Steel bar corrosion damage assessment method and system based on ultrasonic tomography

Abstract

The invention relates to the technical field of steel bar corrosion damage identification, in particular to a steel bar corrosion damage evaluation method and system based on ultrasonic tomography, and the method comprises the steps: installing a plurality of ultrasonic probes at the two opposite sides of a reinforced concrete region respectively, determining travel time and signal amplitude when each ultrasonic probe of the receiving end receives the ultrasonic signal transmitted by the transmitting end during each detection; determining an ultrasonic space-time coefficient of the reinforced concrete area; the reinforced concrete area is equally divided into imaging units based on the number of the installed ultrasonic probes; determining the weight of each imaging unit; and on the basis of weight calculation in the weight correction SIRT algorithm of each imaging unit, ultrasonic tomography is performed on the ultrasonic signal transmitted by the current detection, a sound velocity distribution image of the reinforced concrete area is obtained, and the corrosion damage area of the reinforcing steel bar is identified. Therefore, the accuracy of steel bar corrosion damage evaluation is improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of steel bar corrosion damage identification, in particular to a steel bar corrosion damage evaluation method and system based on ultrasonic tomography. BACKGROUND

[0002] As the main load-bearing system in modern civil engineering, reinforced concrete structures are widely used in various major infrastructures. With the extension of the service life of the infrastructures, and the long-term exposure to complex environmental factors such as chloride salt erosion and freeze-thaw, steel bar corrosion has become the main disease affecting the durability and safety of concrete structures. Therefore, early identification, accurate positioning and quantitative evaluation of steel bar corrosion damage are the key to ensuring the long-term safety of the structure. Among the numerous non-destructive testing techniques for reinforced concrete detection, ultrasonic tomography has become an important means for concrete defect detection due to its non-destructive, strong penetration, and ability to realize internal structure two-dimensional or three-dimensional visualization.

[0003] SIRT (Simultaneous Iterative Reconstruction Technique) algorithm is a common iterative reconstruction algorithm, which is widely used in ultrasonic tomography, CT imaging and other fields. In the SIRT algorithm, weight calculation is a crucial step, which directly affects the quality and calculation efficiency of the reconstructed image. However, in the SIRT algorithm, the balance of weight distribution is often difficult to guarantee, and unreasonable weight distribution may occur, which may lead to low image reconstruction accuracy in local areas or important information being ignored, resulting in low image quality in ultrasonic tomography, affecting the identification sensitivity and detection accuracy of steel bar corrosion damage. SUMMARY

[0004] In order to solve the above technical problems, the purpose of the present application is to provide a steel bar corrosion damage evaluation method and system based on ultrasonic tomography, and the technical solution adopted is as follows: In the first aspect, the application embodiments provide a steel bar corrosion damage evaluation method based on ultrasonic tomography, which comprises the following steps: A plurality of ultrasonic probes are installed on the opposite sides of the reinforced concrete area, and the two sides are the emission end and the receiving end of the ultrasonic signal respectively; the travel time and signal amplitude of the ultrasonic signal emitted by the emission end and received by each ultrasonic probe of the receiving end during each detection are determined; The difference in travel time and the difference in signal amplitude of the same pair of ultrasonic probes during adjacent two detections, the time length of the reflection signal received by the ultrasonic probe of the emission end, and the abnormal position determined by the reflection signal are used to determine the ultrasonic space-time coefficient of the reinforced concrete area; The reinforced concrete region is evenly divided into imaging units based on the number of installed ultrasonic probes; for each ray path of the current detection ultrasonic signal transmission through each imaging unit, the monotonicity of the travel time and the signal amplitude of the two ultrasonic probes in the historical detection process, and the volatility of the travel time and the signal amplitude are analyzed, and the weight of each imaging unit is determined in combination with the ultrasonic space-time coefficient; Based on the weight of each imaging unit, the weight calculation in the SIRT algorithm is corrected, and the ultrasonic tomography of the ultrasonic signal emitted in the current detection is performed to obtain the sound velocity distribution image of the reinforced concrete region, and the reinforced concrete corrosion damage area is identified.

[0005] In one embodiment, each ultrasonic probe of the transmitting end transmits ultrasonic signals in sequence according to the position order, and all ultrasonic probes of the transmitting end transmit ultrasonic signals once as a detection.

