Abstract
Aiming at the key factors affecting the quality and efficiency of high-energy in-beam machining, this paper studies the broadband acoustic focusing effect based on a discrete temperature gradient. Firstly, the basic theory and mathematical model of temperature-controlled acoustic focusing are established. Secondly, the acoustic focusing effect is achieved by combining the design of metasurfaces and discrete temperature. Then, the acoustic pressure and intensity distribution of acoustic focusing under a discrete temperature gradient are simulated and experimentally studied. The results show that the phase delay of transmission and reflection of acoustic wave covers the 2π interval by changing the temperature in different transmission units, which provides a theoretical basis for the processing of the acoustic focusing cavity.
Highlights
The acoustic focusing effect [1,2,3,4] has broad application prospects in the fields of acoustic imaging, ultrasonic medical treatment [5,6], and nondestructive testing [7,8]
The acoustic focusing performance of the metasurfaces depends on the discontinuous distribution of different unit structures; the metasurface unit is composed of at least two kinds of media, which lead to an acoustic impedance mismatch and a narrow working frequency band, sometimes even a single frequency, limiting the practical application of the acoustic focusing device
Using a gradient temperature field can change the refractive index of medium distribution, which can effectively solve the problems of acoustic impedance matching and acoustic energy loss, realize the arbitrary control of the sound wave propagation path, and obtain a series of broadband acoustic anomalies, such as acoustic focusing [23,24], acoustic stealth [25], acoustic absorption [18], and acoustic unidirectional transmission [26]
Summary
The acoustic focusing effect [1,2,3,4] has broad application prospects in the fields of acoustic imaging, ultrasonic medical treatment [5,6], and nondestructive testing [7,8]. Acoustic metasurfaces have a small unit size and a large negative refractive index; it is possible to design a small and ultrathin acoustic focusing lens. The acoustic refractive index of gradient distribution is obtained by arranging different sizes of unit structures, and the acoustic focusing effect is realized [21,22]. Using a gradient temperature field can change the refractive index of medium distribution, which can effectively solve the problems of acoustic impedance matching and acoustic energy loss, realize the arbitrary control of the sound wave propagation path, and obtain a series of broadband acoustic anomalies, such as acoustic focusing [23,24], acoustic stealth [25], acoustic absorption [18], and acoustic unidirectional transmission [26]. A theoretical basis for the internal processing of acoustic focusing is provided
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