An integrated design method for underwater structure functions

Abstract

The present invention discloses an integrated design method for underwater structure functions. The designed pressure-resistant, impact-resistant and sound-insulating unit includes a Y-shaped outer frame, an upper-middle thick beam and a thin inclined beam. The Y-shaped outer frame includes two symmetrically arranged side thick beams and two thick inclined beams, and a lower-middle thick beam coaxially arranged with the upper-middle thick beam. The side thick beams are connected to the lower-middle thick beam through the thick inclined beams, and the lower-middle thick beam is connected to the lower panel. The upper end of the upper-middle thick beam extends outside the Y-shaped outer frame and is connected to the upper panel, and there is a gap between the lower end of the upper-middle thick beam and the lower-middle thick beam. The thin inclined beams are symmetrically arranged about the axis where the upper-middle thick beam is located, and the two ends are respectively connected to the side thick beams and the upper-middle thick beam. The present invention effectively blocks or reflects sound waves through the impedance mismatch between media, which is used to reduce the transmission of equipment noise to the external environment. By taking the effective thickness and the sound insulation level STL as evaluation indexes and adjusting the design parameters, the structure can have both pressure-resistant and impact-resistant properties and excellent sound insulation performance.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater multi-functional structures, and particularly to a design method for an integrated underwater structure with excellent sound insulation performance, pressure resistance and impact resistance functions. Background Art

[0002] With the development of underwater equipment and vehicles, concealment and impact resistance performance have become the key to design. Equipment in the deep sea needs to withstand huge water pressure, requiring the structure to have good pressure resistance performance. At the same time, it also needs to cope with weapon impacts to ensure impact resistance. And to reduce sonar detection, sound insulation performance is also particularly important. The sound insulation structure can reduce the transmission of internal noise of the equipment to the outside, thereby reducing the probability of being detected by sonar. Therefore, the design of underwater multi-functional structures needs to consider how to maximize the isolation of mechanical noise of underwater equipment under the conditions of meeting pressure resistance and impact resistance performance to achieve a concealed effect. Traditional sound insulation materials rely on the high rigidity of the materials to increase the acoustic impedance. However, in the underwater environment, the acoustic impedance of water is similar to that of common solid materials such as metals or polymers, resulting in limited underwater sound insulation effect of traditional methods.

[0003] Chinese Patent CN118520526A discloses a low-frequency sound absorption and broadband impact-resistant superstructure. Its impact-resistant sound absorption unit includes two panels made of pressure-resistant composite materials, an impact-resistant lattice structure and a damping layer with a cavity. Panels are provided at both the upper and lower ends of the damping layer, and the impact-resistant lattice structure is arranged inside the damping layer; the lattice structure is a simple cube of a hexahedral rod unit, including twelve rods with square cross-sections. The upper and lower four cross bars form a rectangular frame that connects the upper and lower parts of the panel respectively. This superstructure has excellent mechanical properties, and the maximum deformation under strong impact is only 6 mm; and it has good underwater sound absorption performance. In its simulation model, within a certain range, the sound absorption coefficient can reach above 0.7, and the sound absorption peak at some positions can reach above 0.9. However, the sound absorption principle of this type of superstructure is to convert the acoustic wave energy into heat energy through the viscoelasticity of the rubber in the structure, thereby reducing the intensity of the acoustic wave when it propagates in water. It is mainly used for noise control of acoustic equipment and interference noise management of underwater communication equipment. Summary of the Invention

[0004] The main purpose of the present invention is to provide a design method for an integrated underwater structure function. The pressure-resistant, impact-resistant and sound-insulating structure designed by this method mainly blocks or reflects acoustic waves effectively through the impedance mismatch between media in the underwater environment, preventing it from penetrating the material or structure. It is mainly applied to reduce the transmission of equipment noise to the external environment, thereby maintaining concealment, so that this pressure-resistant, impact-resistant and sound-insulating structure has both pressure resistance and impact resistance performance and excellent sound insulation performance.

[0005] The technical solution adopted by the present invention is:

[0006] A pressure-resistant, impact-resistant and sound-insulating structure includes an upper panel (10), a lower panel (20), and a number of pressure-resistant, impact-resistant and sound-insulating units (30) arranged in an array between the upper panel and the lower panel; the pressure-resistant, impact-resistant and sound-insulating unit (30) includes a Y-shaped outer frame (31), an upper-middle thick beam (32), and a thin inclined beam (33); the Y-shaped outer frame (31) includes two side thick beams (311) and two thick inclined beams (312) symmetrically arranged about the axis of the upper-middle thick beam (32), and a lower-middle thick beam (313) coaxially arranged with the upper-middle thick beam (32), the side thick beam (311) is connected to the lower-middle thick beam (313) through the thick inclined beam (312), and the lower-middle thick beam (313) is connected to the lower panel (20); the upper end of the upper-middle thick beam (32) extends outside the Y-shaped outer frame (31) and is connected to the upper panel (10), and there is a gap between the lower end of the upper-middle thick beam (32) and the lower-middle thick beam (313); the thin inclined beams (33) are symmetrically arranged about the axis of the upper-middle thick beam (32), and the two ends are respectively connected to the side thick beam (311) and the upper-middle thick beam (32).

