Concrete defect detection device and defect size evaluation method

Abstract

The invention discloses a concrete defect detection device and a defect size evaluation method, and relates to the technical field of nondestructive detection and size evaluation of concrete defects, the device comprises a probe collector, an impact device collector, an electromagnetic excitation device and a signal acquisition controller; all impact hammers in the impact device collector are released in sequence under electromagnetic excitation of the electromagnetic excitation device, and all measuring points on the surface of the to-be-measured concrete structure are knocked in sequence to generate stress wave signals; each probe of the probe collector receives an echo signal at each measuring point; and the signal acquisition controller performs fast Fourier transform to obtain a signal frequency spectrum, extracts an echo dominant frequency, judges whether the measuring point has a defect or not according to the echo dominant frequency, and estimates a defect length and a defect depth according to the echo dominant frequency and a defect characteristic frequency in an echo spectrogram in allusion to a defect position. The detection efficiency of the internal defects of the concrete structure can be improved, and quantitative evaluation of the defects of the concrete structure is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of nondestructive detection and size assessment of concrete defects, and in particular to a concrete defect detection device and a defect size assessment method. Background Art

[0002] Concrete is used in large quantities in building structures. Concrete shrinkage, insufficient vibration, and rough construction may cause defects inside the concrete, thus affecting the safety and performance of the concrete structure. Therefore, rapid and non-destructive quality inspection of concrete structures at the construction site will provide a solid foundation for ensuring the quality of concrete structures and carrying out subsequent construction procedures. At present, the non-destructive testing methods for concrete structures mainly include impact echo detection, ultrasonic detection, infrared thermal imaging detection, and ground penetrating radar detection. Among them, the impact echo detection method has become the mainstream method for current concrete defect detection due to its advantages such as large detection depth, quick and easy testing, and low equipment cost. The impact echo detection method generates stress waves by knocking on the surface of the concrete structure, and fixes the probe on the surface of the concrete structure to detect the echo signal of the stress wave after it is reflected from the bottom of the concrete structure. Since the stress wave will be reflected, diffracted, and converted in mode when passing through the defect, the frequency component of the detected echo signal will change. For common concrete defects such as voids and delamination, it is generally manifested as a decrease in the main frequency of the echo. Therefore, by analyzing the main frequency of the echo, effective identification of defects can be achieved.

[0003] At present, the mainstream impact echo detection device requires the operator to use a steel hammer to hit the surface of the concrete structure to generate stress waves. In order to ensure the test accuracy, the operator is required to accurately hit each measuring point on the surface of the concrete structure every time he hits. The implementation is difficult and the detection accuracy is low. In addition, for large-area concrete structures such as shear walls, the number of grid points on the test surface may reach hundreds or even thousands. If a traditional single-channel impact echo detector is used, the detection efficiency is very low. In addition, the impact echo detection results output by the current impact echo detection device are still in the qualitative stage, and most of them can only determine whether there are defects, but cannot quantitatively evaluate the size of concrete defects. Based on this, how to evaluate the construction quality of concrete structures and improve the detection accuracy and efficiency of concrete structure defects has become a technical problem that needs to be solved in this field. Summary of the invention

[0004] The purpose of this application is to provide a concrete defect detection device and a defect size assessment method, which can improve the detection efficiency of internal defects of concrete structures and realize quantitative assessment of concrete structure defects.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] In a first aspect, the present application provides a concrete defect detection device, which includes a probe collector, an impact device collector, an electromagnetic excitation device, and a signal acquisition controller;

[0007] The signal acquisition controller is respectively connected to the probe collector, the impact device collector, and the electromagnetic excitation device; the electromagnetic excitation device is also connected to the impact device collector;

[0008] The electromagnetic excitation device is used to perform electromagnetic excitation on the impact device collector to drive the impact device collector to strike the surface of the concrete structure to be measured;

[0009] The impact device collector includes a number of impact hammers arranged evenly in sequence. Each impact hammer is disposed directly above the surface of the concrete structure to be measured. Each impact hammer is used to be released in sequence according to the arrangement order under the electromagnetic excitation of the electromagnetic excitation device, and strike each measuring point on the surface of the concrete structure to be measured in sequence, so as to generate stress wave signals at each measuring point in sequence;

[0010] The probe collector includes a number of probes arranged evenly in sequence. Each probe is disposed directly above the surface of the concrete structure to be measured. Each probe corresponds to one impact hammer. Each probe is used to receive the echo signals reflected by the bottom surface of the concrete structure to be measured or internal defects of the concrete structure to be measured at each measuring point respectively;

[0011] The signal acquisition controller is used to collect the echo signals received by each probe, perform fast Fourier transform on each echo signal respectively to obtain a plurality of signal spectra and echo spectrograms, extract the echo main frequencies in each signal spectrum respectively, judge whether there are defects at the corresponding measuring points according to each echo main frequency, and for the defect positions, estimate the defect sizes according to the echo main frequencies and defect characteristic frequencies in the echo spectrograms; the defect sizes include defect length and defect depth.

