A bridge steel plate bonding defect detection method and system based on double-mode sequence insonation ultrasonic C scan

Abstract

The application discloses a kind of bridge steel plate bonding defect detection method and system based on double mode sequence ultrasound C scan, it is related to concrete bridge structure nondestructive testing technical field, method includes for steel plate-glue interface, inside and glue-concrete interface ultrasonic scanning of glue layer, judge void defect.Steel plate-glue interface uses local bright area identification in multiple echo mode and attenuation rate threshold comparison method, first set No. 1 gate to collect C scan image, there is bright area then local void is quantified, no bright area then calculate attenuation rate to judge overall state;On this basis, inside and glue-concrete interface of glue layer use defect depth positioning method in single echo mode, set No. 2 gate to collect C scan image, according to the position of reflection signal to judge defect type, solve the prior art cannot identify three kinds of defects, cannot realize the depth positioning and quantization of defect, the problem of low detection efficiency and strong subjectivity.

Description

Technical Field

[0001] This invention relates to the field of non-destructive testing technology for concrete bridge structures, and more specifically, to a method and system for detecting bonding defects in bridge steel plates based on dual-mode sequential ultrasonic C-scan. Background Technology

[0002] Steel plate bonding reinforcement technology is a commonly used structural reinforcement method in modern bridge engineering. This method improves the load-bearing capacity and service performance of bridges by bonding steel plates to the surface of concrete bridge structures. The composite structure composed of steel plate-adhesive-concrete has become one of the standard processes for bridge reinforcement.

[0003] In practical engineering applications, as per the instruction manual... Figure 1 As shown, bridge steel plate bonding structures may exhibit three typical bonding defects: the first is a gap between the steel plate and the adhesive layer, or a complete absence of adhesive (no adhesive injection), hereinafter referred to as steel plate-adhesive gap; the second is a cavity defect inherent in the adhesive material itself; and the third is a gap between the adhesive layer and the concrete substrate. These defects significantly reduce the effectiveness of the reinforcement, thus affecting the overall structural safety, therefore requiring effective detection methods.

[0004] Currently, the main methods for detecting bonding defects in steel plates include impact testing, infrared thermography, and conventional ultrasonic testing. Impact testing relies on experience, is highly subjective, and has limited accuracy; infrared thermography is significantly affected by ambient temperature, resulting in unstable test results; conventional ultrasonic testing typically uses single-probe point measurements, leading to low efficiency and limited ability to identify deep defects. Phased array ultrasonic technology, as an advanced non-destructive testing method, has demonstrated imaging advantages and detection efficiency in other industrial fields, but its application in detecting bonding defects in bridge steel plates lacks a specific solution.

[0005] Existing detection technologies have the following main shortcomings: (1) Low testing efficiency and high workload: The traditional tapping method requires a lot of manual operation. For structures with large steel-bonded areas, such as large bridges, the testing workload is huge. Usually, only sampling inspection can be used, which inevitably leads to missed inspections. For important structures, in order to improve the reliability, it is even necessary to have two groups of inspectors conduct the inspection independently and then take the average value, which further increases the labor cost and time consumption.

[0006] (2) High subjectivity and insufficient reliability: The tapping method mainly relies on the subjective experience of the testers to judge the bonding quality. Different operators may draw different conclusions. There is a lack of unified quantitative standards. Especially under the conditions of environmental noise interference, the human ear's ability to distinguish sound is further reduced, and the probability of misjudgment is high.

[0007] (3) Inability to achieve quantitative detection: Most traditional detection methods can only provide qualitative results and cannot accurately measure the size, depth and severity of defects. Although conventional ultrasonic methods can provide some quantitative data, they require a large number of waveform records, data processing is complicated, and the ability to distinguish defect types is limited.

[0008] (4) Single defect identification: Existing technologies lack the ability to jointly identify three types of typical defects (steel plate-adhesive separation, adhesive internal cavity, adhesive-concrete separation). Most methods can only identify a single type of defect and cannot comprehensively assess the overall bonding quality of the bonded steel plate structure. In particular, it is difficult to distinguish the specific type and location of the defect.

[0009] In summary, there is an urgent need in this field for a technical solution that can identify three types of defects, as well as assess the depth, location, and quantitative evaluation of defects, with high detection accuracy and efficiency. Summary of the Invention

[0010] The present invention aims to overcome at least one of the defects of the prior art and provide a method and system for detecting bonding defects in bridge steel plates based on dual-mode sequential ultrasonic C-scanning. This method addresses the problems of existing technologies, such as the inability to identify three types of defects, the inability to achieve depth localization and quantification of defects, low detection efficiency, and high subjectivity.

[0011] The technical solution adopted in this invention is a method for detecting bonding defects in bridge steel plates based on dual-mode sequential ultrasonic C-scan, which includes performing ultrasonic scans on the steel plate-adhesive interface, the interior of the adhesive layer, and the adhesive-concrete interface to determine whether there are void defects.