[0006] In one embodiment, the determination of the ultrasonic space-time coefficient of the reinforced concrete region comprises: The travel time of the transmitted signal received by the jth ultrasonic probe when the ith ultrasonic probe emits ultrasonic signals in the nth detection is determined as the first travel time, and the travel time of the transmitted signal received by the jth ultrasonic probe when the ith ultrasonic probe emits ultrasonic signals in the n+1th detection is determined as the second travel time; Based on the difference between the second travel time and the first travel time of all adjacent detections, the propagation time variation measure between the ith ultrasonic probe and the jth ultrasonic probe is determined; Correspondingly, based on the difference between the signal amplitudes of all adjacent detections, the signal intensity variation measure between the ith ultrasonic probe and the jth ultrasonic probe is determined; In combination with the shortest distance between the abnormal position and the steel bar position, the ultrasonic space-time coefficient is determined.

[0007] In one embodiment, the propagation time variation measure is the average of the difference between the second travel time and the first travel time of all adjacent detections.

[0008] In one embodiment, the further determination of the ultrasonic space-time coefficient comprises: The shortest distance is taken as the exponent of the exponential function with a natural constant as the base, and the ratio of the calculation result of the exponential function to the travel time of the reflected signal received after the ith ultrasonic probe emits ultrasonic signals in the current detection is determined; The ultrasonic space-time coefficient is positively correlated with the propagation time variation measure, the signal intensity variation measure between all ultrasonic probes, and the ratio of all ultrasonic probes of the transmitting end.

[0009] In one embodiment, the determining the weight of each imaging unit comprises: For the rth ray path passing through the mth imaging unit during the current detection of the ultrasonic signal transmission, a difference between the travel time of the two ultrasonic probes corresponding to the rth ray path between each detection and its previous detection in history is calculated, denoted as a first difference, and the maximum value of the proportion of non-negative numbers and the proportion of non-positive numbers in the first difference of all adjacent detections is determined; Correspondingly, a difference between the signal amplitude of the two ultrasonic probes corresponding to the rth ray path between each detection and its previous detection in history is calculated, denoted as a second difference, and the maximum value of the proportion of non-negative numbers and the proportion of non-positive numbers in the second difference of all adjacent detections is determined; The fusion result of the dispersion degree of the travel time and the dispersion degree of the signal amplitude of the two ultrasonic probes corresponding to the rth ray path in all detections in history is calculated; The sum of the two maximum values is multiplied by the fusion result, and the weight of the mth imaging unit is positively related to the multiplication result of all ray paths of the mth imaging unit and the ultrasonic space-time coefficient, and is negatively related to the number of ray paths passing through the mth imaging unit.

[0010] In one embodiment, the further determination of the weight of the mth imaging unit comprises: The accumulation sum of the multiplication results of all ray paths passing through the mth imaging unit during the current detection of the ultrasonic signal transmission is calculated, the ratio of the exponential mapping result of the ultrasonic space-time coefficient to the number is determined, and the product of the accumulation sum is calculated; The weight of the mth imaging unit is the proportion of the product of the mth imaging unit in all imaging units in the reinforced concrete region.

[0011] In one embodiment, the correcting the weight calculation in the SIRT algorithm based on the weight of each imaging unit comprises: replacing the weight in the SIRT algorithm with the weight of each imaging unit.

[0012] In one embodiment, the identifying the steel corrosion damage region comprises: A segmentation threshold of the gray value of all pixel points in the sound velocity distribution image is determined, and the region with a gray value less than the segmentation threshold is taken as the steel corrosion damage region.

[0013] In a second aspect, the embodiments of the present application also provide a steel corrosion damage evaluation system based on ultrasonic tomography, which comprises a memory, a processor, and a computer program stored in the memory and running on the processor, and the processor implements the steps of the method in any of the above embodiments when executing the computer program.