[0012] Optionally, grid lines are provided on the surface of the concrete structure to be measured. The grid lines include a number of first grid lines and a number of second grid lines perpendicular to each other. Each measuring point is respectively disposed at the intersection of each first grid line and each second grid line.

[0013] Optionally, the probe is a straight probe, and the straight probe is in close contact with the surface of the concrete structure to be measured.

[0014] Optionally, the probe is an air-coupled microphone, and the air-coupled microphone is not in contact with the surface of the concrete structure to be measured.

[0015] Optionally, the concrete defect detection device further includes a display screen, which is connected to the signal acquisition controller and is used to display the echo spectrogram, the defect position, and the defect size in real time.

[0016] In a second aspect, the present application provides a method for evaluating the size of concrete defects, which includes the following steps:

[0017] Obtain a detection instruction; the detection instruction is an instruction for detecting the defect position and defect size of the concrete structure to be measured; the defect size includes the defect length and the defect depth;

[0018] According to the detection instruction, use a detection device to detect the concrete structure to be measured, and obtain the defect position and the defect size of the concrete structure to be measured; the detection device is the concrete defect detection device described in the first aspect.

[0019] Optionally, before the step of using a detection device to detect the concrete structure to be measured according to the detection instruction and obtaining the defect position and the defect size of the concrete structure to be measured, the method for evaluating the size of concrete defects further includes:

[0020] Clean and level the surface of the concrete structure to be measured for detection, and obtain the preprocessed concrete structure to be measured;

[0021] Draw grid lines on the surface of the preprocessed concrete structure to be measured; the grid lines include a plurality of first grid lines and a plurality of second grid lines that are perpendicular to each other, and each measurement point is respectively set at each intersection of the first grid lines and the second grid lines.

[0022] Optionally, according to the detection instruction, using a detection device to detect the concrete structure to be measured, and obtaining the defect position and the defect size of the concrete structure to be measured specifically includes:

[0023] Collect the echo signals at each measurement point of the concrete structure to be measured;

[0024] Perform fast Fourier transform on each of the echo signals respectively to obtain a plurality of signal spectra and an echo spectrogram;

[0025] Extract the echo main frequencies in each of the signal spectra respectively to obtain a plurality of echo main frequencies;

[0026] Judge whether there are defects at the corresponding measurement points according to each of the echo main frequencies;

[0027] For the defect position, estimate the defect size according to the echo main frequency and the defect characteristic frequency in the echo spectrogram.

[0028] Optionally, determine whether there is a defect at each corresponding measurement point according to the main frequency of each echo; for the defect position, estimate the defect size according to the main frequency of the echo and the defect characteristic frequency in the echo spectrogram, which specifically includes the following steps:

[0029] Judge whether there is a defect at the corresponding measurement point according to the main frequency value of the echo corresponding to each measurement point, and obtain the first judgment result;

[0030] When the first judgment result is negative, do not perform any operation;

[0031] When the first judgment result is positive, take the measurement point position corresponding to the abnormal main frequency value of the echo as the defect position, and calculate the defect size according to the main frequency of the echo and the defect characteristic frequency in the echo spectrogram by using the following formula:

[0032]

[0033] where f d represents the defect characteristic frequency, β represents the shape coefficient of the concrete structure, C p represents the apparent velocity of the concrete structure, d represents the defect depth, f T-move represents the main frequency of the echo measured in the defect area, f T is the main frequency of the echo measured in the intact concrete area, H is the thickness of the concrete structure, a is the distance between the impact point and the detection point, L 1 represents the stress wave propagation length passing through the defect, L represents the defect length, L 0 represents the stress wave propagation length in the intact concrete area.

[0034] According to the specific embodiments provided by the present application, the present application discloses the following technical effects:

[0035] The present application provides a concrete defect detection device and a defect size evaluation method. By integrally arranging a probe aggregator, an impact device aggregator, an electromagnetic excitation device, and a signal acquisition controller, the electromagnetic excitation device performs electromagnetic excitation on the impact device aggregator, so that multiple impact hammers integrally arranged in the impact device aggregator are sequentially released in the arranged order, and each measuring point on the surface of the concrete structure to be measured is sequentially struck, thereby generating stress wave signals at each measuring point in turn. Then, multiple probes integrally arranged in the probe aggregator and uniformly arranged in sequence respectively receive the echo signals at each measuring point, and the echo signals here are the echo signals reflected by the bottom surface of the concrete structure to be measured or internal defects of the concrete structure to be measured during the transmission process of the stress wave signals. Therefore, after the echo signals at each measuring point are collected by each probe in the probe aggregator, the signal acquisition controller analyzes these echo signals (including analysis processes such as fast Fourier transform, extraction of the main frequency of the echo, and drawing of the echo frequency spectrum diagram), and then it can be determined whether there are defects at each measuring point, and the position, length, and depth of the defects can be determined.

