CN217108003U - Local resonance type flat plate structure applied to low-frequency vibration reduction and noise reduction of underwater vehicle - Google Patents
Local resonance type flat plate structure applied to low-frequency vibration reduction and noise reduction of underwater vehicle Download PDFInfo
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Abstract
The utility model discloses a be applied to local resonance type flat plate structure that underwater vehicle low frequency damping was fallen and is made an uproar. The local resonance type flat plate structure is arranged in an underwater vehicle; the local resonance type flat plate structure consists of a four-side simply-supported flat plate and local resonance cells; q is arranged on the four-side simply-supported flat plate along the x direction x A plurality of local resonance unit cells uniformly arranged in the y direction y A local resonance unit cell; each local resonance unit cell comprises a single or a plurality of dynamic vibration absorbers; the total number of the vibration absorbers in the x direction and the y direction of the flat plate is respectively marked as M and N; each dynamic vibration absorberThe device consists of a damper, a spring and an additional mass; the damper and the spring are connected in parallel and fixedly connected between the four-side simply-supported flat plate and the additional mass; the dynamic vibration absorber is a cantilever beam type vibration absorber. The utility model has the advantages of can realize that the damping of small-size, low frequency channel is fallen and is made an uproar, be applicable to underwater vehicle's actual demand more.
Description
Technical Field
The utility model relates to a low frequency vibration and noise control, it is local resonance type flat plate structure that more specifically says so, it is the local resonance type flat plate structure who is applied to underwater vehicle low frequency damping and falls makes an uproar more specifically.
Background
The underwater vehicle inevitably generates vibration and noise in the navigation process, strong vibration and noise can influence the sound stealth performance of the vehicle, and further the viability of the vehicle is reduced, the structure radiation noise is an important branch of the vehicle noise research field, and the low-frequency noise has the characteristics of long propagation distance, strong penetrating power and the like, so the low-frequency noise becomes the main acoustic characteristic of the vehicle to be detected. The flat plate structure is one of the most common basic components in the underwater vehicle, and the inhibition of low-frequency vibration and low-frequency radiation noise of the flat plate structure has important significance for improving the sound stealth performance of the underwater vehicle.
The traditional vibration control mode of a flat plate structure of an underwater vehicle mainly comprises vibration elimination, vibration isolation, structural modification, vibration resistance and vibration absorption, but is limited by the space of the underwater vehicle, and the traditional vibration control mode is difficult to realize vibration reduction and noise reduction with small size and low frequency band.
Therefore, there is a need for a vibration and noise reduction structure suitable for underwater vehicles with small size and low frequency band.
Disclosure of Invention
The utility model aims at providing a be applied to the local resonance type flat plate structure that underwater vehicle low frequency damping was fallen and is made an uproar, realize that the damping of small-size, low frequency channel is fallen and is made an uproar, is applicable to underwater vehicle's actual demand more.
In order to realize the purpose, the technical scheme of the utility model is that: be applied to local resonance type flat plate structure that underwater vehicle low frequency damping was fallen and is made an uproar, its characterized in that: the local resonance type flat plate structure is arranged in the underwater vehicle; the local resonance type flat plate structure consists of a four-side simply-supported flat plate and local resonance cells;
q is arranged on the four-side simply-supported flat plate along the x direction x A plurality of local resonance unit cells uniformly arranged in the y direction y The local resonance unit cells comprise a single or a plurality of different dynamic vibration absorbers; (equivalently, a plurality of identical local resonance cells are arranged on a flat plate structure, and the local resonance cells comprise a plurality of different dynamic vibration absorbers (the dynamic vibration absorbers are different in natural frequency and damping);
the local resonance unit cell comprises a single or a plurality of dynamic vibration absorbers; the total number of the dynamic vibration absorbers in the x direction and the y direction of the flat plate is respectively marked as M and N;
each dynamic vibration absorber consists of a damper, a spring and an additional mass; the damper and the spring are connected in parallel and fixedly connected between the four-side simply-supported flat plate and the additional mass;
the dynamic vibration absorber is a cantilever beam type vibration absorber.
In the above technical solution, the length L of the four-side simply-supported flat plate x 1.1m, width L y 0.9m, 0.003m for thickness h, 2700kg m for density rho -3 Young's modulus E ═ 7X 10 10 Pa and poisson ratio υ are 0.3.
In the above technical solution, the local resonance unit cell is selected from a group consisting of a single-vibrator unit cell, a double-vibrator unit cell, and a quadruple-vibrator unit cell.
