Composite base structure design method, composite base and convex broadband underwater acoustic transducer

Abstract

The invention discloses a composite base structure design method, a composite base and a convex broadband underwater acoustic transducer, and relates to the technical field of underwater acoustic transducers, and the composite base structure design method comprises the steps: obtaining the length l < s > of an internal space of a housing in a natural state and the length l < 0 > of a driving oscillator; the deformation amount x sa of the shell in the long axis direction under the expected water depth is calculated; calculating the deformation x < r > of the driving vibrator compressed under the expected prestress; calculating the interference length m = x r + x sa; and calculating the thickness d of the base according to the formula: d = (ls + m-l0) / 2. The invention aims to improve the electro-acoustic conversion efficiency of the underwater acoustic transducer in deep sea detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of underwater acoustic transducers, and particularly relates to a composite base structure design method, a composite base and a convex broadband underwater acoustic transducer. BACKGROUND

[0002] The super magnetostrictive bending-tension transducer is widely used in underwater long-distance detection and communication fields due to its unique advantages of low frequency, large power and small size. In the super magnetostrictive bending-tension underwater acoustic transducer, the driving vibrator (formed by alternately stacking super magnetostrictive rods and permanent magnets) needs to be in the optimal static pre-stress interval to make the underwater acoustic transducer play the maximum potential and improve the electro-acoustic conversion efficiency. The pre-stress is mainly generated by compressing the driving vibrator through the base of the bending-tension shell, and therefore the thickness of the base directly determines the pre-stress.

[0003] However, the thickness of the base is generally calculated by an empirical formula in the prior art, and only the linear deformation of the shell under the water depth is considered, while the influence of the stiffness of the driving vibrator itself is ignored. In the pre-tightening process, the vibrator is synchronously compressed, and the compression amount accounts for a large proportion of the total interference amount. In the prior art, only the deformation of the shell is considered, which may cause the theoretical thickness of the base to be too small, the actual pre-stress to be lower than the design value, and the electro-acoustic conversion efficiency of the underwater acoustic transducer to be difficult to improve. SUMMARY

[0004] The main purpose of the present application is to provide a composite base structure design method, a composite base and a convex broadband underwater acoustic transducer, which aims to improve the electro-acoustic conversion efficiency of the underwater acoustic transducer.

[0005] To achieve the above purpose, the composite base structure design method provided by the present application is applied to the underwater acoustic transducer, and the composite base structure design method comprises the following steps. obtaining the length of the internal space of the shell in the natural state l s , the length of the driving vibrator l 0; calculating the deformation amount of the shell in the long axis direction under the expected water depth x sa ; calculating the deformation amount of the driving vibrator compressed under the expected pre-stress x r , ; calculating the interference length m=x r +x sa ; calculating the base base thickness d =( l s +m- l 0) / 2; wherein, n r is the number of magnetostrictive rods in each column of single-drive vibrator, n pm is the number of permanent magnets in each column of single-drive vibrator, n pm n r +1; A r is the cross-sectional area of the permanent magnet and the magnetostrictive rod; k r is the stiffness of the magnetostrictive rod, k pm is the stiffness of the permanent magnet; p is the value of the pre-stress under the expected working water depth.

[0006] In an embodiment, the deformation of the shell in the long axis direction under the expected water depth is calculated x sa comprises: calculating the hydrostatic pressure on the outer surface of the shell under the expected water depth p water , p water =ρ gh water ; wherein ρ is the density of water, g is the acceleration of gravity, h water is the expected working water depth; using finite element simulation to simulate the application of hydrostatic pressure on the outer surface of the shell p water , simulate the application of internal gas pressure on the inner surface of the shell p air , simulate the application of the reaction force of the pre-stress on the contact part of the vibrator and the base p f ; According to the simulation results, the deformation of the shell in the long axis direction under the expected water depth is obtained x sa .

[0007] In an embodiment, the composite base comprises a plurality of magnetic conductive blocks, each of which is embedded in the base substrate; each of the magnetic conductive blocks comprises a plurality of silicon steel sheets, each of which is stacked along the width direction of the composite base to form the magnetic conductive block; the number of the magnetic conductive blocks in each of the composite bases is q, q = n / 2; wherein n is the number of columns of driving vibrators, n is an even number and n≥2; the thickness d 1 and the width w of each of the magnetic conductive blocks satisfy: ;​ wherein, N N is the number of turns of the coil, I I is the working current of the coil; l r L is the length of the giant magnetostrictive rod, l pm L is the length of the permanent magnet; 0 is the vacuum permeability, r μ is the relative permeability of the giant magnetostrictive rod, pm μ is the relative permeability of the permanent magnet.

