Low frequency narrow pulse point contact ultrasonic transducer

Abstract

The application discloses a low-frequency narrow pulse point contact ultrasonic transducer, which comprises an upper shell and a lower shell, a first inner cavity is arranged in the upper shell, a second inner cavity is arranged in the lower shell, the first inner cavity and the second inner cavity are communicated, a limiting step is formed at the joint of the upper shell and the lower shell, a flange is arranged on the limiting step, a piezoelectric ceramic crystal arranged in the first inner cavity extends into the second inner cavity through a central through hole of the flange, positive and negative electrodes of the piezoelectric ceramic crystal are respectively welded with positive and negative electrode wires, the positive and negative electrode wires are connected with a BNC cable connector arranged on a top plate of the upper shell, a backing material layer in a spiral winding structure is arranged on a side wall of the piezoelectric ceramic crystal, a mounting hole is formed in a bottom plate of the lower shell, a piezoelectric ceramic matching layer is arranged in the mounting hole, and the piezoelectric ceramic matching layer extends into the piezoelectric ceramic crystal. The device has the characteristics of low frequency, large amplitude, high sensitivity and point contact.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ultrasonic transducers, and particularly relates to a low-frequency narrow-pulse point-contact ultrasonic transducer. BACKGROUND

[0002] Ultrasonic transducers are mainly divided into high-frequency detection ultrasonic transducers and power ultrasonic transducers, wherein the frequency of the high-frequency detection transducer is generally above the megahertz (MHz) level, and the high-frequency detection transducer has the advantages of narrow pulse and small size, but has low radiation energy and short propagation distance, and is mainly applied to metal nondestructive testing and medical detection; in recent years, point-contact narrow-pulse piezoelectric transducers in the high-frequency range (above the megahertz level) have been applied maturely, but due to the small radiation energy of the transducers and the fast attenuation of high-frequency signals, the transducers cannot be applied to nondestructive testing of nonmetallic materials, detection of road bridges, and high-precision seismic physical simulation experiments in the fields of petroleum and coal.

[0003] To realize high-precision nondestructive testing of large-size nonmetallic materials, high-precision detection of road bridges, and high-precision seismic physical simulation experiments in the fields of petroleum and coal, a low-frequency narrow-pulse point-contact ultrasonic transducer needs to be developed, but the low-frequency (tens of kilohertz) transducers in the prior art have the following defects: the radiation energy of the transducer is inversely proportional to the size of the transducer, and the larger the radiation energy, the larger the size of the ultrasonic transducer; the frequency of the transducer is inversely proportional to the size of the transducer, and the lower the frequency, the larger the size; low frequency and narrow pulse are mutually restrictive; the lower the frequency, the greater the radiation energy, the more the pulse tail waves, and the narrower the frequency band, and improvement is urgently needed. SUMMARY

[0004] To solve the above problems in the prior art, the application provides a low-frequency narrow-pulse point-contact ultrasonic transducer to improve the nondestructive testing precision of large-size nonmetallic materials, the detection precision of road bridges, and the seismic physical simulation experiment detection precision in the fields of coal and petroleum.

[0005] To solve the above technical problems, the application adopts the following technical solutions:

[0006] A low-frequency narrow-pulse point-contact ultrasonic transducer comprises an upper shell and a lower shell which are integrally and communicatively arranged, a first inner cavity is arranged in the upper shell, a second inner cavity is arranged in the lower shell, the first inner cavity and the second inner cavity are communicated, a limiting step is formed at the connection position of the upper shell and the lower shell, a flange is arranged on the limiting step, and a piezoelectric ceramic crystal arranged in the first inner cavity extends into the second inner cavity through the center through hole of the flange;

[0007] Positive and negative electrodes of the piezoelectric ceramic crystal are respectively welded with positive and negative electrode leads, the positive and negative electrode leads are respectively led out through the wire outlet holes arranged on the top plate of the upper shell, and are connected with a BNC cable connector arranged on the top plate of the upper shell;

[0008] The piezoelectric ceramic crystal side wall is provided with a backing material layer in a spiral winding structure.

