Acoustic emission detection device for early loosening of bolt

Abstract

The invention discloses an acoustic emission detection device for early loosening of a bolt. The acoustic emission detection device comprises a signal acquisition board, an acoustic emission sensor, a pre-amplifier, an acoustic emission acquisition instrument and a display, the signal acquisition plate is a square thin steel plate, one-dimensional acoustic black hole structures are arranged on three boundaries, and a two-dimensional acoustic black hole structure is embedded in the center; the acoustic emission sensor is adhered to the back surface of the two-dimensional acoustic black hole structure and is used for acquiring an acoustic emission signal generated by early loosening of the bolt; the sensor is connected with an acoustic emission acquisition instrument through a preamplifier, and the acquisition instrument is connected with a display through a data line so as to display monitored acoustic emission signals in real time. According to the invention, the precision and sensitivity of bolt looseness detection, especially early looseness detection of a bolt structure, can be effectively improved, structural failure is prevented, and safe operation of equipment is guaranteed; the device has the advantages of simple structure, accurate detection, convenient operation and the like.

Description

Technical Field

[0001] The invention relates to the technical field of detection devices, and in particular to an acoustic emission detection device for early bolt loosening. Background Art

[0002] Bolted connection is one of the most commonly used connection methods in engineering assembly structures, and plays a key role in transferring loads between interconnected components. Bolted connection not only has the advantages of good force and seismic performance, high connection stiffness and fatigue resistance, but also is easy to disassemble and replace. Therefore, it is widely used in various industries, such as automobile, metallurgy, machinery, electricity, aerospace, aviation, civil engineering and other industries. During the entire service life of the bolted connection, due to the influence of unstable factors such as vibration, impact, variable load and temperature difference, bolt fasteners often loosen or fail due to fatigue, among which loosening failure is the main problem. The gradual accumulation of bolt loosening will greatly reduce the integrity and durability of the structure. If not discovered in time, it may cause huge losses of people's lives and property.

[0003] The loosening behavior of bolts can be divided into two stages: the first stage is the early loosening stage of bolts, during which the preload decreases slowly and continuously, and there is no relative rotation between the bolt and the nut; the second stage is the rapid decrease of preload, during which relative rotation occurs between the bolt and the nut. Since the early loosening stage of bolts is not accompanied by relative rotation of the bolt and the nut, it is difficult for operation and maintenance personnel to detect such loosening behavior in time, resulting in missed inspections. Before the next maintenance inspection, the connection state of the missed bolts is likely to enter the stage of rapid decrease of preload from the early loosening stage, increasing the risk of structural failure. The technology based on acoustic emission can monitor the dynamic changes of the material state in real time based on the damage information of the acoustic emission source itself, and is extremely sensitive to changes in defects. Therefore, the change of preload can be indicated by picking up the acoustic emission signal of the bolt connection interface and analyzing its characteristics.

[0004] However, the acoustic emission signal generated by early bolt loosening is weak and easily interfered by noise, making it difficult to effectively detect and extract features of the signal. Conventional signal processing methods cannot ensure that the signal does not lose key information after noise reduction, and it is still very difficult to find the key features in weak signals under the interference of strong noise signals. Summary of the invention

[0005] The purpose of the present invention is to provide an acoustic emission detection device for early bolt loosening to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above object, the present invention provides a device for obtaining acoustic emission signals of early bolt loosening, comprising:

[0007] A signal acquisition board, the signal acquisition board is installed on the bolt structure, the signal acquisition board is used to transmit the acoustic emission signal generated during the early loosening of the bolt structure; a noise reduction structure and a signal enhancement structure are provided on the signal acquisition board, the noise reduction structure is used to reduce the reflection of the acoustic emission signal by the edge of the signal acquisition board, and the signal enhancement structure is used to maintain the intensity of the acoustic emission signal when it is transmitted in the signal acquisition board;

[0008] A signal acquisition structure is installed in the middle of the signal acquisition board, and the signal acquisition structure and the signal enhancement structure are respectively arranged on both sides of the signal acquisition board, and the signal acquisition structure is used to collect the acoustic emission signal.

[0009] Preferably, the signal acquisition structure adopts an acoustic emission sensor.

[0010] Preferably, the signal acquisition board is a square structure.

[0011] Preferably, the noise reduction structure is a one-dimensional acoustic black hole structure, which is arranged on three sides of the signal acquisition board. The one-dimensional acoustic black hole structure adopts a power function structure, and the thickness of the one-dimensional acoustic black hole structure decreases in the direction away from the middle of the signal acquisition board; the side of the signal acquisition board where the one-dimensional acoustic black hole structure is not arranged is connected to the bolt structure.

[0012] Preferably, the signal enhancement structure is a two-dimensional acoustic black hole structure, the two-dimensional acoustic black hole structure is embedded in the center of the signal acquisition board, the two-dimensional acoustic black hole structure is a blind hole formed in the form of a power function, and the signal acquisition structure is arranged corresponding to the blind hole.

[0013] Preferably, the signal acquisition plate is a square thin steel plate.