[0012] Existing technologies lack the ability to jointly identify three typical defects: steel plate-adhesive separation, internal cavity in the adhesive, and adhesive-concrete separation. They can only identify single types of defects and cannot comprehensively assess the overall bonding quality of the bonded steel plate structure, especially in distinguishing the specific type and location of the defect. This invention achieves accurate identification of these three different types of defects, which is beneficial for the timely detection of potential problems and provides a reliable basis for bridge maintenance and repair.

[0013] Furthermore, the identification of void defects at the steel plate-adhesive interface adopts the method of local bright area identification and attenuation rate threshold comparison under multiple echo mode; the identification of void defects inside the adhesive layer and at the adhesive-concrete interface adopts the method of defect depth localization under single echo mode.

[0014] Because different interfaces have different structures and acoustic characteristics, different identification methods can be used to improve the accuracy and reliability of detection. Dual-mode sequential detection means using two modes, namely multi-echo mode and single-echo mode, to detect bridge steel plate bonding defects step by step according to the logical order and conditional dependencies of two scans.

[0015] Furthermore, the method for identifying local bright areas and comparing attenuation rate thresholds specifically includes: A gate is set up for the steel plate-adhesive interface and a first C-scan image is acquired. A C-scan image is generated based on the signal integration energy of the gate and it is determined whether there are abnormal local bright areas in the C-scan image. If so, the coverage area of ​​the local bright area is the local void defect at the steel plate-adhesive interface, and the area of ​​the local bright area is calculated to quantify the local void defect at the steel plate-adhesive interface. If not, extract the amplitude information of the echo and calculate its amplitude attenuation rate R. If the attenuation rate R is lower than or equal to the safety threshold, it is determined that the steel plate-adhesive interface of the whole region is detached, and the area of ​​the entire C-scan region is calculated to quantify the detachment defect of the steel plate-adhesive interface. If the attenuation rate R is greater than the safety threshold, it is determined that the steel plate-adhesive interface of the whole region is well bonded.

[0016] This invention employs a multiple echo method to identify void defects at the steel plate-adhesive interface: In well-bonded areas, most of the acoustic energy can penetrate the steel plate-adhesive interface and propagate to the underlying concrete medium, resulting in rapid attenuation of the multiple echo signals reflected repeatedly within the steel plate; however, in void areas where air is present, the acoustic waves undergo near total reflection at the steel plate-air interface, leading to slow attenuation of the multiple echo signals and very strong energy. By setting a first gate and acquiring C-scan images, the condition of the steel plate-adhesive interface can be directly observed. Identification of local bright areas can quickly locate local void defects, while the calculation of the attenuation rate can determine the overall bonding condition of the area. The first gate is a time gate, preferably used to monitor the fourth echo signal of the inner wall interface of the steel plate, achieving detection within the corresponding depth range of the steel plate-adhesive interface.

[0017] Furthermore, the defect depth localization method specifically includes: If the defect is determined to be a local void at the steel plate-adhesive interface, a second C-scan image acquisition will not be performed on the local void area. If it is determined that the steel plate-adhesive interface of the whole area is well bonded, a second gate is set for the void defects inside the adhesive layer and the adhesive-concrete interface, and a second C-scan image is acquired. The C-scan image is generated based on the maximum amplitude of the signal from the second gate to determine the location of the defect reflection signal. If the defect reflection signal mainly appears in the middle or upper part of the No. 2 gate, it is determined to be a cavity defect inside the adhesive layer. If the defect reflection signal appears at the end position immediately adjacent to the No. 2 gate, it is determined to be a void defect at the adhesive-concrete interface; If there is no defect reflection signal, it is determined that the adhesive layer and the adhesive-concrete interface are well bonded.

[0018] For the first C-scan image, after identifying all steel plate-adhesive delamination defect areas, for areas marked as Type 1 defects, since the acoustic energy has been strongly reflected and cannot effectively propagate to deeper layers, there is no need to analyze the corresponding second C-scan image for that area; the defect conclusion can be directly recorded. For areas determined to be well-bonded overall in the first C-scan image, the second C-scan image data for the corresponding location is retrieved and analyzed. According to the defect determination method described above, it is determined whether there is a cavity defect inside the adhesive layer (Type 2 defect) or a delamination defect at the adhesive-concrete interface (Type 3 defect). Taking the maximum value of the ultrasonic signal inside the adhesive layer and accurately capturing the reflection time of the defect to distinguish between the two different delamination defects is the core feature extraction method of the second C-scan. The second gate is a time gate, preferably used to monitor the adhesive thickness range below the first echo signal (single echo mode) of the adhesive layer range, realizing detection within the corresponding depth range from the upper edge to the lower edge of the adhesive layer.

