A method for realizing asymmetric transmission of elastic waves

Abstract

The present invention discloses a method for achieving asymmetric transmission of elastic waves, comprising the following steps: constructing a finite period structure as the transmission body, the finite period structure having an elastic wave band gap for transmission in a certain direction; end resonant modes are generated at both ends of the finite period structure due to the truncation of the period, and the end resonant frequencies are within the elastic wave band gap; changing the end structure or the connection method with the outside world to make the end resonant frequencies different, ensuring that the resonant frequency of at least one end remains within the elastic wave band gap; inputting an elastic wave at one end of the finite period structure, and if the frequency of the elastic wave is the same as the resonant frequency of the other end, the wave is transmitted through the elastic wave band gap to the other end of the finite period structure. By constructing the finite period structure using common materials and changing the end structure or the connection method with the outside world, an asymmetric transmission mode corresponding to the end resonant frequency can be generated within the elastic wave band gap of the structure, thereby simply and efficiently achieving asymmetric transmission of elastic waves.

Description

Technical Field

[0001] The present invention belongs to the technical field of elastic wave transmission, and in particular relates to a method for realizing asymmetric transmission of elastic waves. Background Art

[0002] Elastic waves are widely used in earthquake detection, geological exploration, mining, non-destructive testing of materials, earthquake and blast resistance of engineering structures, rock dynamics, and other fields. Controlling elastic wave transmission is crucial for all these applications. Achieving asymmetric elastic wave transmission is key to breaking through current elastic wave control methods.

[0003] However, unlike electromagnetic waves, elastic waves do not possess inherent nonreciprocal properties, and currently, complex methods are required to achieve asymmetric transmission. For example, external energy input can be used to destroy time reversal symmetry using piezoelectric materials or time-varying materials; or nonlinear materials can be used to change the frequency of elastic waves to destroy time reversal symmetry; or spatial inversion symmetry can be destroyed through wave type transformation or wave diffraction. However, these methods generally require special materials and complex overall structures, and their energy transmission efficiency is low. This makes the current methods very expensive to apply, the transmission effect is also limited, and their application is relatively difficult.

[0004] A search revealed that Hu Zhongtao and An Zhiwu's paper, "Asymmetric Propagation of Elastic Waves in Variable-Thickness Plates," discloses a method for designing a variable-thickness plate structure based on the dispersion characteristics of Lamb waves in the plate, enabling asymmetric propagation of elastic waves of specific frequencies. However, existing techniques still require specialized materials and complex overall structures for asymmetric elastic wave propagation, limiting the effectiveness of propagation. Therefore, there is an urgent need for methods to achieve efficient asymmetric transmission of elastic waves using relatively simple materials and structures. Summary of the Invention

[0005] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a method for realizing asymmetric transmission of elastic waves, which realizes asymmetric transmission of elastic waves simply and efficiently.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for realizing asymmetric transmission of elastic waves comprises the following steps: constructing a finite period structure as a transmission body, the finite period structure having an elastic wave band gap for transmission in a certain direction; having end resonance modes at both ends of the finite period structure due to truncation of the period, and the end resonance frequencies being within the elastic wave band gap; changing the end structure or the connection form with the outside world to make the end resonance frequencies different, ensuring that the resonance frequency of at least one end is still within the elastic wave band gap; inputting an elastic wave at one end of the finite period structure, and if the frequency of the elastic wave is the same as the resonance frequency of the other end, the elastic wave is transmitted to the other end of the finite period structure through the elastic wave band gap.

[0008] In the above technical solution, the finite period structure has an elastic wave band gap, which can block elastic waves within this frequency range; and due to the truncation of the period, the finite period structure has a resonant mode at the end, and the end resonance has a significant amplification effect on the elastic waves. Even if the end resonance frequency is within the band gap, the elastic wave frequency with the same end resonance frequency can still show more significant transmittance than other frequencies within the band gap; the end resonance frequency is changed so that the resonance frequencies at both ends are different, thereby realizing asymmetric transmission of elastic waves.

[0009] Furthermore, the period of the finite period structure is truncated, so that the finite period structure has a mode that resonates at only one end at certain frequencies.

[0010] The certain frequencies refer to resonant frequencies at which only one end of the finite period structure resonates when the period of the finite period structure is truncated.

[0011] Furthermore, when an elastic wave is input from one end A of the finite period structure, the elastic wave bandgap of the finite period structure blocks the elastic wave within the frequency range. When the frequency of the elastic wave is the same as the end resonance frequency of the other end B of the finite period structure, the elastic wave can be smoothly transmitted to the B end of the finite period structure through the elastic wave bandgap; and when an elastic wave is input from the B end of the finite period structure, the elastic wave bandgap of the finite period structure blocks the elastic wave within the frequency range. When the frequency of the elastic wave is the same as the end resonance frequency of the A end of the finite period structure, the elastic wave can be smoothly transmitted to the A end of the finite period structure through the elastic wave bandgap.