[0007] In the above solution, the upper panel (10) and the lower panel (20) are made of alloy materials, carbon fiber composite materials or fiberglass composite materials; the pressure-resistant, impact-resistant and sound-insulating unit (30) is made of rigid resin, viscoelastic resin, nylon, carbon fiber composite materials or metal materials.

[0008] In the above solution, two or more groups of the thin inclined beams (33) are arranged along the axis direction of the upper-middle thick beam (32).

[0009] In the above solution, the pressure-resistant, impact-resistant and sound-insulating unit (30) maintains axis mirror symmetry and satisfies , in order to make the two ends of the thin inclined beam (33) maintain the same rigid constraint, maintain , and the upper-middle thick beam (32) and the lower-middle thick beam (313) are of equal thickness.

[0010] The present invention also proposes an underwater structure function integration design method, including the following steps:

[0011] S1. Determine that the underwater structure is integrated with pressure-resistant, impact-resistant and sound-insulating functions, and design a pressure-resistant, impact-resistant and sound-insulating structure with the above-mentioned structural form;

[0012] S2. Determine the working condition requirements of the pressure-resistant, impact-resistant and sound-insulating structure, including hydrostatic pressure , peak shock wave pressure , shock wave attenuation coefficient α , incident sound pressure ;

[0013] S3. Determine the parameters of the pressure-resistant, impact-resistant and sound-insulating structure, including: the total transverse length L of the pressure-resistant, impact-resistant and sound-insulating unit along the x direction, the total longitudinal width W along the y direction; the transverse length L1 and width W0 of the thick beam in the upper middle part; the width W1 of the thick beam at the edge; the length L0 and thickness t of the thin inclined beam, and the angle between the thin inclined beam and the horizontal direction; the thickness h p , length B and width H of the upper panel and the lower panel; the lattice number n of the pressure-resistant, impact-resistant and sound-insulating unit;

[0014] Then, test the equivalent strength and densification strain of the pressure-resistant, impact-resistant and sound-insulating structure through quasi-static compression experiments or finite element simulation calculations;

[0015] S4. Calculate the effective thickness of the pressure-resistant, impact-resistant and sound-insulating structure under the corresponding static pressure and impact conditions through theoretical formulas. The effective thickness is defined as the thickness of the pressure-resistant, impact-resistant and sound-insulating structure when the shock wave is completely dissipated;

[0016] S5. Calculate the sound insulation amount STL of the pressure-resistant, impact-resistant and sound-insulating structure under the corresponding incident sound pressure by combining theoretical formulas and finite element simulations;

[0017] S6. Take the effective thickness and the sound insulation amount STL as evaluation indicators, and adjust the design parameters of the pressure-resistant, impact-resistant and sound-insulating unit, including: the total transverse length L along the x direction, the total longitudinal width W along the y direction; the transverse length L1 and width W0 of the thick beam in the upper middle part; the width W1 of the thick beam at the edge; the length L0 and thickness t of the thin inclined beam, and the angle θ between the thin inclined beam and the horizontal direction; recalculate the effective thickness and the sound insulation amount STL, and optimize the design of the pressure-resistant, impact-resistant and sound-insulating structure to determine the optimal design parameters of the pressure-resistant, impact-resistant and sound-insulating structure.

[0018] In the above method, in step S2, the load-displacement curve of the pressure-resistant, impact-resistant and sound-insulating structure is obtained through quasi-static compression experiments or finite element simulation calculations; the stress-strain curve is obtained by converting the load-displacement curve, and the stress peak in the elastic section of the stress-strain curve is the equivalent strength ; the stress-strain curve is integrated to obtain the energy absorption efficiency-strain curve, and the peak of the energy absorption efficiency-strain curve corresponds to the strain as the densification strain .

[0019] In the above method, in step S3, the effective thickness The calculation formula is as follows:

[0020] (11)

[0021] In the formula, is the effective thickness of the pressure-resistant, impact-resistant and sound-insulating structure, is the peak value of the shock wave pressure, α is the shock wave attenuation coefficient, is the hydrostatic pressure, is the equivalent strength of the pressure-resistant, impact-resistant and sound-insulating structure, is the densification strain, and U2 is the compression amount of the pressure-resistant, impact-resistant and sound-insulating structure under the given peak pressure and the hydrostatic pressure of ; is the propagation speed of the shock wave in water.

