In the Theory of Machines, the term Vibratory motion is defined as the to and fro motion of a body about a fixed point due to the internal forces by the strain energy. Let’s discuss more on the Vibratory Motion of an object and different terms used in the Vibratory motion in this article.
When an elastic body such as a spring, a beam or a shaft are displaced from the equilibrium position due to some external force, and then released, then the body tends to execute the vibrations due to the internal forces araised by the strain energy present in the body. At the release of external force, these internal forces bring the body to its original position again.
When the body reaches its equilibrium position, the whole of the elastic or strain energy is converted into kinetic energy due to which the body continues to move in the opposite direction. The whole of the kinetic energy is converted into the strain energy due to which the body again returns to the equilibrium position. In this way, the vibratory motion repeats indefinitely.
Terms Used in Vibratory Motion
There are some important terms used in the study of the vibratory motion of an object in the theory of machines. Those are
- Period of Vibration
Period of Vibration
Also known as the time period or time interval at which the motion starts repeats itself. This period of Vibration is expressed in seconds.
When a motion completes during one time period is called the Cycle.
The number of cycles described in one-second known as the Frequency. For example in S.I units, this frequency expressed in the Hertz (Hz) which is equal to one cycle per second.
These three basic nomenclatures are frequently used in the study of the vibratory motion. Now let’s see how many types of vibratory motions are there.
Types of Vibrations
There are different types of vibratory motions. Those are
- Free Vibrations or Natural VIbrations
- Forced Vibrations
- Damped Vibrations
Free Vibrations or Natural VIbrations
When an initial displacement is given to a body, and further no external force acts on the body then the body starts vibrating. These vibrations called free or natural vibrations. The frequency of these vibrations is called the Natural frequency.
When a body vibrates due to the influence of an external force, then the body said to be under the forced Vibrations. This external force is a periodic disturbing force created by unbalance. These forced vibrations will have the same frequency as the applied force.
Resonance: When the Frequency of the external force is the same as that of the natural vibrations, then the resonance takes place.
When there is a reduction in the amplitude over every cycle of vibration, the motion is said to be damped vibration. This reduction in the amplitude of vibration is due to a certain amount of energy is possessed by the vibrating system is always dissipated in overcoming the frictional resistance to the motion.
This is a basic introduction to the study of Vibratory motions of a body in Theory of Machines. In the next articles, we have discussed more of the vibratory motion of the body in detail. Next Article
We have discussed what is meant by the vibrations and different types of vibrations. If you have any further thoughts on this topic, let us know in the comment section below.