Underwater acoustic transducer and method for manufacturing backing sound absorbing component thereof

Abstract

An underwater acoustic transducer includes a shell and an impedance converter, a piezoelectric ceramic sheet, an acoustic impedance matching block, a backing sound absorbing assembly, a watertight adhesive layer, and a signal cable passing through the shell and connected to the piezoelectric ceramic sheet. One end of the shell has an opening, the impedance converter is arranged in the middle of the shell, and the acoustic impedance matching block is arranged at the opening of the shell. The piezoelectric ceramic sheet is arranged on the side of the acoustic impedance matching block facing the impedance converter. The backing sound absorbing assembly is arranged between the piezoelectric ceramic sheet and the impedance converter. The watertight adhesive layer is coated on the outside of the impedance converter. In this way, the high-frequency bandwidth is wider, which improves the performance of directional transmission or directional reception and reduces interference. The present invention also provides a method for manufacturing a backing sound absorbing assembly of an underwater acoustic transducer.

Description

Technical Field

[0001] The invention relates to the technical field of transducers, in particular to a method for manufacturing an underwater acoustic transducer and a backing sound-absorbing component thereof. Background Art

[0002] A hydroacoustic transducer is a device that converts sound energy into electrical energy. It is similar to an antenna in a radio device and is a key device for transmitting and receiving sound waves underwater. Underwater detection, identification, communication, as well as marine environmental monitoring and the development of marine resources are all inseparable from hydroacoustic transducers. The high-frequency bandwidth of existing hydroacoustic transducers is relatively narrow. Summary of the invention

[0003] In view of this, the present invention provides a method for manufacturing an underwater acoustic transducer with a wide high-frequency bandwidth and a backing sound-absorbing component thereof to solve the above-mentioned problem.

[0004] A device comprising a shell and an impedance converter, a piezoelectric ceramic sheet, an acoustic impedance matching block, a backing sound absorbing component, a watertight adhesive layer, and a signal cable passing through the shell and connected to the piezoelectric ceramic sheet; one end of the shell has an opening, the impedance converter is arranged in the middle of the shell, and the acoustic impedance matching block is arranged at the opening of the shell; the piezoelectric ceramic sheet is arranged on a side of the acoustic impedance matching block facing the impedance converter; the backing sound absorbing component is arranged between the piezoelectric ceramic sheet and the impedance converter; and the watertight adhesive layer is coated on the outside of the impedance converter.

[0005] Furthermore, the acoustic impedance matching block includes a first matching layer and a second matching layer. The piezoelectric ceramic sheet is fixed to the side of the first matching layer facing the impedance converter by adhesive, and the second matching layer is connected to the side of the first matching layer away from the impedance converter by adhesive. The acoustic impedance of the first matching layer is 10×10 6 Pa·S / m~19×10 6 Pa·S / m, thickness is 168% of the λ / 4 wavelength of the corresponding frequency; the acoustic impedance of the second matching layer is 2.8×10 6 Pa·S / m~5.2×10 6 Pa·S / m, thickness is 120% of the λ / 4 wavelength of the corresponding frequency.

[0006] Furthermore, the first matching layer is glass ceramic, and the second matching layer is polyvinylidene fluoride.

[0007] Furthermore, the backing sound absorbing component includes a damping layer, a sound wave absorbing layer and a sound wave attenuation layer in sequence from a side close to the impedance converter to a side close to the piezoelectric ceramic sheet.

[0008] Furthermore, the damping layer is a thermosetting resin added with a fat-soluble compound; the sound wave absorbing layer is a thermosetting resin added with a high-viscosity powder material; and the sound wave attenuation layer is a thermosetting resin added with a metal oxide or carbide.

[0009] Furthermore, the shell is in the shape of a hollow cylinder, the damping layer, the sound wave absorption layer, the sound wave attenuation layer, the piezoelectric ceramic sheet and the first matching layer are all in the shape of a cylinder, the diameter of the piezoelectric ceramic sheet is smaller than the diameter of the first matching layer, the diameter of the first matching layer is smaller than the diameter of the sound wave attenuation layer, and the sound wave attenuation layer is radially coated on the outside of the piezoelectric ceramic sheet and the first matching layer.

[0010] Furthermore, an external thread is provided on the circumferential outer side of the shell, and a fixing nut is threadedly connected to the external thread.