[0022] In the above method, step S4 specifically includes:

[0023] When the incident sound pressure in the background pressure field is , the incident sound intensity is

[0024] (12)

[0025] In the formula, is the incident sound intensity, p in is the incident sound pressure, is the density of the medium where the incident sound field is located, is the propagation speed of the shock wave in water, represents the wave impedance of the medium where the incident sound field is located;

[0026] Then the incident sound power is:

[0027] (13)

[0028] In the formula, W in is the incident sound power, I in is the incident sound intensity, is the upper surface of the pressure-resistant, impact-resistant and sound-insulating structure, represents the transverse total length direction of the pressure-resistant, impact-resistant and sound-insulating unit, represents the longitudinal total width direction of the pressure-resistant, impact-resistant and sound-insulating unit;

[0029] Similarly, the transmitted sound power is:

[0030] (14)

[0031] In the formula, W outis the transmitted acoustic power, is the lower surface of the pressure-resistant and impact-resistant sound insulation structure, is the transmitted acoustic intensity at the surface, obtained by finite element simulation calculation;

[0032] According to the law of conservation of energy, the sound insulation level STL can be calculated from the incident acoustic power and the transmitted acoustic power, and the formula is:

[0033] (15).

[0034] In the above method, in step S5, in order to meet the requirements of impact resistance and pressure resistance, the effective thickness L eff is not less than 0.5 and not higher than 2.0; in order to meet the stealth requirements, for sound waves in the low-frequency range of 20 Hz to 500 Hz, STL is not less than 30 dB.

[0035] In the above method, in step S5, the method for adjusting the design parameters of the pressure-resistant and impact-resistant sound insulation unit is as follows: First, maintain the mirror symmetry along the axis in the pressure-resistant and impact-resistant sound insulation unit, and satisfy and satisfy , in order to make the two ends of the thin inclined beam maintain the same rigid constraint, maintain , the upper middle thick beam and the lower middle thick beam are of equal thickness; select any two parameters in the structural design parameters as variables, keep other parameters as fixed values, use the bisection method for sampling, evenly divide the value ranges of these two core variables into two-dimensional intervals, ensure that each interval is selected at least once during the sampling process, and calculate the effective thickness L eff and the sound insulation level STL of the pressure-resistant and impact-resistant sound insulation unit; when the calculated result does not meet the engineering index requirements at this time, continue to iteratively optimize and bisect the two core design parameters in the pressure-resistant and impact-resistant sound insulation unit until the engineering index requirements are met.

[0036] The beneficial effects produced by the present invention are:

[0037] The pressure-resistant and impact-resistant sound insulation structure designed by the present invention can effectively control the equivalent strength and densification strain of the structure by controlling the length L0, thickness t of the thin inclined beam of the pressure-resistant and impact-resistant sound insulation unit, and the angle θ between the thin inclined beam and the horizontal direction, thereby overcoming the problem of poor pressure resistance of the air cavity material in the traditional structure and enabling the structure to meet the requirements of pressure resistance and impact resistance; at the same time, by calculating the sound insulation level, the impedance difference between the structure and the medium is further controlled to achieve impedance mismatch between the structure and the medium, realizing strong wave reflection and good sound insulation effect; therefore, the pressure-resistant and impact-resistant sound insulation structure designed by the present invention can effectively block underwater sound waves in the low-frequency band (20 Hz to 500 Hz) and ensure the stability and impact resistance of the structure in a high-pressure environment, and is suitable for the stealth and impact resistance requirements of submarines, ships and other underwater equipment.

[0038] The integrated underwater structure function design method proposed by the present invention uses the effective thickness and the sound insulation level STL as evaluation indicators to adjust the design parameters of the pressure-resistant, impact-resistant and sound-insulating unit. Among them, the effective thickness can well control the pressure-resistant and impact-resistant effects of the structure, and the sound insulation level STL can control the sound insulation effect of the structure, so that the designed pressure-resistant, impact-resistant and sound-insulating structure has both pressure-resistant and impact-resistant properties and excellent sound insulation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0040] Figure 1 is the overall structure schematic diagram of the pressure-resistant, impact-resistant and sound-insulating structure designed by the present invention;

[0041] Figure 2 is Figure 1 the structure schematic diagram of the pressure-resistant, impact-resistant and sound-insulating unit of the pressure-resistant, impact-resistant and sound-insulating structure shown;

[0042] Figure 3 is Figure 1 the structure schematic diagram of the upper and lower panels of the pressure-resistant, impact-resistant and sound-insulating structure shown;

[0043] Figure 4 is the design method flow chart of the pressure-resistant, impact-resistant and sound-insulating structure of the present invention;

[0044] Figure 5 is the typical stress-strain curve of the pressure-resistant, impact-resistant and sound-insulating structure of the present invention under quasi-static compression;

[0045] Figure 6 is the typical energy absorption efficiency-strain curve of the pressure-resistant, impact-resistant and sound-insulating structure of the present invention under quasi-static compression;

[0046] Figure 7 is the unit cell form and sound insulation calculation model of the pressure-resistant, impact-resistant and sound-insulating structure of the present invention;

[0047] Figure 8 is the sound insulation calculation result of the pressure-resistant, impact-resistant and sound-insulating structure of the present invention.

[0048] In the figure: 10, upper panel; 20, lower panel; 30, pressure-resistant, impact-resistant and sound-insulating unit; 31, Y-shaped outer frame; 311, edge thick beam; 312, thick inclined beam; 313, lower middle thick beam; 32, upper middle thick beam; 33, thin inclined beam. Detailed implementation manners

[0049] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0050] It should be noted that the diagrams provided in the embodiments of the present invention only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape and size of the components in actual implementation. The types, quantities and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0051] In the present invention, it should also be noted that when terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application. In addition, when terms such as "first" and "second" appear, they are only used for descriptive and distinguishing purposes, and cannot be understood as indicating or implying relative importance.

