Here are some of the technical fields in which the sonic and ultrasonic engineering may find wide application: oil-well drilling, liquid processing, machining, engraving and welding, underwater signalling, cleaning of metal parts, information storage, molecular analysis and some others. The frequency range covered by these applications is extremely wide and their realization therefore involves widely different acoustic engineering practices.
Most of the applications listed have today reached the stage of successful operations, that is, the usefulness to industry of these techniques and instruments has been widely recognized, the development of reliable equipment is more or less completed, and the manufacture and maintenance of the equipment have proved to be economical.
We now come to the other application of sonics - namely, the processing of materials. It has been found that intense vibrations affect colloidal distribution, equalize electrolytic concentrations, and speed up aging processes by absorption in a certain medium, intense vibrations may produce local heating effects, as for example, in the use of ultrasonics in medical therapy.
A particularly powerful phenomenon is cavitation. This is the breakdown of cohesion of a liquid that is exposed to high tensile forces as the sound wave passes through it.
Under the influence of cavitations steel surfaces may be pitted, oxide layers removed, bacteria disintegrated, or high polymers depolymerized. One of the particular successful applications of surface cavitation is in ultrasonic drilling, another is in the soldering of aluminium.
Progress during recent years has been encouraging and still more valuable contributions of sonics to industry may well be expected.
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