The utility model has the advantages of as follows:
(1) the proposal of the local resonance mechanism provides a new design idea for controlling the low-frequency vibration and noise of the underwater vehicle, and the local resonance structure is a special artificial periodic structure, has the characteristic of low-frequency band gap and can effectively inhibit the vibration and noise of the structure in the frequency range corresponding to the band gap; the utility model relates to a local resonance type flat plate structure applied to the low-frequency vibration and noise reduction of an underwater vehicle can realize the vibration and noise reduction of small size and low frequency band, is more suitable for the actual demand of the underwater vehicle, and makes up the defects of the traditional vibration control mode;
(2) the local resonance type flat plate structure applied to the low-frequency vibration reduction and noise reduction of the underwater vehicle has the advantages that the analysis and research on the sound vibration characteristics show that the local resonance cells arranged on the surface of the flat plate not only can favorably influence the low-frequency vibration and noise of the whole target frequency band, but also can generate a plurality of vibration reduction band gaps and can effectively control the low-frequency vibration and noise of the flat plate under a plurality of excitation frequencies;
(3) the utility model relates to a be applied to the local resonance type flat plate structure that underwater vehicle low frequency vibration damping was fallen and is made an uproar is different from the unlimited border of local resonance field research, but is based on the limited big four sides simply supported flat plate structure in the underwater vehicle, has changed boundary condition and has utilized mode superposition method and harmonic balance method to derive its coupling vibration equation;
(4) the utility model discloses simple structure, be convenient for processing, installation and later maintenance have reduced the application cost, can provide the reference for the design of making an uproar falls in the low frequency damping of underwater vehicle.
The dynamic vibration absorber in the utility model can be realized by a cantilever beam type vibration absorber, has the characteristics of small size and low natural frequency, and the natural frequency of the dynamic vibration absorber determines the position of a vibration reduction frequency band, so that the local resonance type flat plate structure can realize the control of low-frequency-band vibration and noise;
the utility model discloses arrange a plurality of local resonance cells on dull and stereotyped surface, contain the dynamic vibration absorber of a plurality of differences in every local resonance cell, receive the excitation when producing the vibration at dull and stereotyped structure, the anti-resonance effect of dynamic vibration absorber can restrain the vibration of flat board, and then produces the damping band gap near dynamic vibration absorber natural frequency, and the band gap can be widened in the mutual stack of the produced damping band of the dynamic vibration absorber of a plurality of differences in the local resonance cell.
Drawings
Fig. 1 is a diagram of a local resonance plate structure acoustic vibration model in the present invention.
Fig. 2 is a diagram of the present invention for comparing the analytic solution with the finite element solution.
Fig. 3 is a graph showing the influence of the oscillator natural frequency ratio on the plate vibration characteristics according to the present invention.
Fig. 4 is a graph showing the influence of the natural frequency ratio of the oscillator on the acoustic radiation characteristics of the flat panel according to the present invention.
Fig. 5 is an influence diagram of the oscillator damping ratio on the flat panel vibration characteristic in the present invention.
Fig. 6 is an influence diagram of the oscillator damping ratio on the flat panel sound radiation characteristic of the present invention.
FIG. 7 is a graph showing the influence of the cell type on the plate vibration characteristics according to the present invention.
Fig. 8 is a graph showing the influence of the cell type on the acoustic radiation characteristics of the flat panel according to the present invention.
Fig. 9 is a graph of the average vibration velocity of the flat surface in the air before and after optimization according to the present invention.
Fig. 10 is a graph of the sound power level of the flat panel radiation in the air before and after the optimization of the present invention.
Fig. 11 is a schematic view of the connection structure of the damper, the spring and the additional mass according to the present invention.
In the figure, 1-a four-side simply supported flat plate, 2-a local resonance unit cell, 2.1-a dynamic vibration absorber, 2.11-a damper, 2.12-a spring and 2.13-an additional mass.
F in FIG. 1 0 Representing the coordinate (x) acting on the plate 0 ,y 0 ) A simple resonance excitation force; in fig. 1, x, y, and z are x, y, and z coordinates, respectively, in a cartesian rectangular coordinate system.
Detailed Description
The following detailed description of the embodiments of the present invention will be made with reference to the accompanying drawings, which are not intended to limit the present invention, but are merely exemplary. While the advantages of the invention will be clear and readily appreciated by the description.
