Air coupling acoustic emission sensor

Abstract

The utility model belongs to the technical field of acoustic emission sensors, and particularly relates to an air coupling acoustic emission sensor, which is characterized in that a receiver, a piezoelectric transduction device and a coaxial cable are arranged in a matched manner, and internal stress waves of materials enter the sensor from air through a receiving hole in the receiver; a piezoelectric film of the piezoelectric transduction device vibrates, so that the surfaces of an upper electrode and a lower electrode generate polarization proportional to the surface of the piezoelectric film, charges are generated, an array transducer converts the charges into analog quantity electric signals, and the analog quantity electric signals are output from a shielding cable to a coaxial cable through an electrode plate to form analog signal output of the sensor; according to the utility model, the impedance matching layer surrounds the array transducer, so that the influence of external interference on the signal conversion and transmission of the sensor is further reduced. The sensor structure disclosed by the utility model does not need to be in direct contact with a material to realize measurement, so that the limitation of an installation position and an environment on the sensor is reduced, and the measurement precision and stability are improved.

Description

Technical Field

[0001] This utility model belongs to the field of acoustic emission sensor technology, and specifically relates to an air-coupled acoustic emission sensor. Background Technology

[0002] Acoustic emission sensors are advanced non-destructive testing devices that identify defects by monitoring and analyzing changes in stress waves within materials. Their working principle is based on the reflection, refraction, and scattering of sound waves within materials. They non-invasively assess material integrity and locate defects. When defects exist in a material, the corresponding stress waves undergo reflection, refraction, and scattering. The receiving component captures these subtle signals, further analyzing the material's internal structural integrity and identifying defects. Acoustic emission sensors are widely used in structural health monitoring, fault prevention, and scientific research.

[0003] Traditional acoustic emission (AE) sensor structures mainly consist of a sensor housing and a receiving component. During measurement, they typically require direct physical contact with the target to ensure accurate signal transmission. Methods of direct physical contact include clamping, fixing devices, and bonding. The installation position and method directly affect the coupling between the AE sensor and the material. In other implementations, a coupling medium is needed between the AE sensor and the material to improve signal transmission efficiency. These include liquids, thin films, and gels, which form a better coupling interface, facilitating signal transmission and reception.

[0004] However, traditional acoustic emission sensor structures are susceptible to interference from other signals at the contact points because they require direct or indirect contact with materials through coupling media, which affects the accuracy and stability of measurements. They also have high requirements for the flatness of the mounting contact surface and the structural materials, making measurements less flexible. Furthermore, in special environments, the sensors are easily damaged by high temperature, high pressure, or corrosion, requiring higher maintenance costs. Utility Model Content

[0005] The technical problem to be solved by this invention is to overcome the shortcomings of traditional acoustic emission sensors in the prior art, which require contact with materials, resulting in poor measurement accuracy and stability and easy damage to the sensors, thereby providing an air-coupled acoustic emission sensor.

[0006] This invention provides an air-coupled acoustic emission sensor, including a receiver, a piezoelectric transducer, and a coaxial cable. The receiver is fixed to the front end of the sensor and has multiple receiving holes on its surface. The piezoelectric transducer is located inside the housing. The piezoelectric transducer includes an impedance matching layer and a piezoelectric thin film, an array transducer, an electrode plate, and a shielded cable connected in sequence. The piezoelectric thin film is located behind the receiver. The array transducer is electrically connected to the piezoelectric thin film, the electrode plate is electrically connected to the array transducer, and the shielded cable is electrically connected to the electrode plate. The impedance matching layer covers the periphery of the array transducer and surrounds its rear side, filling the area between the array transducer and the inner wall of the housing. The coaxial cable is electrically connected to the shielded cable and is located at the rear end of the sensor.

[0007] Furthermore, it also includes a housing, which is a tubular structure with openings at the front and back, and the receiver, the piezoelectric transducer and the coaxial cable are installed inside the housing.

[0008] Furthermore, it also includes a fixing baffle, which is fixed to the inside of the housing and used to fix the impedance matching layer.

[0009] Furthermore, the fixing baffle is formed of an insulating material.

[0010] Furthermore, the impedance matching layer is a polymer composite material.

[0011] Furthermore, the receiver is circular, and the receiving holes are circular holes, with a total of thirty holes evenly distributed on the surface of the receiver.

[0012] Furthermore, the piezoelectric film is a flexible piezoelectric film made of polyvinylidene fluoride.

[0013] Furthermore, the coaxial cable is a single-core coaxial cable.

[0014] Furthermore, it also includes an insulating sheet disposed around the impedance matching layer.

