An additional slotted acoustic black hole vibration reduction structure

Abstract

The present invention discloses an attached slotted acoustic black hole vibration reduction structure, which relates to the technical field of vibration reduction and noise reduction. In the uniform region of the vibration reduction structure, i.e., the cylindrical region, the propagation velocity and wavelength of waves of a certain frequency remain unchanged. However, in the acoustic black hole portion, the wave propagation velocity decreases as the thickness decreases, the wavelength decreases, and the vibration amplitude of the wave increases, converging toward the region with reduced thickness. When reaching the truncation point, because the vibration reduction structure has an acoustic black hole extension portion, i.e., a first annular portion, the bending wave continues to propagate at a lower wave velocity. The weakest part of the structure occurs at the outermost end of the structure, and the outer end is more susceptible to deformation, making the acoustic black hole effect more likely to occur. In addition, the slotting process destroys the inherent complete symmetry of the disc-shaped structure, generating more modes coupled with the controlled structure, avoiding the limitations of traditional symmetrical acoustic black hole vibration reduction structures, producing a broadening effect on the participating modes of the symmetrical acoustic black hole vibration reduction structure, and achieving a highly efficient vibration reduction and noise reduction effect.

Description

Technical Field

[0001] The present invention relates to the technical field of vibration reduction and noise reduction, and in particular to an additional slotted acoustic black hole vibration reduction structure. Background Art

[0002] Vibration reduction has always been a crucial issue in engineering. Structural vibration and noise are essentially waves generated by multiple reflections at the structure's boundaries, coupled with the coupling of elastic waves with the surrounding acoustic medium. Noise is the wave energy radiated into the air by structural vibration. Therefore, an effective means of reducing structural vibration and noise is to manipulate the elastic waves within the structure. Currently, wave manipulation technologies fall into two main categories: active and passive. Active control generally requires external power and complex system design, making it impractical and challenging to implement on a large scale. The most common passive control method involves applying damping materials. However, for large structures, this requires a large amount of damping material to the surface. While this approach can achieve vibration and noise reduction, it increases costs and introduces excessive mass, hindering lightweighting.

[0003] The Acoustic Black Hole (ABH) effect utilizes changes in the structural impedance to alter the phase and group velocities of flexural waves propagating through the structure, thereby converging the waves in a localized area. Conventional approaches to altering structural impedance involve reducing the thickness of the structure in the form of a power function. This reduces the flexural wave velocity as the thickness of the plate decreases. Ideally, the flexural wave velocity can be reduced to zero, achieving zero reflection of the flexural waves. Combined with damping dissipation, efficient energy dissipation is achieved. ABH combines high efficiency, lightweight, broadband, simple and flexible design, and direct system integration, making it a wave manipulation method with great potential and broad application prospects.

[0004] However, existing acoustic black hole structures (traditional acoustic black hole structures) achieve vibration and noise reduction by tailoring the controlled object, which reduces the stiffness and strength of the structure, which is detrimental to critical structures with strong and stiffness requirements. Existing symmetrical additional acoustic black hole structures also exhibit selective coupling due to their structural symmetry, which severely limits the vibration control effect. Summary of the Invention

[0005] The present invention is designed to provide an additional slotted acoustic black hole vibration reduction structure, which solves the problems in the above-mentioned background technology. In the acoustic black hole part, the acoustic black hole effect is more easily generated, thereby improving the vibration reduction effect.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] An additional slotted acoustic black hole vibration reduction structure, comprising: a symmetrical disk, a first ring extending from the edge of the symmetrical disk, and a slot structure on the symmetrical disk;

[0008] The symmetrical disk includes a cylinder and an acoustic black hole portion covering a side surface of the cylinder;

[0009] The thickness of the acoustic black hole portion decreases exponentially from the side of the cylinder outward; the thickness of the acoustic black hole portion is the thickness in the axial direction of the cylinder;

[0010] The upper end surface of the symmetrical disk is a first circle, and the lower end surface is a second circle. The plane where the first circle is located is parallel to the plane where the second circle is located. The line connecting the center of the first circle and the center of the second circle is perpendicular to the plane where the first circle is located.