The utility model discloses low frequency vibration and noise control to underwater vehicle, use wherein the basal body structure (plate structure) commonly used as the research object, use local resonance mechanism wherein, underwater vehicle's cruise noise is mainly with radiation noise, and low frequency noise is difficult to control among the radiation noise, and the strong propagation distance of penetrating power is far away, become the main acoustic characteristic that underwater vehicle was detected by the enemy, the control mode of high frequency noise has a lot, traditional vibration control mode is basically also to high frequency vibration and noise, for example, the vibration isolation, hinder and shake etc. owing to the restriction in space among the underwater vehicle, it falls to be difficult to realize the damping of low frequency channel and fall the noise. In the frequency range studied, the local resonance type flat plate structure generates a frequency band capable of suppressing the low-frequency vibration and noise thereof near the natural frequency of the dynamic vibration absorber (i.e. the local resonance type flat plate structure generates a frequency band capable of suppressing the low-frequency vibration and noise thereof in the target frequency band, and the frequency position of the frequency band corresponds to the natural frequency of the dynamic vibration absorber in the local resonance unit cell 2); with the increase of the damping of the dynamic vibration absorber, the vibration reduction frequency band is widened and the vibration reduction and noise reduction performance is weakened (namely, with the increase of the damping of the dynamic vibration absorber, the counter vibration effect of the dynamic vibration absorber on the flat plate is weakened, the vibration reduction frequency band is widened, and the vibration reduction and noise reduction performance at the frequency band is weakened at the same time); the multi-vibrator unit cell has a plurality of vibration reduction frequency bands, and the superposition of the frequency bands enables the low-frequency vibration reduction and noise reduction performance of the multi-vibrator unit cell to be superior to that of a single-vibrator unit cell; the low-frequency vibration reduction and noise reduction performance of the local resonance type flat plate structure can be adjusted and controlled by changing all structural parameters of the dynamic vibration absorbers in the local resonance cells.
As can be seen from fig. 1: the local resonance type flat plate structure is applied to low-frequency vibration and noise reduction of an underwater vehicle and is arranged in the underwater vehicle; the local resonance type flat plate structure consists of a four-side simply-supported flat plate 1 and local resonance cells 2;
q is arranged on the four-side simply-supported flat plate 1 along the x direction x A plurality of local resonance unit cells 2 uniformly arranged Q along the y direction y A plurality of local resonance unit cells 2; q x Greater than or equal to 1; q y Greater than or equal to 1; the x direction and the y direction are respectively an x coordinate direction and a y coordinate direction in a Cartesian rectangular coordinate system;
each local resonance unit cell 2 comprises a single or a plurality of dynamic vibration absorbers 2.1; the total number of the dynamic vibration absorbers in the x direction and the y direction of the flat plate is respectively marked as M and N; the values of M and N are not changed, M is 8 on the four-side simple support flat plate 1, N is 10, i.e. 8 × 10 dynamic vibration absorbers are arranged on the flat plate structure, 80 dynamic vibration absorbers and 80 local resonance cells are arranged on the single-vibrator cell, i.e. the four-side simple support flat plate 1, and each local resonance cell contains one dynamic vibration absorber; 80 dynamic vibration absorbers and 40 local resonance cells are arranged on the double-vibrator cell, namely the four-side simply-supported flat plate 1, and each local resonance cell comprises two different dynamic vibration absorbers; the four-vibrator unit cell means that 80 dynamic vibration absorbers and 20 local resonance unit cells are arranged on the four-side simply-supported flat plate 1, and each local resonance unit cell comprises four different dynamic vibration absorbers;
each dynamic vibration absorber 2.1 consists of a damper 2.11, a spring 2.12 and an additional mass 2.13; the damper 2.11 and the spring 2.12 are connected in parallel and fixedly connected between the four-side simply-supported flat plate 1 and the additional mass 2.13;
the dynamic vibration absorber is selected to be a cantilever beam type vibration absorber.
Length L of four-side simply-supported flat plate 1 x 1.1m, width L y 0.9m, 0.003m for thickness h, 2700kg m for density rho -3 Young's modulus E ═ 7X 10 10 Pa and poisson ratio υ are 0.3.
The local resonance unit cell 2 is selected from a group consisting of a single-vibrator unit cell, a double-vibrator unit cell and a four-vibrator unit cell.
Examples