[0009] The lower shell bottom plate is provided with a mounting hole, and a piezoelectric ceramic matching layer is arranged in the mounting hole and penetrates into the piezoelectric ceramic crystal.

[0010] The application also has the following technical features:

[0011] Specifically, the pulse range of the low-frequency narrow pulse point contact ultrasonic transducer is 20-100 kHz.

[0012] Further, the upper shell and the lower shell are both cylindrical, and the diameter of the upper shell is greater than that of the lower shell.

[0013] Further, the backing material layer is made of epoxy resin and silicone rubber with a mass ratio of 1:2.

[0014] Further, the backing material layer is composed of a backing material strip spirally wound on the side wall of the piezoelectric ceramic crystal, and the width of the backing material strip is 1-2 cm and the thickness is 1-2 mm.

[0015] Further, the flange is arranged at the piezoelectric ceramic crystal resonance displacement node x0=0.

[0016] Further, the welding of the positive and negative electrode leads is at the piezoelectric ceramic crystal resonance displacement node x0=0.

[0017] Further, the piezoelectric ceramic matching layer is in a cylindrical structure, and the piezoelectric ceramic crystal is in a cuboid structure.

[0018] Compared with the prior art, the application has the following advantages:

[0019] (1) The device can be used for point contact detection, and the bandwidth of the transducer is improved, and the residual vibration is reduced by arranging the backing material layer on the outer surface of the piezoelectric ceramic crystal and the filling material between the backing material layer and the shell. The device has the characteristics of strong radiation energy, low frequency, large amplitude, high sensitivity and point contact, and can meet the requirements of non-destructive testing precision of large-size non-metallic materials, internal detection precision of roads and bridges, and seismic physical simulation experiment detection precision improvement in coal and petroleum fields.

[0020] (2) The device has simple structure and is easy to use, and has strong popularization value.

[0021] Other features and advantages of the application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a schematic diagram of the overall structure of the device of the present application;

[0023] Figure 2 is a time-domain waveform diagram of the 40 kHz ultrasonic transducer of Example 1;

[0024] Figure 3 is a frequency-domain waveform diagram of the 40 kHz ultrasonic transducer of Example 1.

[0025] The various reference signs in the drawings represent:

[0026] 1 - upper housing, 2 - lower housing, 3 - limiting step, 4 - flange, 5 - piezoelectric ceramic crystal, 6 - positive and negative electrode wires, 7 - BNC cable connector, 8 - backing material layer, 9 - piezoelectric ceramic matching layer.

[0027] The specific content of the present application is further explained in detail below in conjunction with the drawings and specific embodiments. DETAILED DESCRIPTION

[0028] The following gives specific embodiments of the present application, it should be noted that the present application is not limited to the following specific embodiments, any equivalent transformation made on the basis of the technical solutions of the present application falls within the protection scope of the present application.

[0029] In the present application, the orientation words such as "upper, lower, bottom, top" used without the opposite indication are generally defined with the drawing surface of the corresponding drawing as the reference, and "inner, outer" are defined with the outline of the corresponding drawing as the reference.

[0030] Example 1

[0031] Following the above technical solution, as shown in Figure 1 the present embodiment discloses a low-frequency narrow-pulse point-contact ultrasonic transducer, which comprises an upper housing 1 and a lower housing 2 arranged in an integrated and communicating manner, a first inner cavity is arranged in the upper housing 1, a second inner cavity is arranged in the lower housing 2, the first inner cavity and the second inner cavity are in communication, a limiting step 3 is formed at the connection of the upper housing 1 and the lower housing 2, a flange 4 is arranged on the limiting step 3, and a piezoelectric ceramic crystal 5 arranged in the first inner cavity extends into the second inner cavity through the center through hole of the flange 4.