[0036] Compared with the traditional impact echo detection device and single-channel impact echo detector for manual percussion detection, the present application does not require an operator to perform manual percussion and each percussion must accurately hit the measuring point, with low implementation difficulty, low labor intensity, higher detection efficiency, and effectively improves the detection efficiency of concrete defects. Moreover, by using each impact hammer in the impact device aggregator to strike each measuring point, replacing the manual percussion method with this mechanical impact method, stress wave signals can be accurately generated at each measuring point and effectively detected. At the same time, since there is no manual intervention during the entire impact process, the energy and waveform of the generated stress waves can be ensured to be basically the same, effectively improving the detection accuracy of concrete defects. And the defect size values such as length and depth can be accurately quantified, which can improve the detection efficiency of internal defects of the concrete structure, realize the quantitative evaluation of concrete structure defects, and provide a solid foundation for ensuring the quality of the concrete structure and carrying out subsequent construction processes. Description of the Drawings

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0038] Figure 1 It is a schematic structural diagram of a concrete defect detection device provided by an embodiment of the present application.

[0039] Figure 2Schematic diagram of the detection principle of the concrete defect detection device provided in an embodiment of the present application.

[0040] Figure 3 Schematic diagram of the stress wave propagation process through the concrete defect provided in an embodiment of the present application.

[0041] Figure 4 Schematic flow chart of a method for evaluating the size of concrete defects provided in an embodiment of the present application.

[0042] Figure 5 Schematic diagram of the complete implementation process of the method for evaluating the size of concrete defects provided in an embodiment of the present application.

[0043] Reference numerals:

[0044] 1 - Probe aggregator, 2 - Probe, 3 - Impact hammer, 4 - Electromagnetic excitation device, 5 - Impact device aggregator, 6 - Connecting wire, 7 - Signal acquisition controller, 8 - Display screen, 9 - Concrete structure, 10 - Grid line, 11 - Concrete slab, 12 - Void defect, 13 - Impact point, 14 - Detection point, 15 - Thickness of the concrete structure, 16 - Defect depth, 17 - Defect length, 18 - Distance between the impact point and the detection point, 19 - Stress wave propagation path through the defect, 20 - Stress wave propagation path in the intact concrete area. Detailed implementation manners

[0045] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0046] To make the above objects, features, and advantages of the present application more obvious and understandable, the present application will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0047] As Figure 1 shown, this embodiment proposes a concrete defect detection device, which mainly includes a probe aggregator 1, an electromagnetic excitation device 4, an impact device aggregator 5, a signal acquisition controller 7, and a display screen 8.

[0048] Among them, the signal acquisition controller 7 is respectively connected to the probe aggregator 1, the impact device aggregator 5, and the electromagnetic excitation device 4. The electromagnetic excitation device 4 is also connected to the impact device aggregator 5. The display screen 8 is connected to the signal acquisition controller 7.

[0049] In this embodiment, the electromagnetic excitation device 4 is used to perform electromagnetic excitation on the impact device aggregator 5 to drive the impact device aggregator 5 to strike the surface of the concrete structure to be measured.

[0050] In this embodiment, the impact device aggregator 5 includes a number of impact hammers 3 arranged uniformly in sequence. Each of the impact hammers 3 is disposed directly above the surface of the concrete structure to be measured. Each of the impact hammers 3 is used to be released in sequence according to the arrangement order under the electromagnetic excitation of the electromagnetic excitation device 4, and strike each measuring point on the surface of the concrete structure to be measured in sequence, so as to generate stress wave signals at each measuring point in sequence.

[0051] In this embodiment, the probe aggregator 1 includes a number of probes 2 arranged uniformly in sequence. Each of the probes 2 is disposed directly above the surface of the concrete structure to be measured. Each probe 2 corresponds to one impact hammer 3. Each of the probes 2 is used to receive the echo signals reflected by the bottom surface of the concrete structure to be measured or internal defects of the concrete structure to be measured at each measuring point respectively.

[0052] In this embodiment, the probe 2 can be a straight probe 2, and the straight probe 2 is in close contact with the surface of the concrete structure to be measured. Alternatively, the probe 2 can also be an air-coupled microphone, and the air-coupled microphone is not in contact with the surface of the concrete structure to be measured.

[0053] In this embodiment, the signal acquisition controller 7 is used to collect the echo signals received by each of the probes 2, perform fast Fourier transform (FFT) on each of the echo signals respectively to obtain a plurality of signal frequency spectra, thereby generating an echo frequency spectrum diagram, and extract the echo main frequencies in each of the signal frequency spectra respectively. According to each of the echo main frequencies, it is judged whether there are defects at the corresponding measuring points, so as to identify the defect positions. And for the defect positions, according to the echo main frequencies and defect characteristic frequencies in the echo frequency spectrum diagram, the defect sizes are estimated; the defect sizes include the defect length 17 and the defect depth 16.

