
11. A single cylinder oil engine works with a three rotor system, the shaft length is 2.5m and 70mm in diameter, the middle rotor is at a distance 1.5m from one end. Calculate the free torsional vibration frequency for a single node system in Hz if the mass moment of inertia of rotors in Kg-m2 are: 0.15, 0.3 and 0.09. C=84 kN/mm2
12. In a geared system free torsional vibration will take place when the Inertia of gear is taken into consideration.
13. For a gearing system, the equivalent system is made consisting of two rotors. How many nodes will this new equivalent system will have?
14. Which of the following is true regarding Ɛ>1?
15. Free torsional vibrations will occur in a three rotor system only if all rotors have same frequency.
16. In a three rotor system, for the middle rotor, if the stiffness of both the length either side of the rotor is increased to two times what will be the effect on total stiffness of the middle rotor?
17. Keeping the mass moment of inertia of both the shafts in a two rotor system same, if the length of one shaft is doubled what should be the effect on the length of other shaft?
18. In a system with different shaft parameters, the longest shaft is taken for calculations.
19. In a gearing system, pump speed is one third of the motor. Shaft from motor is 6 cm in diameter and 30cm long, the impellar shaft is 10cm diameter and 60cm long. Mass moment of inertia is 1500 Kg-m2, C = 80Gn/m2. Neglecting the inertia of shaft and gears calculate the frequency of free torsional vibrations in Hz.
20. At a nodal point in the shaft, the frequency of vibration is _________
21. For a two rotor system, the mass moment of inertia of one shaft(A) is twice the other(B), then what is the relation between the length of the shafts.
22. A geared system possessed a strain energy if 150kJ, later it was converted into a two-rotor system connected by a shaft. The Strain energy of the equivalent system will be _____
23. For a two rotor system, the length of one shaft(A) is twice the other(B), then what is the relation between the Mass moment of inertia of the shafts.
24. For a gearing system, the equivalent system is made consisting of three rotors. How many nodes will this new equivalent system will have?
25. For occurrence of free torsional vibration in a three rotor system which of the condition is necessary?

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