In the embodiment, a local resonance mechanism is applied to low-frequency vibration and noise control of an underwater vehicle, aiming at a four-side simply-supported flat plate structure, a plurality of local resonance cells are uniformly distributed on the surface of the four-side simply-supported flat plate structure to form the local resonance structure, each local resonance cell comprises a plurality of dynamic vibration absorbers, each dynamic vibration absorber comprises a damping, a spring and an additional mass, the damping and the spring are connected in parallel and fixedly connected between the flat plate structure and the additional mass, a coupling dynamic model shown in figure 1 is established, and the length of a flat plate is L x Width of L y The thickness is h, the elastic modulus is E, the density is rho, and the Poisson ratio is upsilon; the distances between the local resonance cells on the flat plate are denoted as aj and bj along the x and y directions, respectively, the distances between the dynamic vibration absorbers in the cells are denoted as ar and br along the x and y directions, respectively, and the coordinate of each dynamic vibration absorber can be expressed as (x) and ij ,y ij ) (ii) a On the flat plate, Q is arranged along x and y directions x And Q y A plurality of local resonance cells, each local resonance cell contains a single or a plurality of dynamic vibration absorbers, and the total number of the dynamic vibration absorbers in the x and y directions of the flat plate structure can be respectively marked as M and N, and the flat plate structure is arranged in the coordinate (x) 0 ,y 0 ) Is subjected to a simple resonance excitation force F (t) ═ F 0 The vibration is generated under the action of sin and omega t;
the coupled vibration equation of the local resonance type flat plate structure applied to the low-frequency vibration reduction and noise reduction of the underwater vehicle under the simple harmonic excitation can be expressed as follows:
wherein,
is the bending stiffness of the thin plate and,
for the Laplace operator, F is applied to the plate (x) 0 ,y 0 ) Simple resonance excitation force of F ij Is a coordinate (x) ij ,y ij ) The reaction force of the dynamic vibration absorber on the plate is delta () is a Dirac function; m and N are the total number of the vibration absorbers in the x direction and the y direction of the four-side simply-supported flat plate 1 respectively; rho and h are respectively the density and the thickness of the four-side simply-supported flat plate 1; w is w (x, y, t), t is time;
according to the modal superposition method, the lateral vibration displacement w (x, y, t) of the flat plate can be expressed as:
wherein W mn (x, y) and p mn (t) the natural mode functions and the corresponding modal displacements of the four-side simply-supported flat plate at the coordinates (x, y) under the (m, n) -order modes are respectively;
p mn (t)＝A mn sinωt+B mn cosωt (4)
in formulae (5) and (6): a. the mn And B mn Sine components and cosine components of the panel modal displacement are respectively, and omega is the excitation angular frequency; l is x ，L y The length and the width of the simply supported flat plate 1 on the four sides are respectively;
the dynamic vibration absorber is used as a research object, and the force analysis is carried out to know that the reaction force generated by the dynamic vibration absorber to the flat plate is simultaneously caused by the reaction force F of the spring k And reaction force F of damping c The composition, therefore, can be expressed as:
F ij ＝F k +F c (7)
in formula (8):
F k ＝k ij [w(x ij ,y ij ,t)-u ij ] (9)
in formulae (11) and (12): w (x) ij ,y ij ,t)、
Respectively represent coordinates (x) ij ,y ij ) Transverse vibration displacement and transverse vibration speed, k, of the flat plate at time t ij 、c ij 、u ij 、
Respectively represent coordinates (x) ij ,y ij ) The spring stiffness, damping, transverse vibration displacement and transverse vibration speed of the dynamic vibration absorber are controlled;
the unit of transverse vibration speed is m/s, the unit of k is the unit of spring stiffness of the vibration absorber is N/m, and the unit of c vibration absorber is N multiplied by s/m.
u ij ＝u sij sinωt+u cij cosωt (13)
In formula (14): u. of sij And u cij Respectively represent coordinates (x) ij ,y ij ) A sine component and a cosine component of the transverse vibration displacement of the dynamic vibration absorber are determined; omega is the angular frequency of excitation; t is time.And analyzing the coupled vibration of each dynamic vibration absorber and the flat plate to obtain a local vibration coupling equation:
w(x ij ,y ij ,t)、
respectively represent coordinates (x) ij ,y ij ) Transverse vibration displacement and transverse vibration speed, k, of the flat plate at time t ij 、c ij 、u ij 、
Respectively represent coordinates (x) ij ,y ij ) The spring stiffness, damping, transverse vibration displacement and transverse vibration speed of the dynamic vibration absorber are controlled;
multiplying the two sides of the equation (1) by the mode shape function of the four-side simple support flat plate at the coordinate (x, y) under the (r, s) order mode simultaneously
And on the whole surface of the flat plate structure (x is more than or equal to 0 and less than or equal to L) x ,0≤y≤L y ) By performing the integration, one can get:
wherein,
wherein,
(m, n) order mode, k m And k n To simplify the notation of an expression, there is no particular meaning.
