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From Nordan Symposia
Jump to navigationJump to searchNew page: Image:lighterstill.jpgright|frame '''Vibration''' refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic su...
[[Image:lighterstill.jpg]][[Image:Two_dim_standing_wave.gif|right|frame]]
'''Vibration''' refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the [[motion]] of a [[pendulum]] or [[random]] such as the [[movement]] of a tire on a gravel road.
Vibration is occasionally "desirable". For example the motion of a tuning fork, the reed in a woodwind instrument or harmonica, or the cone of a loudspeaker is desirable vibration, necessary for the correct functioning of the various devices.
More often, vibration is undesirable, wasting [[energy]] and creating unwanted [[sound]] – noise. For example, the vibrational motions of engines, electric motors, or any mechanical device in operation are typically unwanted. Such vibrations can be caused by imbalances in the rotating parts, uneven [[friction]], the meshing of gear teeth, etc. Careful [[design]]s usually minimize unwanted vibrations.
The study of [[sound]] and vibration are closely related. Sound, or "pressure waves", are generated by vibrating [[structures]] (e.g. [[vocal cords]]); these pressure waves can also induce the vibration of structures (e.g. [[ear drum]]). Hence, when trying to reduce noise it is often a problem in trying to reduce vibration.
==Types of vibration==
Free vibration occurs when a mechanical system is set off with an initial input and then allowed to vibrate freely. Examples of this type of vibration are pulling a child back on a swing and then letting go or hitting a tuning fork and letting it ring. The mechanical system will then vibrate at one or more of its "natural frequencies" and damp down to zero.
Forced vibration is when an alternating force or motion is applied to a mechanical system. Examples of this type of vibration include a shaking washing machine due to an im[[balance]], transportation vibration (caused by truck engine, springs, road, etc), or the vibration of a building during an [[earthquake]]. In forced vibration the frequency of the vibration is the frequency of the force or motion applied, with order of magnitude being dependent on the actual mechanical system.
==Further reading==
* Inman, Daniel J., Engineering Vibration, Prentice Hall, 2001, ISBN 013726142X
* Rao, Singiresu, Mechanical Vibrations, Addison Wesley, 1990, ISBN 0-201-50156-2
* Thompson, W.T., Theory of Vibrations, Nelson Thornes Ltd, 1996, ISBN 0-412-783908
* Hartog, Den, Mechanical Vibrations, Dover Publications, 1985, ISBN 0-486-647854
==External links==
*Hyperphysics Educational Website, [http://hyperphysics.phy-astr.gsu.edu/hbase/permot.html#permot''Oscillation/Vibration Concepts'']
*Thermotron Industries, [http://www.thermotron.com/resources/vibration_handbook.html''Fundamentals of Electrodynamic Vibration Testing Handbook'']
*Nelson Publishing, [http://www.evaulationengineering.com/ ''Evaluation Engineering Magazine'']
* [http://structdynviblab.mcgill.ca/index.html Structural Dynamics and Vibration Laboratory of McGill University]
* [http://web.mat.bham.ac.uk/C.J.Sangwin/Teaching/CircWaves/waves.html Normal vibration modes of a circular membrane]
[[Category: Physics]]
'''Vibration''' refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the [[motion]] of a [[pendulum]] or [[random]] such as the [[movement]] of a tire on a gravel road.
Vibration is occasionally "desirable". For example the motion of a tuning fork, the reed in a woodwind instrument or harmonica, or the cone of a loudspeaker is desirable vibration, necessary for the correct functioning of the various devices.
More often, vibration is undesirable, wasting [[energy]] and creating unwanted [[sound]] – noise. For example, the vibrational motions of engines, electric motors, or any mechanical device in operation are typically unwanted. Such vibrations can be caused by imbalances in the rotating parts, uneven [[friction]], the meshing of gear teeth, etc. Careful [[design]]s usually minimize unwanted vibrations.
The study of [[sound]] and vibration are closely related. Sound, or "pressure waves", are generated by vibrating [[structures]] (e.g. [[vocal cords]]); these pressure waves can also induce the vibration of structures (e.g. [[ear drum]]). Hence, when trying to reduce noise it is often a problem in trying to reduce vibration.
==Types of vibration==
Free vibration occurs when a mechanical system is set off with an initial input and then allowed to vibrate freely. Examples of this type of vibration are pulling a child back on a swing and then letting go or hitting a tuning fork and letting it ring. The mechanical system will then vibrate at one or more of its "natural frequencies" and damp down to zero.
Forced vibration is when an alternating force or motion is applied to a mechanical system. Examples of this type of vibration include a shaking washing machine due to an im[[balance]], transportation vibration (caused by truck engine, springs, road, etc), or the vibration of a building during an [[earthquake]]. In forced vibration the frequency of the vibration is the frequency of the force or motion applied, with order of magnitude being dependent on the actual mechanical system.
==Further reading==
* Inman, Daniel J., Engineering Vibration, Prentice Hall, 2001, ISBN 013726142X
* Rao, Singiresu, Mechanical Vibrations, Addison Wesley, 1990, ISBN 0-201-50156-2
* Thompson, W.T., Theory of Vibrations, Nelson Thornes Ltd, 1996, ISBN 0-412-783908
* Hartog, Den, Mechanical Vibrations, Dover Publications, 1985, ISBN 0-486-647854
==External links==
*Hyperphysics Educational Website, [http://hyperphysics.phy-astr.gsu.edu/hbase/permot.html#permot''Oscillation/Vibration Concepts'']
*Thermotron Industries, [http://www.thermotron.com/resources/vibration_handbook.html''Fundamentals of Electrodynamic Vibration Testing Handbook'']
*Nelson Publishing, [http://www.evaulationengineering.com/ ''Evaluation Engineering Magazine'']
* [http://structdynviblab.mcgill.ca/index.html Structural Dynamics and Vibration Laboratory of McGill University]
* [http://web.mat.bham.ac.uk/C.J.Sangwin/Teaching/CircWaves/waves.html Normal vibration modes of a circular membrane]
[[Category: Physics]]