[0014] A bolt early loosening acoustic emission detection device, comprising:

[0015] Device for acquiring acoustic emission signals of early bolt loosening;

[0016] A preamplifier, the preamplifier is electrically connected to the signal acquisition structure, and the preamplifier is used to amplify and filter the acoustic emission signal;

[0017] The acoustic emission collector is electrically connected to the preamplifier, and the acoustic emission collector is connected to a display via a data line, and the display is used to display the acoustic emission signal monitored in real time.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] (1) The one-dimensional acoustic black hole structure at the edge of the signal acquisition board can significantly reduce the reflection of sound waves at the edge through the design of gradually reducing the thickness. This design greatly suppresses the signal interference problem caused by boundary reflection, thereby improving the purity of signal acquisition; by reducing the interference of reflected signals on the real acoustic emission signals, the device can maintain a high signal-to-noise ratio in complex environments, ensuring the accuracy and stability of detection.

[0020] (2) The embedded design of the two-dimensional acoustic black hole structure enhances the acoustic emission signal before it reaches the acoustic emission sensor, reducing the attenuation of the signal during propagation, which reduces the risk of losing weak signals and thereby improves the efficiency and accuracy of the overall signal processing.

[0021] (3) The present invention adopts a design embedded with an acoustic black hole, and the overall structure still maintains the characteristics of simplicity and practicality; by combining a signal acquisition board, an acoustic emission sensor, a preamplifier, an acoustic emission acquisition instrument and a display, the device of the present invention can adapt to the needs of bolt loosening monitoring in a variety of industrial environments, and the device can be easily applied to existing detection systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 It is a structural schematic diagram of the acoustic emission detection device for early bolt loosening of the present invention;

[0024] Figure 2 It is a structural schematic diagram of the signal acquisition board of the present invention;

[0025] In the figure: 1. Signal acquisition board; 2. Acoustic emission sensor; 3. Preamplifier; 4. Acoustic emission collector; 5. Display; 11. One-dimensional acoustic black hole structure; 12. Two-dimensional acoustic black hole structure. DETAILED DESCRIPTION

[0026] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0027] See also Figure 1 and Figure 2 The present invention provides an acoustic emission detection device for early bolt loosening, comprising a signal acquisition board 1, an acoustic emission sensor 2, a preamplifier 3, an acoustic emission acquisition instrument 4 and a display 5.

[0028] The signal acquisition board 1 is a square thin steel plate, with one-dimensional acoustic black hole structures 11 provided on its three boundaries and a two-dimensional acoustic black hole structure 12 embedded in the center. Figure 2 The specific arrangement of the one-dimensional acoustic black hole structure 11 and the two-dimensional acoustic black hole structure 12 is shown in detail. The one-dimensional acoustic black hole structure 11 gradually becomes thinner along the three edges of the signal acquisition board 1 in the form of a power function, thereby effectively absorbing and weakening the sound waves reflected from the boundary and reducing signal interference. The two-dimensional acoustic black hole structure 12 is located at the center of the signal acquisition board 1, and forms a blind hole with a gradually decreasing thickness in the form of a power function, which enhances the acoustic emission signal reaching the acoustic emission sensor 2, making the detected signal more accurate.

[0029] The acoustic emission sensor 2 is attached to the back of the two-dimensional acoustic black hole structure 12 to collect the acoustic emission signal generated by the bolt during early loosening. The collected signal is amplified by the preamplifier 3 connected to the acoustic emission sensor 2, and then transmitted to the acoustic emission collector 4 through a data line. The acoustic emission collector 4 is connected to the display 5 to display and record the detected acoustic emission signal in real time.

[0030] The present invention solves the problem of the difficulty in effective detection and feature extraction of acoustic emission signals of early bolt loosening from the source by introducing an acoustic black hole structure, thereby realizing the detection of early bolt loosening. The acoustic black hole structure refers to the thickness of the plate structure that changes smoothly to zero in the form of a power function (exponent greater than or equal to 2) toward its edge. When the incident bending wave propagates from the uniform part to the acoustic black hole part, due to the gradual decrease in the thickness of the structure, the bending wave velocity also gradually decreases, the wavelength is compressed, and the fluctuation amplitude gradually increases; when the thickness gradually decreases to zero, when the bending wave propagates to the edge of the wedge near the acoustic black hole, the accumulated phase will reach infinity. Theoretically, the bending wave will not be able to reach the edge of the structure, and thus will not be able to reflect back from the edge, so that all the fluctuation energy can be concentrated at the tip of the structure. This reduces the interference of the reflected signal on the real acoustic emission signal, enables the device to maintain a high signal-to-noise ratio in a complex environment, and ensures the accuracy and stability of the detection.

[0031] Example

[0032] In specific applications, the detection device can be installed on the flange structure of the wind turbine tower. Since the wind turbine tower is subject to complex external forces during operation, including wind force, vibration and other factors, these factors will cause the tower flange bolts to gradually loosen.