[0019] Furthermore, the step of generating a C-scan image based on the integrated energy of the signal from gate number one specifically includes: In the multiple echo mode, a time window is taken around the expected arrival time of the 4th echo at each scanning point. The squares of the ultrasound signal amplitude at each moment within the window are accumulated over time to obtain the signal integral energy at that point, which is used as the pixel value of the C-scan image. The image brightness represents the reflected energy within the window.

[0020] The ultrasonic signal in the debonded area will be totally reflected, and the total energy of multiple echoes will be much greater than that of the bonded area. By summing up all the ultrasonic signals within the fourth echo time window and converting them into image brightness, the bright area of ​​the local debonded area at the steel plate-adhesive interface becomes more obvious. Energy integration can more stably highlight the energy differences under different states, avoid the random errors of a single signal, and facilitate intuitive identification.

[0021] Furthermore, the calculation of the attenuation rate R of its amplitude specifically includes: Extract the amplitude information of the 3rd and 4th echoes from the same location, and apply the attenuation rate formula:

[0022] In the formula: A3 represents the amplitude value of the third steel plate interface echo, and A4 represents the amplitude value of the fourth steel plate interface echo; the calculated actual attenuation rate is compared with the safety threshold to determine the overall state of the steel plate-adhesive interface, and the safety threshold is set to 30%.

[0023] By comparing the actual attenuation rate with the safety threshold, the overall bonding condition of the steel plate-adhesive interface can be accurately determined.

[0024] Furthermore, the step of generating a C-scan image based on the maximum amplitude of the signal from gate number two specifically includes: During the second C-scan image acquisition, in single-echo mode, within the time window [t] of the second gate corresponding to the adhesive layer a ,t b Within the [input], the maximum amplitude of the ultrasonic signal at each scanning point is taken as the pixel value. By analyzing the arrival time corresponding to the extreme values ​​of the original signal amplitude, it is possible to distinguish whether the defect is inside the adhesive layer or at the adhesive-concrete interface.

[0025] If the signal integration energy calculation method is used, signals from different times will be mixed together, making it impossible to determine the specific depth and location of the defect. Because the ultrasound at the defect will be strongly reflected, the signal intensity will be much greater than that at the normal bonding area. Taking the maximum value will make the brightness of the defect more prominent and not be masked by the weak signal. Using the maximum amplitude value can accurately capture the time of ultrasound reflection from the defect, thereby determining whether the defect is inside the adhesive layer or at the adhesive-concrete interface. Then, by using the occurrence time of the maximum amplitude signal, the location of the delamination defect can be determined.

[0026] Furthermore, the time window [t] a ,t b The steps to determine [ ] are as follows: t a Determined based on the echo signal of the steel plate-adhesive interface at the actual location; t b The steps for determining the thickness are as follows: If the adhesive layer thickness is fixed, then based on the nominal thickness d of the adhesive layer and the propagation speed v of the sound wave in the adhesive layer, calculate the propagation time d / v, t, required for the sound wave to pass through the entire adhesive layer. b =t a +d / v; If the adhesive layer thickness is uncertain, after the first C-scan image analysis, from the points determined to be well-bonded, further select A-scan signals with high signal-to-noise ratio and clear adhesive-concrete interface echoes, calculate the arrival time of the adhesive-concrete interface echoes, and obtain t after statistical processing. b .

[0027] The t a t represents the time it takes for the ultrasound to travel from the steel plate to the adhesive interface. b The time it takes for ultrasound to travel from the steel plate to the concrete interface, i.e., the time window [t]. a ,t b The ultrasonic signal corresponds to the adhesive layer. The value of t is determined based on the adhesive layer thickness and the sound wave propagation speed. b This ensures that signals are acquired within the appropriate time frame, improving the accuracy of detection.

[0028] Another objective of this invention is to provide a bridge steel plate bonding defect detection system based on dual-mode sequential ultrasonic C-scan, comprising: A phased array ultrasonic wheel probe unit is used to transmit ultrasonic waves and receive echo signals; The position encoding and motion control unit is connected to the phased array ultrasonic wheel probe unit to ensure accurate synchronization of scanning position information; The phased array ultrasound host and data acquisition unit are connected to and control the position encoding and motion control unit, which is used to excite the probe, receive the raw signal and perform preliminary processing. A computer and a dedicated analysis unit are connected to the phased array ultrasonic host and data acquisition unit to analyze and calculate the raw signal after preliminary processing. The above-mentioned method for detecting bonding defects in bridge steel plates based on dual-mode sequential ultrasonic C-scan is used to process the analysis data and output the results of the void defect judgment.