[0032] The piezoelectric ceramic crystal 5 is in the shape of a cuboid, the material thereof is a transceiving type piezoelectric ceramic, and the cuboid structure is adopted in order to fully utilize the length extension and contraction vibration mode of the crystal, on the one hand to reduce the frequency, and on the other hand the sound waves in different phases when the long strip-shaped crystal extends and contracts in the length direction, and the residual vibrations cancel each other out, so as to achieve the effect of increasing the bandwidth; the flange 4 is made of a high polymer insulating material; and the backing material layer 8 is made of a high polymer insulating material.

[0033] As a preferred scheme of the embodiment, positive and negative electrodes of the piezoelectric ceramic crystal 5 are respectively welded with positive and negative electrode wires 6, the positive and negative electrode wires 6 are led out through wire holes in the top plate of the upper shell 1 and connected with BNC cable connectors 7 arranged on the top plate of the upper shell 1.

[0034] The piezoelectric ceramic crystal 5 is provided with a backing material layer 8 in a spiral winding structure on the side wall.

[0035] The bottom plate of the lower shell 2 is provided with a mounting hole, and the piezoelectric ceramic matching layer 9 is arranged in the mounting hole.

[0036] In the embodiment, the piezoelectric ceramic matching layer 9 is made of wear-resistant zirconium oxide material, and the piezoelectric ceramic matching layer 9 is inserted into the piezoelectric ceramic crystal 5. After the piezoelectric ceramic matching layer 9 is inserted into the piezoelectric ceramic crystal 5, a stepped structure is formed, the magnification of the stepped structure is large, which can meet the requirements of small size and large amplitude, and finally the conversion efficiency of the transducer can be improved, and the insertion part is fixed and air-dried with silicone. The lower end of the piezoelectric ceramic matching layer 9 can realize point contact detection.

[0037] As a preferred scheme of the embodiment, the pulse range of the low-frequency narrow pulse point contact ultrasonic transducer is 20-100 kHz.

[0038] As a preferred scheme of the embodiment, the upper shell 1 and the lower shell 2 are both cylindrical, and the diameter of the upper shell 1 is greater than the diameter of the lower shell 2.

[0039] As a preferred scheme of the embodiment, the backing material layer is made of epoxy resin and silicone rubber with a mass ratio of 1:2, the backing material layer 8 is composed of a backing material strip spirally wound on the side wall of the piezoelectric ceramic crystal 5, the width of the backing material strip is 1-2 cm, and the thickness is 1-2 mm, and the backing material layer is used to absorb the residual vibration transmitted radially backward and around.

[0040] As a preferred scheme of the embodiment, the gap between the backing material layer 8 and the inner wall of the upper shell 1 is filled with a filling material, the filling material is made by mixing aluminum oxide particles and silicone rubber, and the mass ratio of the aluminum oxide particles to the silicone rubber is 1:1.2-1.5.

[0041] The purpose of filling the filling material is to further absorb the residual vibration transmitted radially backward and around, and to reinforce the piezoelectric ceramic crystal 5.

[0042] Compared with absorbing and inhibiting the residual vibration by heating and dissipating the sound waves conducted backward through the mutual friction inside the damping material, the advantage of directly winding the backing material layer 8 on the piezoelectric ceramic crystal 5 is that the setting time of the backing material layer 8 is short, the thickness of the backing material layer is controllable and can effectively absorb and inhibit the residual vibration, and the backing material layer cannot be changed once it is set and can only be scrapped.

[0043] As a preferred scheme of the embodiment, the flange 4 is arranged at the resonance displacement node x0=0 of the piezoelectric ceramic crystal 5 and the piezoelectric ceramic matching layer 8, and the resonance displacement node is at a position of λ / 4 by calculating the wavelength λ of the piezoelectric ceramic crystal.

