A method for detecting and analyzing arbitrary shape concrete defects based on laser technology

Abstract

The application discloses a detection and analysis method for arbitrary shape concrete defects based on laser technology, which simultaneously adopts a laser exciting device and a plurality of laser vibration measuring devices to measure vibration according to a certain detection method, and then combines the arbitrary shape defect analysis method to analyze the arbitrary shape concrete defects, so that the economy and efficiency of the concrete defect detection are balanced and unified.

Description

Technical Field

[0001] This invention belongs to the field of concrete quality and safety testing technology, specifically relating to a method for detecting and analyzing defects in concrete of arbitrary shapes based on laser technology. Background Technology

[0002] Non-destructive testing (NDT) technology is widely used in the field of civil engineering. In concrete defect detection, the main technical methods include electromagnetic wave methods (such as ground-penetrating radar), impact elastic wave methods (such as ultrasonic instruments), and X-ray methods (such as X-ray imaging instruments). These technologies have achieved certain results in concrete defect detection, but they still face the following technical challenges: The above three methods are all close-contact detection methods, which require close contact (about 10cm) with the concrete to conduct the inspection. In practical engineering applications, it is difficult to achieve close-contact and rapid and efficient inspection operations on engineering structures with varying cross-sectional dimensions and pipelines.

[0003] Laser technology can achieve long-distance and rapid detection of concrete defects. Based on this, (1) Invention patent CN201710458424.6 proposes a method to judge the defect situation by analyzing the vibration velocity of the vibration measurement point. This invention patent gives the solution method of vibration velocity, but does not explain how to analyze the defect situation by vibration velocity; (2) Invention patent CN202210573799.8 proposes a method to judge the position and shape of the defect by peak position and size, but this patent does not explain the specific defect judgment method. At the same time, the invention adopts the assumption that "the defect is a cuboid shape" in the spectrum analysis process, which makes the method limited; (3) Invention patent CN202211073503.2 proposes a method to judge whether there is a defect at the vibration measurement point by vibration energy. This invention patent realizes the defect judgment of a certain point, but does not realize the rapid and efficient detection function of the entire detection surface. At the same time, this invention adopts the integral form when calculating vibration energy, which requires high computing power of the computer when calculating massive engineering detection data. In addition, the high price of rapid scanning laser vibration meters makes them difficult to promote and apply in practical engineering projects. Summary of the Invention

[0004] The purpose of this invention is to provide a method for detecting and analyzing concrete defects of arbitrary shapes based on laser technology. It adopts long-distance non-contact non-destructive testing, which is economical, fast, and can accurately analyze concrete defects of arbitrary shapes.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for detecting and analyzing arbitrary-shaped concrete defects based on laser technology includes the following steps:

[0007] (1) Laser excitation detection: A high-energy laser excitation device is used to emit a laser beam to the concrete surface. At the same time, multiple laser vibration measurement devices are used to emit multiple laser beams to perform multi-point vibration measurement and collect the vibration response signal of each measurement point.

[0008] (2) Modal analysis: The collected vibration response signal is subjected to fast Fourier transform to transform it into power spectral density in the frequency domain. Then, the peak extraction method is used to extract the mode shape of the defect point on the power spectral density function to extract the mode shape of each vibration measurement point.

[0009] (3) Defect judgment of vibration measurement point: In combination with the characteristics of normal concrete in actual civil engineering that cannot be excited to vibrate due to its large volume, the presence or absence of modal vibration at the vibration measurement point is used to qualitatively judge whether the vibration measurement point is a defect point. If the modal analysis results contain modal vibration, then the vibration measurement point is a defect point; otherwise, the vibration measurement point is normal concrete.

[0010] (4) Defect analysis of the area between concrete defect points: The modal vibration modes of each defect point on the same straight line or approximately on the same straight line are fitted to obtain the test modal vibration mode curves of the concrete on the straight line, which are denoted as curve f. The theoretical calculated modal vibration modes of the concrete are obtained through theoretical calculation or computer numerical simulation, which are denoted as curve F. Error analysis is performed between curve f and curve F. If the error converges within the required range, the area is judged to be defective concrete; otherwise, it is judged to be normal concrete.

