Vibration

Vibration is a mechanical phenomenon where an equilibrium point oscillates. The term originates from “shaking, brandishing” Latin vibrationem.

The oscillations can be regular, like a pendulum’s motion— or random, like a tire’s movement on a gravel highway. Vibration may be desirable: for instance, a tuning fork, a woodwind instrument or a harmonica.

noise virbration
Photo by Brett Sayles

Types of Vibration

Free Vibration

Free vibration happens when a mechanical system with an original input is set in movement and free vibration is permitted. Examples of this kind of vibration are to pull a kid back on a swing and let it go or to hit a tuning fork and let it ring.

At one or more of its natural frequencies, the mechanical system vibrates and dampens down to motionlessness.

Forced Vibrations

Forced vibration occurs when a mechanical system is affected by a time-varying disruption (load, displacement or speed). The disruption can be a regular and stable input, a transient input, or a random input.

A harmonic or non-harmonic disruption may be the regular input. Examples of these vibration kinds include a washing machine that shakes owing to an imbalance, transport vibration. 

Damped vibration:

When friction and other resistances gradually dissipate the energy of a vibrating structure, it is said that the vibrations are dampened. The vibrations decrease or alter or cease gradually in frequency or intensity and the system remains in its situation of equilibrium.

The vehicle suspension dampened by the shock absorber is an instance of this sort of vibration.

Vibration Testing

Vibration testing is accomplished by introducing a forcing function into a structure, usually with some type of shaker. Alternately, a DUT (device under test) is attached to the “table” of a shaker.

Vibration testing is performed to examine the response of a device under test (DUT) to a defined vibration environment.

The measured response may be the ability to function in the vibration environment, fatigue life, resonant frequencies or squeak and rattle sound output (NVH).

Squeak and rattle testing are performed with a special type of quiet shaker that produces very low sound levels while under operation. The vibrations decrease or alter or cease gradually in frequency or intensity and the system remains in its situation of equilibrium.

The vehicle suspension dampened by the shock absorber is an instance of this sort of vibration.

This page is the part of Free online course Theory of Machine | This was last topic you learned Go to the Course Homepage to give a free test

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