Substituting the equations (2), (5), (11) and (12) into an equation (10), finishing and simplifying the equations, then combining the equations with an equation (9), taking the front Q multiplied by Q order mode of the flat plate structure to participate in calculation, and writing the equation set into a matrix form:
wherein the vector q is an unknown vector to be solved of the matrix equation
Wherein,
and
sine and cosine components, U, of the transverse vibration displacement of the plate structure, respectively sij ＝[u s11 ,…,u sMN ] T And U cij ＝[u c11 ,…,u cMN ] T Respectively are sine and cosine components of the transverse vibration displacement of each dynamic vibration absorber;
to accurately describe each element in the matrix equation (13), the following expression is defined:
in formulae (23) and (24): r, s, m, n all refer to modesThe order of (a); psi rs,ij And W mn,ij Respectively represent the modal coordinates (x) of the plate in order r × s and m × n ij ,y ij ) The mode shape function of (d);
the matrix Q11 may be expressed in the form of the sum of a diagonal matrix and another common matrix:
Q 11 ＝Λ+C (25)
wherein,
wherein, the diagonal matrix Λ is a matrix of QQ × QQ order, and the elements on the diagonal can be expressed as
The matrix represents the natural vibration characteristics of the flat plate structure; the matrix C is also a QQQQ order matrix which represents the influence of the rigidity component of the dynamic vibration absorber on the vibration characteristic of the flat plate;
the elements and meaning of the matrix Q12 are similar to those of the matrix C and can be expressed as:
the matrix Q12 is a QQ × QQ order matrix representing the influence of the damping component in the dynamic vibration absorber on the plate vibration characteristics;
the matrix Q13 may be represented as:
the matrix Q13 is a QQ × MN order matrix representing the influence of the stiffness component of the dynamic vibration absorber on the intrinsic vibration characteristics of the dynamic vibration absorber;
the matrix Q14 may be represented as:
the matrix Q14 is a QQ × MN order matrix representing the influence of the damping components of the dynamic vibration absorber on the intrinsic vibration characteristics of the dynamic vibration absorber;
the matrix Q33 is a diagonal matrix that can be expressed as:
the diagonal matrix Q33 is an MN × MN order matrix, and the diagonal elements can be represented as K MN ＝m MN ω 2 -k MN The influence of the stiffness component of the individual dynamic-vibration absorber on the vibration characteristics of the dynamic-vibration absorber is represented;
the matrix Q34 is similar to Q33, being a diagonal matrix that can be expressed as:
the diagonal matrix Q34 is an MN × MN order matrix representing the influence of the damping components of a single dynamic vibration absorber on the vibration characteristics of the dynamic vibration absorber;
other unknown matrixes in the left coefficient matrix with equal sign of the matrix equation (13) have the following corresponding relation with the known matrixes: q 21 ＝-Q 12 ，Q 22 ＝Q 11 ，Q 23 ＝-Q 14 ，Q 24 ＝Q 13 ，
Q 43 ＝-Q 34 ，Q 44 ＝Q 33 ；
The right force vector of the matrix equation (13) represents the coordinate (x) acting on the plate 0 ,y 0 ) The influence of the harmonic excitation force on the vibration characteristics of the flat plate can be expressed as:
F＝F 0 [ψ 11,00 ,ψ 12,00 ,…,ψ QQ,00 ,0,…,0] T (33)
the vector is a 2(QQ + MN) x 1-dimensional column vector, the elements in the vector are
Substituting the equations (14) to (25) into a matrix equation (13), solving the matrix equation to obtain a relation function V (omega) of the surface average vibration velocity and the excitation frequency of the local resonance type flat plate structure, and further calculating the surface average vibration velocity level of the local resonance type flat plate structure:
V 0 for calculating the reference vibration velocity, the value is V 0 ＝5×10 -8 m/s；
After a local resonance type flat plate structure coupling equation applied to low-frequency vibration reduction and noise reduction of an underwater vehicle is obtained, the radiation sound power of the flat plate can be obtained by utilizing the surface sound pressure of the flat plate, namely, the product of the structure radiation surface sound pressure and the surface vibration speed is solved in a mode of integrating in the whole radiation surface.
According to the Rayleigh integral formula, the sound pressure p (r) of the flat radiation surface at (x ', y ', z ') in the medium above the flat can be represented by the following integral form:
wherein
Represents the distance from the midpoint (x ', y ', z ') of the medium surrounding the slab to a point (x, y,0) on the slab, where k ═ ω/c is the wave number, c is the speed of sound, ω is the angular frequency of vibration, ρ 0 Is the density of the medium and is,
the transverse vibration speed of the flat plate at coordinates (x, y) is shown, and e is a natural constant; i represents a plurality;
then the integral expression of the radiated acoustic power of the flat plate structure can be obtained:
wherein, and
representing the conjugate and real part of the complex number, respectively.
The cosine and sine components of the radiation sound power of the flat plate structure can be obtained by combining the formula (2) as follows
In which H represents a conjugate transpose, Z mn ＝ζ mn +iχ mn For acoustic radiation impedance, the elements can be expressed as
Therein, ζ mn Hexix- mn Respectively representing the self-radiation resistance and the self-radiation resistance of the structure;
represents the distance from the midpoint (x ', y ', z ') of the medium surrounding the plate to a point (x, y,0) on the plate; k is the wave number, c is the sound velocity, ω is the vibration angular frequency, ρ 0 Is the density of the medium; psi mn (x, y) and ψ' mn (x ', y') represents the mode shape function of the flat plate at the modal coordinates (x, y) of order (m, n) and (x ', y'), respectively, which can be expressed as
Further analysis can obtain the surface radiation sound power calculation expression of the flat plate structure as
Then the acoustic radiation power level:
wherein a reference acoustic power W is taken 0 ＝1×10 -12 W。
The method is characterized in that research is carried out on a sound vibration model of a local resonance type flat plate structure for low-frequency vibration reduction and noise reduction of an underwater vehicle, a simple example of theoretical calculation is given, and comparison theoretical calculation is carried out through an analytic method and finite element software COMSOL. Considering that the local resonance type flat plate structure applied to low-frequency vibration and noise reduction of the underwater vehicle in the calculation example is a four-side simply-supported flat plate in an air medium, an exciting force is applied to the middle point of the flat plate, the amplitude of the exciting force is 1N, and the exciting frequency range isThe periphery is 5-300Hz, the geometric and material parameters of the flat plate are shown in Table 1, wherein rho, E and upsilon respectively represent the density, Young modulus and Poisson ratio of the flat plate, and L x 、L y And h represent the length, width, and thickness of the plate, respectively, and the first 5 × 5 order natural frequency of the plate structure is calculated as shown in table 2.