[0008] In an embodiment, the length of each of the magnetic conductive blocks is l dc satisfies: wherein, d coil D is the outer diameter of the coil, d rod D is the diameter of the giant magnetostrictive rod, d c S is the spacing between the coils.

[0009] The application also provides a composite base designed by the composite base structure design method described above; the composite base comprises a base substrate and a plurality of magnetic conductive blocks, each of the magnetic conductive blocks being embedded in the base substrate.

[0010] The application also provides a convex broadband underwater acoustic transducer; the convex giant magnetostrictive low-frequency broadband transducer comprises a shell and a driving unit, the driving unit comprising a coil, a driving vibrator, and a composite base as claimed in claim 5. The giant magnetostrictive rod and the permanent magnet are coaxially and alternately bonded to form the driving vibrator, the coil is arranged around the outer periphery of the driving vibrator, and the two ends of the driving vibrator abut against the base substrate; the side of the base substrate away from the driving vibrator abuts against the inner peripheral wall of the shell.

[0011] In an embodiment, the cross section of the shell along the length direction of the shell is elliptical; the two ends of the shell along the minor axis direction of the shell are respectively provided with a protruding structure outward.

[0012] In an embodiment, the base substrate is made of a non-magnetic metal material with a relative permeability of 1.

[0013] In the technical solution of the application, the composite base structure design method comprises obtaining the length of the internal space of the shell in a natural state l s the length of the driving vibrator l 0; calculating the deformation amount of the shell in the major axis direction at the expected water depthx sa ; calculate the deformation of the driving vibrator compressed under the expected prestress x r , ; calculate the interference length m=x r +x sa ; calculate the thickness of the base d ( l s +m- l 0) / 2. In the technical solution of the application, by introducing the driving vibrator compression amount parameter, the coupling deformation model of the shell and the driving vibrator is established, the interference length is accurately determined, the composite base thickness design value is more in line with the actual working condition requirements, and therefore the electro-acoustic conversion efficiency of the underwater acoustic transducer is improved. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained according to the structures shown in the drawings without creative labor for those skilled in the art.

[0015] Figure 1 The flow chart of the embodiment of the composite base structure design method provided by the application; Figure 2 The structure diagram of the composite base; Figure 3 The structure diagram of the driving vibrator in the composite base; Figure 4 The structure diagram of an embodiment of the shell; Figure 5 The model diagram of the finite element simulation of an embodiment of the shell; Figure 6 The displacement distribution cloud diagram of the finite element simulation of an embodiment of the shell; Figure 7 The structure diagram of an embodiment of the convex broadband underwater acoustic transducer provided by the application; Figure 8 The structure diagram of another embodiment of the convex broadband underwater acoustic transducer.

[0016] Explanation of reference numerals: 100, composite base; 1, base substrate; 2, permanent magnet; 1000, convex broadband underwater acoustic transducer; 3, shell; 31, convex structure; 40, driving vibrator; 41, coil; 42, giant magnetostrictive rod material; 5, magnetic conducting block.

[0017] The objectives, functional characteristics and advantages of the present application will be further described with reference to the embodiments in combination with the accompanying drawings. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0019] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications also change accordingly.

[0020] In addition, if the embodiments of the present application involve descriptions of “first”, “second”, etc., the descriptions of “first”, “second”, etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by “first” and “second” can explicitly or implicitly include at least one of the features. In addition, “and / or” or “and / or” appearing throughout the text means that the three parallel schemes are included, for example, “A and / or B” includes A scheme, or B scheme, or A and B simultaneously satisfy the scheme. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist and is not within the protection scope claimed by the present application.

[0021] In the prior art, the super magnetostrictive bending and stretching transducer generates a pre-stress by compressing the driving vibrator through the deformation of the shell. However, the traditional method only considers the single-sided deformation amount of the shell and ignores the influence of the stiffness of the driving vibrator itself on the compression amount, resulting in that the proportion of the compression amount of the vibrator to the interference amount is underestimated, and finally the calculated value of the thickness of the base is too small, the actual pre-tightening force is insufficient, and the electro-acoustic conversion efficiency of the transducer is limited.

[0022] To solve the above problems, the present application provides a composite base structure design method, Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 and Figure 6 The schematic diagram of the embodiment of the composite base structure design method provided by the present application.