[0011] The grooved structure is a structure in which the cylinder in the symmetrical disk remains unchanged, and grooves are cut along the width direction in the acoustic black hole part and the first annular part by a mechanical cutting method.

[0012] Preferably, the power function is expressed as h(r)=ε(r-r2) m +h1,(r1≤r≤r2), where h(r) represents the thickness of the acoustic black hole portion, r1 is the radius of the cylinder in the symmetrical disk, r2 is the radius of the symmetrical disk, h1 is the thickness of the cylinder in the symmetrical disk, r is the radius from the center of the cylinder in the symmetrical disk to any point on the first circle, ε represents a coefficient, and m is greater than or equal to two.

[0013] Preferably, the vibration-damping structure further includes a second ring-shaped portion, which is made of damping material. The second ring-shaped portion is pasted above the edge of the symmetrical disk, and the outer diameter of the second ring-shaped portion is the same as the outer diameter of the first ring-shaped portion.

[0014] Preferably, the second annular damping material is butyl rubber material.

[0015] Preferably, the first annular thickness is equal to the minimum thickness of the acoustic black hole portion.

[0016] Preferably, the symmetrical disc and the first ring are made of aluminum.

[0017] Preferably, the first circular diameter of the symmetrical disk is 120 mm, and the cylinder diameter in the symmetrical disk is 30 mm; the width of the first ring is 6 mm; the maximum thickness of the acoustic black hole part is 3 mm, and the minimum thickness is 0.2 mm.

[0018] Preferably, the groove structure has three grooves, which are 0°, 180°, and 245°, and the groove width is 1 mm.

[0019] According to the specific embodiments provided by the present invention, the present invention discloses the following beneficial effects:

[0020] The present invention discloses an additional slotted acoustic black hole vibration reduction structure. In the uniform area of ​​the vibration reduction structure, i.e., the cylindrical area, the wave propagation speed and wavelength of a certain frequency remain unchanged. In the acoustic black hole part, the wave propagation speed decreases as the thickness decreases, the wavelength decreases, the vibration amplitude of the wave increases, and it gathers towards the area with smaller thickness. At the truncation point, since the vibration reduction structure has an acoustic black hole extension part, i.e., the first annular part, the bending wave continues to propagate at a small wave speed. The weak part of the structure occurs at the outermost end of the structure and the outer end is more easily deformed, and the acoustic black hole effect is more likely to occur. Moreover, since the acoustic black hole area in the symmetrical disk is slotted, the coupling between the acoustic black hole vibration reduction structure and the controlled structure is strengthened, and the effect of the acoustic black hole vibration reduction is improved. In addition, damping material is pasted on the upper end of the first annular part to achieve efficient energy loss, thereby achieving high-efficiency broadband vibration reduction and noise reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a cross-sectional view of an additional slotted acoustic black hole vibration reduction structure according to an embodiment of the present invention;

[0023] Figure 2 This is a top view of an additional slotted acoustic black hole vibration reduction structure according to an embodiment of the present invention;

[0024] Figure 3 A cross-sectional view of the slotted position of an additional slotted acoustic black hole vibration reduction structure according to an embodiment of the present invention;

[0025] Figure 4 Schematic diagram of the propagation of elastic waves in the acoustic black hole vibration reduction structure provided by the present invention;

[0026] Figure 5 A top view of an embodiment of the present invention installed on a uniform plate;

[0027] Figure 6 A comparison diagram of the damping characteristics of a uniform plate according to an embodiment of the present invention, a uniform plate with an additional vibration-damping structural system according to the present invention, and an additional control group structural system;

[0028] Figure 7This is a comparison diagram of vibration characteristics of a uniform plate according to an embodiment of the present invention, a uniform plate with an additional vibration damping structure system according to the present invention, and an additional control group structure system. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] The purpose of the present invention is to provide an additional slotted acoustic black hole vibration reduction structure, so as to realize that a single device controls multiple modes of a controlled object, significantly reduces the peak values ​​of certain specific frequencies, and improves the vibration reduction effect.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] like Figure 1 As shown, the present invention discloses an additional slotted acoustic black hole vibration reduction structure, including a vibration reduction structure, which includes: a symmetrical disk, a first ring 3 extending from the edge of the symmetrical disk, and a groove structure on the symmetrical disk;

[0033] The symmetrical disk includes a cylinder 1 and an acoustic black hole portion 2 wrapped around the side of the cylinder;

[0034] The upper end surface of the symmetrical disk is a first circle 21, and the lower end surface is a second circle 22. The plane where the first circle 21 is located is parallel to the plane where the second circle 22 is located. The line connecting the center of the first circle and the center of the second circle is perpendicular to the plane where the first circle 21 is located.