[0012] Furthermore, by changing the end resonance frequency, the resonance frequency of the finite period structure end A is different from that of the finite period structure end B. Therefore, the elastic wave transmitted from the finite period structure end A to the finite period structure end B has a different frequency from the elastic wave transmitted from the finite period structure end B to the finite period structure end A, thereby realizing asymmetric transmission of elastic waves.

[0013] Furthermore, if the elastic wave input from end A or end B of the finite period structure is within the elastic wave band gap frequency range and the frequency of the elastic wave is different from the resonant frequency of the other end, it cannot pass through the finite period structure.

[0014] Preferably, two or more materials are arranged periodically to construct a finite period structure.

[0015] Preferably, periodicity is constructed from one material through shape change, so that a finite periodic structure can be constructed using only a general material.

[0016] Preferably, the material used to construct the finite period structure is metal or polymer, so as to achieve asymmetric transmission of elastic waves without relying on special materials.

[0017] Preferably, the finite periodic structure is composed of 3 to 50 periodic units.

[0018] Preferably, the number of periodic units is determined by the degree of response required for the end output, so that the resonance peak within the band gap can be changed by changing the number of periodic units.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention truncates the period of a finite period structure so that the end portion has a resonant mode, thereby propagating an elastic wave frequency within the elastic wave band gap of the structure that is the same as the resonant frequency of the end portion; the end structure of at least one end of the structure is changed so that the resonant frequencies of the two ends are different, thereby achieving propagation of elastic waves at the same frequency as the resonant frequency of the end portion at both ends, thereby solving the technical problem of the difficulty in achieving asymmetric transmission of elastic waves in the prior art;

[0021] (2) The present invention does not rely on special materials. It can achieve asymmetric transmission of elastic waves by constructing a finite periodic structure using general materials, thus solving the technical problem of asymmetric transmission of elastic waves that cannot be easily achieved in the prior art.

[0022] (3) The present invention does not require the construction of a complex structure. It can regulate the frequency of asymmetric transmission of elastic waves by simply changing the end structure or the connection form with the outside world based on a finite period structure, thus solving the technical problem of the inability to efficiently realize asymmetric transmission of elastic waves in the prior art.

[0023] (4) The present invention utilizes end resonance to amplify elastic waves, which can effectively improve energy transmission efficiency;

[0024] (5) The method of the present invention is simple and easy to implement. It can effectively reduce the difficulty and cost of implementing asymmetric transmission of elastic waves, and is conducive to its wide application in practical engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of a finite period structure with end difference according to an embodiment of the present invention;

[0026] Figure 2 Graph showing the amplitude-frequency response function of the right end of the structure according to an embodiment of the present invention after the left end is incident with 0-1200 Hz vibration excitation in the x-direction;

[0027] Figure 3 Graph showing the amplitude-frequency response function of the right end of the structure according to an embodiment of the present invention after the left end is incident with 0-1200 Hz vibration excitation in the y direction;

[0028] Figure 4 Graph showing the amplitude-frequency response function of the left end of the structure according to an embodiment of the present invention after the right end is incident with 0-1200 Hz vibration excitation in the x-direction;

[0029] Figure 5 Graph showing the amplitude-frequency response function of the left end of the structure according to an embodiment of the present invention after the right end is incident with 0-1200 Hz vibration excitation in the y direction;

[0030] In the figure: 1, periodic structure; 2, additional straight rod segment; 3, first end; 4, second end; 5, highest point; 6, lowest point. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions of various embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] Example

[0033] This embodiment provides a method for asymmetric elastic wave transmission. By constructing a finite-period structure using common materials and modifying the end structure of the structure, an asymmetric transmission mode corresponding to the end resonant frequency can be generated within the elastic wave band gap of the structure, thereby achieving asymmetric elastic wave transmission simply and efficiently. The method includes the following steps:

[0034] S1. Construct a finite periodic structure as the main body of transmission, such as Figure 1 As shown in FIG, a sawtooth periodic structure 1 in the xy plane is constructed by a circular cross-section aluminum rod with a diameter of 0.004 m. The periodic structure 1 has 4 periods along the x direction. The length of each period along the x direction is 0.143 m. The total length of the 4 periods along the x direction is 0.572 m. The highest point 5 and the lowest point 6 are both 0.035 m away from the connecting line of the head and tail. Figure 2-5 As shown in FIG, according to the amplitude-frequency response function diagram obtained after the finite period structure is incident with 0~1200Hz vibration excitation, it is determined that the finite period structure has an elastic wave band gap in the range of 302~1057Hz.