[0052] As Figure 1 shown, a pressure-resistant, impact-resistant and sound-insulating structure designed by the present invention is similar to the structure of a diode, and includes an upper panel 10, a lower panel 20, and a plurality of pressure-resistant, impact-resistant and sound-insulating units 30 arranged in an array between the upper panel and the lower panel. As Figure 2 shown, the pressure-resistant, impact-resistant and sound-insulating unit 30 includes a Y-shaped outer frame 31, an upper-middle thick beam 32 and a thin inclined beam 33; the Y-shaped outer frame 31 includes two side thick beams 311 and two thick inclined beams 312 symmetrically arranged about the axis of the upper-middle thick beam 32, and a lower-middle thick beam 313 coaxially arranged with the upper-middle thick beam 32. The side thick beam 311 is connected to the lower-middle thick beam 313 through the thick inclined beam 312, and the lower-middle thick beam 313 is connected to the lower panel 20; the upper end of the upper-middle thick beam 32 extends outside the Y-shaped outer frame 31 and is connected to the upper panel 10, and there is a gap between the lower end of the upper-middle thick beam 32 and the lower-middle thick beam 313; the thin inclined beam 33 is symmetrically arranged about the axis of the upper-middle thick beam 32, and both ends are respectively connected to the side thick beam 311 and the upper-middle thick beam 32.

[0053] For the pressure-resistant, impact-resistant and sound-insulating structure designed by the present invention, by controlling the length L0 of the thin inclined beam 33 of the pressure-resistant, impact-resistant and sound-insulating unit, the thickness t , the included angle between the thin inclined beam 33 and the horizontal directionθ , it can effectively control the equivalent strength and densification strain of the structure, enabling the structure to meet the requirements of pressure resistance and impact resistance; at the same time, by calculating the sound insulation quantity, the impedance difference between the structure and the medium is further controlled, realizing the impedance mismatch between the structure and the medium, achieving strong wave reflection and good sound insulation effect; thus, the structure has both pressure resistance and impact resistance and excellent sound insulation performance. For the parameters of the pressure-resistant, impact-resistant and sound-insulating structure, see Figure 2 , the total transverse length of the pressure-resistant, impact-resistant and sound-insulating unit 30 along the x direction is L, and the total longitudinal width along the y direction is W; the transverse length of the upper-middle thick beam 32 is L1, and the width is W0; the width of the edge thick beam 311 is W1; the main load-bearing and deforming part is the middle thin inclined beam 33, its length is L0, and its thickness is t , the included angle between the thin inclined beam 33 and the horizontal direction is . See Figure 3 , the total transverse length of the upper panel and the lower panel along the x direction is B, the total longitudinal width along the y direction is H, and the thickness is h p . The lattice number of the pressure-resistant, impact-resistant and sound-insulating unit 30 is n .

[0054] Further optimized, the pressure-resistant, impact-resistant and sound-insulating unit 30 maintains axis mirror symmetry and satisfies , in order to make the two ends of the thin inclined beam 33 maintain the same rigid constraint, maintain , the upper-middle thick beam 32 and the lower-middle thick beam 313 are of equal thickness.

[0055] Further optimized, the upper panel 10 and the lower panel 20 adopt alloy materials (such as aluminum alloy, titanium alloy, etc.), carbon fiber composite materials or fiberglass composite materials, etc. These materials usually have extremely high strength and anti-fatigue characteristics and can withstand large mechanical stresses and impact forces. The pressure-resistant, impact-resistant and sound-insulating unit (30) adopts rigid resin, viscoelastic resin, nylon, carbon fiber composite materials or metal materials, etc. These materials have good mechanical properties and dimensional stability and can provide better support and structural strength.

[0056] Further optimized, two groups or more than two groups of thin inclined beams 33 are arranged along the axis where the upper-middle thick beam 32 is located.

[0057] The present invention also proposes an underwater structure function integration design method, see Figure 4 , including the following steps:

[0058] S1. Determine that the underwater structure is integrated with pressure resistance, impact resistance and sound insulation functions, and design a pressure-resistant, impact-resistant and sound-insulating structure with the structural form as shown in Figure 1 ;

[0059] S2. Determine the working conditions requirements of the pressure-resistant, impact-resistant and sound-insulating structure, including the hydrostatic pressure , the peak shock wave pressure , the shock wave attenuation coefficient α , the incident sound pressure .

[0060] Hydrostatic pressure It can be calculated through the corresponding water depth as follows:

[0061] (1)

[0062] In the formula, is the hydrostatic pressure, is the density of water, is the acceleration due to gravity, h is the water depth.

