CN106706760A - Acoustic emission source positioning method of composite material plate of omnidirectional dual circular array - Google Patents

Abstract

The invention discloses a method for locating an acoustic emission source of a composite material plate with an omnidirectional double circular array. A circular array of dual acoustic emission sensors is used. The radius of the circular array, that is, the distance between every two sensors, is used to determine the radius of the circular array. Calculate the wave velocity of the wave arrival time difference; verify the multi-set wave velocity array and the omnidirectional experimental results of the 360° wave velocity that have been calculated, select the closest velocity and match it with the corresponding direction, Delete gradually to narrow the scope of the detection area, repeat the experiment, and finally realize the accurate area location of the acoustic emission source of the damage to the composite plate structure.

Description

Acoustic Emission Source Localization Method for Composite Panels Based on Omnidirectional Dual Circular Array

technical field

The invention belongs to the technical field of acoustic emission non-destructive testing, and in particular relates to a method for locating an acoustic emission source of a composite material plate based on an omnidirectional bicircular array.

technical background

As a structural component widely used in engineering practice, plate structure has more and more diversified detection methods with the advancement of science and technology and the deepening of people's research work. Non-destructive testing methods for large plate structures mainly include eddy current method, ultrasonic testing method, acoustic emission testing method, thermal imaging method, optical fiber testing method, computer tomography testing method, microwave testing method, penetration method, laser holographic testing method, etc. More than 10 methods. Different testing methods have different advantages and limitations: eddy current testing can realize non-contact testing, but it is only suitable for conductive materials; ultrasonic can not only detect the position and size of defects in plate-shaped components, but also for composite material plates. The detection of delamination and fiber orientation also plays a role, but it needs to scan the structure point by point, and the detection efficiency is low; the acoustic-ultrasonic method is suitable for material integrity evaluation, but it is not sensitive to single and scattered defects, and the signal and noise are difficult to detect. Distinguish; the thermal imaging method can provide a full-field image but requires a good heat absorption rate on the surface of the specimen. Acoustic Emission (AE for short) is a phenomenon in which a material or component is deformed, fractured, or the internal stress exceeds the yield limit by an external force and enters an irreversible plastic deformation stage, releasing strain energy in the form of a transient elastic wave. Acoustic emission technology is a passive measurement non-destructive testing technology. Compared with conventional non-destructive testing methods such as ultrasound, it has three advantages: (1) The acoustic emission signal comes from the measured object itself, so it can realize the measurement of the measured object. Real-time online monitoring; (2) Acoustic emission technology has a wide coverage. For large components, no mobile sensors are needed to scan the structure, and only a sufficient number of sensors can be arranged to realize the monitoring of large components; (3) Wide application , almost all materials can be tested by acoustic emission. Acoustic emission technology is used to study the acoustic emission sources existing in the structure, so as to realize the positioning research of the acoustic emission sources in the plate structure and the assessment of the overall health status.

Acoustic emission source location is a very important application in acoustic emission technology. At present, the time difference positioning method is the main method of acoustic emission source location. It mainly uses parameters such as time difference, wave velocity, and sensor spacing to perform complex mathematical operations to determine the source of acoustic emission. The position is a relatively accurate but complicated positioning method, which is widely used in the detection of large plate-like components or large containers. However, time difference positioning is easy to lose a large number of low-amplitude signals, and the positioning accuracy is easily affected by multiple parameters such as wave velocity, attenuation, and waveform. Especially in composite material structures, acoustic emission signals propagate in different directions due to the anisotropy of materials. Therefore, it is often difficult to accurately locate the source of acoustic emission for composite panels by the time-of-flight positioning method.

Contents of the invention

Purpose of the present invention: at present, the main method of acoustic emission source location is the time difference positioning method. In the composite material structure, due to the anisotropy of the material, the propagation speed of the acoustic emission signal in different directions is not the same, therefore, the time difference method is adopted Accurate localization of AE sources on composite panels requires addressing the anisotropy of wave propagation due to the anisotropy of the composite material. Aiming at this problem, the present invention proposes a method for locating the acoustic emission source of the composite material plate based on the omnidirectional bicircular array of wave velocity.

To achieve the above object, the present invention adopts the following technical solutions:

A method for locating an acoustic emission source of a composite material plate with an omnidirectional double circular array comprises the following steps:

Step 1: Arrange two circular acoustic emission sensor arrays in the composite material plate to be tested. The circular arrays are arranged with one acoustic emission sensor on the center of the circle, and several acoustic emission sensors are evenly arranged in the counterclockwise direction on the arc. Sensors, the positions of the two circular sensor arrays can be arranged arbitrarily, and the distance between the arrays is as far as possible;

Step 2: Connect the acoustic emission sensor to the acoustic emission detection instrument connected to the computer through the preamplifier;