[0035] The thickness of the acoustic black hole part 2 decreases in the form of a power function from the side of the cylinder 1 to the outside; the thickness of the acoustic black hole part 2 is the thickness in the axial direction of the cylinder 1; the expression of the power function is h(r) = ε(r-r2) m +h1,(r1≤r≤r2), where h(r) represents the thickness of the acoustic black hole part, r1 is the radius of the cylinder in the symmetric disk, r2 is the radius of the symmetric disk, h1 is the thickness of the cylinder in the symmetric disk, r is the radius from the center of the cylinder in the symmetric disk to any point on the first circle, ε represents the coefficient, and m is greater than or equal to two;

[0036] The grooved structure is that the cylinder (1) in the symmetrical disk is kept unchanged, and grooves are cut along the width direction in the acoustic black hole part (2) and the first annular part (3) by a mechanical cutting method.

[0037] like Figure 2 As shown, the circular upper end surface of the cylinder 1 constitutes r1, the circular upper end surfaces of the cylinder 1 and the acoustic black hole region 2 constitute r2, and the circular upper end surfaces of the cylinder 1, the acoustic black hole region 2 and the first ring 3 constitute r3.

[0038] The vibration reduction structure also includes: a second ring 4, which is a damping material. The second ring 4 is pasted above the edge of the symmetrical disk. The outer diameter of the second ring 4 is the same as the outer diameter of the first ring. The second ring 4 is made of butyl rubber material. The thickness of the first ring 3 is equal to the minimum thickness of the acoustic black hole part 2. The symmetrical disk and the first ring 3 are made of aluminum.

[0039] like Figure 3 As shown, the number of slots in the slot structure is n=3, and the angles are 0°, 180°, and 245°.

[0040] The acoustic black hole vibration reduction structure of the present invention is based on the fact that the bending waves in the solid medium decrease according to a certain power function as the thickness of the structure decreases, and the corresponding phase velocity and group velocity also decrease, thereby concentrating the broadband bending waves in the area where the thickness of the structure becomes thinner on a certain spatial scale, such as Figure 4 As shown, the energy on the controlled structure can be transferred to the acoustic black hole vibration reduction structure 2 through the cylinder 1 of the symmetrical disk. In the uniform area of ​​the vibration reduction structure, that is, the cylinder 1 of the symmetrical structure, the wave propagation speed and wavelength of a certain frequency remain unchanged. However, in the acoustic black hole area 2, the wave propagation speed decreases as the thickness decreases, the wavelength decreases, and the vibration amplitude of the wave increases, and it gathers in the area with smaller thickness. When it reaches the truncation point, since the acoustic black hole vibration reduction structure of the present invention has the acoustic black hole extension part 3, the bending wave continues to propagate at a small wave speed, and the weak part of the structure occurs again in the structure. The outermost end of the structure is more easily deformed, and the acoustic black hole effect is more likely to occur. In addition, due to the grooving processing of the acoustic black hole area 2 in the symmetrical disk, the originally symmetrical structure becomes complicated. At the low frequency stage, it can be regarded as three fan-shaped acoustic black hole vibration absorbers. The vibration reduction effect on the structure is produced by the joint action of the three parts, which strengthens the coupling between the acoustic black hole vibration reduction structure and the controlled structure and improves the effect of the acoustic black hole vibration reduction. In addition, by combining the annular damping material 4, most of the bending wave energy is consumed, thereby achieving the purpose of high-efficiency energy absorption or vibration reduction and noise reduction.