[0054] In this embodiment, grid lines 10 are provided on the surface of the concrete structure to be measured. The grid lines 10 include a number of first grid lines 10 and a number of second grid lines 10 that are perpendicular to each other. Each measuring point is respectively disposed at each intersection of the first grid lines 10 and the second grid lines 10. Among them, the distance between adjacent two grid lines 10, the distance between adjacent two impact hammers 3, and the distance between adjacent two probes 2 can all be set to 5 cm, or can be set to other values, and can be encrypted or thinned according to the specific situation. For example, for the rapid detection requirement of large-volume concrete structures, the grid line spacing can be increased to reduce the number of measuring points (i.e., grid points); for the situation where it is necessary to accurately judge concrete defects, the grid line spacing can be reduced to increase the number of measuring points.

[0055] In this embodiment, the display screen 8 is used to display the echo spectrogram, defect position, defect size, etc. in real time, realizing the visualization of detection data.

[0056] As an alternative implementation, all the impact hammers 3 in the impact device aggregator 5 are arranged in sequence and evenly on the same straight line, and all the probes 2 in the probe aggregator 1 are also arranged in sequence and evenly on the same straight line. This straight line can be the first grid line 10 or the second grid line 10, so as to realize the line-scanning detection method. Along the length or width direction of the concrete structure to be measured, using the impact hammers 3 with a specific arrangement in the impact device aggregator 5 and the probes 2 with a specific arrangement in the probe aggregator 1, line-scanning detection is carried out on each measuring point on each first grid line 10 or second grid line 10.

[0057] As an alternative implementation, the concrete defect detection device can also be provided with a moving device. This moving device can be connected to the signal acquisition controller 7 and, under the control of the signal acquisition controller 7, carry the probe aggregator 1, the impact device aggregator 5, and the electromagnetic excitation device 4 through the moving device for automatic movement, realizing automatic line-scanning detection.

[0058] As Figure 1 shown, in this embodiment, by integrating the probe aggregator 1, the impact device aggregator 5, and the electromagnetic excitation device 4, a concrete defect detection device for line-scanning in a single direction is built, which can realize the rapid impact echo detection of multiple measuring points. The concrete defect detection device includes components such as a probe aggregator 1, a probe 2, an impact hammer 3, an electromagnetic excitation device 4, an impact device aggregator 5, a connecting wire 6, a signal acquisition controller 7, a display screen 8, concrete, and a grid line 10. Among them, multiple probes 2 are arranged in sequence and integrated in the probe aggregator 1, and the distance between two adjacent probes 2 is set to be equal to the spacing of the grid lines 10 on the surface of the concrete structure 9, generally about 5 cm. The distance between two adjacent probes 2 is adjustable within a certain range, so as to meet different grid division requirements.

[0059] In this embodiment, the probe 2 is detachable and replaceable. The center frequency of the probe 2 reflects the measurable stress wave frequency range of the probe 2, and the stress wave signals near the center frequency can be captured with high fidelity. Therefore, it is necessary to select probes 2 with different center frequencies according to the depth of the concrete structure 9. Generally, for a thicker concrete structure 9, a probe 2 with a lower center frequency should be selected.

[0060] In this embodiment, the probe 2 is a straight probe 2, which only receives the stress waves reflected by the bottom surface or defects of the concrete. In actual application, the probe 2 needs to be in close contact with the surface of the concrete structure 9, so as to improve the quality of the received echo signal.

[0061] In this embodiment, an air-coupled microphone can also be used to replace the direct probe 2 to achieve non-contact stress wave measurement, reduce the influence of the surface state of the concrete structure 9 on the echo signal, and improve the detection accuracy.

[0062] In this embodiment, the probe 2 essentially belongs to a piezoelectric transducer. The echo of the stress wave signal will cause the piezoelectric element to vibrate. Therefore, an electrical signal is generated by the direct piezoelectric effect, and multiple electrical signals collected by the probe 2 are input into the corresponding multi-channels of the signal acquisition controller 7 through the connecting wire 6.

[0063] In this embodiment, corresponding to the layout mode of the probe 2, multiple impact hammers 3 are arranged in sequence and integrated in the impact device aggregator 5. The distance between two adjacent impact hammers 3 is set to be equal to the spacing of the grid lines 10 on the surface of the concrete structure 9, generally about 5 cm. The spacing between two adjacent impact hammers 3 is adjustable within a certain range. The impact hammer 3 can be replaced with steel hammers of different diameters, and the diameter range is 5-25 mm. Each impact hammer 3 is connected to the main body of the impact device aggregator 5 through a spring, that is, both ends of the spring are respectively connected to the main body of the impact device aggregator 5 and the impact hammer 3, and the impact hammer 3 is driven by the electromagnetic excitation device 4. The electromagnetic excitation switch of the electromagnetic excitation device 4 is used to control the spring to release the impact hammer 3, so as to strike the surface of the concrete structure 9 to generate a stress wave signal. Since there is no manual intervention during the entire impact process, the energy and waveform of the generated stress wave can be ensured to be basically the same, thereby effectively improving the detection accuracy.

