Deck 3: Vibration Analysis and Torsional Vibration in Shaft Systems

Question 1

For a vibration system having different shaft parameters, calculate which of the following cannot be the diameter of the equivalent shaft if the diameters of shafts in m are: 0.05, 0.06, 0.07.

A)0.05
B)0.06
C)0.07
D)0.08

Answer 1

0.08

Question 2

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

A)171
B)181
C)191
D)201

Answer 2

171

Question 3

At a nodal point in the shaft, the frequency of vibration is _________

A)Zero
B)Double than at the ends
C)Minimum
D)Maximum

Answer 3

Zero

Question 4

For a gearing system, the equivalent system is made consisting of two rotors. How many nodes will this new equivalent system will have?

A)0
B)1
C)2
D)3

Question 5

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 Kgm2, C = 80Gn/m2. Neglecting the inertia of shaft and gears calculate the frequency of free torsional vibrations in Hz.

A)4.7
B)5.7
C)4.5
D)5.5

Question 6

When inertia of gearing is taken into consideration, then which of the following should be taken into account.

A)Addition of rotor
B)Addition of gear
C)Addition of shaft
D)Addition of pump

Question 7

For occurrence of free torsional vibration which of the condition is necessary?

A)Rotors moving in same direction
B)Rotors having same frequency
C)Rotors having different frequency
D)Rotors rotate in the same sense

Question 8

n the given figure if N is the node then NQ acts as which of the following system?

A)Single rotor system
B)Two rotor system
C)Three rotor system
D)Four rotor system

Question 9

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?

A)Doubled
B)Halved
C)Constant
D)increased to 4 times

Question 10

In which of the following condition torsional vibration will not take place, considering 3 rotors A, B and C. A is rotating in clockwise direction.

A)B in clockwise C in anticlockwise
B)C in clockwise B in anticlockwise
C)B and C in clockwise
D)B and C in anticlockwise

Question 11

For occurrence of free torsional vibration in a three rotor system which of the condition is necessary?

A)Rotors moving in same direction
B)Rotors having same frequency
C)Rotors having different frequency
D)Rotors rotate in the same sense

Question 12

A vertical circular disc is supported by a horizontal stepped shaft as shown below. Determine equivalent length of shaft when equivalent diameter is 20 mm.

A)1.559 m
B)0.559 m
C)0.633 m
D)None of the above

Question 13

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

A)Remains constant
B)Decreases by two times
C)Increases by two times
D)Increases by 4 times

Question 14

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 two 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

A)257
B)281
C)197
D)277

Question 15

Increasing which of the following factor would result in increase of free torsional vibration?

A)Radius of gyration
B)Mass moment of inertia
C)Polar moment of inertia
D)Length

Question 16

The frequency of the free torsional vibration depends on…....

A)number of rotors
B)the number of nodes
C)Both a and b
D)Only b

Question 17

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.

A)2L(A) = L(B)
B)L(A) = 2L(B)
C)L(A) = L(B)
D)2L(A) = 3L(B)

Question 18

Which of the following is true for centrifugal force causing unbalance?

A)Direction changes with rotation
B)Magnitude changes with rotation
C)Direction and magnitude both change with rotation
D)Direction and magnitude both remain unchanged with rotation

Question 19

If the unbalanced system is not set right then.

A)Static forces develop
B)Dynamic forces develop
C)Tangential forces develop
D)Radial forces develop

Question 20

What is the effect of a rotating mass of a shaft on a system?

A)Bend the shaft
B)Twist the shaft
C)Extend the shaft
D)Compress the shaft

Question 21

In a revolving rotor, the centrifugal force remains balanced as long as the centre of the mass of the rotor lies ___________

A)Below the axis of shaft
B)On the axis of the shaft
C)Above the axis of shaft
D)Away from the axis of shaft

Question 22

Often an unbalance of forces is produced in rotary or reciprocating machinery due to the ______

A)Centripetal forces
B)Centrifugal forces
C)Friction forces
D)Inertia forces

Question 23

The mass used to balance the mass defect is known as ______

A)Balancing mass
B)Defect mass
C)Replacement mass
D)Fixing mass