TABLE 1 parameters of the plates
TABLE 2 first 5X 5 order natural frequency (Hz) of the plate
Uniformly arranging an 8X 10 dynamic vibration absorber array on the surface of the flat plate structure, and taking the initial calculation parameters of the dynamic vibration absorbers on the assumption that the parameters of each dynamic vibration absorber are the same: mass m is 0.0225kg, natural frequency ratio λ is 4.2, and damping ratio ζ is 0.02. The average vibration velocity level curve of the surface of the flat plate structure is obtained by calculation through an analytic method and a finite element method respectively, and comparison is carried out as shown in fig. 2. As can be seen from fig. 2, a plurality of resonance peaks and vibration damping frequency bands appear in the vibration velocity curves obtained by the target frequency band analysis method and the finite element method, and the frequency positions of the frequency bands correspond to the natural frequency (62.87Hz) of the dynamic vibration absorber. The average error degree of the two data at each frequency position is only 0.58 percent by further processing the data, and the data have higher goodness of fit, which also indicates the effectiveness of the analytic calculation method.
The method comprises the steps of carrying out research on the influence rule of the natural frequency ratio, the damping ratio and the cell type of the local resonance type additional dynamic vibration absorber of the flat plate structure for low-frequency vibration reduction and noise reduction of the underwater vehicle on the flat plate sound vibration characteristic, assuming that the boundary condition of the flat plate structure is four-side simple support, uniformly arranging an 8 x 10 dynamic vibration absorber array on the surface of the flat plate, dividing the additional dynamic vibration absorber array on the flat plate into single-vibrator cells, analyzing the influence rule of the natural frequency ratio lambda of the dynamic vibration absorber in the cells on the flat plate sound vibration characteristic, assuming that the damping ratio zeta of each dynamic vibration absorber is 0.02, wherein the natural frequency ratio of the dynamic vibration absorber refers to the ratio of the natural frequency of the dynamic vibration absorber to the order natural frequency of the flat plate (1,1), and taking the values of lambda 1, lambda 5.8, lambda 7.4 and lambda 15.4 respectively, and the corresponding frequencies of 14.97Hz, 86.83Hz, 110.78Hz and 230.54Hz respectively. The curves of the local resonance type flat plate structure surface average vibration speed level and the radiation sound power level applied to the low-frequency vibration reduction and noise reduction of the underwater vehicle in the range of 5-300Hz under different natural frequency ratios of the dynamic vibration absorber are respectively calculated and are shown in fig. 3 and 4. As can be seen from fig. 3 and 4: after the single-vibrator unit cells are added on the surface of the flat plate in the embodiment, a remarkable vibration reduction frequency band exists in a target frequency band, the frequency position of each frequency band corresponds to the natural frequency of the dynamic vibration absorber, and the frequency band moves to a high frequency and is always kept near the natural frequency of the dynamic vibration absorber along with the increase of the natural frequency ratio of the dynamic vibration absorber. The formants on the left side and the right side of the frequency band respectively show a law of moving to high frequency and low frequency, and the peak values are reduced, which shows that the arrangement of the local resonance cells on the surface of the flat plate not only can generate a vibration reduction frequency band, but also can influence the size and the frequency position of the formants of the flat plate structure at other frequency positions. It can be seen that the natural frequency affects the position of the bandgap. Therefore, for the low-frequency vibration and noise reduction design of the local resonance type flat plate structure applied to the low-frequency vibration and noise reduction of the underwater vehicle, the selection of the natural frequency ratio of the dynamic vibration absorber needs to be determined according to the target vibration reduction frequency range.
FIG. 2 is a comparison of results of finite element and analytical solutions, which are consistent to illustrate the correctness of the analytical method.
Fig. 3 to 8 show the influence law of the natural frequency, damping and the types of the cells of the dynamic vibration absorber on the plate vibration and noise, and fig. 9 and 10 show the results of the optimization by the particle swarm optimization.
