What is vibration?
What is vibration?
- Vibration can be defined as simply the cyclic or oscillating motion of a machine or machine component from its position of rest.
- An important class of dynamics concerning the linear and angular motions of bodies that respond to the applied disturbances in the presence of restoring forces.
- Examples are the response of building structure to an earthquake, unbalanced axle rotation, flow-induced vibrations of a car body, and the rattling of tree leaves etc
Basic concepts
- Vibration sources are characterized by their time and frequency domain properties.
- Categorized principally as:
- Periodic
- originate from the HVAC, DG, fans, etc
- simplest form of periodic disturbance is harmonic.
- In the time domain, this is represented as a sinusoid, and in the frequency domain by a single line spectrum.
- Random disturbances
- originate from footsteps sounds, conversations, etc
- only statistical representations are possible.
- generally represented by its power spectrum
What causes vibration?
Repeating force
Looseness
Resonance
What causes vibration?
Change in direction with time, such as the force generated by a rotating unbalance.
Change in amplitude or intensity with time, such as the unbalanced magnetic forces generated in a motor due to an unequal air gap between the armature and stator.
Friction between rotating and stationary machine components like between the bow and the violin string to vibrate.
Impacts, such as gear tooth contacts or the impacts generated by the rolling elements of a bearing passing over flaws in the bearing raceways.
Randomly generated turbulence force devices such as fans, blowers, pumps, gas turbines, or boilers.
Improper installation without proper or improper mounts, isolators, etc.
Flanking transmission path in piping, building, etc.
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