[0011] Furthermore, the watertight adhesive layer is at least partially located between the backing sound absorbing component and the impedance converter.

[0012] A method for manufacturing a backing sound-absorbing component of an underwater acoustic transducer comprises the following steps:

[0013] Step S1: weigh 50-70 wt% of the resin and heat it to increase fluidity;

[0014] Step S2: weighing 18-42 wt% of tungsten carbide, 2-4 wt% of dibutyl phthalate, and 6-8 wt% of nitrile rubber, and adding them to the resin in sequence, and stirring and mixing;

[0015] Step S3: placing the prepared mixture into a backing mold;

[0016] Step S4: performing high-speed centrifugal action on the backing mold and the mixture inside thereof.

[0017] A method for manufacturing a backing sound-absorbing component of an underwater acoustic transducer comprises the following steps:

[0018] Step S11: adding 18-42 wt % of tungsten carbide powder into a housing having an acoustic impedance matching block and a piezoelectric ceramic sheet installed therein;

[0019] Step S12: weighing 16-23wt% of resin and 0.7-1.3wt% of dibutyl phthalate, mixing them thoroughly and adding them into the shell again, and heating the entire shell until the resin has good fluidity, so that the resin penetrates into the gaps of the tungsten carbide powder;

[0020] Step S13: After the mixture of the resin and dibutyl phthalate is cured, 6 to 8 wt % of nitrile rubber is added into the housing;

[0021] Step S14: Weigh 34-47wt% of resin and 1.3-2.7wt% of dibutyl phthalate, mix them thoroughly and add them into the shell, and heat the entire shell until the resin has good fluidity so that the resin and the nitrile rubber are fully combined, and then the mixture of the resin and dibutyl phthalate is cured.

[0022] Compared with the prior art, the underwater acoustic transducer of the present invention includes a shell and an impedance converter, a piezoelectric ceramic sheet, an acoustic impedance matching block, a backing sound absorbing assembly, a watertight adhesive layer, and a signal cable passing through the shell and connected to the piezoelectric ceramic sheet; one end of the shell has an opening, the impedance converter is arranged in the middle of the shell, and the acoustic impedance matching block is arranged at the opening of the shell; the piezoelectric ceramic sheet is arranged on the side of the acoustic impedance matching block facing the impedance converter; the backing sound absorbing assembly is arranged between the piezoelectric ceramic sheet and the impedance converter 20; and the watertight adhesive layer is coated on the outside of the impedance converter. In this way, the high-frequency bandwidth is wider, and the performance of directional transmission or directional reception is improved, and interference is reduced. The present invention also provides a method for manufacturing a backing sound absorbing assembly of an underwater acoustic transducer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The embodiments of the present invention are described below in conjunction with the accompanying drawings, wherein:

[0024] Figure 1 This is a cross-sectional schematic diagram of the underwater acoustic transducer provided by the present invention.

[0025] Figure 2 for Figure 1 A local enlarged schematic diagram of the .

[0026] Figure 3 This is a curve diagram showing the relationship between acoustic impedance and acoustic transmission coefficient.

[0027] Figure 4 A schematic diagram of the half-power bandwidth of the underwater acoustic transducer provided by the present invention. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention are further described in detail below based on the accompanying drawings. It should be understood that the description of the embodiments of the present invention herein is not intended to limit the protection scope of the present invention.

[0029] Please refer to Figure 1 The underwater acoustic transducer provided by the present invention includes a shell 10 and an impedance converter 20, a piezoelectric ceramic sheet 30, an acoustic impedance matching block 40, a backing sound absorbing component 50, a watertight adhesive layer 60, a signal cable 70 passing through the shell 10 and connected to the piezoelectric ceramic sheet 30, and a fixing nut 80 sleeved on the shell 10.

[0030] The outside of the acoustic impedance matching block 40 away from the impedance converter 20 is the target medium.

[0031] The housing 10 is in the shape of a hollow cylinder, and an opening is provided at the bottom.

[0032] The impedance converter 20 is disposed in the middle of the housing 10 , and the acoustic impedance matching block 40 is disposed at an opening at one end of the housing 10 .

[0033] The piezoelectric ceramic sheet 30 is disposed on a side of the acoustic impedance matching block 40 facing the impedance converter 20 .

[0034] The backing sound absorbing component 50 is disposed between the piezoelectric ceramic sheet 30 and the impedance transformer 20 .