[0023] Referring to Figure 1 , Figure 2 , Figure 3 and Figure 4 , the present application proposes a composite base structure design method, comprising obtaining the length of the internal space of the shell 3 in the natural state l s , the length of the driving vibrator 40 l 0; calculating the deformation amount of the shell 3 in the long axis direction under the expected water depth x sa ; calculating the deformation amount of the driving vibrator 40 compressed under the expected prestress x r , ; calculating the interference length m=x r +x sa ; calculating the thickness of the base substrate 1 d =( l s +m- l 0) / 2.

[0024] Wherein, the length of the internal space of the shell 3 in the natural state refers to the cavity size of the shell 3 in the internal long axis direction when not subjected to external force, which can be obtained by laser scanner measurement. The length of the driving vibrator 40 refers to the total length of the driving unit formed by the alternately stacked super-magnetostrictive rod 42 and permanent magnet 2 in the free state. The deformation amount of the shell 3 in the long axis direction is calculated by finite element simulation combined with water pressure load, reflecting the deformation characteristics of the shell 3 under deep sea pressure. The deformation amount of the driving vibrator 40 compressed is determined by the ratio of the prestress and the equivalent stiffness, which needs to be calculated comprehensively considering the stiffness parameters of the super-magnetostrictive rod 42 and the permanent magnet 2. The interference length, as the superposition amount of the deformation of the shell 3 and the compression of the vibrator, is used to compensate for the displacement difference of the two in the pre-tightening process. The thickness of the base substrate 1 is calculated through geometric relationship to ensure that the shell 3 and the driving vibrator 40 reach the preset prestress value after assembly.

[0025] Specifically, the method first establishes the mechanical model of the shell 3 and the driving vibrator 40, calculates the deformation amount of the shell 3 under the target water depth through simulation, and calculates the compression amount of the driving vibrator 40 under the preset prestress according to the material stiffness parameters. After superimposing the total interference amount, the difference between the internal space length of the shell 3 and the original length of the driving vibrator 40 is used to deduce the theoretical thickness of the base combined with the interference amount. This process takes into account the deformation of the shell 3 under the action of external water pressure and the influence of the material stiffness of the driving vibrator 40 on the compression amount, avoiding the calculation error of the base thickness caused by ignoring the stiffness of the vibrator in the traditional method.

[0026] Compared with the prior art, the traditional method only takes the deformation amount of the shell 3 as the calculation basis of the interference amount, while the scheme introduces the compression amount parameter of the driving vibrator 40, establishes the coupling deformation model of the shell 3 and the driving vibrator 40, and accurately calculates the total interference amount. In the prior art, the thickness design value of the composite base 100 is small due to the failure to consider the stiffness of the driving vibrator, while the scheme superimposes the two deformation amounts, so that the calculated value of the base thickness is closer to the actual demand, thereby ensuring that the pre-tightening force reaches the design target value.

[0027] Through the above technical scheme, the pre-tightening force deficiency problem caused by the failure to consider the stiffness of the driving vibrator 40 in the traditional base thickness design method is effectively solved. By simultaneously calculating the deformation amount of the shell 3 and the compression amount of the driving vibrator 40, the interference length is accurately determined, so that the thickness design value of the composite base 100 is more in line with the actual working condition demand, thereby improving the electro-acoustic conversion efficiency of the underwater acoustic transducer. The method provides a reliable theoretical calculation basis for the pre-stress control in the deep-sea exploration equipment, and avoids the performance attenuation caused by the base thickness error.

[0028] Please refer to Figure 5 and Figure 6 In an embodiment of the present application, the deformation amount of the shell 3 in the long axis direction at the expected water depth is calculated x sa including calculating the hydrostatic pressure on the outer surface of the shell 3 at the expected water depth p water , p water =ρ gh water ; wherein ρ is the density of water, g is the acceleration of gravity, h water is the expected working water depth; the finite element simulation is used to simulate the application of the hydrostatic pressure on the outer surface of the shell 3 p water , the internal gas pressure is simulated on the inner surface of the shell 3 p air , the counterforce of the pre-tightening force is simulated on the contact part of the driving vibrator 40 and the base p f ; according to the simulation result, the deformation amount of the shell 3 in the long axis direction at the expected water depth is obtained x sa .