[0063] Peak shock wave pressure , shock wave attenuation coefficient α can be calculated through the corresponding charge amount and explosion distance in the working conditions. The shock wave generated by underwater explosion is the type of shock wave faced by the pressure-resistant, impact-resistant and sound-insulating structure. Peak shock wave pressure The calculation formula is:

[0064] (2)

[0065] In the formula, is the peak shock wave pressure, W represents the charge amount, R represents the distance from the explosion center, R 0 represents the charge radius.

[0066] Shock wave attenuation coefficient α The calculation formula is:

[0067] (3)

[0068] In the formula, c is the shock wave velocity; is the charge radius normalization coefficient, and there is:

[0069] (4)

[0070] S3. Determine the design parameters of the pressure-resistant, impact-resistant and sound-insulating structure, including: the total transverse length L of the pressure-resistant, impact-resistant and sound-insulating unit along the x direction, the total longitudinal width W along the y direction; the transverse length L1 and width W0 of the upper-middle thick beam; the width W1 of the edge thick beam; the length L0 and thickness t of the thin inclined beam, the angle between the thin inclined beam and the horizontal direction; the thickness of the upper panel and the lower panelh p , length B, width H; the lattice number of the pressure-resistant, impact-resistant and sound-insulating unit n .

[0071] Then, the equivalent strength of the pressure-resistant, impact-resistant and sound-insulating structure is tested through quasi-static compression experiments or calculated by finite element simulation and the densification strain .

[0072] In this embodiment, the specific dimensions of a group of designed pressure-resistant, impact-resistant and sound-insulating structures are as follows: L = 23 mm, W = 10 mm, t = 0.8 mm, W 1 = W 0 = 2 mm, n = 10, = 35°, B = 230 mm, H = 100 mm, L 1 = 15 mm, h p = 0.5 mm. Finite element calculations are performed using ABAQUS. The mesh size for the calculation is 0.1 mm, the loading speed is 2 mm / min, and dynamic analysis steps are used for the calculation. General contact is set in the calculation, and hard contact and a penalty constraint with a friction coefficient of 0.2 are adopted. In addition, the upper panel is set as a rigid panel, and the load-displacement curve of the pressure-resistant, impact-resistant and sound-insulating structure is extracted.

[0073] Convert the load-displacement curve to obtain the stress-strain curve of the pressure-resistant, impact-resistant and sound-insulating structure as shown in Figure 5 . The conversion formula is:

[0074] (5)

[0075] In the formula, is the structural stress, is the structural strain, is the axial load, is the initial cross-sectional area of the structure, is the compression displacement, is the initial height.

[0076] As shown in the annotation of Figure 5 , the stress peak in the elastic section of the stress-strain curve is the equivalent strength .

[0077] To judge the densification strain , it is necessary to plot the energy absorption efficiency-strain curve. Integrate the stress-strain curve to obtain the energy absorption efficiency-strain curve as shown in Figure 6 . The energy absorption efficiency calculation formula is:

[0078] (6)

[0079] Wherein, is the energy absorption efficiency of the structure, is expressed as a function of stress and strain , is the maximum stress in the strain range from 0 to , is the maximum strain during the compression of the structure.

[0080] As Figure 6 indicated by the annotation in, the strain corresponding to the peak of the energy absorption efficiency - strain curve is the densification strain .

[0081] S4. Calculate the effective thickness of the pressure - resistant, impact - resistant and sound - insulating structure under the corresponding static pressure and impact conditions , and the effective thickness is defined as the thickness of the pressure - resistant, impact - resistant and sound - insulating structure when the shock wave is completely dissipated.

[0082] The numerical fitting result of the compression of the normalized pressure - resistant, impact - resistant and sound - insulating structure is:[[]]

[0083] (7)

[0084] Wherein, U is the compression of the pressure - resistant, impact - resistant and sound - insulating structure, is the propagation speed of the shock wave in water, generally 1500 m / s, α is the shock wave attenuation coefficient, is the equivalent strength of the pressure - resistant, impact - resistant and sound - insulating structure, is the peak value of the shock wave pressure.

[0085] Solve for the equivalent strength according to Equation (7) as for a given pressure - resistant, impact - resistant and sound - insulating structure at a given peak pressure and hydrostatic pressure of 0:

[0086] (8)

[0087] Wherein, U 1 is the compression of the pressure - resistant, impact - resistant and sound - insulating structure when , is the hydrostatic pressure.

[0088] The fitting function of the known compression increase rate of the pressure - resistant, impact - resistant and sound - insulating structure is:[[]]

[0089] (9)

[0090] In the formula, is the compression rate increase of the pressure-resistant, impact-resistant and sound-insulating structure.

[0091] Combining the above formula to solve for the equivalent strength as of a given pressure-resistant, impact-resistant and sound-insulating structure at a given peak pressure and hydrostatic pressure of when the compression amount is:

[0092] (10)

[0093] In the formula, U2 is the compression amount of the pressure-resistant, impact-resistant and sound-insulating structure under the given conditions of and given.

[0094] Calculate the effective thickness of the pressure-resistant, impact-resistant and sound-insulating structure:

[0095] (11)

[0096] In the formula, is the effective thickness of the pressure-resistant, impact-resistant and sound-insulating structure, is the peak shock wave pressure, α is the shock wave attenuation coefficient, is the hydrostatic pressure, is the equivalent strength of the pressure-resistant, impact-resistant and sound-insulating structure, is the densification strain.