[0015] Furthermore, the array transducer is an array-type composite material piezoelectric crystal.

[0016] Beneficial Effects: This utility model discloses an air-coupled acoustic emission sensor. Through the coordinated arrangement of a receiver, a piezoelectric transducer, and a coaxial cable, the internal stress wave of the material enters the sensor through the receiving hole on the receiver. The piezoelectric thin film of the piezoelectric transducer vibrates, causing polarization on the upper and lower electrode surfaces proportional to the distortion of the piezoelectric thin film surface, thereby generating an electric charge. The array transducer converts the charge into an analog electrical signal, which is output from the shielded cable to the coaxial cable through the electrode plates to form the sensor's analog signal output. The design of the impedance matching layer surrounding the array transducer further reduces the impact of external interference on the sensor's signal conversion and transmission. The sensor structure disclosed in this utility model does not require direct contact with the material for measurement, reducing the limitations of installation location and environment on the sensor, and improving measurement accuracy and stability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the overall cross-sectional structure of this utility model;

[0019] Figure 2 This is a schematic diagram of the receiver structure of this utility model;

[0020] Figure 3 This is a schematic diagram of the overall structure of this utility model.

[0021] Explanation of reference numerals in the attached drawings: 1. Receiver; 11. Receiver aperture; 21. Piezoelectric film; 22. Array transducer; 23. Electrode sheet; 24. Shielded cable; 25. Impedance matching layer; 3. Coaxial cable; 4. Housing; 41. Fixing baffle; 5. Insulating sheet. Detailed Implementation

[0022] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0023] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0024] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0025] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0026] Reference Figures 1-3As shown, this embodiment provides an air-coupled acoustic emission sensor, including a receiver 1, a piezoelectric transducer, and a coaxial cable 3. The receiver 1 is fixed to the front end of the sensor and has multiple receiving holes 11 on its surface. The piezoelectric transducer is located inside the housing 4. The piezoelectric transducer includes an impedance matching layer 25 and a piezoelectric film 21, an array transducer 22, an electrode plate 23, and a shielded cable 24 connected in sequence. The piezoelectric film 21 is located behind the receiver 1. The array transducer 22 is electrically connected to the piezoelectric film 21. The electrode plate 23 is electrically connected to the array transducer 22. The shielded cable 24 is electrically connected to the electrode plate 23. The impedance matching layer 25 covers the periphery of the array transducer 22 and surrounds the rear side of the array transducer 22, filling the area between the array transducer 22 and the inner wall of the housing 4. The coaxial cable 3 is electrically connected to the shielded cable 24 and is located at the rear end of the sensor.

[0027] In this embodiment, the impedance matching layer 25 fills the area between the array transducer 22 and the inner wall of the housing 4, allowing external interference signals to directly reach the impedance matching layer 25 upon entering the housing 4, further achieving impedance matching. This makes signal transmission more stable, reduces signal loss during transmission, and ensures signal transmission quality. Specifically, the impedance matching layer 25 is cylindrical in shape, with a narrowed front portion connecting to the front edge of the array transducer 22, surrounding the array transducer 22 and the electrode plate 23. The front side of the array transducer 22 protrudes from the front side of the impedance matching layer 25, and the shielded cable 24 extends from the rear side of the impedance matching layer 25. The periphery of the impedance matching layer 25 contacts the inner side of the housing 4.

[0028] In some other embodiments of this utility model, the impedance matching layer 25 is indirectly contacted and fixed to the inner side of the outer shell 4 by the fixing baffle 41, and the whole forms a gap with the inner side of the outer shell 4.

[0029] This embodiment provides an air-coupled acoustic emission sensor. Through the coordinated arrangement of a receiver 1, a piezoelectric transducer, and a coaxial cable 3, internal stress waves from the material enter the sensor via the receiving hole 11 on the receiver 1. The piezoelectric thin film 21 of the piezoelectric transducer vibrates, causing polarization on the upper and lower electrode surfaces proportional to the surface distortion of the piezoelectric thin film 21, thus generating an electric charge. The array transducer 22 converts this charge into an analog electrical signal, which is then output from the shielded cable 24 to the coaxial cable 3 via the electrode sheet 23, forming the sensor's analog signal output. The design of the impedance matching layer 25 surrounding the array transducer 22 further reduces the impact of external interference on the sensor's signal conversion and transmission. The sensor structure disclosed in this invention does not require direct contact with the material for measurement, reducing the limitations imposed by installation location and environment on the sensor, and improving measurement accuracy and stability.

