CN219911616U

CN219911616U - Sandwich beam

Info

Publication number: CN219911616U
Application number: CN202321717091.1U
Authority: CN
Inventors: 刘春燕; 董超; 郭振坤
Original assignee: Beijing University of Civil Engineering and Architecture
Current assignee: Beijing University of Civil Engineering and Architecture
Priority date: 2023-07-03
Filing date: 2023-07-03
Publication date: 2023-10-27
Anticipated expiration: 2033-07-03

Abstract

The utility model provides a sandwich beam, which comprises a plurality of sandwich Liang Shanti, wherein a sandwich Liang Shanti comprises a first foundation beam and a second foundation beam which are arranged in parallel, and a pyramid-shaped sandwich structure is arranged between the first foundation beam and the second foundation beam; the pyramid-shaped sandwich structure comprises a plurality of struts, the struts are converged from the upper surface of the second foundation beam to the lower surface of the first foundation beam to form a pyramid tower top, and a local oscillator structure is arranged in the pyramid-shaped sandwich structure; the local oscillator structure comprises a mass block, a plurality of first elastic elements are arranged on the side face of the mass block in a surrounding mode, the first elastic elements are respectively connected with a supporting rod nearest to the mass block, a second elastic element is arranged at the bottom of the mass block, and the second elastic element is connected with a second foundation beam. In the scheme, the sandwich beam is simple in processing design and low in manufacturing cost, has enough rigidity, strength and other statics, can meet the requirements of low-frequency and ultralow-frequency vibration reduction and noise reduction, and can be widely applied to life and engineering.

Description

Sandwich beam

Technical Field

The utility model relates to the technical field of mechanical vibration and noise control, in particular to a sandwich beam.

Background

Along with the improvement of the aerospace technical requirements, the requirements of the corresponding spacecraft on pointing precision, stability, maneuverability and the like are higher and higher, and the limitation on the vibration amplitude of the spacecraft caused by micro-vibration is also more and more strict, so that the influence of the micro-vibration must be considered in the design of the high-precision spacecraft, and the micro-vibration is one of key technologies which must be solved in the development of the high-precision spacecraft.

There are a large number of vibration sources in the microgravity environment of the spacecraft, such as the rotating parts of momentum wheels and reaction wheels on the spacecraft, the mechanical movement of flexible accessories, the atmospheric resistance, the impact of space particle flow on the spacecraft, etc. The micro-vibrations generated by the in-orbit spacecraft, although of small amplitude, because the environmental damping in space is very small, can be transmitted to the internal environment of the spacecraft through various structures and excite the vibrations of the critical instrument positions of the internal environment, thereby causing a series of adverse effects. The active and semi-active vibration isolation technology in the low frequency band has complex structure, consumes energy and sometimes causes the problem of environmental pollution. Therefore, a novel ultralow frequency passive vibration isolation structure which does not need external energy input needs to be designed at present so as to meet the low frequency or even ultralow frequency vibration damping and noise reduction requirements in the current field.

The rapid development of phonon crystals and acoustic metamaterials provides a new direction for solving the vibration reduction and noise reduction problems. When the elastic wave propagates in the periodic structure, the vibration and noise reduction result in a certain frequency band is achieved through the interaction between the micro units and surrounding units and media in the whole structure, so that abundant and flexible degrees of freedom are provided for vibration and noise reduction regulation and design, and the structure has certain limitation in the control of low-frequency waves. The corresponding low-frequency sound insulation performance of the local resonance type beam structure has excellent vibration and noise reduction performance at the resonance frequency. It should be noted that when the local resonance type structure is adopted to reduce the peak frequency of sound insulation, the peak frequency is generally achieved by increasing the mass of the mass block or reducing the rigidity of the spring, but this also increases the overall areal density or reduces the bearing function of the spring.

Disclosure of Invention

The utility model provides a sandwich beam, which does not need to reduce the rigidity of a metamaterial or increase the additional mass, and overcomes the defect that the rigidity of a spring is reduced or the mass of a mass block is increased when the traditional local resonance type structure reduces the sound insulation peak frequency, so as to solve the technical problem that low-frequency and ultra-low-frequency elastic waves are difficult to inhibit.