[0029] Figure 5 is a schematic diagram of the simulation model of the shell 3 in an embodiment of the composite base structure design method, wherein the light blue arrow represents the pressure of the simulated hydrostatic pressure on the outer surface of the shell 3 at the expected water depth p water , and the red arrow represents the counterforce of the driving vibrator 40 on the base p f, the dark blue arrows represent the pressure exerted by the internal gas on the inner surface of the shell 3 p air To indicate the different sources of force, the different color arrows of the color drawing are therefore used to distinguish them.

[0030] Figure 6 The cloud chart of the displacement distribution of the shell 3 in the long axis direction after the finite element simulation in an embodiment of the composite base structure design method, unit: millimeter. Different colors represent different displacement sizes, so it is more intuitive and necessary to use color drawings.

[0031] Among them, the hydrostatic pressure refers to the water pressure borne by the outer surface of the shell 3, which can be calculated by the formula of the water density, the gravitational acceleration and the expected working water depth, and is used to reflect the external load of the shell 3 at the target working depth. Finite element simulation refers to the analysis of the mechanical response of the shell 3 under the composite load by numerical simulation method, which can specifically establish a three-dimensional model of the shell 3 by using commercial finite element software and apply boundary conditions to simulate the deformation behavior of the shell 3 under the combined action of hydrostatic pressure, internal gas pressure and prestress reaction force. The internal gas pressure refers to the pressure of the gas in the cavity of the shell 3 on the inner surface of the shell 3, which can be set by the actual working condition pressure value to reflect the influence of the internal environment of the shell 3 on the deformation. The reaction force of the prestress is the force applied to the shell 3 during the compression of the driving vibrator 40, which can be calculated by the stiffness and compression amount of the driving vibrator 40 to reflect the constraint effect of the prestress on the deformation of the shell 3 in the simulation.

[0032] Specifically, when calculating the deformation of the shell 3, first calculate the corresponding external hydrostatic pressure value according to the target working water depth, which directly acts on the outer surface of the shell 3. Then, a complete mechanical model including the shell 3, the driving vibrator 40 and the base is established by finite element simulation, and the hydrostatic pressure load is applied to the outer surface of the shell 3, and the internal gas pressure is applied to the inner surface of the shell 3 to simulate the pressure balance state in the actual working environment. At the same time, the reaction force of the prestress is applied to the contact area between the driving vibrator 40 and the base, which is determined by the elastic force generated when the driving vibrator 40 is compressed. By solving the finite element equation under the composite load condition, the deformation of the shell 3 in the long axis direction can be accurately obtained. This simulation method fully considers the coupling effect of the external water pressure, the internal gas pressure and the reaction force of the prestress of the shell 3, and avoids the error caused by only considering a single load in the traditional method.

[0033] By introducing the hydrostatic pressure, the internal gas pressure and the reaction force of the prestress through finite element simulation, the composite stress state of the shell 3 under the actual working condition can be more accurately reflected. This multi-factor coupling analysis method significantly improves the calculation accuracy of the deformation of the shell 3, and overcomes the problem of overestimation of the deformation of the shell 3 caused by ignoring the reaction force of the prestress in the traditional empirical formula.

[0034] Through the above technical solution, this application can accurately predict the actual deformation of the shell 3 at the target working water depth, providing a reliable basis for the accurate calculation of the base thickness. By comprehensively considering the constraint effect of the prestress reaction force on the deformation of the shell 3, the design error of the base thickness caused by the deviation in deformation calculation is effectively avoided, thereby ensuring that the drive oscillator 40 obtains an accurate pre-compression amount, enabling the underwater acoustic transducer to maintain the optimal prestress state in deep water environment. This improvement directly solves the problem of insufficient prestress caused by neglecting the stiffness of the drive oscillator 40 in the prior art, effectively improving the electroacoustic conversion efficiency of the underwater acoustic transducer.

[0035] In one embodiment of the present invention, the composite base 100 includes a plurality of magnetically conductive blocks 5, each magnetically conductive block 5 being embedded in the base substrate 1; each magnetically conductive block 5 includes a plurality of silicon steel sheets, each silicon steel sheet being stacked along the width direction of the composite base 100 to form the magnetically conductive block 5; the number of magnetically conductive blocks 5 in each composite base 100 is q, q=n / 2; where n is the number of columns of the driving oscillator 40, n is an even number and n≥2; The thickness of each magnetic block 5 d 1 and width w satisfy: ; in, N The number of turns of coil 41, I This is the operating current of coil 41; l r The length of the super magnetostrictive rod 42, l pm The length of permanent magnet 2; 0 is the permeability of free space. r The relative permeability of the supermagnetostrictive rod is 42. pm denoted as 2, representing the relative permeability of the permanent magnet.