[0064] In this embodiment, before actual operation, the position of the impact device aggregator 5 needs to be adjusted so that each impact hammer 3 is on the same vertical grid line 10 as the corresponding probe 2 above it, and the distance between the two is the spacing of two adjacent grid lines 10. The electromagnetic excitation device 4 is connected to the signal acquisition controller 7 through the connecting wire 6, and the signal acquisition controller 7 controls the impact hammers 3 to be released sequentially from left to right. This line-scanning impact echo device measures and analyzes the propagation of stress wave signals between adjacent measurement points on the vertical grid line 10. Therefore, the impact hammers 3 are released sequentially from left to right to ensure that only the stress wave signal generated by the impact hammer 3 is detected by the corresponding probe 2 above the impact hammer 3 each time. Since the stress wave enters the concrete structure 9 from the surface of the concrete structure 9 and is transmitted, when it reaches the bottom surface of the concrete structure 9 or the defect inside the concrete structure 9, a corresponding echo will be reflected back, such as Figure 3 the solid single arrow in shows the stress wave propagation path 19 passing through the defect and the dotted single arrow shows the stress wave propagation path 20 in the complete concrete area. By setting the control software, each probe 2 only receives the echo signal generated by the impact hammer 3 below it. All the collected echo signals are subjected to fast Fourier transform to obtain the signal spectrum and extract the maximum frequency value in the signal spectrum, that is, the echo main frequency (f IE)。Draw the echo spectrogram of all grid points and represent the echo spectrogram on the display screen 8, f IE The abnormal points are the defect positions of the potential concrete structure 9. After the impact echo detection of all grid points at one height is completed, both the probe aggregator 1 and the impact device aggregator 5 are lifted upward by one grid line 10 to carry out the impact echo detection on the corresponding grid points. Repeat this process until the impact echo detection of all grid points on the surface of the entire concrete structure 9 is completed.

[0065] In this embodiment, the echo signal can be understood as the reflected wave of the stress wave signal at the bottom of the concrete structure 9. Then, when there are no defects in the concrete structure 9, the frequency components of the echo measured each time are basically the same, that is, the main frequency of the echo is basically the same. For example, taking the plate-shaped concrete structure 9 (i.e., the concrete slab 11) as an example, when measuring the concrete slab 11 with a thickness of 20 cm, the main frequency of the echo at the defect-free position is generally about 6 kHz. When there are defects in the concrete, the stress wave will be reflected, diffracted, mode-converted, etc. when passing through the defect, which will cause a significant change in the main frequency of the echo signal. By analyzing the change of the main frequency, the defects of the concrete structure 9 can be accurately identified. Therefore, the abnormal feature is that the main frequency changes significantly. For example, when there is a cavity, the main frequency generally decreases significantly, such as becoming 5 kHz; when encountering steel bars or steel plates, the main frequency will increase significantly, such as becoming 7 kHz.

[0066] In this embodiment, by combining traditional single-channel impact echo detectors into an integrated concrete defect detection device, the echo signals of all grid points along the length direction can be measured at one time, realizing line-scan impact echo detection and greatly improving the detection efficiency. In addition, using an electromagnetic excitation impact device to replace the manual tapping method makes the energy and waveform of the stress wave excited at each grid point similar, reducing the experimental error caused by the deviation of the impact source and the difference in impact energy, and improving the accuracy of defect detection.

[0067] The detection principle of the concrete defect detection device in this embodiment is as Figure 2 shown. First, based on this concrete defect detection device, judge whether there are defects according to the echo main frequency f IE . Generally speaking, the defects of the concrete structure 9 will cause f IE to decrease. For the f IE abnormal points, the defect size can be estimated. The depth of the defect in the concrete structure 9 will affect the spectral distribution of the echo. First, use a small-diameter impact hammer 3 to strike the surface of the concrete structure 9, and the high-frequency components of the generated echo signal will be more. The defect will cause a new characteristic peak to appear in the high-frequency band of the echo spectrum, which is expressed as the following formula:

[0068]

[0069] Among them, fd Represents the defect characteristic frequency, and the defect characteristic frequency is f d Actually, it is the center frequency of the concrete structure 9 above the defect. β represents the shape factor of the concrete structure 9, and C p Represents the apparent velocity of the concrete structure 9, and d represents the defect depth 16. Therefore, based on f d The burial depth of the defect in the concrete structure 9 can be preliminarily estimated, that is, the defect depth 16.

[0070] Then, estimate the defect length 17. Taking the existence of a cavity defect 12 in the concrete structure 9 as an example, the process of the concrete defect detection device for evaluating the size of the cavity defect 12 is described in detail. Figure 3 Shows the situation where there is a cavity inside the concrete slab 11. For a complete concrete, the stress wave propagates along the thickness 15 of the concrete structure and undergoes one reflection at the bottom surface of the concrete structure 9. Then, the stress wave propagation length L in the complete concrete area 0 Is expressed as the following formula:

[0071]

[0072] Among them, L 0 Represents the stress wave propagation length in the complete concrete area, H is the thickness 15 of the concrete structure, that is, the thickness of the concrete slab 11, and a is the distance between the impact point and the detection point 18, that is, the distance between adjacent intersection points of the grid line 10. Among them, the impact point 13, the intersection point of the grid line 10, and the measurement point refer to the same point because the impact echo test is carried out at the intersection point of the grid line 10, that is, the measurement point.