Step 3: Turn on the power, and set the parameters of each channel on the acoustic emission signal acquisition instrument, and then conduct a lead-breaking experiment on the composite material board to be tested, and observe whether the waveform displayed by each channel is normal, and if it is normal, perform data analysis. collection;

Step 4: Assuming that the velocity of the acoustic emission wave is constant, calculate the propagation velocity of the acoustic emission signal between each sensor on the arc and the sensor on the center of the circle, and verify the calculation results with the 360° omnidirectional experimental results of the wave velocity. Select The arrangement position corresponding to the approximation value is matched with it, and the intersection area of the wave arrival directions of the matched acoustic emission signals in the two circular arrays is used as the first main area where the acoustic emission source is located;

Step 5: According to the reduced detection main area, rearrange multiple sensors, repeat the experiment, and further determine the second or third partition in the first main area of the acoustic emission source to subdivide the main area and delineate the positioning area;

Step 6: The location of the determined acoustic emission source area is the intersection area of the arrival directions of the waves of the matched acoustic emission signals in the two sensor arrays that are finally rearranged.

Preferably, step 4 is specifically: the distance between each sensor on the arc and the sensor on the center of the circle is ΔL, and the arrival time difference of the acoustic emission waves reaching the two sensors is Δt, then the acoustic emission waves propagate along this direction The speed of can be calculated by the following formula:

According to the omnidirectional curve of the acoustic emission signal propagating in all directions in the range of 360° in the composite material plate, by arranging multiple sets of sensor arrays and combining the relative angle relationship between the acoustic emission source and the sensor array in the composite material plate, And determine the position of the first main area of the acoustic emission source.

The invention proposes a method for locating an acoustic emission source of a composite material plate based on an omnidirectional double-circular array, and uses the idea of hypothesis testing to scan the 360° omnidirectional direction of the wave velocity of the acoustic emission signal. Assuming that the wave velocity in the composite material plate is constant, the obtained results are verified with the omnidirectional experimental results of the 360° wave velocity obtained, and the closest velocity is selected and matched with the corresponding direction, and gradually deleted to narrow the detection The scope of the area, repeat the experiment, and finally achieve a more accurate area location of the acoustic emission source of the composite plate damage.

Description of drawings

Fig. 1 is the artificial lead breaking experimental schematic diagram of composite material board acoustic emission source localization method of the present invention;

Fig. 2 is a schematic diagram of the scanning mode and the position of the sensor within the 360° range of the acoustic emission sensor;

Fig. 3 is the omnidirectional curve of acoustic emission signal along each direction and propagation velocity within 360° range in the composite material plate;

Fig. 4 is the intersecting area of the arrival direction of the waves of the matched acoustic emission signals in two circular arrays, i.e. the first main area of the acoustic emission source;

Fig. 5 is the intersection area of the arrival direction of the waves of the matched acoustic emission signals in the two sensor arrays that are finally arranged, that is, the location area of the acoustic emission source;

The labels in the figure are explained as follows: 1-position of artificially simulated acoustic emission source, 2-circular acoustic emission sensor array, 3-preamplifier, 4-carbon fiber reinforced composite material plate, 5-acoustic emission signal detector, 6-computer , 7-position of the artificially simulated acoustic emission source, 8-360° scanning mode of the acoustic emission sensor, 9-acoustic emission sensor, 10-the first main area of the acoustic emission source, 11-the final positioning area of the acoustic emission source, 12 - Last reset of the AE sensor array.

detailed description

In conjunction with the following description, the present invention will be described in detail for exemplary implementation.

An embodiment of the present invention provides a method for locating the acoustic emission source of a composite material panel based on an omnidirectional double-circular array. The field of non-destructive testing technology. The steps are:

1. Arrange two circular acoustic emission sensor arrays in the composite material plate to be tested, that is, arrange an acoustic emission sensor on the center of the circle, arrange several acoustic emission sensors evenly in the counterclockwise direction on the arc, and two circular sensors The position of the array can be arranged arbitrarily, and the distance between the arrays is as far as possible;

2. Connect the acoustic emission sensor to the acoustic emission detector connected to the computer through the preamplifier;

3. Turn on the power, set the parameters of each channel of the acoustic emission signal acquisition instrument, and then conduct a lead breaking experiment on the composite material board to be tested to observe whether the waveform displayed by each channel is normal, and if it is normal, perform data acquisition;

4. Assuming that the velocity of the acoustic emission wave is constant, calculate the propagation velocity of the acoustic emission signal between each sensor on the arc and the sensor on the center of the circle, and verify the calculation results with the 360° omnidirectional experimental results of the wave velocity, and select The arrangement position corresponding to the approximate value matches it, and the intersection area of the wave arrival directions of the matched acoustic emission signals in the two circular arrays is used as the first main area where the sound source is located;

5. According to the reduced detection main area, rearrange multiple sensors, repeat the experiment, and further determine the second or third partition in the first main area to subdivide the main area and delineate the positioning area;

Sixth, the determined location of the acoustic emission source area is the intersection area of the arrival directions of the matched acoustic emission signals in the two sensor arrays that are finally rearranged.