[0029] Furthermore, the computer and dedicated analysis unit specifically include: The system control and acquisition module is used to set scanning parameters, receive encoder signals, and control synchronous data acquisition. The dual C-scan image generation module is connected to the system control and acquisition module, and uses the acquired data to realize the real-time generation of the first C-scan image and the second C-scan image; The intelligent discrimination and analysis module is connected to the dual C-scan image generation module. It uses the collected data and dual C-scan images to realize the local bright area identification and attenuation rate threshold comparison method and defect depth localization method, as well as the dual-mode sequential ultrasound C-scan joint discrimination logic. The visualization module, connected to the intelligent discrimination and analysis module, is used to display A-scan, B-scan, and C-scan images in real time and highlight the three types of defects.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects: 1. Comprehensive Detection Capability: For the first time, it achieves comprehensive detection of all types of void defects in three-layer bonded steel plate structures, overcoming the limitations of traditional methods that can only detect single types of defects. It has a unique advantage in detecting defects such as internal cavities in the adhesive, which are difficult to identify using traditional methods.

[0031] 2. High detection accuracy and quantitative assessment: Through a dual-mode sequential ultrasonic C-scan image joint analysis mechanism, this invention can distinguish three different types of void defects, solving the problem of insufficient identification capability of traditional methods for multi-layer structure defects. Especially for the detection of voids at the steel plate-adhesive interface, the quantitative assessment of the defect can be achieved by utilizing the energy attenuation characteristics of multiple echoes.

[0032] 3. Strong objectivity and reduced influence of human factors: This invention employs standardized signal processing, eliminating the reliance on human experience in the tapping method, resulting in more objective and reliable results. The joint discrimination logic effectively avoids misjudgment of defects, improving the credibility of the detection results.

[0033] 4. Significantly Improved Detection Efficiency: The electronic scanning characteristics of phased array technology, combined with intelligent discrimination logic, enable rapid detection over large areas. A single scan provides comprehensive defect information, far surpassing the efficiency of point-by-point detection required by the tapping method. Furthermore, it eliminates the cumbersome pre-calibration process of traditional quantitative detection, achieving rapid and reliable detection "without a reference" by extracting the relative characteristics (attenuation rate) of the signal itself.

[0034] 5. Excellent economic efficiency: Identification of all three types of defects can be completed in a single inspection, reducing the cost of repeated inspections. Early detection of void defects can prevent more serious structural damage, significantly extend the service life of bridges, and has significant economic and social benefits.

[0035] This invention effectively solves the problems of low efficiency, strong subjectivity, and inability to quantify traditional detection methods by using an innovative dual-mode sequential ultrasonic C-scan image joint discrimination mechanism, providing a comprehensive, accurate, and efficient solution for detecting bonding defects in bridge steel plates. Attached Figure Description

[0036] Figure 1 A schematic diagram illustrating the types of defects caused by the detachment of steel plates bonded to bridges.

[0037] Figure 2 This is a flowchart of the joint discrimination of dual-mode sequential ultrasound C-scan images in Embodiment 1 of the present invention.

[0038] Figure 3 This is a schematic diagram of the gate configuration of the present invention.

[0039] Figure 4 The first C-scan image when there is a local void at the steel plate-adhesive interface.

[0040] Figure 5 This shows the actual situation of partial delamination at the steel plate-adhesive interface.

[0041] Figure 6 This is a schematic diagram of Embodiment 2 of the present invention. Detailed Implementation

[0042] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the invention. To better illustrate the following embodiments, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions; it is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1 like Figure 1 As shown, this embodiment presents a method for detecting bonding defects in bridge steel plates based on dual-mode sequential ultrasonic C-scan. It employs a dual-mode sequential ultrasonic C-scan image joint discrimination mechanism, utilizing a linear array wheel probe to acquire data through linear scanning, achieving accurate identification and classification of three typical void defects in the three-layer structure of steel plate-adhesive layer-concrete. This method eliminates the need for complex pre-calibration procedures, achieving rapid defect identification by analyzing the characteristics of specific echo signals.

[0045] The physical basis of this method is that sound waves have drastically different reflection characteristics at the solid-gas interface and the solid-well bonded adhesive layer interface. Table 1 shows the acoustic impedance and interfacial acoustic pressure reflectivity of steel plate, adhesive, concrete, and air. For a single echo of the steel plate, the reflectivity of steel-adhesive and steel-air is not significantly different, making it difficult to determine defects. This invention uses a multiple echo method to identify void defects at the steel plate-adhesive interface: In well-bonded areas, most of the sound wave energy can penetrate the steel plate-adhesive interface and propagate to the underlying concrete medium, resulting in rapid attenuation of the multiple echo signal energy reflected repeatedly within the steel plate; however, in void areas (where air is present), the sound wave undergoes near total reflection at the steel plate-air interface, resulting in slow attenuation of the multiple echo signal energy, which is very strong.

