Acoustic lubrication
Encyclopedia
Acoustic or sonic lubrication occurs when sound (measurable in a vacuum by placing a microphone on one element of the sliding system) permits vibration to introduce separation between the sliding faces. This could happen between two plates or between a series of particles. The frequency of sound required to induce optimal vibration, and thus cause sonic lubrication, varies with the size of the particles (high frequencies will have the desired, or undesired, effect on sand and lower frequencies will have this effect on boulders).
tank treads lubricated by their own squeak provide the most famous, if serendipitous
, example.
Another example occurs during landslides. Most landslides do not involve this effect, but occasionally the frequency of vibrations caused by the landslide is optimal to cause the boulders to vibrate. In this case, feedback causes the boulders to slide much farther and more quickly than typical, which can pose an increased danger to those in their path. One notable feature of such a landslide is that it appears to resemble flowing water, or mud, and not the dry sliding rocks that they were seconds earlier.
A third, more common, instance is when a mobile phone or pager is placed on a slightly sloping table. If the vibration motor is activated, the phone will slide along the table.
The new Gillete razor with a vibrating head may also be an example.
Examples
If there is a dynamic coefficient of friction between two objects of 0.20, and vibration causes them to be in contact only half of the time, that would be equivalent to a constant coefficient of friction of 0.10. This substantial reduction in friction can have a profound effect on the system. World War II PanzerPanzer
A Panzer is a German language word that, when used as a noun, means "tank". When it is used as an adjective, it means either tank or "armoured" .- Etymology :...
tank treads lubricated by their own squeak provide the most famous, if serendipitous
Serendipity
Serendipity means a "happy accident" or "pleasant surprise"; specifically, the accident of finding something good or useful without looking for it. The word has been voted as one of the ten English words hardest to translate in June 2004 by a British translation company. However, due to its...
, example.
Another example occurs during landslides. Most landslides do not involve this effect, but occasionally the frequency of vibrations caused by the landslide is optimal to cause the boulders to vibrate. In this case, feedback causes the boulders to slide much farther and more quickly than typical, which can pose an increased danger to those in their path. One notable feature of such a landslide is that it appears to resemble flowing water, or mud, and not the dry sliding rocks that they were seconds earlier.
A third, more common, instance is when a mobile phone or pager is placed on a slightly sloping table. If the vibration motor is activated, the phone will slide along the table.
Applications
Besides the study of landslides, there could be many other applications for acoustic lubrication, particularly where variable friction is required or traditional lubricants can't be used. One case might be drilling wells (for water, oil, etc.) through sand. The optimal pitch of the sound (measurement of frequency) could reduce the friction between the drill bit and sand considerably.The new Gillete razor with a vibrating head may also be an example.
In fiction
- The protagonist in the videogame Shadow ComplexShadow ComplexShadow Complex is a platform-adventure video game developed by Chair Entertainment in association with Epic Games and published by Microsoft Game Studios for Xbox Live Arcade, and is powered by Unreal Engine 3...
can acquire a "friction dampener" that uses acoustic lubrication; this enables him to run at very high speeds.