[0073] When there is a cavity in the concrete structure 9, the stress wave diffracts at the cavity, and the propagation path is significantly increased. Ignoring the thickness of the cavity, the stress wave propagation length L passing through the defect 1 Is expressed as the following formula:

[0074]

[0075] Among them, L 1 Represents the stress wave propagation length passing through the defect, and L represents the defect length 17.

[0076] In this embodiment, a large-diameter impact hammer 3 is used to strike the surface of the concrete structure 9. The cavity will cause a decrease in the main frequency of the echo. The main frequency of the echo measured at the cavity position, that is, the defect area, is f T-move According to the basic principle of measuring the structure thickness by impact echo, it is expressed as the following formula:

[0077]

[0078] Among them, h represents the thickness of the measured structure, and f IEIndicates the main frequency of the echo. The main frequency of the echo measured in the intact concrete area is f T , and the main frequency of the echo measured in the defect area is f T-move . According to equations (2), (3), and (4), the following equation can be obtained:

[0079]

[0080] where f T-move represents the main frequency of the echo measured in the defect area, f T is the main frequency of the echo measured in the intact concrete area, H is the thickness of the concrete structure, which is 15, a is the distance between the impact point and the detection point, which is 18, L 1 represents the propagation length of the stress wave passing through the defect, L represents the length of the defect, which is 17, L 0 represents the propagation length of the stress wave in the intact concrete area, d represents the depth of the defect, which is 16, and can be calculated by equation (1). Therefore, the value of the defect length, that is, the value of the cavity length, can be calculated through equation (6), and used as the final size evaluation result of the concrete cavity defect.

[0081] It can be understood that this embodiment takes a cavity as an example to illustrate, and the above method of this embodiment is also applicable to other types of defects in concrete, and the length size evaluation results of the corresponding defects can be obtained.

[0082] Based on the existing impact echo technology that can only qualitatively detect concrete defects, this embodiment forms a defect size evaluation method for the defect depth and defect length by studying the change of the echo main frequency and the essence of the derived high-frequency characteristic peaks, realizing semi-quantitative defect assessment.

[0083] As Figure 4 shown, this embodiment provides a method for evaluating the size of concrete defects. This method for evaluating the size of concrete defects is actually the corresponding method of the aforementioned concrete defect detection device. This method for evaluating the size of concrete defects includes the following steps:

[0084] Step 101, obtain a detection instruction. Among them, the detection instruction is an instruction to detect the defect position and defect size of the concrete structure to be measured; the defect size includes the defect length, which is 17, and the defect depth, which is 16.

[0085] Step 102, according to the detection instruction, use the detection device to detect the concrete structure to be measured, and obtain the defect position and the defect size of the concrete structure to be measured. The detection device is the aforementioned concrete defect detection device.

[0086] In this embodiment, before step 102 of using a detection device to detect the concrete structure to be measured according to the detection instruction and obtaining the defect position and defect size of the concrete structure to be measured, the following steps are further included:

[0087] Clean and level the surface of the concrete structure to be measured for detection to obtain the pre-treated concrete structure to be measured.

[0088] Draw grid lines 10 on the surface of the pre-treated concrete structure to be measured; the grid lines 10 include a plurality of first grid lines and a plurality of second grid lines that are perpendicular to each other, and each measurement point is respectively set at each intersection of the first grid lines and the second grid lines.

[0089] In this embodiment, step 102 of using a detection device to detect the concrete structure to be measured according to the detection instruction and obtaining the defect position and defect size of the concrete structure to be measured specifically includes the following steps:

[0090] Step 1021: Collect the echo signals at each measurement point of the concrete structure to be measured.

[0091] Step 1022: Perform fast Fourier transform on each of the echo signals respectively to obtain a plurality of signal spectra and an echo spectrogram.

[0092] Step 1023: Extract the echo main frequency in each of the signal spectra respectively to obtain a plurality of echo main frequencies.

[0093] Step 1024: Judge whether there is a defect at the corresponding measurement point according to each of the echo main frequencies, and identify the defect position;

[0094] Step 1025: For the defect position, estimate the defect size according to the echo main frequency and the defect characteristic frequency in the echo spectrogram.

[0095] Steps 1024 and 1025 of this embodiment identify the defect position and estimate the defect size, and specifically include the following steps:

[0096] Judge whether there is a defect at the corresponding measurement point according to the echo main frequency value corresponding to each measurement point to obtain a first judgment result, including the following two situations:

[0097] (1) When the first judgment result is negative, it means that there is no defect at the current measurement point, and no operation is performed at this time.