The method comprises the steps of dividing an additional dynamic vibration absorber array on a flat plate into single-vibrator cells, analyzing the influence rule of the damping ratio zeta of the dynamic vibration absorbers in the cells on the sound vibration characteristics of the flat plate, and assuming that the natural frequency ratio of each dynamic vibration absorber is lambda-5.8, and the damping ratio of each dynamic vibration absorber is zeta 0.02, 0.1 and 0.2. The curves of the local resonance type flat plate structure surface average vibration speed level and the radiation sound power level applied to the low-frequency vibration reduction and noise reduction of the underwater vehicle in the range of 5-300Hz under different damping ratios of the dynamic vibration absorber are respectively calculated and are shown in fig. 5 and 6. As can be seen from fig. 5 and 6, after a plurality of single-element cells are arranged on the surface of the flat plate in the present embodiment, a significant vibration reduction frequency band occurs in the target frequency band and corresponds to the natural frequency (86.83Hz) of the dynamic vibration absorber, as the damping ratio of the dynamic vibration absorber is gradually increased from 0.02 to 0.2, the anti-resonance effect of the dynamic vibration absorber on the flat plate is weakened, the vibration reduction performance at the frequency band position is reduced, the frequency band is widened, the curve gradually becomes smooth in the whole target frequency band, and the amplitude of each resonance peak is reduced. Therefore, the damping of the dynamic vibration absorber does not change the frequency band and the position of each formant, and only influences the vibration reduction and noise reduction performance and the frequency bandwidth at the frequency band, and the vibration of the whole target frequency band flat plate structure is reduced by the increase of the damping of the dynamic vibration absorber. It can be seen that the damping of the dynamic vibration absorber affects the performance of vibration and noise reduction at the band gap and the width of the band gap. Therefore, for the low-frequency vibration and noise reduction design of the local resonance type flat plate structure applied to the low-frequency vibration and noise reduction of the underwater vehicle, the damping regulation and control function of the dynamic vibration absorber is also considered.
The influence rules of the natural frequency ratio and the damping ratio of the additional dynamic vibration absorber on the flat plate on the sound vibration characteristic of the flat plate are analyzed, and the influence rules are all directed to single vibrator cells. In order to further study the influence rule of the cellular type on the acoustic vibration characteristics of the flat plate, the dynamic vibration absorber array added on the flat plate is divided into single-vibrator, double-vibrator and four-vibrator cellular, firstly, the damping ratio of each dynamic vibration absorber is assumed to be zeta 0.02, the inherent frequency ratio lambda of the dynamic vibration absorber in the single-vibrator cellular is taken to be 4.2, and the corresponding frequency is 62.87 Hz; the natural frequency ratio of the dynamic vibration absorber in the double-vibrator unit cell is as follows: lambda [ alpha ] 1 ＝4.2、λ 2 5.8, the corresponding frequencies are: 62.87Hz, 86.83 Hz; the natural frequency ratio of the dynamic vibration absorber in the four-vibrator unit cell is as follows: lambda [ alpha ] 1 ＝4.2、λ 2 ＝5.8、λ 3 ＝7.4、λ 4 The corresponding frequency is 9.2: 62.87Hz, 86.83Hz, 110.78Hz and 137.68 Hz. Respectively calculating the low altitude of the underwater vehicle within the range of 5-300Hz under different cell typesThe curves of the average vibration velocity level and the radiated sound power level of the surface of the frequency-damping noise-reduction local resonance type flat plate structure are shown in fig. 7 and 8. As can be seen from fig. 7 and 8, in this embodiment, one, two, and four vibration reduction frequency bands respectively appear on the flat-plate structure acoustic vibration curves under the single-vibrator, double-vibrator, and four-vibrator cells in the target frequency band, and the frequency position of each frequency band respectively corresponds to the natural frequency of each dynamic vibration absorber in the cell, and under the condition that the total number of the dynamic vibration absorbers is constant, the low-frequency vibration reduction performance of the single-vibrator cell is higher than that of the multi-vibrator cell at the same frequency band. It can be seen from fig. 7 and 8 that the frequency position of the vibration damping frequency band is determined only by the natural frequency of the dynamic vibration absorbers in the cells, and the number of frequency bands depends only on the type of the dynamic vibration absorbers in the cells, and is independent of the magnitude of the vibration excitation frequency and the position of the resonance peak.