[0046] Table 1. Acoustic impedance and interfacial acoustic pressure reflectivity of steel plate, adhesive, concrete, and air

[0047] like Figure 2 As shown, the joint discrimination mechanism of dual-mode sequential ultrasound C-scan images specifically includes the following steps: A gate is set up for the steel plate-adhesive interface and a first C-scan image is acquired. A C-scan image is generated based on the signal integration energy of the gate and it is determined whether there are abnormal local bright areas in the C-scan image. If so, the coverage area of ​​the local bright area is the local void defect at the steel plate-adhesive interface, and the area of ​​the local bright area is calculated to quantify the local void defect at the steel plate-adhesive interface. If not, extract the amplitude information of the echo and calculate its amplitude attenuation rate R. If the attenuation rate R is lower than or equal to the safety threshold, it is determined that the steel plate-adhesive interface of the whole region is detached, and the area of ​​the entire C-scan region is calculated to quantify the detachment defect of the steel plate-adhesive interface. If the attenuation rate R is greater than the safety threshold, it is determined that the steel plate-adhesive interface of the whole region is well bonded.

[0048] If the defect is determined to be a local void at the steel plate-adhesive interface, a second C-scan image acquisition will not be performed on the local void area. If it is determined that the steel plate-adhesive interface of the whole area is well bonded, a second gate is set for the void defects inside the adhesive layer and the adhesive-concrete interface, and a second C-scan image is acquired. The C-scan image is generated based on the maximum amplitude of the signal from the second gate to determine the location of the defect reflection signal. If the defect reflection signal mainly appears in the middle or upper part of the No. 2 gate, it is determined to be a cavity defect inside the adhesive layer. If the defect reflection signal appears at the end position immediately adjacent to the No. 2 gate, it is determined to be a void defect at the adhesive-concrete interface; If there is no defect reflection signal, it is determined that the adhesive layer and the adhesive-concrete interface are well bonded.

[0049] The specific operating procedure is as follows: Firstly, for the steel plate-adhesive interface, the first C-scan image acquisition and analysis was performed in multi-echo mode, and the phased array instrument parameters were adjusted, such as... Figure 3 As shown, the fourth echo signal of the inner wall interface of the monitoring steel plate of gate No. 1 is set. The signal integration energy within the set multiple echo time window at each scanning point is mapped onto a two-dimensional plane to generate the C-scan image corresponding to gate No. 1.

[0050] The integral energy E of the signal extracted from the corresponding gate for the pixel value G1(x, y) in the first C scan:

[0051] Where t4 is the expected arrival time of the 4th echo, Δt is a small time window, and I(x, y, t) represents the amplitude of the final ultrasonic signal received at time t at the spatial location point corresponding to the horizontal coordinate (x, y) of the detection surface after beamforming by the phased array system. The image brightness directly reflects the reflected energy within this time window.

[0052] A preliminary judgment is made by identifying whether there are abnormal local bright areas in the image. If such local bright areas exist, such as... Figure 4 As shown, this indicates that the sound wave energy in the corresponding area is strongly reflected, and it can be directly determined that the area covered by the bright area is a local void defect at the steel plate-adhesive interface. Figure 5As shown, the defect can be quantified by calculating the area of ​​this bright area.

[0053] If no significant local bright areas are found, a more refined overall interface condition assessment is required to distinguish between overall voids and good overall adhesion. At this point, the amplitude information of the 3rd and 4th echoes from the same location is extracted simultaneously, and their amplitude attenuation rate is calculated. The attenuation rate is calculated using the following formula:

[0054] Where R is the attenuation rate, A3 represents the amplitude value of the third steel plate interface echo, and A4 represents the amplitude value of the fourth steel plate interface echo.

[0055] The attenuation rate R is a key physical indicator: in well-bonded areas, acoustic energy can be effectively transmitted to the underlying medium, resulting in rapid attenuation of multiple echoes reflected back and forth within the steel plate, manifested as a high amplitude attenuation rate. Conversely, if there are voids at the interface, most of the acoustic energy is reflected back, resulting in slow attenuation of multiple echoes and a significantly lower amplitude attenuation rate R. By comparing the calculated actual amplitude attenuation rate with a preset threshold (30%), the overall interface condition can be determined. If the attenuation rate R ≤ 30%, it indicates low energy leakage, and the entire steel plate-adhesive interface is identified as having voids; calculating the area of ​​the entire C-scan region quantifies the defect. If the attenuation rate R > 30%, the entire steel plate-adhesive interface is considered well-bonded.

[0056] This method uses the relative change (attenuation rate) of the echo signal itself for judgment, without the need for comparison with an external calibration benchmark.

[0057] After the first C-scan is completed, if it is determined that the overall bonding of the steel plate-adhesive interface is good, a second C-scan is carried out to identify cavities and defects inside the adhesive material and the interface between the adhesive layer and the concrete base layer.

[0058] Adjust the phased array instrument parameters. In single-echo mode, set the adhesive thickness range below the first echo signal for the adhesive layer monitored by gate 2. Figure 3 As shown, a C-scan image corresponding to gate number two is generated. This image only displays the signal strength extracted within the time gate of the adhesive layer set above.