[0098] (2) When the first judgment result is yes, it indicates that there is a defect at the current measuring point. At this time, the measuring point position corresponding to the main frequency value of the abnormal echo is taken as the defect position. According to the main frequency of the echo and the defect characteristic frequency in the echo spectrum diagram, the defect dimensions such as the defect depth 16 and the defect length 17 are calculated using formulas (1)-(6).

[0099] like Figure 5 As shown in the figure, the complete evaluation process of the concrete defect size evaluation method in actual operation includes the following steps:

[0100] Step S1: Clean and level the test area and draw grid lines 10.

[0101] The surface of the concrete structure to be tested is cleaned and leveled, and grid lines 10 are drawn in the test area. The intersections of the grid lines 10 are the measurement points of the impact echo.

[0102] Step S2: Fix the concrete defect detection device on the grid line 10 to ensure that the concrete defect detection device is in close contact with the surface of the concrete structure 9 .

[0103] The concrete defect detection device is fixed on the grid line 10 of the area to be tested along the length direction, and the probe 2 is pressed tightly against the surface of the concrete structure 9 to ensure the quality of the received echo signal.

[0104] Step S3: The grid points are tapped in sequence to generate shock waves, and the corresponding probe 2 receives echo signals.

[0105] The impact hammer 3 is used to strike each grid point in turn, thereby generating a shock wave at each measuring point. At this time, the echo signal is received by the corresponding probe 2 and transmitted to the signal acquisition controller 7.

[0106] Step S4: Collect the echo signal and perform fast Fourier transform to obtain the signal spectrum and echo spectrum diagram.

[0107] After the echo signal is acquired by the signal acquisition controller 7, a fast Fourier transform is performed on the acquired echo signal to obtain a signal spectrum corresponding to the echo signal, thereby forming an echo spectrum diagram.

[0108] Step S5: Extract the main frequency of the echo. The grid points with abnormal main frequency need to be re-measured.

[0109] Based on the signal spectrum, the maximum frequency value in the signal spectrum, i.e. the echo main frequency, is extracted. Then the echo main frequency is compared and analyzed, and the grid points with abnormal main frequency are re-measured to ensure that the echo main frequency of each grid point is normal and effective.

[0110] Step S6: Repeat steps S3-S5 along the moving detection device until all grid points are traversed.

[0111] By means of the movement detection device, all grid points within the test area are traversed so that each grid point has a corresponding main echo frequency.

[0112] Step S7: Draw the echo spectrogram to achieve defect identification and positioning.

[0113] Based on the main echo frequencies corresponding to all grid points, an echo spectrogram is drawn. The area with abnormal main frequencies in the echo spectrogram is identified as a potential defect area, thereby determining the defect location. Further, in combination with Figure 2 the implementation process in and formulas (1)-(6) to evaluate and calculate the defect size, and complete the identification and positioning of concrete defects.

[0114] The actual application object of the concrete defect detection device and the defect size evaluation method in this embodiment is the concrete structure 9. The concrete structure 9 may be horizontal, such as a concrete road surface, or may be vertical, such as a concrete wall. This concrete defect detection device and the defect size evaluation method are applicable to both horizontal and vertical concrete structures 9, as long as it is ensured as much as possible that the probe 2 is in close contact with the surface of the concrete structure 9 so that echo signals can be fully received and the quality of the received echo signals can be ensured. The effective reception of echo signals in the vertical state can be achieved by pressing the probe 2 tightly or adding an acoustic couplant between the probe 2 and the surface of the concrete structure 9.

[0115] Compared with the traditional impact echo detection device and single-channel impact echo detector for manual percussion detection, this application does not require operators to perform manual percussion and each percussion must accurately hit the measuring point. The implementation difficulty is small, the labor intensity is low, the detection efficiency is higher, and the detection efficiency of concrete defects is effectively improved. Moreover, by using each impact hammer 3 in the impact device aggregator 5 to strike at each measuring point, the mechanical impact method is used to replace the manual percussion method, stress wave signals can be accurately generated at each measuring point and effectively detected. At the same time, since there is no manual intervention during the entire impact process, the energy and waveform of the generated stress waves can be ensured to be basically the same, effectively improving the detection accuracy of concrete defects. And the defect size values such as length and depth can be accurately quantified, and the defect size of the concrete structure 9 can be accurately evaluated, providing a solid foundation for ensuring the quality of the concrete structure 9 and carrying out subsequent construction processes.

[0116] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, 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, it should be considered as the scope described in this specification.

[0117] In this specification, specific examples are used to illustrate the principles and implementation manners of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation on the present application.

