Because of the short wavelength of ultrasound, ultrasonic rays can be reflected, refracted, and focused just like light, and . Obey the laws of geometric optics. That is, ultrasonic rays reflected from the surface of a material, the angle of incidence is equal to the angle of reflection, when the rays through a material into another material with a different density will produce refraction, that is, to change the direction of its insertion, the greater the difference between the density of the two substances, the greater the refraction.
Absorption properties
Sound waves propagate in various substances, with the increase of the propagation distance, the intensity will gradually weaken, this is because the substance to absorb its energy. For the same substance, the higher the frequency of the sound wave, the stronger the absorption. For a sound wave of a certain frequency, it is absorbed most strongly in gases, less strongly in liquids, and least strongly in solids.
The energy transfer characteristics of ultrasonic waves
Ultrasonic waves so to the various industrial sectors have a wide range of applications, the main point
Also lies in the sound waves than have a much stronger power. Why is there a strong power? Because when the sound wave reaches a material, due to the role of the sound wave so that the molecules in the material also follow the vibration, vibration frequency and sound wave frequency - the same, the frequency of molecular vibration determines the speed of molecular vibration. The higher the frequency, the greater the speed. Material molecules due to the vibration of the energy obtained in addition to the quality of the molecules, is determined by the molecular vibration speed of the square, so if the higher the frequency of the sound wave, that is, the material molecules more can get higher energy, ultrasonic frequency than the sound wave can be a lot higher, so it can make the material molecules to obtain a lot of energy; in other words, ultrasonic waves itself can supply the material is large enough to the power.
Sound pressure characteristics of ultrasonic waves
When the sound wave passes into an object, due to acoustic vibration of the molecules of the material to produce compression and dilution of the role of the material will be subjected to changes in the pressure of the material. The phenomenon of additional pressure due to the vibration of sound waves is called acoustic pressure.
Because the ultrasonic wave has a lot of energy, it is possible to make the material molecules to produce a significant acoustic pressure, for example, when the water through the general intensity of the ultrasonic wave, the additional pressure can reach several atmospheric pressure. Liquid stored in such a huge acoustic pressure effect, it
will cause noteworthy phenomena. When the ultrasonic vibration makes the liquid molecules compressed, as if the molecules are coming straight from all sides of the pressure; when the ultrasonic vibration makes the liquid molecules sparse, as if by the outward dispersion of the tension, for the liquid, they are more able to withstand the action of the additional pressure, so in the compression of the force; will not be produced by the General Assembly of the anomalous situation. But under the action of the tension, the liquid will not support, in the tension concentrated
place, the liquid will break, this fracture is particularly likely to occur in the liquid in the presence of impurities or bubbles in the place, because of the strength of the liquid in these places is particularly
low, but also particularly unable to withstand several times the atmospheric pressure of the action of the tension. As a result of the fracture, many small bubble-like cavities are created in the liquid, which exist for a short period of time and close up in an instant. When the cavity closes, it
generates a large transient pressure, typically up to thousands or even tens of thousands of atmospheres. The temperature of the liquid under this strong transient pressure increases abruptly.
The transient pressure caused by fracture can cause the surface of the solid suspended in the liquid
to be dramatically damaged. We often call this cavitation.
Ultrasonic applications are characterized by the following:
Ultrasonic waves have good directivity - the higher the frequency, the stronger the directivity. This is a major consideration in applications such as flaw detection and underwater acoustic communications.
Higher frequencies result in shorter wavelengths, so that the wavelength can be comparable to, or even much smaller than, the size of the specimen material through which the ultrasound is traveling. This is very important in applications where thickness dimensions are very small, as well as in high-resolution flaw detection applications.
Ultrasonic waves are so quiet that people can't hear them. This is especially important in high-intensity work situations. These intense jobs are often more efficient when done with audible frequency sound waves, but unfortunately, the noise generated by audible sound waves is unbearable and sometimes even harmful.