[0059] The principle is that when sound waves propagate in the adhesive layer, they encounter internal cavities or the interface between the adhesive and concrete (i.e., where air is present), resulting in strong reflected echoes due to the drastic change in acoustic impedance. Table 1 shows a significant difference in the acoustic pressure reflectivity at the adhesive-concrete and adhesive-air interfaces. Combined with the depth information of the adhesive layer echo, this can effectively distinguish between different types of voids.

[0060] The pixel value G2(x, y) of the second C scan is extracted from the maximum amplitude of the signal within the depth range of the "adhesive layer": G2(x,y)=F{I(x,y,t)} , t∈t a ,t b Where F{} is the feature extraction function, which calculates the maximum amplitude of the signal within the time window, t a and t b These represent the time it takes for the acoustic signal to reach the steel-adhesive interface and the adhesive-concrete interface, respectively, and also reflect the range of the gate.

[0061] t a The value of t can be determined based on the echo signal at the steel-adhesive interface at the actual location. b The determination method is as follows: (a) If the adhesive layer thickness is determined, then the propagation time d / v, t required for the sound wave to pass through the entire adhesive layer is calculated based on the nominal thickness (d) of the adhesive layer and the propagation speed (v) of the sound wave in the adhesive. b =t a +d / v.

[0062] (b) If the adhesive layer thickness is uncertain, after the first C-scan analysis, at the point i where the bond is determined to be good, an A-scan signal with a high signal-to-noise ratio and clear adhesive-concrete interface echo is further selected, and the arrival time t of the adhesive-concrete interface echo is calculated. bi Then, statistical processing (such as taking the median or mean) is performed to obtain a global t. b .

[0063] Unlike the first C-scan which uses energy integration, the second C-scan uses a feature extraction function F{} applied to the original amplitude signal I(x, y, t) after beamforming, taking its maximum absolute value max{|I(x, y, t)|} within the gate time. This design is based on the different detection physical mechanisms of the two: the first C-scan aims to evaluate the cumulative energy characteristics of multiple echoes within the steel plate, where energy integration most stably highlights the differences; while the second C-scan aims to accurately locate the depth of the discrete defect reflection interface within the adhesive layer, and directly analyzing the amplitude extrema of the original signal most accurately captures the arrival time t of the reflected pulse. max This allows for reliable differentiation of defects located within the adhesive layer (t). a <t max <t b ) or glue-concrete interface (t max ≈t b ): In well-bonded areas, sound waves pass smoothly through the adhesive layer and into the concrete. The reflected signal inside the gate is weak, and the image appears dark. When defects exist, the signal strength inside the gate is significantly enhanced, and the corresponding position in the image appears bright.

[0064] When strong defect reflection signals mainly appear in the middle or upper part of the gate, that is, corresponding to the inside of the adhesive layer, it is determined to be an internal cavity defect of the adhesive layer (Type II defect).

[0065] When a strong defect reflection signal is close to the end position of the gate, that is, at the interface between the adhesive layer and the concrete, it is determined to be an adhesive-concrete interface delamination defect (Type III defect).

[0066] Example 2 like Figure 6 As shown, this embodiment is a bridge steel plate bonding defect detection system based on dual-mode sequential ultrasonic C-scan, specifically including: (1) Phased array ultrasonic wheel probe unit, which is the core data acquisition unit of the system, responsible for transmitting ultrasonic waves and receiving echo signals, specifically including: Linear array transducer: Encapsulated inside the probe, it consists of multiple (no less than 32) independent piezoelectric crystals arranged linearly, with a preferred center frequency of 5MHz to balance detection resolution and penetration capability in steel plates; Flexible fluid-filled tire and coupling module: The array chip is sealed in a flexible rubber tire filled with coupling fluid (such as water or special gel). This design allows the probe to fit tightly and roll stably on the uneven surface of the bridge's bonded steel plate, achieving continuous and uniform acoustic coupling, which is the key to ensuring long-distance, high-quality data acquisition. The scanning mode employs linear scanning. In this mode, the probe is fixed in a specific position, and a set of crystals is electronically excited sequentially to generate a sound beam at a specific angle (typically 0° or a small-angle longitudinal wave). Then, electronic control causes the excited crystal set to move linearly along the array direction, allowing the sound beam to electronically scan a certain width area under the steel plate without probe movement. Finally, through the combination of the probe's physical rolling (mechanical scanning) and internal electronic scanning, a two-dimensional data volume covering the entire detection area is rapidly acquired, generating a projected C-scan image.

[0067] For detecting voids in bridge steel plates, the C-scan image is a top view along the detection surface (xy plane), and the gray value G(x, y) of each pixel (x, y) is determined by the acoustic characteristics of the corresponding spatial location (x, y, z).