Claims

1. A concrete defect detection device, characterized in that: The concrete defect detection device comprises a probe collector, an impact device collector, an electromagnetic excitation device and a signal acquisition controller; The signal acquisition controller is connected to the probe collector, the impact device collector and the electromagnetic excitation device respectively; the electromagnetic excitation device is also connected to the impact device collector; The electromagnetic excitation device is used to electromagnetically excite the impact device collector to drive the impact device collector to knock on the surface of the concrete structure to be tested; The impact device collector includes a plurality of impact hammers arranged uniformly in sequence, each of which is arranged directly above the surface of the concrete structure to be measured, and each of which is used to be released in sequence in the order of arrangement under the electromagnetic excitation of the electromagnetic excitation device, and to strike each measuring point on the surface of the concrete structure to be measured in sequence, thereby generating stress wave signals in sequence at each measuring point; The probe collector includes a plurality of probes arranged evenly in sequence, each of which is arranged directly above the surface of the concrete structure to be tested, each of which corresponds to one of the impact hammers, and each of which is used to receive echo signals reflected by the bottom surface of the concrete structure to be tested or internal defects of the concrete structure to be tested at each measuring point; The signal acquisition controller is used to collect the echo signals received by each of the probes, and perform fast Fourier transform on each of the echo signals to obtain multiple signal spectra and echo spectrum diagrams, and respectively extract the echo main frequency in each of the signal spectra, and judge whether there is a defect at the corresponding measuring point according to each of the echo main frequencies, and estimate the defect size according to the echo main frequency and the defect characteristic frequency in the echo spectrum diagram for the defect position; The defect size includes defect length and defect depth.

2. The concrete defect detection device according to claim 1, characterized in that: The surface of the concrete structure to be measured is provided with grid lines, and the grid lines include a plurality of first grid lines and a plurality of second grid lines which are perpendicular to each other, and each measuring point is respectively provided at each intersection of the first grid lines and the second grid lines.

3. The concrete defect detection device according to claim 1, characterized in that: The probe is a straight probe, and the straight probe is in close contact with the surface of the concrete structure to be tested.

4. The concrete defect detection device according to claim 1, characterized in that: The probe is an air-coupled microphone, and the air-coupled microphone is not in contact with the surface of the concrete structure to be measured.

5. The concrete defect detection device according to claim 1, characterized in that: The concrete defect detection device also includes a display screen, which is connected to the signal acquisition controller and is used to display the echo spectrum, the defect position and the defect size in real time.

6. A method for evaluating the size of concrete defects, characterized in that: The concrete defect size assessment method comprises: Obtaining a detection instruction; the detection instruction is an instruction for detecting the defect position and defect size of the concrete structure to be tested; the defect size includes defect length and defect depth; According to the detection instruction, the concrete structure to be detected is detected using a detection device to obtain the defect position and the defect size of the concrete structure to be detected; the detection device is the concrete defect detection device according to any one of claims 1-5.

7. The method for evaluating concrete defect size according to claim 6, characterized in that: Before the step of detecting the concrete structure to be detected using a detection device according to the detection instruction to obtain the defect position and the defect size of the concrete structure to be detected, the concrete defect size assessment method further includes: Cleaning and leveling the surface of the concrete structure to be tested to obtain a pre-treated concrete structure to be tested; Grid lines are drawn on the pre-processed surface of the concrete structure to be measured; the grid lines include a plurality of first grid lines and a plurality of second grid lines that are perpendicular to each other, and each measuring point is respectively set at each intersection of the first grid lines and the second grid lines.

8. The method for evaluating concrete defect size according to claim 6, characterized in that: According to the detection instruction, using a detection device to detect the concrete structure to be detected to obtain the defect position and the defect size of the concrete structure to be detected specifically includes: Collecting echo signals at various measuring points of the concrete structure to be measured; Performing fast Fourier transform on each of the echo signals to obtain a plurality of signal spectra and an echo spectrum diagram; Extracting the echo main frequencies in each of the signal spectra respectively to obtain a plurality of echo main frequencies; Judging whether there is a defect at the corresponding measuring point according to the main frequency of each echo; With respect to the defect position, the defect size is estimated according to the echo main frequency and the defect characteristic frequency in the echo spectrum diagram.

9. The method for evaluating concrete defect size according to claim 8, characterized in that: Judging whether there is a defect at the corresponding measuring point according to the main frequency of each echo; For the defect location, the defect size is estimated according to the echo main frequency and the defect characteristic frequency in the echo spectrum diagram, specifically including: According to the echo main frequency value corresponding to each measuring point, it is judged whether there is a defect at the corresponding measuring point to obtain a first judgment result; When the first judgment result is no, no operation is performed; When the first judgment result is yes, the measuring point position corresponding to the abnormal echo main frequency value is taken as the defect position, and the defect size is calculated according to the echo main frequency and the defect characteristic frequency in the echo spectrum diagram using the following formula: Among them, f d represents the defect characteristic frequency, β represents the shape coefficient of the concrete structure, C p represents the apparent velocity of the concrete structure, d represents the defect depth, and f T-move Indicates the main frequency of the echo measured in the defect area, f T is the main frequency of the echo measured in the intact concrete area, H is the thickness of the concrete structure, a is the distance between the impact point and the detection point, L1 is the propagation length of the stress wave passing through the defect, L is the defect length, and L0 is the propagation length of the stress wave in the intact concrete area.

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