In order to solve the technical problems, the utility model provides the following technical scheme:

a sandwich beam, comprising a plurality of sandwich Liang Shanti, wherein the sandwich Liang Shanti comprises a first foundation beam and a second foundation beam which are arranged in parallel, and a pyramid-shaped sandwich structure is arranged between the first foundation beam and the second foundation beam; the pyramid-shaped sandwich structure comprises a plurality of struts, the struts are converged to the lower surface of the first foundation beam by the upper surface of the second foundation beam at a preset angle to form a pyramid tower top, and a local oscillator structure is arranged in the pyramid-shaped sandwich structure; the local oscillator structure comprises a mass block, a plurality of first elastic elements are arranged on the side face of the mass block in a surrounding mode, the first elastic elements are connected with struts nearest to the mass block respectively, second elastic elements are arranged at the bottom of the mass block, and the second elastic elements are connected with the second foundation beam.

Wherein, first elastic element with branch one-to-one corresponds.

The number of the supporting rods is 4, and correspondingly, the number of the first elastic elements is 4.

The mass block is cuboid, one end of the first elastic element is connected with the supporting rod, and the other end of the first elastic element is connected with the center of the side face of the mass block.

The first elastic element is obliquely arranged, and the connection position of the first elastic element and the support rod is higher than the connection position of the first elastic element and the mass block.

The second elastic element is vertically arranged under the mass block, one end of the second elastic element is connected with the bottom surface of the mass block, and the other end of the second elastic element is connected with the upper surface of the second foundation beam.

Wherein the first foundation beam and the second foundation beam are the same in size.

The bottom of the supporting rod is welded and fixed at the edge of the upper surface of the second foundation beam, and the top of the supporting rod is converged and welded and fixed at the center of the lower surface of the first foundation beam.

Wherein the first elastic element and the second elastic element have different stiffness coefficients.

Wherein the first elastic element and the second elastic element are springs.

The technical scheme of the utility model has the following beneficial effects:

in the scheme, the sandwich beam is simple in processing design, low in manufacturing cost, free of external energy input, capable of achieving favorable vibration reduction and noise reduction performance only by using pure passive elements, high in rigidity, strength and other statics, capable of meeting the requirements of low-frequency and ultra-low frequency vibration reduction and noise reduction, and capable of being widely applied to life and engineering.

Drawings

FIG. 1 is a front view of a sandwich beam of the present utility model;

fig. 2 is a view of a sandwich beam Zuo Shitu of the present utility model;

FIG. 3 is a schematic view of the sandwich beam of the present utility model;

fig. 4 is a 45 view of the sandwich Liang Shanti of the present utility model;

fig. 5 is a schematic diagram of the frame of the sandwich Liang Shanti of the present utility model.

[ reference numerals ]

1. A first foundation beam; 2. a support rod; 3. a pyramid-shaped sandwich structure; 4. a second foundation beam;

5. a mass block; 6. a first elastic element; 7. a second elastic element; 8. local oscillator structure.

Detailed Description

In order to make the technical problems, technical solutions and advantages to be solved more apparent, the following detailed description will be given with reference to the accompanying drawings and specific embodiments.

As shown in fig. 1 to 5, the embodiment of the utility model provides a sandwich beam, which comprises a plurality of sandwich Liang Shanti, wherein a plurality of sandwich beam monomers are sequentially connected to form a linear sandwich beam, and the number of the sandwich beam monomers can be determined according to engineering or experimental requirements, so that the length of the sandwich beam is determined, and the sandwich beam is simple, convenient and easy to adjust. The sandwich Liang Shanti comprises a first foundation beam 1 and a second foundation beam 4 which are arranged in parallel, the first foundation beam 1 and the second foundation beam 4 have the same size, and a pyramid-shaped sandwich structure 3 is arranged between the first foundation beam 1 and the second foundation beam 4; the pyramid-shaped sandwich structure 3 comprises a plurality of struts 2, the struts 2 are converged to the lower surface of the first foundation beam 1 by the upper surface of the second foundation beam 4 at a preset angle to form a pyramid tower top, and a local oscillator structure 8 is arranged in the pyramid-shaped sandwich structure 3; the local oscillator structure 8 comprises a mass block 5, a plurality of first elastic elements 6 are arranged on the side face of the mass block 5 in a surrounding mode, the first elastic elements 6 are respectively connected with a supporting rod 2 nearest to the first elastic elements, a second elastic element 7 is arranged at the bottom of the mass block 5, and the second elastic element 7 is connected with a second foundation beam 4.