[0041] Figure 5 This is a top view of an example of the present invention installed on a uniform plate, as shown in FIG. Figure 5As shown, a uniform plate with a length of 300 mm, a width of 240 mm, and a thickness of 6 mm was selected as the controlled object. With the center of the uniform plate as the origin, an additional slotted acoustic black hole vibration damping structure was attached to the uniform plate at (-120, -90) mm. A unit excitation was applied at (100, 50) mm above the plate. The vibration damping structure includes a symmetrical disk with a first circular diameter of 120 mm, a cylinder 1 with a diameter of 30 mm, and a first ring 3 extending from the edge of the symmetrical disk with a width of 6 mm. The maximum thickness of the symmetrical disk is 3 mm, and the minimum thickness of the edge is 0.2 mm. The uniform plate, the symmetrical disk, and the first ring 3 are all made of aluminum. The vibration damping structure also includes a second ring 4, which is made of damping material with an outer diameter of 132 mm, a width of 30 mm, and a thickness of 2 mm. It is made of butyl rubber and the material loss factor is set to 0.1. For comparative research, a completely symmetrical acoustic black hole disk structure of the same size was also designed as a control group.

[0042] The outer diameter of the second ring 4 is the same as that of the first ring, and the thickness is 2 mm, which is determined based on the thickness of common damping materials in practice. The pasting width does not exceed the black hole area, and more damping material is selected to be pasted without adding too much extra mass.

[0043] The attached slotted acoustic black hole vibration damping structure was modeled in ABAQUS using the finite element method, and the damping level and vibration velocity response of the structure were calculated through steady-state dynamic analysis and modal superposition method.

[0044] Analysis of calculation results:

[0045] (1) Damping characteristics analysis

[0046] like Figure 6 As shown, SABH-DVA is a symmetrical acoustic black hole vibration reduction structure, and P3ABH-DVA is an additional acoustic black hole vibration reduction structure with three slots in this example. The acoustic black hole vibration reduction structure of the present invention can greatly improve the inherent damping of the structure, and its system damping ratio is improved by up to 400 times. Compared with the completely symmetrical control group, at certain frequencies, the damping level of the structure is still greatly increased, especially at 1962Hz, its system damping ratio is improved by nearly 200 times compared with the control group, and the damping characteristics are poor only at one mode near 300Hz; generally speaking, the additional slotted acoustic black hole vibration reduction structure can greatly improve the damping characteristics of the uniform plate, which is more superior than the completely symmetrical structure, which is of great benefit to the vibration suppression of the elastic structure and will not cause damage to the controlled object.

[0047] (2) Analysis of vibration control characteristics

[0048] like Figure 7As shown in the figure, SABH-DVA is a symmetrical acoustic black hole vibration reduction structure, and P3ABH-DVA is an additional acoustic black hole vibration reduction structure with three slots in this example. In order to evaluate the vibration level of the system, the origin response of the system is selected as the evaluation index. Figure 7 It can be found that after adding the symmetrical acoustic black hole vibration reduction structure, the vibration of the system can still be suppressed to a certain extent, which also shows that the symmetrical acoustic black hole vibration reduction structure without special size design can indeed bring a certain vibration suppression effect to the controlled structure; in addition, after pasting the additional slotted acoustic black hole vibration reduction structure of the present invention, compared with the symmetrical acoustic black hole vibration reduction structure, the additional slotted acoustic black hole vibration reduction structure has better effects than the symmetrical acoustic black hole vibration reduction structure in reducing certain specific peaks, especially at 218Hz, 640Hz, 967Hz and 1962Hz, the peak of P3ABH-DVA is further attenuated by 8dB, 19dB, 15dB and 25dB compared with SABH-DVA. This is because after the slotting treatment, the low-frequency additional slotted acoustic black hole vibration reduction structure can be regarded as three fans The vibration suppression effect of the fan-shaped acoustic black hole vibration absorber on the rectangular plate is actually produced by the joint action of three parts. As the frequency increases, the three fan-shaped acoustic black hole vibration absorbers will gradually be excited to produce petal-shaped modes with a large circumferential order; secondly, after the slotting treatment, within the same frequency range, the additional slotted acoustic black hole vibration reduction structure increases the number of modes and increases the coupling probability with the controlled structure. In addition, the additional slotted acoustic black hole vibration reduction structure has more modes coupled with the controlled structure within the same frequency range, thereby producing a better vibration suppression effect; finally, the additional slotted acoustic black hole vibration reduction structure can produce a widening effect on the participating mode attachments of the symmetrical acoustic black hole vibration reduction structure, which also explains why the additional slotted acoustic black hole vibration reduction structure has better effects than the symmetrical acoustic black hole vibration reduction structure at certain specific frequencies.