[0035] The watertight adhesive layer 60 is coated on the outside of the impedance transformer 20, and is filled between the impedance transformer 20 and the housing 10, and between the impedance transformer 20 and the backing sound absorbing component 50. Specifically, the watertight adhesive layer 60 is filled between the impedance transformer 20 and the housing 10 in the radial direction, and is filled between the impedance transformer 20 and the backing sound absorbing component 50 at the bottom position.

[0036] An external thread 11 is provided on the circumferential outer side of the shell 10 , and at least one fixing nut 80 is threadedly connected to the external thread 11 . The fixing nut 80 is used to connect to an external object such as a ship hull or a buoy.

[0037] Please refer to Figure 2 The acoustic impedance matching block 40 includes a first matching layer 41 and a second matching layer 42. The piezoelectric ceramic sheet 30 is fixed to the side of the first matching layer 41 facing the impedance converter 20 by adhesive, and the second matching layer 42 is connected to the side of the first matching layer 41 away from the impedance converter 20 by adhesive.

[0038] In this embodiment, the first matching layer 41 is made of glass ceramics, and the acoustic impedance is 10×10 6 Pa·S / m~19×10 6 Pa·S / m, and the thickness is 168% of the wavelength of λ / 4 of the frequency of the underwater acoustic transducer; the second matching layer 42 is polyvinylidene fluoride (PVDF), and the acoustic impedance is 2.8×10 6 Pa·S / m~5.2×10 6 Pa·S / m, thickness is 120% of the λ / 4 wavelength of the frequency of the hydroacoustic transducer.

[0039] The first matching layer 41 and the second matching layer 42 of the acoustic impedance matching block 40 adopt a multi-layer composite impedance matching method with asymmetric thickness. The acoustic impedance matching block 40 uses two different acoustic impedance ratio materials for matching. According to the ideal acoustic impedance ratio expression (Z1 and Z2 are the ideal acoustic impedance ratios of different matching layers, Z0 and Z LThe ideal impedance of the corresponding acoustic impedance matching layer can be calculated by using the acoustic impedance of the piezoelectric ceramic sheet 30 and the target radiation medium. Obviously, in this structure, we can calculate that the ideal impedance of the two layers is 14.14×106Pa·s / m and 3.14×106Pa·s / m respectively.

[0040] However, in reality, it is impossible to obtain a material that is completely consistent with the calculated value, or the actual acoustic impedance matching layer should be a range of values. Based on this point of view, without considering sound absorption, we use the expression of the double-layer plate transmittance: (Z f , Z m , Z b are the acoustic impedances of the source medium, transition medium and target medium, respectively, and K m is the frequency constant of the transition medium, l is the plate thickness), when K m Under certain conditions, this expression can be used to draw the following Figure 3 The acoustic transmittance under different acoustic impedance ratios is shown in the figure. In the figure, the Y axis R represents the transmittance, and the X axis Z represents the acoustic impedance ratio. R1 and R2 represent the transmittance of the first matching layer 41 adjacent to the piezoelectric ceramic sheet 30 and the acoustic transmittance of the second matching layer 42 adjacent to the target medium. We can find that the acoustic impedance ratios are 10×10 6 Pa·S / m~19×10 6 Pa·S / m and 2.8×10 6 Pa·S / m~5.2×10 6 The acoustic transmittance greater than 0.9 can be obtained in the range of Pa·S / m.

[0041] According to the above calculation conclusions, we have a wide range of matching layer material selection. Considering the processing performance of the matching layer material, aluminum, duralumin, aluminum-magnesium alloy, quartz glass, glass ceramics and other materials with acoustic impedance ratios between 10×10 6 Pa·S / m~19×10 6 Materials within the Pa·S / m range are used as the materials of the first matching layer 41 adjacent to the piezoelectric ceramic sheet 30 in the underwater acoustic transducer. In particular, glass ceramics have better processing performance than quartz glass, and compared with metals, have a lower linear expansion coefficient and are more suitable for use as matching layer materials.