[0097] In this embodiment, the effective thickness = 1.2765 calculated according to formula (11).

[0098] S5. Calculate the sound insulation amount STL of the pressure-resistant, impact-resistant and sound-insulating structure at the corresponding incident sound pressure by combining the theoretical formula and finite element simulation.

[0099] When the incident sound pressure in the background pressure field is , the incident sound intensity is

[0100] (12)

[0101] In the formula, is the incident sound intensity, p in is the incident sound pressure, is the density of the medium where the incident sound field is located, is the propagation speed of the shock wave in water, represents the wave impedance of the medium where the incident sound field is located.

[0102] Then the incident sound power is:

[0103] (13)

[0104] In the formula, W in is the incident sound power, I in is the incident sound intensity, is the upper surface of the pressure-resistant, impact-resistant and sound-insulating structure, represents the transverse total length direction of the pressure-resistant, impact-resistant and sound-insulating unit, represents the longitudinal total width direction of the pressure-resistant, impact-resistant and sound-insulating unit.

[0105] Similarly, the transmitted sound power is:

[0106] (14)

[0107] In the formula, W out is the transmitted sound power, is the lower surface of the pressure-resistant, impact-resistant and sound-insulating structure, is the transmitted sound intensity at the

[0108] Specifically, obtained through finite element simulation calculation, the unit cell calculation model is as shown in the appendix Figure 7 The model from bottom to top is successively the water perfect matching layer, water area, pressure-resistant, impact-resistant and sound-insulating structure unit cell, air domain, and air domain perfect matching layer. The function of the water perfect matching layer is to simulate the infinite large water area outside, and the function of the air domain perfect matching layer is to simulate the infinite large air domain inside. The plane sound wave generated by the equipment is vertically incident on the pressure-resistant, impact-resistant and sound-insulating structure unit cell from the air domain. The four sides of the model are set as Floquet boundary conditions. The pressure magnitude of the plane wave is 1 MPa, the mesh uses quadratic tetrahedral elements, the mesh size is 0.5 mm, and the scanning frequency range is from 10 Hz to 1000 Hz.

[0109] According to the law of conservation of energy, the sound insulation quantity STL can be calculated from the incident sound power and the transmitted sound power, and the formula is:

[0110] (15)

[0111] Specifically, in this embodiment, the sound insulation quantity STL calculated for the pressure-resistant, impact-resistant and sound-insulating structure and the frequency results are as shown in the appendix Figure 8As shown, it can be seen from the figure that the sound insulation quantity gradually decreases in the low-frequency band (10 Hz to 100 Hz). In particular, a significant valley value appears when approaching 100 Hz, and the sound insulation effect deteriorates significantly. Subsequently, in the frequency band of 100 Hz to 1000 Hz, the sound insulation quantity shows a fluctuating trend, and relatively high sound insulation values are achieved in multiple frequency bands, with the highest approaching 80 dB, indicating good sound insulation performance at higher frequencies. This shows that the structure has a significant sound insulation effect in the high-frequency band, but has poor sound insulation performance at the resonance frequency in the low-frequency band and near 100 Hz, which requires further optimization through calculation to obtain better sound insulation performance.

[0112] S6. Using the effective thickness and the sound insulation quantity STL as evaluation indicators, adjust the design parameters of the pressure-resistant and impact-resistant sound insulation unit, including: the total transverse length L along the x direction, the total longitudinal width W along the y direction; the transverse length L1 and width W0 of the thick beam in the upper middle part; the width W1 of the thick beam at the edge; the length L0 and thickness t of the thin inclined beam, and the angle θ between the thin inclined beam and the horizontal direction. Calculate the effective thickness through the theoretical formula (11), and calculate the sound insulation quantity STL by repeatedly iterating formula (15) through the finite element method to optimize the design of the pressure-resistant and impact-resistant sound insulation structure to determine the optimal design parameters of the pressure-resistant and impact-resistant sound insulation structure.

[0113] To meet the requirements of impact resistance and pressure resistance, the effective thickness L eff is not less than 0.5. However, an excessive L eff will result in an overweight structure and high manufacturing costs. Therefore, L eff is not higher than 2.0. To meet the stealth requirements of underwater structures, in the low-frequency range (20 Hz to 500 Hz), the STL usually needs to reach 30 dB. In high-precision underwater acoustic systems, the STL requirement even exceeds 60 dB. The method for adjusting the design parameters of the pressure-resistant and impact-resistant sound insulation unit is as follows:

[0114] Specifically, in this embodiment, the bisection method is used for sampling to optimize the structure design. Select the thickness t of the thin inclined beam and the angle between the thin inclined beam and the horizontal direction in the optimized pressure-resistant and impact-resistant sound insulation structure. The value range of the thickness t of the thin inclined beam is from 0.1 mm to 1 mm, and the value range of the angle is . Compare the effective thickness t at the two endpoints of 0.1 - 0.5 mm of the thickness of the thin inclined beam with the effective thickness , determine whether it meets the above-mentioned impact and pressure resistance requirements. On the basis of meeting the above requirements, if the effective thickness of the former is less than that of the latter, then continue to bisect within the end point difference of the former. At this time, the bisection intervals are 0.1 - 0.25 mm and 0.25 mm - 0.5 mm, and continue to judge the effective thickness L eff to determine whether it meets the conditions, so as to determine the thickness of the thin inclined beam in the impact and pressure resistant sound insulation structure on the basis of ensuring the bearing capacity of the maximum impact and pressure resistant structure t , and calculate its sound insulation quantity STL through finite element method. In addition, it is also necessary to comprehensively compare the included angle of the thin inclined beam in and the effective thickness and the magnitude of the sound insulation quantity STL in the two intervals. The comparison method is the same as the previous method for the thickness of the thin inclined beam. Iteratively compare in this way until the effective thickness and the sound insulation quantity STL in the two divided intervals simultaneously meet the above-mentioned impact and pressure resistant sound insulation evaluation indexes, and the difference in the structural parameters at the two end points is less than 1%. At this time, the design parameters of the impact and pressure resistant sound insulation structure are the optimal parameters

[0115] It should be noted that according to the needs of implementation, each step / component described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention

[0116] The magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined according to its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application

[0117] It should be understood that those of ordinary skill in the art can make improvements or transformations according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention

Claims

1. A pressure-resistant, impact-resistant and sound-insulating structure, comprising an upper panel (10), a lower panel (20), and a plurality of pressure-resistant, impact-resistant and sound-insulating units (30) arranged in an array between the upper panel and the lower panel; characterized in that, The pressure-resistant, impact-resistant and sound-insulating unit (30) includes a Y-shaped outer frame (31), an upper-middle thick beam (32) and thin inclined beams (33); the Y-shaped outer frame (31) includes two side thick beams (311) and two thick inclined beams (312) symmetrically arranged about the axis where the upper-middle thick beam (32) is located, and a lower-middle thick beam (313) coaxially arranged with the upper-middle thick beam (32), and the side thick beam (311) is connected to the lower-middle thick beam (313) through the thick inclined beam (312), and the lower-middle thick beam (313) is connected to the lower panel (20); the upper end of the upper-middle thick beam (32) extends outside the Y-shaped outer frame (31) and is connected to the upper panel (10), and there is a gap between the lower end of the upper-middle thick beam (32) and the lower-middle thick beam (313); the thin inclined beams (33) are symmetrically arranged about the axis where the upper-middle thick beam (32) is located, and the two ends are respectively connected to the side thick beam (311) and the upper-middle thick beam (32).

2. The pressure-resistant, impact-resistant and sound-insulating structure according to claim 1, characterized in that, The upper panel (10) and the lower panel (20) are made of alloy materials, carbon fiber composite materials or fiberglass composite materials; the pressure-resistant, impact-resistant and sound-insulating unit (30) is made of rigid resin, viscoelastic resin, nylon, carbon fiber composite materials or metal materials.

3. The pressure-resistant, impact-resistant and sound-insulating structure according to claim 1, characterized in that Two or more groups of the thin inclined beams (33) are arranged along the axis direction where the upper-middle thick beam (32) is located.

4. The pressure-resistant, impact-resistant and sound-insulating structure according to claim 1, wherein The pressure-resistant, impact-resistant and sound-insulating unit (30) maintains axis mirror symmetry and satisfies , in order to keep the same rigid constraints at both ends of the thin inclined beam (33), keep , the upper-middle thick beam (32) and the lower-middle thick beam (313) have the same thickness; W is the total longitudinal width of the pressure-resistant, impact-resistant and sound-insulating unit in the y direction, W0 is the width of the upper-middle thick beam, W1 is the width of the edge thick beam, L0 is the length of the thin inclined beam, is the angle between the thin inclined beam and the horizontal direction.