[0036] Specifically, the ratio of the number of magnetically conductive blocks 5 to the number of rows of driving oscillators 40 is set to 1:2, ensuring a symmetrical magnetic field distribution on both sides of each row of driving oscillators 40, thereby eliminating prestress deviation caused by magnetic field asymmetry. The thickness of the magnetically conductive blocks 5 is calculated by combining the number of turns of the coil 41, the operating current, and the material's permeability parameters. For example, when the number of turns of the coil 41 is 200, the thickness can be dynamically adjusted based on the current intensity and magnetic circuit length to ensure that the bias magnetic field intensity is always within the optimal operating range of the magnetostrictive material. The width of the magnetically conductive blocks 5 is determined by the geometric relationship between the outer diameter and spacing of the coil 41. For example, when the outer diameter of the coil 41 is 10 mm, the width can be adapted based on the circumferential arrangement density, thereby maximizing the utilization of magnetic flux within a limited space.

[0037] In an embodiment of the present application, the length of each magnetic conducting block 5 is l dc satisfies: ; wherein, d coil is the outer diameter of the coil 41, d rod is the diameter of the giant magnetostrictive rod 42, d c is the distance between the coils 41.

[0038] The outer diameter of the coil 41 specifically refers to the maximum transverse dimension of the outer edge of the cylinder formed after the coil 41 is wound, which can be realized by measuring the distance between the outermost two points of the coil 41 winding layer, and is used to determine the occupation reference of the magnetic conducting block 5 in the axial space layout. The diameter of the giant magnetostrictive rod 42 specifically refers to the maximum radial dimension of the cross section of the rod, which directly affects the length matching of the magnetic conducting block 5 required for the magnetic circuit to be closed. The distance between the coils 41 specifically refers to the spacing distance between the center axes of adjacent coils 41, which can be realized by adjusting the distribution position of the coil 41 winding, and is used to balance the magnetic field uniformity and space utilization.

[0039] Specifically, the determination of the length of the magnetic conducting block 5 is based on the half value of the sum of the outer diameter of the coil 41, the diameter of the giant magnetostrictive rod 42 and the distance between the coils 41. This calculation method makes the magnetic conducting block 5 in the axial layout be able to completely cover the superimposed area of the coil 41 and the rod, ensuring that the magnetic circuit reduces the magnetic leakage phenomenon in the closed path. By setting the length of the magnetic conducting block 5 as the half value of the sum of the three parameters, it can avoid the magnetic circuit not being closed due to the outer diameter of the coil 41 or the diameter of the rod being too large, and prevent the magnetic field from interfering with each other due to the distance between the coils 41 being too small.

[0040] By establishing the mathematical relationship of the three, the length of the magnetic conducting block 5 is accurately matched with the actual assembly requirement, the magnetic circuit is optimized in the limited space, the problem of magnetic energy loss caused by improper design of the length of the magnetic conducting block 5 is solved, the physical size of the coil 41 and the rod is accurately matched, and the formation of the effective closed path of the magnetic field is ensured, thereby improving the energy conversion efficiency of the driving vibrator 40, and avoiding the risk of assembly interference caused by length mismatch.

[0041] In an embodiment of the present application, the magnetic conducting block 5 can be replaced with a magnetic conducting block formed by stacking magnetic conducting silicon steel sheets. The thickness of a single layer of magnetic conducting silicon steel sheets can be 0.2mm, and the surface is coated with an insulating coating.

[0042] Further, in an embodiment of the present application, the width w of the magnetic conducting block 5 is greater than the diameter of the giant magnetostrictive rod 42 ’ d rod .

[0043] ​In one embodiment of the present invention, the magnetic conductive block 5 is made of 160 sheets with a thickness of... d 1 is made of stacked silicon steel sheets, each 0.2mm thick, 110mm long, and 12mm wide; that is, the width of magnetic block 5 is w. ’ =32mm. First scanned by a laser scanner. Figure 4 From shell 3, the length of the major axis space inside shell 3 can be obtained. l s =245.013mm. Then scan using a laser scanner. Figure 3 The length of the driving oscillator 40 can be obtained from the driving oscillator 40. l 0 = 205.029 mm. The deformation of shell 3 along its major axis was calculated using finite element method (FEM) simulation. x sa In the specific calculation, ρ = 1000 kg / m³. g =9.8m / s², h water =40m, p air =1×10 5 Pa, p f = p re =24MPa. Calculations show that... x sa =0.394mm. Equivalent stiffness of the supermagnetostrictive rod 42 k rod 3.60×10 8 N / m, equivalent stiffness of permanent magnet 2 k pm It is 1.41×10 10 N / m, calculate the amount of deformation of the oscillator under the desired prestress. x r = A r p re ( n r / k rod + n pm / k pm =0.146mm.