[0011] (5) Analysis of defects in concrete of arbitrary shape: Color each defect area and draw a defect cloud map.

[0012] Preferably, the specific method of step (1) is as follows: In combination with the actual engineering detection accuracy requirements, design the vibration measurement form and select an appropriate number and position of vibration measurement points on the engineering body to be tested. Place the laser excitation device and the laser vibration measurement device on the moving platform and adjust the relative positions of the two types of devices to form a detection device. This device can rotate with the axis where the excitation beam is located as the rotation axis.

[0013] A vibration excitation point is selected on the concrete of the engineering structure. A laser excitation device emits a high-energy laser beam to this point to excite the concrete. A laser vibration measurement device emits multiple laser beams to detect the vibration response signals at multiple points on the concrete surface, and the vibration response signals are collected. A new excitation point is selected, and the above steps are repeated to form a scanning measurement effect of the concrete vibration signal. The vibration response signal is one of the following forms: acceleration, displacement, or velocity.

[0014] Preferably, in step (1), the selection of the detection position is as follows: Let the laser excitation point be O. Draw concentric circles with O as the center, with equal radii between each concentric circle. Progress from small circles to large circles sequentially, rotating counterclockwise by a set angle, and sequentially selecting n (…). (n) points, and finally point O and the selected n points are used as vibration measurement points.

[0015] Preferably, in step (2), the specific method of modal analysis is as follows: the collected vibration signal (such as acceleration, velocity, or displacement) is processed by fast Fourier transform to transform it into power spectral density in the frequency domain. Then, peak values ​​are extracted from the power spectral density function using techniques such as peak extraction. Finally, the mode shape is estimated by the first-order left singular vector of the power spectral density function matrix at the peak value. The mode shape refers to the shape of each mode vibration. Specifically, the mode shape is the position function of these measuring points. Since the engineering structure has an infinite number of modes, each mode shape is different. Therefore, the mode shape is a function of the structural position and the modal order.

[0016] Preferably, in step (2), peak extraction is used in the frequency domain to identify peaks in the spectrum. Commonly used peak extraction algorithms include thresholding, derivative methods, and curve fitting. These algorithms will find prominent peaks in the spectrum, which correspond to the inherent frequencies of the structure.

[0017] Preferably, in step (2), the method for estimating the mode shape using the first-order left singular vector is typically related to singular value decomposition in modal analysis. In this method, we first construct a modal response matrix, where rows correspond to different measurement points and columns correspond to different time steps. Then, we perform singular value decomposition on this matrix to obtain: ,in, It is the modal response matrix. It is a left singular vector matrix. It is a diagonal matrix containing singular values. It is a right singular vector matrix; a left singular vector matrix The columns correspond to the mode shapes, while the right singular vector matrix... The rows contain the weights of the measurement points in each mode shape. By selecting the column associated with the maximum singular value, we can obtain the first-order mode shape and its corresponding weight distribution, which indicates the degree of participation of each measurement point in this mode.

[0018] Preferably, in step (4), the specific method for analyzing the defect situation in the area between concrete defect points is as follows: perform error analysis on curve f and curve F, if... , If the error sensitivity parameter is used, then the area between defect points on the straight line is defective concrete; otherwise, the area between defect points is normal concrete.

[0019] Preferably, in step (4), the curve fitting method refers to a data processing method that uses a computer to fit a set of data onto a curve and then solves the equation of the fitted curve. Specifically, the least squares method or other methods can be used to fit the equation of the curve.

[0020] By adopting the above technical solution, the present invention has the following beneficial effects:

[0021] (1) Long-distance non-contact detection. Compared with existing detection methods such as ultrasonic and radar, the use of laser excitation and laser vibration measurement devices can realize long-distance detection of objects at high altitudes from the ground; at the same time, long-distance operation is beneficial to the personal safety of construction workers and reduces risks and hidden dangers.