[0014] The application has at least the following beneficial effects: The application can effectively reduce the detection dead angle or information loss caused by unreasonable probe arrangement by installing multiple ultrasonic probes on the opposite sides of the reinforced concrete area. During each detection, the early changes of the steel bar corrosion damage can be accurately captured by the changes of the signal travel time and amplitude received by the receiving end ultrasonic probe. By comparing the travel time difference and signal amplitude change of the adjacent two detections, the accuracy of the steel bar corrosion detection result can be improved according to the change relationship of the travel time and signal amplitude in the historical multiple detections. Secondly, the reflection characteristics of the ultrasonic signal can reveal the structural changes inside the reinforced concrete. Combined with the abnormal position obtained according to the length of the reflection signal, the damage position can be accurately determined. Not only the obvious corrosion area can be identified, but also the potential small corrosion or early corrosion can be found. Especially for the area where the early damage is not obvious, the problem of missed positioning of corrosion damage caused by traditional detection methods can be effectively avoided. Further, by analyzing the monotonicity and fluctuation of the travel time and signal amplitude of the ultrasonic probe corresponding to the ray path in the historical detection, the change law of the steel bar corrosion with time is verified, which is helpful to the accuracy of the subsequent determination of the weight of the pixel, avoids the decline of the image quality caused by the signal fluctuation, and ensures to obtain more stable and accurate detection results. Finally, the weight calculation in the SIRT algorithm is corrected based on the weight of the pixel, so that the ultrasonic tomography can better present the sound velocity distribution image of the reinforced concrete area. In the imaging process, considering the weight of each imaging unit, the details of each area in the image can be ensured to be clearer, especially in the damage area, the subtle changes can be accurately captured. In addition, the resolution of the imaging image is improved, so that the small traces and local structural changes of the steel bar corrosion are easier to be detected, thereby improving the imaging accuracy of the ultrasonic tomography and the positioning ability of the steel bar corrosion damage, and improving the recognition sensitivity and detection accuracy of the steel bar corrosion damage. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creating any creative labor.

[0016] Figure 1 The step flow chart of the steel bar corrosion damage evaluation method based on ultrasonic tomography provided by an embodiment of the present application is shown in the figure. Figure 2 The weight determination flow chart of the pixel in the reinforced concrete area to be detected is shown in the figure. DETAILED DESCRIPTION

[0017] To further illustrate the technical means and effects adopted by this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of the steel reinforcement corrosion damage assessment method and system based on ultrasonic tomography proposed in this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0019] The following description, in conjunction with the accompanying drawings, details the specific scheme of the steel reinforcement corrosion damage assessment method and system based on ultrasonic tomography provided in this application.

[0020] Please see Figure 1 The diagram illustrates a flowchart of a method for assessing steel corrosion damage based on ultrasonic tomography, according to an embodiment of this application. The method includes the following steps: S1, multiple ultrasonic probes are installed on opposite sides of the reinforced concrete area, the two sides being the transmitting end and receiving end of the ultrasonic signal, respectively; the travel time and signal amplitude of the ultrasonic signal received by each ultrasonic probe at the receiving end from the transmitting end are determined during each test.

[0021] In this embodiment, a linear array of ultrasonic probes is arranged in the reinforced concrete area to be inspected. The linear array is arranged by installing one column on one side of the reinforced concrete area to be inspected. An ultrasonic probe is installed on one side, and the same number of ultrasonic probes are installed on the opposite side. The excitation frequency of the ultrasonic probes is 100kHz. Each ultrasonic probe is a transceiver integrated ultrasonic probe. In this embodiment... The implementer can set the parameters according to the actual situation, and this embodiment does not impose any restrictions. When conducting inspections in reinforced concrete areas, one side is fixed as the transmitting end and the other side as the receiving end. The ultrasonic probes at the transmitting end emit ultrasonic signals sequentially according to their positional order. Specifically, after the ultrasonic probe at the receiving end receives an ultrasonic signal, the next adjacent ultrasonic probe at the transmitting end continues to emit an ultrasonic signal. Each emission of an ultrasonic signal by all ultrasonic probes at the transmitting end constitutes one inspection. The ultrasonic probes at both the transmitting and receiving ends are evenly arranged.

[0022] After the ultrasonic probe at the transmitting end emits an ultrasonic signal, the travel time and signal amplitude of the ultrasonic signal received by the ultrasonic probe at the receiving end are recorded. In addition, the travel time of the reflected signal received by the ultrasonic probe at the transmitting end after the ultrasonic probe at the transmitting end emits an ultrasonic signal is also recorded.