[0042] The acoustic impedance of various polymer materials, including epoxy resin, phenolic resin, acrylic resin, and a large number of thermoplastic materials and composite materials based on the above materials, is between 2.8×10 6 Pa·S / m~5.2×10 6All materials within the Pa·S / m range can be used as the material of the second matching layer 42 in contact with the target medium. However, when actually selecting, attention should be paid to the bonding strength caused by the low surface energy material and the weather resistance and medium resistance of the material. In the present invention, polyvinylidene fluoride (PVDF) is more recommended as the material of the matching layer, which is a low surface energy material, but its bonding ability can be improved by some physical and chemical methods.

[0043] According to the calculation formula of the thickness of the acoustic impedance matching layer The theoretical calculated value of the thickness of each corresponding acoustic impedance matching layer can be obtained, but we have found through practice that the calculated value often has some deviations from the optimal actual application thickness, and it is necessary to comprehensively consider comprehensive factors such as the matching layer's bandwidth, frequency, and echo signal strength for the underwater acoustic transducer. The present invention specifically summarizes this structure and finds that when the thickness of the first matching layer 41 is increased by 68% compared to the theoretical calculated value, and the thickness of the second matching layer 42 is increased by 20% compared to the theoretical calculated value, the center frequency of the underwater acoustic transducer can be made closer to the anti-resonance frequency point of the thickness vibration mode of the piezoelectric ceramic sheet 30, thereby enabling the underwater acoustic transducer to obtain higher working efficiency and sensitivity.

[0044] The backing sound absorbing assembly 50 can enable the underwater acoustic transducer to obtain better impulse response performance and passband bandwidth.

[0045] The bandwidth of the underwater acoustic transducer is proportional to the acoustic impedance of the backing sound absorbing component 50 and inversely proportional to the Q value of the underwater acoustic transducer. When the acoustic impedance of the backing sound absorbing component 50 is 3×10 6 Pa·s / m, the half-power bandwidth (3dB) of the underwater acoustic transducer is only 9% of the entire passband, but when the acoustic impedance of the backing sound absorbing component 50 is increased to 33.7×10 6 When the impedance is 400 Pa·s / m, the half-power bandwidth can reach 80%, and the Q value is also reduced to 10% of the backing sound absorbing component 50. However, the high impedance backing sound absorbing component 50 will introduce the problem of low transmission efficiency, resulting in it being unsuitable for a dual-purpose underwater acoustic transducer. Therefore, 4-7×10 6 The backing sound absorbing assembly 50 with a medium impedance of Pa·s / m is more suitable for a dual-purpose hydroacoustic transducer.

[0046] In this embodiment, the backing sound absorbing component 50 includes a damping layer 51, a sound wave absorbing layer 52 and a sound wave attenuation layer 53 in sequence from the side close to the impedance transformer 20 to the side close to the piezoelectric ceramic sheet 30, wherein the sound wave attenuation layer 53 is radially coated on the outside of the piezoelectric ceramic sheet 30 and the first matching layer 41.

[0047] The damping layer 51 is based on a thermosetting resin, with a small amount of fat-soluble compounds added, especially phthalates, such as di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP) and diethyl phthalate (DEP). It is recommended to use dibutyl phthalate (DBP) and mix it evenly with the thermosetting resin.

[0048] The sound wave absorbing layer 52 is based on a thermosetting resin, and a certain amount of high viscosity powder material is added as a modified additive, especially a rubber material vulcanized at high temperature, and then ground and crushed to form solid powder. It is recommended to use nitrile rubber powder as the modified additive of this layer. The prepared mixture needs to be stirred and mixed effectively so that the rubber particles can be evenly distributed in the base material, or the sound wave absorbing layer 52 is formed by high-speed centrifugal sedimentation.

[0049] The sound wave attenuation layer 53 is based on a thermosetting resin, and a certain amount of spherical oxides, flaky oxides, carbides, etc., such as metal oxides or non-metal oxides, are added. Lead oxide (Pb3O4), aluminum oxide (Al2O3), tungsten oxide (WO3), tungsten carbide (WC) and other materials can be used. It is recommended to use spherical tungsten carbide (WC) with a higher stacking density as a modified additive for this layer, and form a dense sound wave attenuation layer 53 by free gravity sedimentation or high-speed centrifugal sedimentation.