[0022] (2) Non-destructive testing. Compared with the hammer test method commonly used in engineering, the energy of the beam emitted by laser testing technology is much lower than the destructive strength of concrete, and will not cause damage to the structure being tested.

[0023] (3) Economical and practical. Currently, laser excitation and vibration measurement devices are expensive. Single-point laser excitation and vibration measurement devices, through simple combination, can achieve scanning detection effects to a certain extent.

[0024] (4) High efficiency and speed. By selecting several designed test points on a certain area of ​​the concrete surface of the engineering body for testing, from point to line and finally to surface, the overall testing of the area can be achieved, improving testing efficiency and meeting the actual needs of the project, especially the need for short testing time in subway tunnels. Attached Figure Description

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] Figure 1 The diagram shows the process of selecting vibration measurement points.

[0027] Figure 2 This refers to the scope and shape of concrete defect detection.

[0028] Figure 3 Acceleration data collected for a laser vibration measurement device.

[0029] Figure 4 is the power spectral density function.

[0030] Figure 5 (1) is the fitting curve of the first mode shape of the BD line. Figure 5 (2) is the fitting curve of the second mode shape of the BD line. Figure 5 (3) is the fitting curve of the third mode shape of the BD line.

[0031] Figure 6 This is a defect cloud map for concrete of arbitrary shape. Detailed Implementation

[0032] A method for detecting and analyzing arbitrary-shaped concrete defects based on laser technology includes the following steps:

[0033] (1) Laser-excited vibration detection: A set of laser detection equipment includes one laser excitation device and five laser vibration measuring devices, such as Figure 1 As shown, the laser excitation point is O. Concentric circles are drawn with the laser excitation point O as the center. The radius of each concentric circle is the same. The small circle transitions to the large circle in turn. The circle is rotated 90 degrees counterclockwise. Four points (A, B, C, D) are selected. Finally, point O and the four selected points (A, B, C, D) are used as the vibration measurement points.

[0034] In conjunction with actual engineering projects, select an appropriate number and location of excitation points on the engineering body being tested, such as... Figure 2 As shown, for each detection point, with excitation point O as the center, a laser vibration measuring device performs four rotational vibration measurements around this center. Each rotation is 90 degrees, and the rotation direction is counterclockwise, forming... Figure 3 The concrete testing area and shape are shown.

[0035] (2) Modal analysis: such as Figure 3 As shown, the collected acceleration data is first processed by Fast Fourier Transform to transform it into power spectral density in the frequency domain, such as... Figure 4 As shown, the peak extraction method is then used on the power spectral density function to find the peak value through curve fitting. Finally, the mode shape is estimated by the first-order left singular vector of the power spectral density function matrix at the peak value.

[0036] (3) Defect judgment of vibration measurement point: Based on the results of modal analysis and the characteristics of normal concrete in actual civil engineering that cannot be excited to vibrate due to its large volume, the presence or absence of modal vibration at the vibration measurement point can be used to qualitatively determine whether the vibration measurement point is a defect point. If the results of modal analysis contain modal vibration, then the vibration measurement point is a defect point; otherwise, the vibration measurement point is normal concrete.

[0037] (4) Defect analysis of the area between concrete defect points: After determining the defect points and their modal modes through step (3), the modal modes of each defect point on the same straight line or approximately on the same straight line are extracted. Then, curve fitting is performed using the modal modes of each defect point, such as... Figure 5 (1)- Figure 5 (3) As shown, taking the straight line where the defect points B and D are located as an example, the first three modal vibration modes are extracted and analyzed to form the approximate modal vibration mode curves f of the tested concrete on the straight line. Finally, the theoretical modal vibration mode curves F and f are compared to select the error sensitivity parameter. The value is 25, and calculations show that... Then the area between the defect points on line BD is the defective concrete.

[0038] (5) Defect analysis of concrete of arbitrary shape: After determining the defect situation between defect points through step (3), the defect areas are colored by computer program to draw defect cloud map, such as Figure 6 As shown. Because the detection range extends from points to lines and then to surfaces, the arrangement of vibration measurement points can be determined according to the project dimensions and detection accuracy requirements, enabling the analysis of defects in concrete of any shape.

