High-energy ultrasound has a unique acoustic effect

High-energy ultrasound has a unique acoustic effect. Ultrasonic vibration is introduced during the metal solidification process, the solidification structure changes from coarse columnar crystals to uniform fine equiaxed crystals, and the macroscopic and microscopic segregation of the metal is improved. At present, some foreign research results in this area have been applied in production, but there are few domestic relevant research reports.

1 Ultrasound and its characteristics

Ultrasound usually refers to high-frequency sound waves that vibrate more than 20,000 times in 1 second. When the intensity is low, ultrasound can be used as the carrier and medium for detecting load information, which is called detection ultrasound. When its intensity exceeds a certain value, it interacts with the sound transmission medium, which can change or even destroy the state, nature and structure of the sound transmission medium, which is called high-energy ultrasound or power ultrasound. This article mainly deals with high-energy ultrasound.

Ultrasound has the following four basic characteristics:

(1) Beam characteristics. Ultrasound has a short wavelength and can be concentrated into a beam of rays.
(2) Absorption characteristics. Ultrasonic waves are absorbed in air, liquids and solids. The absorption in the air is the strongest, and the absorption in the solid is the weakest.
(3) High power. Due to the high frequency, the power of ultrasonic waves is much greater than that of sound waves. It can not only cause rapid movement of the acting medium, but even destroy its molecular structure.
(4) Sound pressure effect. The sound wave vibration causes the material molecules to produce compression and thinning. This additional pressure phenomenon caused by the sound wave vibration is called the sound pressure effect.

The above-mentioned four basic characteristics cause ultrasonic waves to cause the following five effects in the media: mechanical effects, thermal effects, optical effects, electrical effects and chemical effects.