[0044] Under the fundamental frequency vibration, the amplitude at the resonance displacement node x0=0 of the piezoelectric ceramic crystal 5 is equal to zero, and the amplitude of the end point farthest from the resonance displacement node is the largest. In order to avoid other spurs of the piezoelectric ceramic crystal 5, the flange 4 must be fixed at the position.

[0045] As a preferred scheme of the embodiment, the welding of the positive and negative electrode wires 6 is at the resonance displacement node x0=0 of the piezoelectric ceramic crystal 5, because the vibration is the weakest at the resonance displacement node x0=0. By arranging the welding point at the position, other spurs caused by the vibration of the wire can be avoided.

[0046] As a preferred scheme of the embodiment, the piezoelectric ceramic matching layer 8 is in a cylindrical structure, and the piezoelectric ceramic crystal 5 is in a cuboid structure.

[0047] The assembly process of the device is as follows:

[0048] (1) Prepare the piezoelectric ceramic crystal;

[0049] (2) Prepare the piezoelectric ceramic matching layer made of zirconium oxide, use an ultrasonic hole puncher to punch a mounting hole with a depth of 5-7 mm on the end face of the piezoelectric ceramic crystal, and the mounting hole is perpendicular to and centered on the end face of the piezoelectric ceramic crystal;

[0050] (3) Insert the piezoelectric ceramic matching layer into the mounting hole, and then use AB glue to bond the gap;

[0051] (4) Weld the wire, and then install the flange;

[0052] (5) Wrap the backing material strip on the side wall of the piezoelectric ceramic crystal;

[0053] (6) Put the piezoelectric ceramic crystal into the shell, and then fill the filling material.

[0054] (7) Connect the positive and negative electrode wires to the BNC cable connector, and complete the packaging.

[0055] After the assembly is completed, when detecting, the ultrasonic transducer and the receiving transducer provided by the embodiment are respectively placed on one side of the object to be detected to form a transmission observation system. The ultrasonic transducer converts the electric pulse signal into an ultrasonic vibration signal on one side, the receiving transducer converts the vibration signal into an electric signal after receiving the vibration signal on the other side, and then the collected signal is stored and analyzed and interpreted.

[0056] The 40 kHz ultrasonic transducer provided by the embodiment is used to detect in a manner that the transducer directly interfaces with the transducer without other measured objects in between, and time-domain waveform diagrams as shown in Figure 2 and frequency-domain waveform diagrams as shown in Figure 3 are obtained. Figure 2 It can be seen that the ultrasonic transducer provided by the embodiment excites a narrow pulse waveform, almost without residual vibration, and has large radiation energy. Figure 3 It can be seen that the main frequency of the transducer is about 40 kHz, and low frequency is achieved.

[0057] Comparative Example 1

[0058] In the present comparative example, an existing ultrasonic transducer is used, which is structured by sequentially bonding a matching layer, a piezoelectric ceramic sheet and a backing material layer from front to back. The piezoelectric crystal adopts a conventional piezoelectric ceramic sheet, and the backing material layer adopts tungsten powder + high plasticity metal powder mixed material / thermoplastic plastic powder or resin material, which is bonded on the piezoelectric ceramic crystal after high pressure or hot pressing.

[0059] After detection, the resonance frequency of the ultrasonic transducer provided by the present comparative example is 460 kHz-470 kHz, which cannot achieve the low frequency index of the embodiment 1; the backing material layer can only be pasted on the back of the piezoelectric ceramic sheet, and cannot absorb the radial vibration of the clutter; and point contact cannot be achieved.

[0060] During detection, the transducer is too large in diameter and can only be placed on a thin plate to form a reflection observation system, and cannot achieve a transmission observation system collection.