The analysis obtains the influence rule of the natural frequency ratio, the damping ratio and the cell type of the dynamic vibration absorber in the range of 5-300Hz on the acoustic vibration characteristics of the panel, and the embodiment utilizes the particle swarm optimization to optimally design the local resonance panel structure applied to the low-frequency vibration reduction and noise reduction of the underwater vehicle under the condition of single vibrator, double vibrator and four vibrator cells respectively: supposing that an exciting force is applied to the midpoint position of a four-side simply-supported flat plate in an air medium, the amplitude of the exciting force is 1N, the range of exciting frequency is 5-300Hz, and the air density is rho 0 ＝1.293kg/m 3 The speed of sound is c 0 344 m/s; the geometry and material parameters of the flat plate are shown in Table 1, wherein ρ, E, and ρ represent the density, Young's modulus, Poisson's ratio, and L of the flat plate respectively x 、L y H respectively represents the length, width and thickness of the flat plate, and the first 5 multiplied by 5 order natural frequency of the flat plate structure is calculated and shown in the table 2; uniformly arranging 8 multiplied by 10 dynamic vibration absorber arrays on the surface, taking optimized variables as the natural frequency ratio lambda and the damping ratio zeta of the dynamic vibration absorbers in the cells, and taking the average vibration speed level L of the surface of the flat plate within the range of 5-300Hz of an objective function v (omega) and radiated acoustic power level L p (ω) the relational expression J, expressed as:
J＝αmean(L s (ω))+βmax(L s (ω))
L s (ω)＝L v (ω)+L p (ω)
wherein S is the total number of frequencies participating in calculation of the target frequency band, α and β are weight coefficients of an average value and a maximum value of an average vibration velocity level and a radiation sound power level allocated to the surface of the flat panel, where α is 0.4 and β is 0.6, and a value range of an optimization variable is determined as follows:
after the optimization by the particle swarm optimization, the results of the parameters for optimizing the natural frequency ratio λ and the damping ratio ζ of the dynamic vibration absorber in each cell in the embodiment are shown in table 3:
table 3 dynamic vibration absorber parameter optimization results
In this embodiment, the parameters of the dynamic vibration absorbers in the optimized cells are substituted into the coupled vibration equation, and the curves of the average vibration velocity level of the flat surface and the radiated sound power level of the target frequency band are calculated as shown in fig. 9 and 10. As can be seen from fig. 9 and 10, the optimized local resonance type flat plate structure applied to low-frequency vibration and noise reduction of an underwater vehicle according to the present embodiment has improved surface average vibration velocity level and radiation sound power level, and especially, the control of each formant is particularly obvious. The target function values under the substrate, the single vibrator, the double vibrator and the four vibrator cells are 414.49dB, 305.49dB, 291.08dB and 293.71dB respectively, the data are further processed to respectively obtain the vibration reduction efficiencies of the single vibrator, the double vibrator and the four vibrator cells in a target frequency band, the vibration reduction efficiencies are 26.3%, 29.8% and 29.1%, the vibration reduction efficiency of the optimized double vibrator cells is higher than that of the single vibrator and the four vibrator cells, but the four vibrator cells have more obvious vibration reduction frequency bands, and have better control effects on low-frequency vibration and noise under certain frequencies. In order to simplify the design of the local resonance type flat plate structure applied to low-frequency vibration and noise reduction of the underwater vehicle in the embodiment, a double-vibrator cell design is adopted; and the average damping efficiency of the existing damping technology in the underwater vehicle is generally about 10-20%, the utility model discloses a local resonance structure has realized the vibration and the noise control of small-size, low frequency channel to effectively improve damping and noise reduction efficiency.
And (4) conclusion: the local resonance type flat plate structure of making an uproar falls in being applied to underwater vehicle low frequency damping under the limited boundary of this embodiment design provides effective reference for underwater vehicle's low frequency vibration and noise control, and the size is little, fall the vibration of low frequency channel and fall the noise efficiency high, and simple structure be convenient for install and maintain, the utility model discloses each structure material is engineering material commonly used, and is economical feasible.
Other parts not described belong to the prior art.
Claims (3)
1. Be applied to local resonance type flat plate structure that underwater vehicle low frequency damping was fallen and is made an uproar, its characterized in that: the local resonance type flat plate structure is arranged in the underwater vehicle; the local resonance type flat plate structure consists of a four-side simply-supported flat plate (1) and local resonance cells (2);
q is arranged on the four-side simply-supported flat plate (1) along the x direction x A plurality of local resonance cells (2) uniformly arranged Q along the y direction y A plurality of local resonance cells (2);
the local resonance unit cell (2) comprises a single or a plurality of dynamic vibration absorbers (2.1); the total number of the dynamic vibration absorbers (2.1) in the x direction and the y direction of the flat plate is respectively marked as M and N;
the dynamic vibration absorber (2.1) is composed of a damper (2.11), a spring (2.12) and an additional mass (2.13); the damper (2.11) and the spring (2.12) are connected in parallel and fixedly connected between the four-side simply-supported flat plate (1) and the additional mass (2.13);
the dynamic vibration absorber (2.1) is an cantilever beam type vibration absorber.
2. The structure of claim 1, wherein the structure is applied to the low-frequency vibration and noise reduction of underwater vehicles and is of a local resonance type flat plate structureIs characterized in that: length L of four-side simply-supported flat plate (1) x 1.1m, width L y 0.9m, 0.003m for thickness h, 2700kg m for density rho -3 Young's modulus E ═ 7X 10 10 Pa and poisson ratio υ are 0.3.
3. The structure of the local resonance type flat plate applied to the low-frequency vibration and noise reduction of the underwater vehicle as claimed in claim 2, is characterized in that: the local resonance unit cell (2) is selected from a single-vibrator unit cell, a double-vibrator unit cell and a four-vibrator unit cell.
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