In this embodiment, the inclination angle of each strut 2 is the same, and the height of the pyramid-shaped sandwich structure 3 can be changed by changing the predetermined angle of the strut 2, so as to realize a wide sound insulation band and fewer sound insulation valleys, and achieve a better sound insulation effect.

As shown in fig. 3, the first elastic elements 6 are in one-to-one correspondence with the struts 2. The number of struts is preferably 4 in this embodiment, and correspondingly the number of first elastic elements 6 is 4.

Wherein, the quality piece 5 is the cuboid, and the one end of first elastic element 6 glues with branch 2, and the other end glues with the center department of quality piece 5 side.

As shown in fig. 4, the first elastic elements 6 are obliquely arranged, the inclination angle of each first elastic element 6 is the same, and the connection position of the first elastic element 6 and the strut 2 is higher than the connection position of the first elastic element 6 and the mass block 5.

Wherein, the second elastic element 7 is vertically arranged under the mass block 5, one end of the second elastic element 7 is glued with the bottom surface of the mass block 5, and the other end is glued with the upper surface of the second foundation beam 4.

As shown in fig. 5, the bottom of the strut 2 is welded and fixed at the edge of the upper surface of the second base beam 4, and the top of the strut 2 is joined and welded and fixed at the center of the lower surface of the first base beam 1, and the first base beam 1, the second base beam 4, and the strut 2 together form a frame of the sandwich Liang Shanti.

In this embodiment, the first elastic element 6 and the second elastic element 7 are springs, and the stiffness coefficients of the first elastic element 6 and the second elastic element 7 are different. The second elastic element is used as a positive stiffness elastic element to bear main load, and the first elastic element is a negative stiffness adjusting mechanism and is used for counteracting the stiffness of the positive stiffness elastic element, so that the stiffness of the whole system at a static balance position tends to zero. When the sandwich beam unit is deformed under stress, the pre-compression deformation of the first elastic element and the second elastic element is changed or the rigidity ratio of the first elastic element and the second elastic element is changed, so that the local resonance frequency can be moved in a lower direction, the vibration reduction and sound insulation effects are realized at low frequency or even at ultra-low frequency, and the vibration reduction and sound insulation effects are more obvious along with the increase of the pre-compression amount and the rigidity ratio.

The working principle of the sandwich beam provided by the utility model is as follows:

when the whole system is in the initial static balance position, the elastic force of the second elastic element 7 is balanced with the gravity of the mass 5. After a forced deformation, the equivalent stiffness of the system is changed by changing the amount of compression of the first 6 and second 7 elastic elements.

While keeping the stiffness ratio of the first elastic element 6 and the second elastic element 7 unchanged, the restoring force can be influenced by adjusting the pre-compression amount of the first elastic element 6 and the second elastic element 7, thereby reducing the system equivalent stiffness at the static equilibrium position even to a negative value. Therefore, the problem that the dynamic stiffness of the system is smaller than the static stiffness is solved, and the effect of negative stiffness can be realized. For example, when the precompression amount is adjusted, that is, the ratio of the initial precompression amount to the initial original length of the first elastic element 6 is 0.38, the local resonance frequency of the system can be reduced to 10Hz, and 30dB of sound insulation amount is achieved, and a band gap appears between 150 Hz and 180Hz, so that elastic waves in the frequency range cannot be transmitted, and the purposes of vibration reduction and noise reduction are achieved in the low frequency range.

The precompression amount of the first elastic element 6 and the second elastic element 7 can be kept unchanged, and the stiffness ratio of the first elastic element 6 and the second elastic element 7 is adjusted to change the equivalent stiffness of the system, for example, the stiffness ratio of the first elastic element 6 and the second elastic element 7 is increased, so that the equivalent stiffness is reduced, the local resonance frequency is shifted to a low frequency, and the sound insulation amount of 80dB is achieved at about 40 Hz. By adjusting the rigidity, a band gap can be formed between 50 and 70Hz of the metamaterial sandwich beam, so that elastic waves in the frequency range cannot be transmitted.