[0023] Reinforced concrete, a commonly used building material, is crucial for the safety of engineering projects. However, due to factors such as the environment and conditions under which it is used, steel corrosion can occur, seriously threatening the durability of reinforced concrete. Therefore, the detection of steel corrosion inside reinforced concrete is extremely important. Ultrasonic tomography, with its non-destructive nature and ability to visualize internal structures, has become an important method for non-destructive testing of reinforced concrete.

[0024] When performing ultrasonic tomography, ultrasonic signal detection is required first, followed by tomographic imaging based on the characteristic changes of the ultrasonic signal. In existing technologies, tomographic imaging is often performed using a single characteristic change in the ultrasonic signal. This method results in poor sensitivity for detecting rebar corrosion and makes it difficult to identify different defects. In fact, rebar corrosion damage has unique variation characteristics, which are also reflected in the ultrasonic signal. Therefore, this embodiment first analyzes the characteristics of the ultrasonic signal to preliminarily determine the probability of rebar corrosion damage; then, based on this, tomographic imaging is performed to achieve internal visualization and further determine the rebar corrosion damage area within the reinforced concrete.

[0025] S2 determines the ultrasonic spatiotemporal coefficient of the reinforced concrete area by the difference in travel time and signal amplitude of the same pair of ultrasonic probes in two adjacent detections, the duration of the ultrasonic probe at the transmitting end receiving the reflected signal, and the abnormal location determined by the reflected signal.

[0026] Steel corrosion is a dynamic and progressive form of damage. In the early stages of steel corrosion, only unevenly distributed point-like corrosion usually appears in localized areas. These point-like corrosions are small and relatively thin, so they have little impact on the velocity of sound. However, these point-like corrosions partially damage the oxide film on the surface of the steel, causing a small amount of scattering and refraction of the ultrasonic signal, which gradually reduces the amplitude of the ultrasonic signal. As the corrosion gradually worsens, the corrosion area gradually expands and the corrosion depth gradually increases, which affects both the intensity and velocity of the ultrasonic signal.

[0027] Secondly, steel corrosion also has its unique spatial distribution characteristics. Under normal circumstances, steel corrosion occurs because water vapor, chloride ions, and oxygen gather on the surface of the steel bars, destroying the oxide film and causing corrosion. These corrosion cells then connect with the corroded parts, forming a galvanic cell, which further exacerbates the corrosion. Therefore, steel corrosion first occurs in areas with thinner concrete cover layers and gradually extends deeper. At the same time, one of the reasons for corrosion expansion is the electrochemical corrosion caused by the galvanic cell on the steel bar. Since the formation of the galvanic cell requires connection with the steel bar, the expansion of corrosion is distributed along the steel bar.

[0028] Based on the above analysis, the entire steel reinforced concrete region to be detected is discretized in this embodiment, divided into small grids, recorded as imaging units, and referred to as pixels. The entire region to be detected is uniformly divided into Then, the spatial distribution position of the steel bars in the steel reinforced concrete structure to be detected is determined through construction drawings, and the position is determined in the coordinate system of the region to be detected. In this embodiment, the lower left corner of the region to be detected is taken as the coordinate origin, and the left side length and the bottom side length are taken as the coordinate axes.

[0029] The ultrasonic space-time coefficient of the steel reinforced concrete region is determined, which is used to measure the change trend and characteristics of the anomaly in the steel reinforced concrete in time sequence and space. Specifically, First, the travel time of the transmission signal received by the jth ultrasonic probe when the ith ultrasonic probe emits an ultrasonic signal in the nth detection is recorded as the first travel time, and the travel time of the transmission signal received by the jth ultrasonic probe when the ith ultrasonic probe emits an ultrasonic signal in the n+1th detection is recorded as the second travel time. The ith ultrasonic probe and the jth ultrasonic probe are taken as a pair of ultrasonic probes. Based on the difference between the second travel time and the first travel time of all adjacent detections, the propagation time variation measure between the ith ultrasonic probe and the jth ultrasonic probe is determined. The difference represents the difference between two variables, which can be calculated by difference, absolute value of difference, square of difference, ratio, etc. This embodiment does not limit this. The expression of the propagation time variation measure in this embodiment is: ; In the formula, is the propagation time variation measure between the ith ultrasonic probe and the jth ultrasonic probe, N is the historical detection times of the steel reinforced concrete region before the current, is the travel time of the transmission signal received by the jth ultrasonic probe when the ith ultrasonic probe emits an ultrasonic signal in the n+1th detection, recorded as the second travel time, is the travel time of the transmission signal received by the jth ultrasonic probe when the ith ultrasonic probe emits an ultrasonic signal in the nth detection, recorded as the first travel time.