[0030] In this embodiment, the piezoelectric film 21 has a multi-layer folded structure with its thickness direction perpendicular to the receiver 1. Specifically, it has a five-layer folded structure, which results in a higher resonant frequency of the piezoelectric film 21 in the thickness direction of its stretching vibration, and a wider flat response. This makes the frequency response width better than that of ordinary piezoelectric ceramic transducers, and makes it easier to control the convergence point of sound waves to reduce the energy loss of ultrasonic signals.

[0031] Specifically, it also includes a housing 4, which is a tubular structure with openings at the front and back. The receiver 1, the piezoelectric transducer and the coaxial cable 3 are installed inside the housing 4.

[0032] As a further improvement to this embodiment, a fixing baffle 41 is also included. The fixing baffle 41 is fixed to the inner side of the outer shell 4 and is used to fix the impedance matching layer 25. In this embodiment, the fixing baffle 41 is formed of insulating material. Specifically, the fixing baffle 41 has a ring structure, with its outer ring fixed to the inner side of the outer shell 4 and its inner ring fixed to the impedance matching layer 25. The fixing method is adhesive fixation.

[0033] The impedance matching layer 25 is a polymer composite material. Specifically, the impedance matching layer 25 is a composite material made of epoxy resin and alumina powder. By using different materials to conduct experiments, the efficiency and attenuation of sound waves or stress waves after propagation in the medium are tested. Through different levels of impedance matching, a more ideal acoustic impedance matching material is selected, thereby improving the efficiency of the transducer.

[0034] In a preferred embodiment, the receiver 1 is circular, and the receiving holes 11 are circular holes, with a total of thirty holes evenly distributed on the surface of the receiver 1. The receiver 1 has thirty receiving holes 11, specifically arranged in seven rows and six columns, with each row having two, four, six, six, six, four, and two receiving holes 11 from top to bottom, forming a near-circular arrangement.

[0035] In this embodiment, the piezoelectric film 21 is a flexible polyvinylidene fluoride piezoelectric film 21. The coaxial cable is a single-core coaxial cable 3. The array transducer 22 is an array of composite material piezoelectric crystals.

[0036] As a preferred embodiment, an insulating sheet 5 is also included, which is disposed around and surrounds the impedance matching layer 25.

[0037] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0038] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An air-coupled acoustic emission sensor, characterized in that, It comprises a receiver (1), a piezoelectric transducer device and a coaxial cable (3); the receiver (1) is fixed to the front end of the sensor, and a plurality of receiving holes (11) are formed on the surface; the piezoelectric transducer device is located inside the shell (4); the piezoelectric transducer device comprises an impedance matching layer (25) and a piezoelectric film (21), an array transducer (22), an electrode sheet (23) and a shielded cable (24) connected in sequence, the piezoelectric film (21) is located behind the receiver (1), the array transducer (22) is electrically connected with the piezoelectric film (21), the electrode sheet (23) is electrically connected with the array transducer (22), the shielded cable (24) is electrically connected with the electrode sheet (23), the impedance matching layer (25) covers the periphery of the array transducer (22) and surrounds the back side of the array transducer (22), and fills the area between the array transducer (22) and the inner wall of the shell (4); the coaxial cable (3) is electrically connected with the shielded cable (24) and located at the rear end of the sensor.

2. An air-coupled acoustic emission sensor according to claim 1, wherein, The shell (4) is a tubular structure with front and rear openings, the receiver (1), the piezoelectric transducer device and the coaxial cable (3) are installed inside the shell (4).

3. An air-coupled acoustic emission sensor according to claim 2, wherein, It further comprises a fixed baffle (41) fixed to the inner side of the shell (4) for fixing the impedance matching layer (25).

4. An air-coupled acoustic emission sensor according to claim 3, wherein, The fixed baffle (41) is formed of an insulating material.

5. An air-coupled acoustic emission sensor according to claim 1, wherein, The impedance matching layer (25) is a polymer composite material.

6. An air-coupled acoustic emission sensor according to claim 1, wherein, The receiver (1) is circular, the receiving holes (11) are circular holes, and there are thirty of them, evenly distributed on the surface of the receiver (1).

7. An air-coupled acoustic emission sensor according to claim 1, wherein, The piezoelectric film (21) is a polyvinylidene fluoride flexible piezoelectric film.

8. An air-coupled acoustic emission sensor according to claim 1, wherein, The coaxial cable is a single-core coaxial cable (3).

9. An air-coupled acoustic emission sensor according to claim 1, wherein, It further comprises an insulating sheet (5) arranged around the impedance matching layer (25).

10. An air-coupled acoustic emission sensor according to claim 1, wherein, The array transducer (22) is an array composite piezoelectric crystal.

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