Where the system is of positive equivalent stiffness, the localized resonance frequency may be shifted to lower frequencies by increasing the precompression amount or stiffness ratio of the elastic element. The sensitivity of the system to the amount of precompression of the elastic element is higher than the stiffness ratio and the amount of precompression of the elastic element is easier to adjust.

When the system is of negative equivalent rigidity, the low-frequency large-broadband sound insulation effect can be realized by adjusting the rigidity ratio. The rigidity nonlinear term overcomes the defect that the linear vibration and noise reduction mechanism is difficult to meet the requirement at low frequency, so that the static bearing capacity of the system is strong, the structural deformation is small, and the larger the rigidity ratio or precompression amount of the elastic element is, the better the vibration isolation capacity is.

In the scheme, the sandwich beam is added with a spring-mass resonance unit on the basis of the structure of the periodic metamaterial sandwich beam. The periodic sandwich beam is formed by connecting a positive stiffness elastic element and a negative stiffness adjusting structure in parallel by applying the idea of a local resonance structure, so that a quasi-zero stiffness system is formed to realize vibration reduction and noise reduction of an ultralow frequency band.

The sandwich beam can carry out rigidity adjustment on the positive rigidity mechanism at the balance position and the nearby point thereof by arranging the negative rigidity adjusting device, so that the relatively high bearing capacity is maintained, the integral natural frequency of the metamaterial sandwich beam can be reduced, and the local resonance band gap of the metamaterial can move towards low frequency, thereby widening the frequency band of vibration reduction and noise reduction towards low frequency and even ultra-low frequency.

The sandwich beam is simple in processing design, low in manufacturing cost, free of external energy input, capable of achieving favorable vibration and noise reduction performance by only using the pure passive element, high in rigidity, strength and other statics, capable of meeting the requirements of low-frequency and ultra-low frequency vibration and noise reduction, and capable of being widely applied to life and engineering.

While the foregoing is directed to the preferred embodiments of the present utility model, it will be appreciated by those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present utility model, and such modifications and adaptations are intended to be comprehended within the scope of the present utility model.

Claims

1. A sandwich beam, comprising a plurality of sandwich Liang Shanti, wherein the sandwich Liang Shanti comprises a first foundation beam and a second foundation beam which are arranged in parallel, and a pyramid-shaped sandwich structure is arranged between the first foundation beam and the second foundation beam;

the pyramid-shaped sandwich structure comprises a plurality of struts, the struts are converged to the lower surface of the first foundation beam by the upper surface of the second foundation beam at a preset angle to form a pyramid tower top, and a local oscillator structure is arranged in the pyramid-shaped sandwich structure;

the local oscillator structure comprises a mass block, a plurality of first elastic elements are arranged on the side face of the mass block in a surrounding mode, the first elastic elements are connected with struts nearest to the mass block respectively, second elastic elements are arranged at the bottom of the mass block, and the second elastic elements are connected with the second foundation beam.

2. The sandwich beam of claim 1, wherein the first resilient elements are in one-to-one correspondence with the struts.

3. The sandwich beam of claim 2, wherein the number of struts is 4 and the corresponding number of first resilient elements is 4.

4. A sandwich beam according to claim 3, wherein the mass is cuboid, one end of the first elastic element is connected to the strut, and the other end is connected to the centre of the side of the mass.

5. The sandwich beam of claim 1, wherein the first elastic element is disposed obliquely and the connection of the first elastic element to the strut is higher than the connection of the first elastic element to the mass.

6. The sandwich beam of claim 1, wherein the second elastic element is disposed vertically directly under the mass, one end of the second elastic element is connected to the bottom surface of the mass, and the other end is connected to the upper surface of the second base beam.

7. The sandwich beam of claim 1, wherein the first and second base beams are the same size.

8. The sandwich beam of claim 1, wherein the bottom of the strut is welded to the upper surface edge of the second foundation beam and the top of the strut is joined and welded to the center of the lower surface of the first foundation beam.

9. The sandwich beam of claim 1, wherein the first and second elastic elements have different stiffness coefficients.

10. The sandwich beam of claim 1, wherein the first and second elastic elements are springs.