Mechanical Engineering >> MV

Question 1 : What do you mean by vibration?

Answer : Any motion that repeats itself after an equal interval of time is called vibration. It may be periodic such as swinging of simple pendulum as shown in fig (a) or it may be random such as movement of wheel on the road as shown on fig (b).

Question 2 : What are the types of Vibration?

Answer : Some of important types are given below:
a. Free vibration and forced vibration.
b. Damped and undamped vibration.
c. Linear and non-linear vibration.
d. Deterministic and Random Vibration.
e. Longitudinal, Transverse and Torsional vibrations.
f. Transient Vibrations.

Question 3 : What are the three elementary parts of a vibrating system?

Answer : Vibrating System basically consists of three parts.

Question 4 : Define the degree of freedom (DOF) of a vibrating system

Answer : The minimum number of independent coordinates required to describe completely the motion of a system at any instant of time is called degree of freedom of the system.
For example:
1. Simple pendulum has single D.O.F.
2. A continuous system as cantilever beam as shown in fig. (a) has infinite degree of freedom. As the beam has an infinite number of mass points, so we need an infinite number of coordinates to specify its deflected configuration.

Question 5 : Define Resonance

Answer : In a lightly damped system when the forced frequency of vibration nears the natural frequency of vibration of a system, the amplitude of vibration gets extremely high. This phenomenon is called Resonance .It leads toward the failure of the system.

Question 6 : What parameters are necessary so that the vibration may occur?
What are the reasons of unbalance in the system?
What are the possible causes of vibration?

Answer : Some of necessary parameters or possible causes are:
1.External force or excitation applied on the system.
2.Due to faulty design, improper material distribution and poor manufacturing.
3.Elastic nature of the system, e.g. spring.
4.Natural phenomena such as earth quake.
5.Wind also produces vibration in some cases.

Question 7 : Write the Basic concepts of vibration.

Answer : The basic concept behind vibration is alternately transfer of potential energy (P.E) to kinetic energy (K.E) and K.E to P.E, due to the application of external force applied on the system. For example: The swinging of simple pendulum as shown in fig(a).

Question 8 : What is self excited vibration?
What is free vibration?
What is natural vibration?

Answer : This is a type of vibration, in which after giving initial disturbance, the system vibrates its own due to inherent forces in the systems and no external force is present.
For example:
1. Oscillation of simple pendulum with only initial disturbance only.
2. Movement of electrons.
3.Hitting a turing fork and lifting it ring.
4.Spring-Mass system with initial applied force only as shown in fig.8.a.

Question 9 : Define Forced Vibration.

Answer : This is one of the type of vibration and in this, vibrations are due to initial conditions as well as external force applied on the system. In this vibration occur due to repeatally forces are applied on the system.
For Example:
1. Vibration in building during earthquake.
2. Electric bell.
3. Spring Mass System with continuously applied force as shown in fig.9.

Question 10 : Define Damped vibration

Answer : This is type of vibration, in which amplitude of forced vibration or self induced vibrations are damped or stopped to causing further trouble or inconvenience. A device “damper” is used for this purpose.
For example: Spring Mass system in which damper is provided to control the movement or vibrations produced in mass due to applied force, as shown in fig below.

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