[0030] Correspondingly, based on the difference between the signal amplitudes of all adjacent detections, the signal intensity variation measure between the ith ultrasonic probe and the jth ultrasonic probe is determined, and the specific expression is: ; In the formula, is the signal intensity variation measure between the ith ultrasonic probe and the jth ultrasonic probe, Let be the signal amplitude of the transmitted signal received by the j-th ultrasonic probe when the i-th ultrasonic probe emits an ultrasonic signal during the (n+1)-th detection. Let be the signal amplitude of the transmitted signal received by the j-th ultrasonic probe when the i-th ultrasonic probe emits an ultrasonic signal during the n-th detection.

[0031] Furthermore, this embodiment determines the spatial distribution metric of anomalies in the reinforced concrete region to be detected when the i-th ultrasonic probe emits an ultrasonic signal. The specific expression is: ; In the formula, This is the current test number. The travel time of the reflected wave signal received after an ultrasonic probe emits an ultrasonic signal. Through the first The method for determining the abnormal location by means of reflected waves is as follows: the location corresponding to half of the product of the travel time of the reflected wave signal received by the i-th ultrasonic probe and the propagation speed of the medium is taken as the abnormal location, where e is a natural constant.

[0032] Finally, the expression for the ultrasonic spatiotemporal coefficient of the reinforced concrete region is: In the formula, It is the ultrasonic spatiotemporal coefficient of the reinforced concrete area to be tested. It is a normalization function. This refers to the number of ultrasonic probes at the transmitting end of the reinforced concrete area.

[0033] It should be understood that when the probability of steel corrosion damage in the reinforced concrete area being tested is high or the degree of damage is severe, steel corrosion, as a dynamically developing type of damage, shows relatively small changes in sound velocity in the early stages of corrosion, but the ultrasonic signal amplitude will decrease. As the corrosion becomes more severe, the decrease in both sound velocity and ultrasonic signal amplitude becomes more significant. Simultaneously, steel corrosion usually preferentially occurs in areas where the concrete cover is relatively thin, resulting in shorter travel times of reflected waves at these locations. Furthermore, the corrosion damage is distributed along the steel reinforcement, meaning the distance between the abnormal damage and the reinforcement is relatively small, thus leading to a relatively large ultrasonic spatiotemporal coefficient. Conversely, when there is no steel corrosion, this dynamic development trend and spatial distribution characteristics are relatively weaker, resulting in a smaller ultrasonic spatiotemporal coefficient.

[0034] S3. For each ray path that passes through each imaging unit during the current ultrasound signal transmission, analyze the monotonicity of the travel time and the signal amplitude of the two ultrasound probes corresponding to the ray path during the historical detection process, as well as the fluctuation of the travel time and the signal amplitude. Combined with the ultrasound spatiotemporal coefficient, determine the weight of each imaging unit.

[0035] In the original ultrasonic tomography process, all pixels have the same weight. Tomography performed in this way applies the same measurement to all anomalies within the reinforced concrete area, making it difficult to accurately distinguish between steel corrosion anomalies. In fact, because different ultrasonic rays pass through different pixels, and the probability and degree of steel corrosion anomalies vary within different pixels, the influence weight of different pixels on steel corrosion damage assessment is also different. Furthermore, the steel corrosion condition within each pixel can be reflected by changes in the corresponding ultrasonic ray path. Therefore, this embodiment measures the anomalies in the reinforced concrete within each corresponding pixel based on the ultrasonic signal characteristics corresponding to each ultrasonic ray path.