5. An integrated design method for underwater structure functions, characterized in that, It includes the following steps: S1. Determine that the underwater structure is integrated with pressure-resistant, impact-resistant and sound-insulating functions, and design a pressure-resistant, impact-resistant and sound-insulating structure with the structural form described in any one of claims 1-4; S2. Determine the working conditions requirements of the pressure-resistant, impact-resistant and sound-insulating structure, including the hydrostatic pressure , the peak value of the shock wave pressure , the shock wave attenuation coefficient α , the incident sound pressure ; S3. Determine the parameters of the pressure-resistant, impact-resistant and sound-insulating structure, including: the total transverse length L of the pressure-resistant, impact-resistant and sound-insulating unit along the x direction, the total longitudinal width W along the y direction; the transverse length L1 and width W0 of the thick beam in the upper middle part; the width W1 of the thick beam at the edge; the length L0 and thickness of the thin inclined beam t , the included angle between the thin inclined beam and the horizontal direction; the thickness h p , length B and width H of the upper panel and the lower panel; the lattice number n of the pressure-resistant, impact-resistant and sound-insulating unit; Then, the equivalent strength of the pressure-resistant, impact-resistant and sound-insulating structure is tested through quasi-static compression experiments or calculated by finite element simulation and the densification strain ; S4. Calculate the effective thickness of the pressure-resistant, impact-resistant, and sound-insulating structure under the corresponding static pressure and impact conditions through theoretical formulas , where the effective thickness is defined as the thickness of the pressure-resistant, impact-resistant, and sound-insulating structure when the shock wave is completely dissipated; S5. Calculate the sound transmission loss STL of the pressure-resistant, impact-resistant and sound-insulating structure under the corresponding incident sound pressure through the combination of theoretical formulas and finite element simulations ; S6. Using the effective thickness and the sound insulation level STL as evaluation indicators, adjust the design parameters of the pressure-resistant and impact-resistant sound insulation unit, including: the total transverse length L along the x direction, the total longitudinal width W along the y direction; the transverse length L1 and width W0 of the thick beam in the upper middle part; the width W1 of the thick beam at the edge; the length L0 and thickness t of the thin inclined beam, and the angle θ between the thin inclined beam and the horizontal direction; calculate the effective thickness and the sound insulation level STL again, optimize the design of the pressure-resistant and impact-resistant sound insulation structure to determine the optimal design parameters of the pressure-resistant and impact-resistant sound insulation structure.

6. The integrated design method for underwater structure functions according to claim 5, characterized in that, In step S3, the load-displacement curve of the pressure-resistant, impact-resistant and sound-insulating structure is obtained through quasi-static compression experiment test or finite element simulation calculation; The stress-strain curve is obtained by converting the load-displacement curve, and the stress peak in the elastic section of the stress-strain curve is the equivalent strength ; Integrate the stress-strain curve to obtain the energy absorption efficiency-strain curve, and the peak value of the energy absorption efficiency-strain curve corresponds to the strain at densification .

7. The integrated underwater structure function design method according to claim 5, characterized in that In step S4, the effective thickness is calculated by the formula: （11） In the formula, is the effective thickness of the pressure-resistant, impact-resistant and sound-insulating structure, is the peak value of the shock wave pressure, α is the shock wave attenuation coefficient, is the hydrostatic pressure, is the equivalent strength of the pressure-resistant, impact-resistant and sound-insulating structure, is the densification strain, and U2 is the compression amount of the pressure-resistant, impact-resistant and sound-insulating structure under the given peak pressure and the hydrostatic pressure of The following is the compression amount of the pressure-resistant, impact-resistant and sound-insulating structure, is the propagation speed of the shock wave in water.

8. The integrated underwater structure functional design method according to claim 5, characterized in that Step S5 specifically includes: The incident sound pressure in the background pressure field is , then the incident sound intensity is （12） In the formula, is the incident sound intensity, p in is the incident sound pressure, is the density of the medium where the incident sound field is located, is the propagation speed of the shock wave in water, represents the wave impedance of the medium where the incident sound field is located; Then the incident sound power is: （13） Wherein, W in is the incident sound power, I in is the incident sound intensity, is the upper surface of the pressure-resistant, impact-resistant and sound-insulating structure, represents the transverse total length direction of the pressure-resistant, impact-resistant and sound-insulating unit, represents the longitudinal total width direction of the pressure-resistant, impact-resistant and sound-insulating unit; Similarly, the transmitted sound power is: （14） In the formula, W out is the transmitted acoustic power, is the lower surface of the pressure-resistant and impact-resistant sound insulation structure, is the transmitted acoustic intensity at the surface, obtained by finite element simulation calculation; According to the law of conservation of energy, the sound insulation quantity STL is calculated through the incident sound power and the transmitted sound power, and the formula is: （15）。 9. The integrated design method for underwater structure functions according to claim 5, wherein In step S6, to meet the requirements of impact resistance and pressure resistance, the effective thickness L eff is not less than 0.5 and not more than 2.0; to meet the stealth requirements, for sound waves in the low-frequency range of 20 Hz to 500 Hz, the STL is not less than 30 dB.

10. The integrated design method for underwater structure functions according to claim 5, characterized in that In step S6, the method for adjusting the design parameters of the pressure-resistant, impact-resistant, and sound-insulating unit is as follows: First, maintain the mirror symmetry along the axis of the pressure-resistant, impact-resistant, and sound-insulating unit, satisfying and satisfying , in order to keep the same rigid constraints at both ends of the thin inclined beam, maintain , the upper middle thick beam and the lower middle thick beam are of equal thickness; select any two parameters from the structural design parameters as variables, keep the other parameters as fixed values, use the bisection method for sampling, evenly divide the value ranges of these two core variables into two-dimensional intervals, ensure that each interval is selected at least once during the sampling process, and calculate the effective thickness L eff and the sound insulation quantity STL of the pressure-resistant, impact-resistant, and sound-insulating unit; when the calculated result at this time does not meet the requirements of the engineering indicators, continue to iteratively optimize and bisect the two core design parameters in the pressure-resistant, impact-resistant, and sound-insulating unit until the requirements of the engineering indicators are met.

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