[0068] Probe housing and connector: Provides mechanical protection and includes a high-frequency coaxial cable interface for connection to the ultrasound unit.

[0069] (2) Position encoding and motion control unit, used to ensure precise synchronization of scanning position information, is the basis for generating C-scan images with accurate spatial coordinates, specifically including: High-precision encoder: It is directly mechanically connected to the wheel axle or driven wheel of the wheel probe. When the probe rolls, the encoder generates pulse signals in real time. Each pulse corresponds to a fixed travel distance. This pulse signal serves as the reference for triggering data acquisition and marking the scanning position (x, y), realizing the precise digitization of the scanning path. Optional mechanical scanning frame: For scenarios requiring extremely high repeatability or large-scale automated inspection, wheeled probes can be mounted on an electric scanning frame, driven by a motor to move at a constant speed along a preset path, with the encoder integrated into the scanning frame motor.

[0070] (3) Phased array ultrasound host and data acquisition unit, used to excite the probe, receive the raw signal and perform preliminary processing, specifically including: Pulse transmitting / receiving circuit: generates high-voltage electric pulses to excite the probe chip to emit ultrasonic waves and receives weak echo voltage signals with high sensitivity; Multi-channel digital delay and beam combiner: This is the core hardware of phased array technology. According to the preset focusing law, it applies nanosecond-level precision electronic delay to the transmitted and received signals of each channel, completes beam combining in real time, and outputs the focused A-scan signal sequence I(x, y, t). High-speed data acquisition card: Digitizes and stores analog ultrasound signals at high speed and high resolution.

[0071] (4) Computer and dedicated analysis unit: The bridge steel plate bonding defect detection method based on dual-mode sequential ultrasonic C-scanning as described in Example 1 is used to process the analysis data and output the results of the void defect judgment. This unit realizes the entire process of control, processing, analysis and result output, specifically including: Main control computer: runs dedicated analysis software to control the parameter settings, scanning process, and data flow of the entire system; The dedicated analysis software includes the following four main modules: System control and acquisition module: sets scanning parameters (gain, pulse repetition frequency, scanning mode), receives encoder signals, and controls synchronous data acquisition; Dual C-scan image generation module: The algorithm realizes the real-time generation of images of the first C-scan (multiple echo energy integration) and the second C-scan (adaptive gate signal feature extraction); Intelligent discrimination and analysis module: This is the software implementation of the method's logic, used to implement the local bright area identification and attenuation rate threshold comparison method and the defect depth localization method. It includes: the "local bright area identification" and "amplitude attenuation rate (R) calculation and threshold comparison" algorithms for the first C-scan; and the "adaptive reference t" algorithm for the second C-scan.b Automatic extraction algorithm and defect depth localization algorithm; state machine of dual-mode sequential ultrasonic C-scan joint discrimination logic.

[0072] Visualization module: Displays A-scan, B-scan, and C-scan images in real time, highlighting the three types of defects.

[0073] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A method for detecting bonding defects in bridge steel plates based on dual-mode sequential ultrasonic C-scanning, characterized in that, In both modes, ultrasonic scanning was performed on the steel plate-adhesive interface, the interior of the adhesive layer, and the adhesive-concrete interface to determine whether there were void defects. The identification of void defects at the steel plate-adhesive interface adopts the method of local bright area identification and attenuation rate threshold comparison under multiple echo mode; the identification of void defects inside the adhesive layer and at the adhesive-concrete interface adopts the method of defect depth localization under single echo mode. The method for identifying local bright areas and comparing attenuation rate thresholds specifically includes: A gate is set up for the steel plate-adhesive interface and a first C-scan image is acquired. A C-scan image is generated based on the signal integration energy of the gate and it is determined whether there are abnormal local bright areas in the C-scan image. If so, the coverage area of ​​the local bright area is the local void defect at the steel plate-adhesive interface, and the area of ​​the local bright area is calculated to quantify the local void defect at the steel plate-adhesive interface. If not, extract the amplitude information of the echo and calculate its amplitude attenuation rate R. If the attenuation rate R is lower than or equal to the safety threshold, it is determined that the steel plate-adhesive interface of the whole region is detached, and the area of ​​the entire C-scan region is calculated to quantify the detachment defect of the steel plate-adhesive interface. If the attenuation rate R is greater than the safety threshold, it is determined that the steel plate-adhesive interface of the whole region is well bonded.