[0036] First, the structural distribution of the reinforced concrete area to be tested is determined based on the construction drawings. Then, combined with the physical properties of the materials used, a theoretical velocity model for the reinforced concrete area to be tested is determined. The velocity model represents the sound velocity at different media within the reinforced concrete area. Determining the sound velocity by combining material physical properties is a well-known technique in this field, and the specific process will not be elaborated further. Using the theoretical velocity model of the reinforced concrete area, the coordinates of the transmitting ultrasonic probe, the coordinates of the receiving ultrasonic probe, and the grid information as input, a linear time-interpolation ray tracing algorithm is employed to determine each ray path during ultrasonic signal transmission. Each ray path consists of a series of coordinate points in the grid, and each ray path refers to the propagation path from a source point (transmitting ultrasonic probe) to a specific receiving point (receiving ultrasonic probe). The linear time-interpolation ray tracing algorithm is a well-known technique, and the specific process will not be elaborated further.

[0037] In the current detection process, ultrasonic probe c emits ultrasonic waves, and ultrasonic probe b receives the transmitted ultrasonic waves. The amplitude values ​​of the ultrasonic waves emitted by ultrasonic probe c and received by ultrasonic probe b in all historical detection processes are arranged in chronological order to form an amplitude sequence between ultrasonic probe c and ultrasonic probe b. Similarly, the travel times of the ultrasonic waves emitted by ultrasonic probe c and received by ultrasonic probe b in all historical detection processes are arranged in chronological order to form a travel time sequence between ultrasonic probe c and ultrasonic probe b. The first-order difference sequences of the amplitude sequence and the travel time sequence are obtained respectively. The elements in the first-order difference sequence of the travel time sequence are denoted as the first difference, and the elements in the first-order difference sequence of the amplitude sequence are denoted as the second difference.

[0038] Based on the above analysis, the weight of each imaging unit is calculated to measure the anomalies of reinforced concrete within each pixel along the ultrasound beam path. The specific expression is as follows: ; ; In the formula, Let be the weight of the m-th pixel in the reinforced concrete region to be detected. Let be the local ultrasonic difference coefficient of the m-th pixel in the reinforced concrete area to be inspected. It is the ultrasonic spatiotemporal coefficient of the reinforced concrete area to be tested, where e is the natural constant. This represents the number of ray paths that pass through the m-th imaging unit during the transmission of the ultrasound signal in the current detection. This is the set of all ray paths that pass through the m-th imaging unit during the transmission of the ultrasound signal in the current detection. This represents the maximum proportion of non-negative and non-positive values ​​in the first-order difference sequence of the amplitude sequences of the two ultrasound probes corresponding to the r-th ray path passing through the m-th imaging unit during the current ultrasound signal transmission. This represents the maximum value of the proportion of non-negative and non-positive numbers in the first-order difference sequence of the travel time sequences of the two ultrasound probes corresponding to the r-th ray path passing through the m-th imaging unit during the current ultrasound signal transmission. This is the fusion result of the dispersion of the amplitude sequence and the dispersion of the travel time sequence of the two ultrasound probes corresponding to the r-th ray path passing through the m-th imaging unit during the current ultrasound signal transmission. This indicates the number of pixels in the reinforced concrete area to be detected. Let be the local ultrasonic difference coefficient of the k-th pixel in the reinforced concrete region to be inspected. The flowchart for determining the weights of pixels in the reinforced concrete region to be inspected is shown below. Figure 2 As shown.

[0039] It should be noted that fusion means combining multiple variables, which can be done by methods such as addition, multiplication, addition-multiplication combination, and averaging. In this embodiment, averaging is used as the calculation method for fusion. The degree of dispersion can be calculated by methods such as variance, standard deviation, and coefficient of variation. In this embodiment, variance is used as the calculation method for the degree of dispersion.