[0050] The present invention also provides a method for manufacturing the above-mentioned backing sound-absorbing assembly, comprising the following steps:

[0051] Step S1: weigh 50-70 wt% of the resin and heat it to increase fluidity;

[0052] Step S2: weighing 18-42 wt% of tungsten carbide, 2-4 wt% of dibutyl phthalate, and 6-8 wt% of nitrile rubber, and adding them to the resin in sequence, and stirring and mixing;

[0053] Step S3: placing the prepared mixture into a backing mold;

[0054] Step S4: performing high-speed centrifugal action on the backing mold and the mixture inside the backing mold, so that the mixture inside the backing mold forms a composite material backing with increasing density from top to bottom.

[0055] In another embodiment, the backing sound absorbing assembly 50 can also be prepared by the following steps:

[0056] Step S11: adding 18-42 wt % of tungsten carbide powder into the housing on which the acoustic impedance matching block 40 and the piezoelectric ceramic sheet 30 are installed;

[0057] Step S12: weighing 16-23wt% of resin and 0.7-1.3wt% of dibutyl phthalate, mixing them thoroughly and adding them into the shell again, and heating the entire shell until the resin has good fluidity, so that the resin penetrates into the gaps of the tungsten carbide powder;

[0058] Step S13: After the mixture of the resin and dibutyl phthalate is cured, 6 to 8 wt % of nitrile rubber is added into the housing;

[0059] Step S14: 34-47 wt% of resin and 1.3-2.7 wt% of dibutyl phthalate are weighed, mixed thoroughly and added into the shell, and the entire shell is heated until the resin has good fluidity so that the resin and the nitrile rubber are fully combined. After the mixture of the resin and dibutyl phthalate is cured, the backing sound absorbing component 50 is finally formed.

[0060] Please refer to Figure 4 The half-power bandwidth of the underwater acoustic transducer provided by the present invention reaches 1000KHz, and the Q value is only 3. The Y-axis dB value in the figure is the signal gain strength of the transducer tested by the reflection method, and the half-power bandwidth refers to the peak gain obtained by the transmission method test (about -5dB in the figure) dropped by 3dB (Y = -2dB) and the corresponding peak width of the graph is 1000KHz (3.5MHz-2.5MHz = 1.0MHz). Since the Q value is the value measured by the instrument, Figure 4 Not reflected in.

[0061] It can be seen from the above test data that in the HF band (HF band is defined as 3MHz~30MHz, 3MHz is selected as the design sample in the example), using the above design method, piezoelectric ceramic materials can also obtain lower Q value and wider half-power bandwidth (the lower the Q value, the flatter the phase, the larger the half-power bandwidth, and the easier it is to obtain broadband communication capabilities), without the need to use other materials (such as polarized PVDF) as receiving transducers to obtain higher passbands as designed by others. In particular, the piezoelectric coefficient D33 of PVDF is very weak, and the obtained signal strength is low. A circuit with a high amplification coefficient is required for amplification processing, and it is easy to introduce noise interference, which increases the difficulty of circuit design. The D33 of piezoelectric ceramic materials is large, the signal strength is high, and the structure is consistent with the circuit characteristic impedance through internal impedance transformation, and the transmission signal loss is small.

[0062] Compared with the prior art, the underwater acoustic transducer of the present invention includes a shell 10 and an impedance converter 20, a piezoelectric ceramic sheet 30, an acoustic impedance matching block 40, a backing sound absorbing component 50, a watertight adhesive layer 60, and a signal cable 70 passing through the shell 10 and connected to the piezoelectric ceramic sheet 30; one end of the shell 10 has an opening, the impedance converter 20 is arranged in the middle of the shell 10, and the acoustic impedance matching block 40 is arranged at the opening of the shell 10; the piezoelectric ceramic sheet 30 is arranged on the side of the acoustic impedance matching block 40 facing the impedance converter 20; the backing sound absorbing component 50 is arranged between the piezoelectric ceramic sheet 30 and the impedance converter 20; and the watertight adhesive layer 60 is coated on the outside of the impedance converter 20. In this way, the high-frequency bandwidth is wider. In addition, the directional performance of the existing underwater acoustic transducer is weak, and it is easily interfered by the sound signal transmitted from the non-specified direction. The present invention has strong directional transmission or directional reception capabilities and strong anti-interference capabilities.

[0063] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modification, equivalent substitution or improvement within the spirit of the present invention is included in the scope of the claims of the present invention.

