VIBRATION

 Vibration is a periodic motion of small magnitude. But for sake of simplicity we can assume that it as simple harmonic motion of small amplitude.

Some important term of vibration :-

Period :- It is a time taken by a motion to repeat itself, and it is measure in seconds.

Cycle :- It is the motion completed during one time period.

Frequency :- frequency is the number of cycles of motion completed in one second. It is expressed in hertz (Hz) and is equal to one cycle per second.

Resonance :When the frequency of the external force is the same as that of the natural frequency of the system, a state of resonance is said to have been reached. Resonance results in large amplitude of vibrations and this may be dangerous.


TYPE OF VIBRATION :-

 Free vibration :- Elastic vibration in which there are no friction and external forces after the initial release of the body, are known as free or natural vibrations.

Forced vibrations :- When a repeated force continuously acts on a system, the vibrations are said to be forced vibration. The frequency of the vibrations is that of

the applied force and is independent of there own natural frequency of vibrations.

Damped vibration :- When the energy of the vibrating system is gradually dissipated by friction and other resistance the vibrations are said to be damped vibration.

Un-damped vibration :- When there is no friction and resistance present in system to contaract vibration then body execute un-damped vibration.

Longitudinal vibration :- If the shaft is elongate and shortened so that the same moves up and down resulting in tensile and compressive stresses in the shaft, the vibration are said to be longitudinal.

Transverse vibration :- When the shaft is bent alternately and tensile and compressive stresses due to bending results, the vibration are said to be transverse vibration.

Torsional vibration :- When the shaft is twisted and untwisted alternately and torsional shear stresses are induced. the vibrations are known as torsional vibration.