[0040] It should be understood that, , It is a measure of the monotonicity of amplitude and travel time information in the amplitude and travel time sequences of the two ultrasound probes corresponding to the r-th ray path. This is a measure of the volatility of the amplitude and travel time sequences. It should be noted that the exponential function is used to increase the influence weight of the ultrasonic spatiotemporal coefficient, ensuring a strong ability to identify rebar corrosion damage, avoiding errors caused by non-rebar corrosion damage, and reducing the probability of misjudging rebar corrosion damage. When the probability of a pixel having rebar corrosion damage is higher or the influence of rebar corrosion damage is greater, because rebar corrosion damage has dynamic and irreversible characteristics, the corrosion will become increasingly severe, leading to monotonic changes in travel time information and ultrasonic signal intensity. Simultaneously, the higher the probability of rebar corrosion damage in the reinforced concrete area being detected, or the more severe the damage, the larger the ultrasonic spatiotemporal coefficient, and therefore the larger the corresponding local ultrasonic difference coefficient. Furthermore, when the probability of rebar corrosion damage in a pixel is higher or the influence of rebar corrosion damage is greater, it should be given greater weight during tomographic imaging, thereby enhancing the tomographic imaging results' ability to identify rebar corrosion damage.

[0041] S4. Based on the weight calculation in the SIRT algorithm of each imaging unit, ultrasonic tomography is performed on the ultrasonic signal emitted in the current detection to obtain the sound velocity distribution image of the reinforced concrete area and identify the steel corrosion damage area.

[0042] When detecting steel reinforcement corrosion damage, firstly, the weights of each pixel in the reinforced concrete area to be detected are obtained as described above. Then, the acquired ultrasonic signal is used as input for ultrasonic tomography. The travel time information of the ultrasonic signal is used as the imaging information. A ray-based ultrasonic tomography method is employed, using a linear travel time interpolation algorithm as the ray path tracing method. The inversion algorithm uses a weighted joint iterative reconstruction algorithm (SIRT), outputting a sound velocity distribution image. In this image, areas with higher sound velocities are converted into larger gray values ​​and relatively higher brightness, and vice versa. Ultrasonic tomography is a well-known technique and will not be described in detail here. During image reconstruction using the SIRT inversion algorithm, to enhance the ability to identify steel reinforcement corrosion damage, the weights of each pixel in the reinforced concrete area to be detected are introduced into the update formula of the SIRT algorithm, replacing the weights in the formula. The weighted joint iterative reconstruction algorithm is also a well-known technique and will not be described in detail here. Using the grayscale values ​​of each pixel in the sound velocity distribution image as input, the Otsu thresholding algorithm is used to output a segmentation threshold. Regions with grayscale values ​​less than the segmentation threshold are marked as areas of rebar corrosion damage. The larger the proportion of rebar corrosion damage to the entire sound velocity distribution image, the more severe the rebar corrosion damage. Otsu thresholding is a well-known technique and will not be elaborated further.

[0043] Based on the same inventive concept as the above methods, this application also provides a steel reinforcement corrosion damage assessment system based on ultrasonic tomography, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any one of the above-described steel reinforcement corrosion damage assessment methods based on ultrasonic tomography.

[0044] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments of this specification have been described above. Additionally, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some implementations, multitasking and parallel processing are possible or may be advantageous.

[0045] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0046] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the protection scope of this application.

Claims

1. A method for assessing steel reinforcement corrosion damage based on ultrasonic tomography, characterized in that, The method includes the following steps: Multiple ultrasonic probes are installed on opposite sides of a reinforced concrete area, with the two sides being the transmitting and receiving ends of the ultrasonic signal, respectively; the travel time and signal amplitude of the ultrasonic signal received by each ultrasonic probe at the receiving end from the transmitting end are determined for each test. The ultrasonic spatiotemporal coefficient of the reinforced concrete area is determined by the difference in travel time and signal amplitude of the same pair of ultrasonic probes in two adjacent detections, the duration of the ultrasonic probe at the transmitting end receiving the reflected signal, and the abnormal location determined by the reflected signal. The reinforced concrete area is divided into imaging units based on the number of installed ultrasonic probes. For each ray path that passes through each imaging unit during the current detection of ultrasonic signal transmission, the monotonicity of the travel time and the signal amplitude of the two ultrasonic probes corresponding to the ray path during the historical detection process, as well as the fluctuation of the travel time and the signal amplitude, are analyzed. Combined with the ultrasonic spatiotemporal coefficient, the weight of each imaging unit is determined. Based on the weight calculation in the SIRT algorithm of each imaging unit, ultrasonic tomography is performed on the ultrasonic signal emitted in the current detection to obtain the sound velocity distribution image of the reinforced concrete area and identify the area of ​​steel corrosion damage.