[0033] First, the thickness of the signal acquisition board 1 in the device is controlled between 3mm and 10mm. In this embodiment, the thickness of the signal acquisition board 1 is 5mm. The maximum diameter of the blind hole is determined according to the center frequency of the acoustic emission signal of the bolt interface. The diameter range is set between 10mm and 50mm. The maximum diameter of the blind hole in this embodiment is controlled at 30mm. The smaller the depth of the blind hole, the better. However, in order to be able to process, the depth of the blind hole in this embodiment is set to 0.2mm. In the present invention, the signal acquisition board 1 can be very conveniently installed on the flange structure of the wind turbine tower. In terms of connection mode, one end of the signal acquisition board 1 without an acoustic black hole structure is connected to the flange structure of the wind turbine tower. This connection form can be adopted in a variety of ways according to actual needs, including welding, gluing and riveting, etc., and is not limited to a single form. This diversified connection method improves the installation flexibility of the device and ensures reliable installation and detection in different application environments. Then the acoustic emission sensor 2 is installed on the back of the two-dimensional acoustic black hole structure 12 in the center of the signal acquisition board 1 to achieve accurate collection of weak acoustic emission signals during bolt loosening. The three edges of the signal acquisition board 1 are designed as a one-dimensional acoustic black hole structure 11. This design can effectively absorb the redundant noise signals from the bolt structure and the surrounding environment, avoid the reflection interference of these signals, thereby reducing the background noise and significantly improving the signal-to-noise ratio of the detection. The two-dimensional acoustic black hole structure 12 located in the center of the signal acquisition board 1 can focus and enhance the acoustic emission signal from the loosening process of the bolt through its specific geometric design. This focusing effect ensures that the weak acoustic emission signal will not be significantly attenuated before being transmitted to the acoustic emission sensor 2, thereby improving the detection sensitivity and reliability of the signal. After installation, the acoustic emission sensor 2 transmits the captured acoustic emission signal to the preamplifier 3 for amplification and filtering to ensure the clarity and strength of the signal. Subsequently, the signal is transmitted to the acoustic emission acquisition instrument 4 via a data line, and the detection results are displayed and recorded in real time through the connected display 5. The operator can timely grasp the status information of the flange bolts through the display 5, so as to give early warning of possible loosening, take corresponding maintenance measures, and avoid potential failures of the wind turbine caused by loose bolts.

[0034] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A device for acquiring acoustic emission signals of early bolt loosening, characterized in that: include: A signal acquisition board (1), the signal acquisition board (1) being mounted on a bolt structure, the signal acquisition board (1) being used to transmit an acoustic emission signal generated during early loosening of the bolt structure; a noise reduction structure and a signal enhancement structure being provided on the signal acquisition board (1), the noise reduction structure being used to reduce reflection of the acoustic emission signal by the edge of the signal acquisition board (1), and the signal enhancement structure being used to maintain the strength of the acoustic emission signal when being transmitted in the signal acquisition board (1); A signal acquisition structure, wherein the signal acquisition structure is installed in the middle of the signal acquisition board (1), and the signal acquisition structure and the signal enhancement structure are respectively arranged on both sides of the signal acquisition board (1), and the signal acquisition structure is used to collect the acoustic emission signal.

2. The device for acquiring early bolt loosening acoustic emission signals according to claim 1, characterized in that: The signal collection structure adopts an acoustic emission sensor (2).

3. The device for acquiring early bolt loosening acoustic emission signals according to claim 1, characterized in that: The signal collection board (1) is a square structure.

4. The device for acquiring early bolt loosening acoustic emission signals according to claim 3 is characterized in that: The noise reduction structure is a one-dimensional acoustic black hole structure (11), which is arranged on three sides of the signal acquisition board (1), and the one-dimensional acoustic black hole structure (11) adopts a power function structure, and the thickness of the one-dimensional acoustic black hole structure (11) decreases in a direction away from the middle of the signal acquisition board (1); the side of the signal acquisition board (1) where the one-dimensional acoustic black hole structure (11) is not arranged is connected to the bolt structure.

5. The device for acquiring early bolt loosening acoustic emission signals according to claim 3, characterized in that: The signal enhancement structure is a two-dimensional acoustic black hole structure (12), the two-dimensional acoustic black hole structure (12) is embedded in the center of the signal acquisition board (1), the two-dimensional acoustic black hole structure (12) is a blind hole formed in the form of a power function, and the signal acquisition structure is arranged corresponding to the blind hole.

6. The device for acquiring acoustic emission signals of early bolt loosening according to claim 3 is characterized in that: The signal collection plate (1) is a square thin steel plate.

7. A bolt early loosening acoustic emission detection device, characterized in that: include: The device for acquiring acoustic emission signals of early bolt loosening according to any one of claims 1 to 6; A preamplifier (3), the preamplifier (3) being electrically connected to the signal acquisition structure, and the preamplifier (3) being used to amplify and filter the acoustic emission signal; The acoustic emission collector (4) is electrically connected to the preamplifier (3), and the acoustic emission collector (4) is connected to a display (5) via a data line, and the display (5) is used to display the acoustic emission signal monitored in real time.

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