[0044] According to the composite base structure design method of the present invention, the over-interference length is calculated. m = x r + x sa =0.54mm; Calculate the thickness of base 1. d =(l s + m - l 0) / 2=19.722mm.

[0045] The application further provides a composite base 100, please refer to Figure 2 The composite base structure design method is designed by referring to the above-mentioned embodiments. Since the composite base 100 adopts all the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here. Among them, the composite base 100 includes a base substrate 1 and a plurality of magnetic conductive blocks 5, and each magnetic conductive block 5 is embedded in the base substrate 1.

[0046] The application further provides a convex broadband underwater acoustic transducer 1000, please refer to Figure 7 And Figure 8 The convex broadband underwater acoustic transducer 1000 includes a shell 3 and a driving unit, the driving unit includes a coil 41, a driving vibrator 40 and a composite base 100, the specific structure of the composite base 100 refers to the above-mentioned embodiments. Since the convex broadband underwater acoustic transducer 1000 adopts all the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here. Among them, each magnetostrictive rod 42 is coaxially and alternately bonded with each permanent magnet 2 to form a driving vibrator 40, the coil 41 is wound on the outer periphery of the driving vibrator 40, and the two ends of the driving vibrator 40 abut against the base substrate 1; the side of the base substrate 1 away from the driving vibrator 40 abuts against the inner circumferential wall of the shell 3.

[0047] Among them, the shell 3 refers to the structure of the shell 3 with an oval cross section along the length direction, which can be realized by alloy material processing. The driving unit refers to an energy conversion component composed of magnetostrictive rods 42, permanent magnets 2 and coils 41, which specifically realizes the conversion from electric energy to mechanical energy by alternately stacking magnetostrictive rods 42 and permanent magnets 2 to form a driving vibrator 40, and combining the alternating magnetic field generated by the coil 41. The composite base 100 refers to a support structure embedded by a non-magnetic metal base and a magnetic conductive block 5, which specifically forms a rigid connection by embedding the magnetic conductive block 5 into the base substrate 1, which not only provides the mounting interface of the driving vibrator 40, but also transmits the compression amount of the shell 3 through the base deformation to apply the prestress. Coaxial and alternate bonding refers to the alternate arrangement of magnetostrictive rods 42 and permanent magnets 2 along the axial direction and the fixation by adhesive, which can realize the interface bonding by using epoxy resin to ensure the continuity of the magnetic circuit inside the driving vibrator 40 and reduce the magnetic energy loss.

[0048] Specifically, the shell 3 is deformed in the long axis direction, and the pre-tightening force is transmitted to the drive vibrator 40 through the base substrate 1, so that both ends of the drive vibrator 40 are compressed. The drive vibrator 40 is composed of alternately stacked super-magnetostrictive rods 42 and permanent magnets 2, and the coil 41 surrounds the outer periphery of the drive vibrator 40. After being energized, the coil 41 generates an alternating magnetic field, which drives the super-magnetostrictive rods 42 to stretch and contract, thereby driving the shell 3 to vibrate and radiate sound waves. The magnetic conductive block 5 is embedded in the base substrate 1, which not only provides a magnetic circuit for the drive vibrator 40, but also avoids magnetic circuit short circuiting through the non-magnetic properties of the base substrate 1, thereby improving the utilization rate of the magnetic field.

[0049] By alternately stacking the super-magnetostrictive rods 42 and the permanent magnets 2, the magnetic circuit distribution inside the drive vibrator 40 is optimized. Meanwhile, by embedding the magnetic conductive block 5 in the composite base 100, the rigidity of the base is ensured, and the deformation amount of the base is accurately matched with the compression requirement of the shell 3, thereby avoiding pre-stress deviation. The problem of insufficient pre-stress caused by thickness calculation deviation of the base in the prior art is solved. Meanwhile, by the alternately stacked structure and the composite base 100 design, the magnetic field distribution of the drive vibrator 40 is optimized, so that the underwater acoustic transducer can still maintain a stable pre-stress state in a deep water environment, and the electro-acoustic conversion performance is significantly improved.