[0039] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A method for detecting and analyzing concrete defects of arbitrary shape based on laser technology, characterized in that, The steps include: (1) Laser excitation detection: A high-energy laser excitation device is used to emit a laser beam to the concrete surface. At the same time, multiple laser vibration measurement devices are used to emit multiple laser beams to perform multi-point vibration measurement and collect the vibration response signal of each measurement point; (2) Modal analysis: Modal analysis is performed on the collected vibration response signal to extract the mode shapes of each vibration point; (3) Defect judgment of the vibration point: The presence or absence of mode shapes at the vibration point is used to qualitatively determine whether the vibration point is a defect point. If the result of the modal analysis contains mode shapes, then the vibration point is a defect point; otherwise, the vibration point is normal concrete; 4) Defect analysis of the area between concrete defect points: The modal vibration of each defect point on the same straight line or approximately on the same straight line is curve fitted to obtain the test modal vibration curves of the concrete on the straight line, which are denoted as curve f. The theoretical calculated modal vibration of each concrete is obtained through theoretical calculation or computer numerical simulation, which are denoted as curve F. The error analysis of curve f and curve F is performed. If the error converges within the required range, the area is judged to be defective concrete; otherwise, it is judged to be normal concrete. (5) Defect analysis of concrete of arbitrary shape: Each defect area is colored and a defect cloud map is drawn.

2. The method for detecting and analyzing arbitrary-shaped concrete defects based on laser technology according to claim 1, characterized in that, The specific method of step (1) is as follows: Combine the actual engineering detection accuracy requirements, design the vibration measurement form, select an appropriate number and position of vibration measurement points on the engineering body to be tested, place the laser excitation device and the laser vibration measurement device on the moving platform, and adjust the relative positions of the two types of devices to form a detection device. This device can rotate with the axis where the excitation beam is located as the rotation axis.

3. The method for detecting and analyzing arbitrary-shaped concrete defects based on laser technology according to claim 2, characterized in that, In step (1), the detection position is selected as follows: set the laser excitation point as O, draw concentric circles with the laser excitation point O as the center, and the radius of each concentric circle is the same. The small circle is gradually transitioned to the large circle. Rotate counterclockwise by a set angle and select n points in sequence. Finally, point O and the selected n points are used as the vibration measurement points.

4. The method for detecting and analyzing arbitrary-shaped concrete defects based on laser technology according to claim 1, characterized in that, In step (2), the specific method of modal analysis is as follows: the collected vibration signal is processed by fast Fourier transform to transform it into power spectral density in the frequency domain, and then the peak extraction method is used to extract the mode shapes of each vibration measurement point on the power spectral density function.

5. The method for detecting and analyzing arbitrary-shaped concrete defects based on laser technology according to claim 1, characterized in that, In step (4), the specific method for analyzing the defect situation in the area between concrete defect points is as follows: Perform error analysis on curve f and curve F. If , If the error sensitivity parameter is used, then the area between defect points on the straight line is defective concrete; otherwise, the area between defect points is normal concrete.

6. The method for detecting and analyzing arbitrary-shaped concrete defects based on laser technology according to claim 1, characterized in that, In step (4), the specific method for analyzing the defect situation in the area between concrete defect points is as follows: After determining the defect points and their modal modes in step (3), firstly, extract the modal modes of each defect point on the same straight line or approximately on the same straight line, then use the modal modes of each defect point to perform curve fitting, forming the approximate modal mode curves f of the tested concrete on the straight line, and finally compare the theoretical modal mode curves F with the approximate modal mode curves f. If , If the error sensitivity parameter is used, then the area between defect points on the straight line is defective concrete; otherwise, the area between defect points is normal concrete.

7. The method for detecting and analyzing arbitrary-shaped concrete defects based on laser technology according to claim 1, characterized in that: In step (4), the curve fitting method is a data processing method that uses a computer to fit a set of data onto a curve and then solves the equation of the fitted curve. Specifically, the least squares method can be used to fit the equation of the curve.

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