2. The method for detecting bonding defects in bridge steel plates based on dual-mode sequential ultrasonic C-scanning according to claim 1, characterized in that, The defect depth localization method specifically includes: If the defect is determined to be a local void at the steel plate-adhesive interface, a second C-scan image acquisition will not be performed on the local void area. If it is determined that the steel plate-adhesive interface of the whole area is well bonded, a second gate is set for the void defects inside the adhesive layer and the adhesive-concrete interface, and a second C-scan image is acquired. The C-scan image is generated based on the maximum amplitude of the signal from the second gate to determine the location of the defect reflection signal. If the defect reflection signal mainly appears in the middle or upper part of the No. 2 gate, it is determined to be a cavity defect inside the adhesive layer. If the defect reflection signal appears at the end position immediately adjacent to the No. 2 gate, it is determined to be a void defect at the adhesive-concrete interface; If there is no defect reflection signal, it is determined that the adhesive layer and the adhesive-concrete interface are well bonded.

3. The method for detecting bonding defects in bridge steel plates based on dual-mode sequential ultrasonic C-scanning according to claim 1, characterized in that, The process of generating a C-scan image based on the integrated energy of the signal from gate number one specifically includes: In the multiple echo mode, a time window is taken around the expected arrival time of the 4th echo at each scanning point. The squares of the ultrasound signal amplitude at each moment within the window are accumulated over time to obtain the signal integral energy at that point, which is used as the pixel value of the C-scan image. The image brightness represents the reflected energy within the window.

4. The method for detecting bonding defects in bridge steel plates based on dual-mode sequential ultrasonic C-scanning according to claim 1, characterized in that, The calculation of the attenuation rate R of its amplitude specifically includes: Extract the amplitude information of the 3rd and 4th echoes from the same location, and apply the attenuation rate formula: In the formula: A3 represents the amplitude value of the third steel plate interface echo, and A4 represents the amplitude value of the fourth steel plate interface echo; the calculated actual attenuation rate is compared with the safety threshold to determine the overall state of the steel plate-adhesive interface, and the safety threshold is set to 30%.

5. The method for detecting bonding defects in bridge steel plates based on dual-mode sequential ultrasonic C-scanning according to claim 2, characterized in that, The process of generating a C-scan image based on the maximum amplitude of the signal from gate number two specifically includes: During the second C-scan image acquisition, in single-echo mode, within the time window [t] of the second gate corresponding to the adhesive layer a ,t b Within the [input], the maximum amplitude of the ultrasonic signal at each scanning point is taken as the pixel value. By analyzing the arrival time corresponding to the extreme values ​​of the original signal amplitude, it is possible to distinguish whether the defect is inside the adhesive layer or at the adhesive-concrete interface.

6. The method for detecting bonding defects in bridge steel plates based on dual-mode sequential ultrasonic C-scanning according to claim 5, characterized in that, The time window [t] a ,t b The steps to determine [ ] are as follows: t a Determined based on the echo signal of the steel plate-adhesive interface at the actual location; t b The steps for determining the thickness are as follows: If the adhesive layer thickness is fixed, then based on the nominal thickness d of the adhesive layer and the propagation speed v of the sound wave in the adhesive layer, calculate the propagation time d / v, t, required for the sound wave to pass through the entire adhesive layer. b =t a +d / v; If the adhesive layer thickness is uncertain, after the first C-scan image analysis, from the points determined to be well-bonded, further select A-scan signals with high signal-to-noise ratio and clear adhesive-concrete interface echoes, calculate the arrival time of the adhesive-concrete interface echoes, and obtain t after statistical processing. b .

7. A bridge steel plate bonding defect detection system based on dual-mode sequential ultrasonic C-scan, characterized in that, include: A phased array ultrasonic wheel probe unit is used to transmit ultrasonic waves and receive echo signals; The position encoding and motion control unit is connected to the phased array ultrasonic wheel probe unit to ensure accurate synchronization of scanning position information; The phased array ultrasound host and data acquisition unit are connected to and control the position encoding and motion control unit, which is used to excite the probe, receive the raw signal and perform preliminary processing. A computer and a dedicated analysis unit are connected to the phased array ultrasonic host and data acquisition unit to analyze and calculate the raw signal after preliminary processing. The bridge steel plate bonding defect detection method based on dual-mode sequential ultrasonic C-scan as described in any one of claims 1-6 is used to process the analysis data and output the results of the void defect judgment.

8. The bridge steel plate bonding defect detection system based on dual-mode sequential ultrasonic C-scanning according to claim 7, characterized in that, The computer and dedicated analysis unit specifically include: The system control and acquisition module is used to set scanning parameters, receive encoder signals, and control synchronous data acquisition. The dual C-scan image generation module is connected to the system control and acquisition module, and uses the acquired data to realize the real-time generation of the first C-scan image and the second C-scan image; The intelligent discrimination and analysis module is connected to the dual C-scan image generation module. It uses the collected data and dual C-scan images to realize the local bright area identification and attenuation rate threshold comparison method and defect depth localization method, as well as the dual-mode sequential ultrasound C-scan joint discrimination logic. The visualization module, connected to the intelligent discrimination and analysis module, is used to display A-scan, B-scan, and C-scan images in real time and highlight the three types of defects.

Images