[0050] Sound waves are currently the only known physical carrier that can achieve long-distance information transmission in seawater. The underwater acoustic system constructed by using this characteristic has become the core means of underwater early warning reconnaissance, submarine covert communication, target fine identification, marine resource exploration (oil and gas, mineral resources), seabed mapping and long-term monitoring of marine environment. Generally speaking, the lower the frequency of the sound signal, the smaller the seawater absorption attenuation, and the farther the propagation distance; the wider the working bandwidth, the greater the amount of information that can be carried, and the stronger the anti-multipath and anti-reverberation ability. Therefore, a low-frequency broadband sound source is a key device commonly pursued by various high-end underwater acoustic equipment.

[0051] However, low-frequency emission requires the transducer to have low rigidity or / and large mass, which often leads to a sharp increase in volume and weight; broadband emission requires exciting multiple adjacent resonant modes, but the traditional structure usually only has a single main resonance, which makes it difficult to form effective coupling within the -3dB attenuation range, resulting in limited bandwidth expansion. If the frequency response is widened by damping or additional mass, the sound source level (output power) will also decrease significantly. Therefore, how to balance between “low frequency, wide bandwidth, high power and miniaturization” has always been a technical bottleneck in the field of underwater acoustic transducers.

[0052] To solve this problem, please refer to Figure 7 and Figure 8 In an embodiment of the present application, the cross section of the shell 3 along the length direction of the shell 3 is elliptical; and the two ends of the shell 3 along the short axis direction of the shell 3 are respectively provided with a protruding structure 31 outward.

[0053] The elliptical section refers to the cross-sectional shape of the shell 3 in the length direction as an elliptic curve, which can be realized by mold forming or mechanical processing. The deformation coordination of the shell 3 in the long axis and short axis direction is realized through the geometric characteristics of the ellipse, so as to optimize the stress distribution of the shell 3 under the prestress. The convex structure 31 refers to the local thickening area formed by the outward extension of the shell 3 at both ends in the short axis direction, which can be realized by welding, casting or additive manufacturing.

[0054] The "low frequency-wide band-high power" triangular contradiction is rooted in the fact that the traditional elliptical shell 3 can only provide one effective resonance peak. The shell 3 is geometrically continuous and has uniform stiffness, which is equivalent to a single degree of freedom system in the low frequency range. The bandwidth is determined by the quality factor, and cannot be widened. By adding a rectangular protrusion in the middle of the short axis of the elliptical shell 3, two coupling effects can be triggered in turn, so that the system transits from single degree of freedom to double degree of freedom, and then forms adjacent double peaks, meeting the continuous negative three decibel wide band condition. First, the local mass effect; the protrusion concentrates additional mass, the equivalent mass increases, and the main resonance frequency naturally shifts downward, without the need to enlarge the size of the shell 3 to reduce the frequency. Second, the local stiffness effect; the "beam-plate" transition occurs at the connection between the protrusion and the ellipse, the local bending stiffness decreases; at the same time, the protrusion itself becomes a short beam, producing a secondary bending mode at a higher frequency, forming adjacent double peaks. The rounded transition reduces stress concentration and ensures structural integrity under large amplitude.

[0055] In an embodiment of the present application, the base substrate 1 is made of a non-magnetic metal material with a relative magnetic permeability of 1.

[0056] The non-magnetic metal material with a relative magnetic permeability of 1 refers to a non-ferromagnetic metal alloy with a magnetic permeability equal to that of vacuum. Specifically, aluminum alloy, titanium alloy or austenitic stainless steel can be used to realize this type of material, which will not produce additional magnetization effect in a magnetic field environment. The base substrate 1 refers to a support structure for carrying the permanent magnet 2 and contacting the shell 3. Specifically, it needs to be formed into a plate-shaped component with a predetermined thickness by mechanical processing, and its material needs to meet the structural strength requirements.

[0057] Specifically, the base substrate 1 is configured to simultaneously withstand the prestress transmitted by the shell 3 and the reaction force of the drive vibrator 40. When a non-magnetic metal material is used, the static magnetic field generated by the permanent magnet 2 forms a closed magnetic circuit inside the drive vibrator 40, avoiding magnetic field distortion caused by the difference in magnetic permeability of the base substrate 1 material. For example, during assembly, the drive vibrator 40 formed by alternately stacking the giant magnetostrictive rod 42 and the permanent magnet 2 is compressed between the two base substrates 1. At this time, the non-magnetic property of the base substrate 1 can eliminate the additional magnetic resistance in the magnetic circuit, ensuring uniform distribution of the magnetic field inside the drive vibrator 40.