[0049] The additional slotted acoustic black hole vibration reduction structure of the present invention cleverly combines the characteristics of the acoustic black hole and the dynamic vibration absorber, avoiding the limitations of the traditional symmetrical acoustic black hole vibration reduction structure. The symmetrical disk is divided into three fan-shaped acoustic black hole structures by slotting, which destroys the inherent complete symmetry of the disk structure, improves the modal density, and generates more modes coupled with the controlled structure. The participating modal accessories of the symmetrical acoustic black hole vibration reduction structure produce a broadening effect, achieving an efficient vibration reduction effect at certain frequencies. The present invention can perform parameter design according to the frequency characteristics of the controlled object, etc., and can further improve the broadband characteristics.

[0050] The additional slotted acoustic black hole vibration reduction structure of the present invention has a small additional mass, is easy to meet engineering applications, and has the characteristics of high efficiency.

[0051] Compared with the prior art, the present invention has the advantages of good vibration reduction effect, convenient design, easy processing, low cost, etc.

[0052] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0053] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. An additional slotted acoustic black hole vibration reduction structure, comprising a vibration reduction structure, characterized in that: The vibration reduction structure comprises: a symmetrical disc, a first ring (3) extending from the edge of the symmetrical disc, and a groove structure on the symmetrical disc; The symmetrical disk comprises a cylinder (1) and an acoustic black hole portion (2) covering the side of the cylinder (1); The upper end surface of the symmetrical disk is a first circle (21), and the lower end surface is a second circle (22). The plane where the first circle (21) is located is parallel to the plane where the second circle (22) is located. The line connecting the center of the first circle (21) and the center of the second circle (22) is perpendicular to the plane where the first circle (21) is located. The thickness of the acoustic black hole part (2) decreases from the side of the cylinder (1) outward in the form of a power function; the thickness of the acoustic black hole part (2) is the thickness in the axial direction of the cylinder (1); the expression of the power function is: ,in, , represents the thickness of the acoustic black hole part (2), is the radius of the cylinder in the symmetric disk, is the radius of the symmetric disk, is the thickness of the cylinder in the symmetric disk, is the radius from the center of the cylinder in the symmetrical disk to any point on the first circle (21), represents the coefficient, greater than or equal to two; The grooved structure is a structure in which the cylinder (1) in the symmetrical disk is kept unchanged, and grooves are cut along the width direction in the acoustic black hole part (2) and the first annular part (3) by a mechanical cutting method.

2. The additional slotted acoustic black hole vibration reduction structure according to claim 1, characterized in that: The vibration reduction structure further comprises: a second ring (4), the second ring (4) is made of damping material, the second ring (4) is adhered above the edge of the symmetrical disk, and the outer diameter of the second ring (4) is the same as the outer diameter of the first ring (3).

3. The additional slotted acoustic black hole vibration reduction structure according to claim 2, characterized in that: The second annular (4) damping material is butyl rubber material.

4. The additional slotted acoustic black hole vibration reduction structure according to claim 1, characterized in that: The thickness of the first ring (3) is equal to the minimum thickness of the acoustic black hole part (2).

5. The additional slotted acoustic black hole vibration reduction structure according to claim 1, characterized in that: The symmetrical disc and the first ring (3) are made of aluminum.

6. The additional slotted acoustic black hole vibration reduction structure according to claim 1, characterized in that: The diameter of the first circle (21) of the symmetrical disk is 120 mm, the diameter of the cylinder in the symmetrical disk is 30 mm, and the width of the first ring (3) is 6 mm; the maximum thickness of the acoustic black hole part (2) is 3 mm, and the minimum thickness is 0.2 mm.

7. The additional slotted acoustic black hole vibration reduction structure according to claim 3, characterized in that: The second ring (4) has an outer diameter of 132 mm, a width of 30 mm and a thickness of 2 mm.

8. The additional slotted acoustic black hole vibration reduction structure according to claim 1, characterized in that: The number of slots in the slot structure is 3, and the angles are , the slot width is 1mm.

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