[0061] In summary, the device of the present application can perform point contact detection, and the bandwidth of the transducer is improved and the residual vibration is reduced by setting the backing material layer on the outer surface of the piezoelectric ceramic crystal and the filling material between the backing material layer and the shell. The device of the present application has the characteristics of strong radiation energy, low frequency, large amplitude, high sensitivity and point contact, and can meet the requirements of improving the precision of non-destructive testing of large-size non-metallic materials, the precision of internal detection of roads and bridges, and the precision of seismic physical simulation experiments in the field of coal and petroleum.

[0062] In the above description, unless otherwise explicitly specified and limited, the terms such as "setting", "connecting" and the like should be understood in a broad sense, for example, can be fixedly connected, or detachably connected or integrated; can be directly connected, or indirectly connected, and the like. For those skilled in the art, the specific meanings of the above terms in the technical solution can be understood according to the specific circumstances.

[0063] In the above specific embodiments, each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, as long as it does not deviate from the idea of the present application, and should also be regarded as disclosed by the present application.

Claims

1. A low-frequency narrow-pulse point-contact ultrasonic transducer comprising an upper shell (1) and a lower shell (2) arranged in integrated communication, a first inner cavity is arranged in the upper shell (1), a second inner cavity is arranged in the lower shell (2), the first inner cavity and the second inner cavity are in communication, characterized in that, The connecting part of the upper shell (1) and the lower shell (2) forms a limiting step (3), a flange (4) is arranged on the limiting step (3), and a piezoelectric ceramic crystal (5) arranged in a first inner cavity extends into a second inner cavity through a central through hole of the flange (4). Positive and negative electrodes of the piezoelectric ceramic crystal (5) are respectively welded with positive and negative electrode wires (6), the positive and negative electrode wires (6) are connected with a BNC cable connector (7) arranged on the top plate of the upper shell (1) after being pulled out through a wire outlet hole arranged on the top plate of the upper shell (1). A backing material layer (8) in a spiral winding structure is arranged on the side wall of the piezoelectric ceramic crystal (5). An installation hole is arranged on the bottom plate of the lower shell (2), and a piezoelectric ceramic matching layer (9) is arranged in the installation hole and extends into the piezoelectric ceramic crystal (5).

2. The low-frequency narrow-pulse point-contact ultrasonic transducer of claim 1, wherein, The pulse range of the low-frequency narrow pulse point contact ultrasonic transducer is 20-100 kHz.

3. The low-frequency narrow-pulse point-contact ultrasonic transducer of claim 1, wherein, The upper shell (1) and the lower shell (2) are both cylindrical, and the diameter of the upper shell (1) is greater than the diameter of the lower shell (2).

4. The low-frequency narrow-pulse point-contact ultrasonic transducer of claim 1, wherein, The backing material layer (8) is made of epoxy resin and silicone rubber with a mass ratio of 1:

2.

5. The low-frequency narrow-pulse point-contact ultrasonic transducer of claim 1, wherein, The backing material layer (8) is composed of a backing material strip spirally wound on the side wall of the piezoelectric ceramic crystal (5), and the width of the backing material strip is 1-2 cm and the thickness is 1-2 mm.

6. The low-frequency narrow-pulse point-contact ultrasonic transducer of claim 1, wherein, The gap between the backing material layer (8) and the inner wall of the upper shell (1) is filled with a filling material, and the filling material is made of aluminum oxide particles and silicone rubber with a mass ratio of 1:(1.2-1.5).

7. The low-frequency narrow-pulse point-contact ultrasonic transducer of claim 1, wherein, The flange (4) is arranged at the resonance displacement node x0=0 of the piezoelectric ceramic crystal (5).

8. The low-frequency narrow-pulse point-contact ultrasonic transducer of claim 1, wherein, The welding of the positive and negative electrode wires (6) is at the resonance displacement node x0=0 of the piezoelectric ceramic crystal (5).

9. The low-frequency narrow-pulse point-contact ultrasonic transducer of claim 1, wherein, The piezoelectric ceramic matching layer (9) is a cylindrical structure, and the piezoelectric ceramic crystal (5) is a cuboid structure.

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