Claims

1. An underwater acoustic transducer, characterized in that: The invention comprises a shell and an impedance converter, a piezoelectric ceramic sheet, an acoustic impedance matching block, a backing sound-absorbing component, a watertight adhesive layer, and a signal cable passing through the shell and connected to the piezoelectric ceramic sheet; one end of the shell has an opening, the impedance converter is arranged in the middle of the shell, and the acoustic impedance matching block is arranged at the opening of the shell; the piezoelectric ceramic sheet is arranged on the side of the acoustic impedance matching block facing the impedance converter; the backing sound-absorbing component is arranged between the piezoelectric ceramic sheet and the impedance converter; the watertight adhesive layer is coated on the outside of the impedance converter; the acoustic impedance matching block comprises a first matching layer and a second matching layer, the piezoelectric ceramic sheet is fixed to the side of the first matching layer facing the impedance converter by adhesive, and the second matching layer is connected to the side of the first matching layer away from the impedance converter by adhesive; the acoustic impedance ratio of the first matching layer is 10×10 6 Pa·S / m~19×10 6 Pa·S / m, thickness is 168% of the λ / 4 wavelength of the corresponding frequency; the acoustic impedance of the second matching layer is 2.8×10 6 Pa·S / m~5.2×10 6 Pa·S / m, and a thickness of 120% of the wavelength of λ / 4 of the corresponding frequency; the backing sound-absorbing component includes a damping layer, a sound wave absorbing layer and a sound wave attenuation layer in sequence from the side close to the impedance transformer to the side close to the piezoelectric ceramic sheet; the damping layer is a thermosetting resin added with a fat-soluble compound; the sound wave absorbing layer is a thermosetting resin added with a high-viscosity powder material; The sound wave attenuation layer is a thermosetting resin added with metal oxides or carbides; the shell is in the shape of a hollow cylinder, the damping layer, the sound wave absorption layer, the sound wave attenuation layer, the piezoelectric ceramic sheet and the first matching layer are all in the shape of cylinders, the diameter of the piezoelectric ceramic sheet is smaller than the diameter of the first matching layer, the diameter of the first matching layer is smaller than the diameter of the sound wave attenuation layer, and the sound wave attenuation layer is radially coated on the outside of the piezoelectric ceramic sheet and the first matching layer.

2. The underwater acoustic transducer according to claim 1, characterized in that: The first matching layer is glass ceramic, and the second matching layer is polyvinylidene fluoride.

3. The underwater acoustic transducer according to claim 1, characterized in that: The outer circumferential side of the shell is provided with an external thread, and the external thread is threadedly connected with a fixing nut.

4. The underwater acoustic transducer according to claim 1, characterized in that: The watertight adhesive layer is at least partially located between the backing sound absorbing component and the impedance transformer.

5. A method for manufacturing a backing sound-absorbing component of an underwater acoustic transducer, wherein the backing sound-absorbing component is the backing sound-absorbing component of any one of claims 1 to 4, characterized in that: The following steps are involved: Step S1: weigh 50-70 wt% of the resin and heat it to increase fluidity; Step S2: weighing 18-42 wt% of tungsten carbide, 2-4 wt% of dibutyl phthalate, and 6-8 wt% of nitrile rubber, and adding them to the resin in sequence, stirring and mixing to obtain a mixture; Step S3: placing the prepared mixture in step S2 into a backing mold; Step S4: performing high-speed centrifugal action on the backing mold and the mixture inside thereof.

6. A method for manufacturing a backing sound-absorbing component of an underwater acoustic transducer, wherein the backing sound-absorbing component is the backing sound-absorbing component of any one of claims 1 to 4, characterized in that: The following steps are involved: Step S11: adding 18-42 wt% of tungsten carbide powder into a housing having an acoustic impedance matching block and a piezoelectric ceramic sheet installed therein; Step S12: weigh 16-23 wt% of resin and 0.7-1.3 wt% of dibutyl phthalate, mix them thoroughly and add them into the shell again, and heat the entire shell until the resin has fluidity, so that the resin penetrates into the gaps of the tungsten carbide powder; Step S13: After the mixture of the resin and dibutyl phthalate is cured, 6-8 wt% of nitrile rubber is added into the housing; Step S14: Weigh 34-47 wt% of resin and 1.3-2.7 wt% of dibutyl phthalate, mix them thoroughly and add them into the shell, and heat the entire shell until the resin has fluidity, so that the resin and nitrile rubber are fully combined, and then the mixture of resin and dibutyl phthalate is cured.

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