[0058] The scheme effectively avoids the magnetic energy loss caused by the base material in the magnetic circuit by limiting the magnetic permeability parameter of the base substrate 1 material, maintains the consistency of the internal magnetic field strength of the driving vibrator 40 with the design value, thereby maintaining the stability of the internal magnetic field of the driving vibrator 40, ensuring that the super magnetostrictive rod 42 generates accurate magnetostrictive deformation under the predetermined prestress, and thereby improving the electroacoustic conversion efficiency and working bandwidth of the underwater acoustic transducer.

[0059] The above is only an exemplary embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made under the technical concept of the present application, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A composite base structure design method, applied to underwater acoustic transducers, characterized in that, The composite base structure design method includes: Obtain the length of the internal space of the shell in its natural state. l s The length of the driving oscillator l 0; Calculate the deformation of the shell along its major axis at the desired water depth. x sa ; Calculate the amount of deformation of the driven oscillator under the desired prestress. x r , ; Calculate the interference length m=x r +x sa ; Calculate the thickness of the base plate d =( l s +m- l 0) / 2; in, n r The number of supermagnetostrictive rods in each single-drive oscillator column. n pm The number of permanent magnets in each single-drive oscillator. n pm = n r +1; A r The cross-sectional area of ​​the permanent magnet and the supermagnetostrictive rod; k r For the stiffness of the supermagnetostrictive rod, k pm The stiffness of the permanent magnet; p This represents the desired prestress value.

2. The composite base structure design method as described in claim 1, characterized in that, The calculation involves the deformation of the hull along its long axis at the desired water depth. x sa include: Calculate the hydrostatic pressure on the outer surface of the shell at the desired water depth. p water , p water =ρ gh water Where ρ is the density of water, g It is the acceleration due to gravity. h water The desired work is in a deep water; The hydrostatic pressure was simulated on the outer surface of the shell using finite element simulation. p water Simulate applying internal gas pressure on the inner surface of the shell. p air The reaction force of prestress is simulated at the contact point between the oscillator and the base. p f ; Based on the simulation results, the deformation of the shell along the long axis at the desired water depth is obtained. x sa .

3. The composite base structure design method as described in claim 1, characterized in that, The composite base includes multiple magnetically conductive blocks, each of which is embedded in the base substrate; each magnetically conductive block includes multiple silicon steel sheets, which are stacked along the width direction of the composite base to form the magnetically conductive block; the number of magnetically conductive blocks in each composite base is q, where q = n / 2; and n is the number of columns of the driving oscillator, n is an even number and n ≥ 2; The thickness of each of the magnetic blocks d 1 and width w satisfy: ; in, N The number of coil turns. I This refers to the coil's operating current. l r For the length of the supermagnetostrictive rod, l pm The length of the permanent magnet; 0 is the permeability of free space. r The relative permeability of the supermagnetostrictive rod. pm is the relative permeability of the permanent magnet.

4. The composite base structure design method as described in claim 3, characterized in that, The length of each of the magnetic blocks l dc satisfy: ;in, d coil The outer diameter of the coil. d rod The diameter of the magnetostrictive rod is [value missing]. d c This refers to the spacing between the coils.

5. A composite base for use in underwater acoustic transducers, characterized in that, The composite base is designed using the composite base structure design method as described in any one of claims 1 to 4; The composite base includes a base base and a plurality of magnetic blocks, each of which is embedded in the base base.

6. A convex broadband underwater acoustic transducer, characterized in that, The convex broadband underwater acoustic transducer includes a housing and a driving unit, the driving unit including a coil, a driving vibrator and the composite base as described in claim 5; Each of the super magnetostrictive rods and each of the permanent magnets are coaxially and alternately bonded to form a driving oscillator. The coil is wound around the outer periphery of the driving oscillator, and both ends of the driving oscillator abut against the base base. The side of the base base away from the driving oscillator abuts against the inner peripheral wall of the housing.

7. The convex broadband underwater acoustic transducer as described in claim 6, characterized in that, The shell has an elliptical cross-section along its length; the shell has a protruding structure protruding outward at both ends along its minor axis.

8. The convex broadband underwater acoustic transducer as described in claim 6 or 7, characterized in that, The base is made of a non-magnetic metal material with a relative magnetic permeability of 1.

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