As shown in Figure 1, the schematic diagram of the lead breaking experiment, the orthotropic composite material plate with different layup methods is the structure to be tested, with a total of 16 layers, a length and width of 1000 mm × 1000 mm, and a total thickness of 2.24 mm. The way to simulate the source of acoustic emission.

The specific implementation steps are described in conjunction with the schematic diagram as follows:

First, as shown in Figure 2, two circular acoustic emission sensor arrays are arranged, that is, one acoustic emission sensor is arranged on the center of the circle, eight acoustic emission sensors are evenly arranged counterclockwise on the arc, and each circular array has a total of nine Acoustic emission sensor. The positions of the two circular sensor arrays are arranged along the length direction or the width direction, and the distance between the arrays is as far as possible;

Secondly, assuming that the velocity of the acoustic emission wave is constant, the acoustic emission signal propagation velocity between each sensor on the arc and the center sensor is calculated separately. The calculation results are similar to the schematic diagram of the scanning mode and sensor position within the 360° range of the acoustic emission sensor in Figure 2 The measured acoustic emission signal is verified by the results shown in Figure 3 along the omnidirectional curves of various directions and propagation speeds within the 360° range of the composite material plate, and the layout position corresponding to the approximate value is selected to match it. Two The intersection area of the arrival directions of the waves of the matched acoustic emission signals in the circular array is used as the first main area where the acoustic emission source is located, as shown in Figure 4;

The details are as follows: the distance between each sensor on the arc and the sensor on the center of the circle is ΔL, and the arrival time difference of the acoustic emission waves arriving at the two sensors is Δt, then the formula Calculate the velocity of the acoustic emission wave propagating in this direction, and according to the drawn omnidirectional curve of the acoustic emission signal propagating in all directions within the range of 360° in the composite material plate, by arranging multiple sets of sensor arrays, combined with the acoustic wave in the composite material plate The relative angular relationship between the emission source and the sensor array, and determine the position of the first main area of the acoustic emission source, as shown in Figure 4;

Finally, according to the reduced detection main area, multiple sensors are rearranged. In the present invention, it is recommended to arrange seven sensors for repeated experiments, and further determine the second or third partition in the main area so as to subdivide the main area and delineate accurate The localization area, that is, the intersection area of the arrival directions of the waves of the matched acoustic emission signals in the two sensor arrays arranged last, is shown in FIG. 5 .

Claims (2)

1. A composite material plate acoustic emission source localization method of omnidirectional dual circular array, is characterized in that, comprises the following steps: Step 1: Arrange two circular acoustic emission sensor arrays in the composite material plate to be tested. The circular arrays are arranged with one acoustic emission sensor on the center of the circle, and several acoustic emission sensors are evenly arranged in the counterclockwise direction on the arc. Sensors, the positions of the two circular sensor arrays can be arranged arbitrarily, and the distance between the arrays is as far as possible; Step 2: Connect the acoustic emission sensor to the acoustic emission detection instrument connected to the computer through the preamplifier; Step 3: Turn on the power, and set the parameters of each channel on the acoustic emission signal acquisition instrument, and then conduct a lead-breaking experiment on the composite material board to be tested, and observe whether the waveform displayed by each channel is normal, and if it is normal, perform data analysis. collection; Step 4: Assuming that the velocity of the acoustic emission wave is constant, calculate the propagation velocity of the acoustic emission signal between each sensor on the arc and the sensor on the center of the circle, and verify the calculation results with the 360° omnidirectional experimental results of the wave velocity. Select The arrangement position corresponding to the approximation value is matched with it, and the intersection area of the wave arrival directions of the matched acoustic emission signals in the two circular arrays is used as the first main area where the acoustic emission source is located; Step 5: According to the reduced detection main area, rearrange multiple sensors, repeat the experiment, and further determine the second or third partition in the first main area of the acoustic emission source to subdivide the main area and delineate the positioning area; Step 6: The location of the determined acoustic emission source area is the intersection area of the arrival directions of the waves of the matched acoustic emission signals in the two sensor arrays that are finally rearranged. 2. The method for locating the composite material plate acoustic emission source of the omnidirectional dual circular array as claimed in claim 1, wherein step 4 is specifically: the distance between each sensor on the arc and the sensor on the center of the circle The distance is ΔL, and the arrival time difference of the acoustic emission waves arriving at the two sensors is Δt, then the speed of the acoustic emission waves propagating in this direction can be calculated by the following formula: $\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; t</span>}}$ According to the omnidirectional curve of the acoustic emission signal propagating in all directions in the range of 360° in the composite material plate, by arranging multiple sets of sensor arrays and combining the relative angle relationship between the acoustic emission source and the sensor array in the composite material plate, And determine the position of the first main area of the acoustic emission source.