[0035] Specifically, the theoretical band gap range can be obtained by theoretically calculating the dispersion relation of an infinite periodic structure.

[0036] S2. The finite period structure has an end resonance mode because both ends are exposed due to period truncation. The end resonance frequency of the finite period structure is measured to be 672 Hz.

[0037] Specifically, the end resonance frequency can be determined to be 672 Hz based on the amplitude-frequency response function diagram obtained after the finite period structure is subjected to 0-1200 Hz vibration excitation. This process can be calculated or tested.

[0038] S3. Change the end structure to make the end resonant frequency different. In order to make the resonant frequencies at the two ends different, maintain the original state of the first end 3 of the finite period structure, and only change the structure of the second end 4 of the finite period structure so that the resonant frequencies at both ends of the finite period structure are still within the elastic wave band gap. The resonant frequency of the second end of the finite period structure is measured to be 546 Hz.

[0039] Specifically, a section of rod that is identical to the additional straight rod section 2 is adhered to the additional straight rod section 2 where the second end 4 is located.

[0040] Specifically, the end resonance frequency can be determined to be 546 Hz based on the amplitude-frequency response function diagram obtained after the finite period structure is incident with a vibration excitation of 0 to 1200 Hz. This process can be calculated or tested.

[0041] Specifically, a finite periodic structure must be truncated at both ends, exposing two ends, but these two ends may be connected to other components or not.

[0042] S4. An elastic wave is inputted into one end of the finite period structure. If the frequency of the elastic wave is the same as the resonant frequency of the other end, the elastic wave is transmitted to the other end of the finite period structure through the elastic wave band gap.

[0043] Specifically, when the excitation frequency applied to the first end 3 of the finite period structure is 546 Hz, it is within the band gap range of 302 to 1057 Hz and can still be smoothly transmitted to the right end; when the excitation frequency applied to the second end 4 of the finite period structure is 672 Hz, it is within the band gap range of 302 to 1057 Hz and can still be smoothly transmitted to the left end.

[0044] S5. If the elastic wave input from the first end 3 or the second end 4 of the finite period structure is within the elastic wave band gap frequency range and the frequency of the elastic wave is different from the resonant frequency of the other end, it cannot pass through the finite period structure.

[0045] Specifically, when the excitation frequency applied to the second end 4 of the finite period structure is 546 Hz, it cannot be transmitted to the left end; when the excitation frequency applied to the first end 3 of the finite period structure is 672 Hz, it cannot be transmitted to the right end.

[0046] This simple and efficient approach achieves asymmetric elastic wave transmission. By varying the number of periodic units, the resonant peak within the band gap can be adjusted to achieve the desired response. By varying the material, size, and connection method of the additional rod at the right end, combined with structural changes at the left end, the resonant frequency at the end can be altered, thereby flexibly adjusting the asymmetric transmission frequency.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for realizing asymmetric transmission of elastic waves, characterized in that: The steps include: Constructing a finite period structure as the main body of transmission, the finite period structure has an elastic wave band gap for transmission in a certain direction; The two ends of the finite period structure have end resonance modes due to the truncation of the period, and the end resonance frequency is located within the elastic wave band gap; Changing the end structure or the connection form with the outside world makes the end resonant frequency different, ensuring that the resonant frequency of at least one end is still within the elastic wave band gap; When an elastic wave is input at one end of a finite period structure, if the frequency of the elastic wave is the same as the resonant frequency of the other end, it will be transmitted to the other end of the finite period structure through the elastic wave band gap. If the elastic wave input from the first end or the second end of the finite period structure is within the frequency range of the elastic wave band gap and the frequency of the elastic wave is different from the resonant frequency of the other end, it will not be able to pass through the finite period structure.

2. A method for realizing asymmetric transmission of elastic waves according to claim 1, characterized in that: A finite periodic structure is constructed by periodically arranging two or more materials.

3. The method for realizing asymmetric transmission of elastic waves according to claim 1, characterized in that: By constructing periodicity through shape change of a material, a finite periodic structure is constructed.

4. A method for realizing asymmetric transmission of elastic waves according to claim 2 or 3, characterized in that: The materials used to construct the finite periodic structure are metals or polymers.

5. The method for realizing asymmetric transmission of elastic waves according to claim 1, characterized in that: The finite periodic structure is composed of 3 to 50 periodic units.

6. The method for realizing asymmetric transmission of elastic waves according to claim 5, characterized in that: The number of periodic units is determined by the degree of responsiveness required of the terminal output.

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