Types of vibration. Pdf showing the types of vibrations. PDF

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Types of vibration. Pdf showing the types of vibrations....

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Types of vibration Introduction Any motion that has the tendancy to repeat itself after an interval of time is called vibration, or alternatively oscillation. Examples of vibrating systems include: • • • • • •

Pendulums Guitar string Engines Unbalanced machinery Electronic circuits ... and many more

Classification of Vibration Vibration can be classified into four types: • • • •

Undamped Free vibration Damped Free vibration Undamped Forced vibration Damped Forced vibration

Free vs Forced Free Vibration: If a system, after an initial disturbance, is left to vibrate on its own, the ensuing vibration is known as free vibration. No external force acts on the system. The oscillation of a simple pendulum is an example of free vibration. Forced Vibration: If a system is subjected to an external force (often, a repeating type of force), the resulting vibration is known as forced vibration.

Undamped vs Damped Undamped Vibration: If no energy is lost or dissipated in friction or other resistance during oscillation, the vibration is known as undamped vibration. Damped Vibration: If any energy is lost, it is called damped vibration.

Undamped Free vibration

Many systems if friction is negligible, can be modelled as undamped.

Damped Free vibration

Damping often modelled as viscous, force proportional to velocity Other types of damping does exist (e.g. Coulomb, hysterisis) but usually only use if needed.

Undamped and Damped Forced vibration

Forced vibration has energy from an external source contributing to the system's response. External energy can be supplied either directly through a force, through a displacement or through a driven imbalance. Often the vibration of the system with a harmonic excitation is analysed.

Undamped Forced Vibration:

Damped Forced Vibration:

Base Vibration:

Rotating Unbalanced Mass:

Links and references Textbooks: Rao, Mechanical Vibrations, 5th Edition, Chapers 2 and Chapter 3.

Online: https://en.wikipedia.org/wiki/Vibration...