The ultrasound technology › General principles

History of ultrasound 

Ultrasound consists of elastic waves with a frequency of between around 16 kHz and several hundred Megahertz.


Frenchman Paul Langevin carried out the first work on ultrasound production techniques for SONAR at the end of the First World War. The applications and industrial uses of ultrasound developed towards the end of the 1950s. At this time a number of laboratories also demonstrated the extreme diversity of the applications of ultrasound.


Some of this work led rapidly to applications in the area of medical diagnostics and control, whilst aside from cleaning and welding, the use of high-power ultrasound in industry was not as widely spread. During the 1980s, the rapid development of modelling techniques led to significant progress being made in ultrasound technology.

Types of application

The performance of materials associated with developments in electronics today offer new opportunities for ultrasound to be used in industry.

  The applications of ultrasound are generally classified into two categories:

  •  low-power ultrasound for diagnostics, measuring and control,
  •  high-power ultrasound.

 

Ultrasound is considered to be high-power when it changes the environment in which it is propagated. The main actions are mechanical, thermal and/or chemical.

 

The application of ultrasound in solids can produce a rise in temperature when welding, a vibration, leading to a change in the apparent friction coefficient or the unclogging of sieves.

 

In liquids, cavitation is the predominant phenomenon caused by ultrasound. Cavitation is produced by emitting very intense ultrasound waves which create areas of alternate compression and dilation. Above a certain threshold, they induce the implosion of micro-cavities causing a significant localised heat increase and a wave of pressure several thousand times greater than atmospheric pressure. Ultrasonic cleaning, sonochemisty, declogging and powder dispersion are based on this phenomenon...

 

In gases, over short distances, it is possible to create very intense acoustic fields which enable liquids to be sprayed, powders to be debulked, or suspended particles to be amassed together...

 

The large variety of applications of ultrasound means that producing an exhaustive list is not possible. Ultrasound should be considered as a particular form of energy with multiple properties depending on the way in which is it used.

 

See also:

  

Piezoelectric effect

Transducers
Electronics and signal packaging

Effects of ultrasound


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