2. The method for assessing steel corrosion damage based on ultrasonic tomography as described in claim 1, characterized in that, During each test, each ultrasonic probe at the transmitting end emits ultrasonic signals in sequence according to its position. Each test is considered to have been completed when all ultrasonic probes at the transmitting end emit an ultrasonic signal once.

3. The method for assessing steel corrosion damage based on ultrasonic tomography as described in claim 1, characterized in that, The determination of the ultrasonic spatiotemporal coefficient of the reinforced concrete region includes: The time taken for the j-th ultrasonic probe to receive the transmitted signal when the i-th ultrasonic probe emits an ultrasonic signal during the n-th detection is recorded as the first time taken. The time taken for the j-th ultrasonic probe to receive the transmitted signal when the i-th ultrasonic probe emits an ultrasonic signal during the (n+1)-th detection is recorded as the second time taken. Based on the difference between the second travel time and the first travel time in all adjacent detections, a measure of the change in the propagation time of the ultrasonic signal between the i-th ultrasonic probe and the j-th ultrasonic probe is determined. Accordingly, based on the difference in signal amplitude between all adjacent detections, a measure of the change in signal intensity of the ultrasonic signal between the i-th and j-th ultrasonic probes is determined. The ultrasonic spatiotemporal coefficient is determined by combining the propagation time change metric, the signal intensity change metric, and the shortest distance between the abnormal location and the rebar location.

4. The method for assessing steel corrosion damage based on ultrasonic tomography as described in claim 3, characterized in that, The propagation time variation metric is the average difference between the second travel time and the first travel time for all adjacent detections.

5. The method for assessing steel corrosion damage based on ultrasonic tomography as described in claim 3, characterized in that, Further determination of the ultrasonic spatiotemporal coefficients includes: The shortest distance is used as the exponent of an exponential function with the natural constant as the base, and the ratio of the calculated result of the exponential function to the travel time of the reflected signal received after the current detection of the i-th ultrasonic probe emits an ultrasonic signal is determined. The ultrasonic spatiotemporal coefficient is positively correlated with the propagation time variation measure, the signal intensity variation measure, and the ratio of all ultrasonic probes at the transmitting end.

6. The method for assessing steel corrosion damage based on ultrasonic tomography as described in claim 1, characterized in that, The determination of the weights of each imaging unit includes: For the r-th ray path that passes through the m-th imaging unit during the current ultrasound signal transmission, calculate the time difference between the two ultrasound probes corresponding to the r-th ray path and the previous detection in each historical detection, and record it as the first difference. Determine the maximum value of the proportion of non-negative and non-positive numbers among the first differences of all adjacent detections. Accordingly, the difference in signal amplitude between the two ultrasound probes corresponding to the r-th ray path and the previous detection is calculated and recorded as the second difference. The maximum value of the proportion of non-negative and non-positive numbers in the second difference of all adjacent detections is determined. Calculate the fusion result of the dispersion of the travel time and the dispersion of the signal amplitude of the two ultrasonic probes corresponding to the r-th ray path in all historical detections; The sum of the two maximum values ​​is multiplied by the fusion result. The weight of the m-th imaging unit is positively correlated with the result of the multiplication of all its ray paths and the ultrasonic spatiotemporal coefficient, and negatively correlated with the number of ray paths passing through the m-th imaging unit.

7. The method for assessing steel corrosion damage based on ultrasonic tomography as described in claim 6, characterized in that, The further determination of the weight of the m-th imaging unit includes: Calculate the sum of the results of multiplication of all ray paths passing through the m-th imaging unit during the current ultrasound signal transmission, determine the ratio of the exponential mapping result of the ultrasound spatiotemporal coefficient to the number of paths, and calculate the product with the sum. The weight of the m-th imaging unit is the proportion of the product of the m-th imaging unit among all imaging units in the reinforced concrete region.

8. The method for assessing steel corrosion damage based on ultrasonic tomography as described in claim 1, characterized in that, The weight calculation in the SIRT algorithm based on the weight correction of each imaging unit includes replacing the weights in the SIRT algorithm with the weights of each imaging unit.

9. The method for assessing steel corrosion damage based on ultrasonic tomography as described in claim 1, characterized in that, The identification of areas of steel bar corrosion damage includes: Determine the segmentation threshold for the grayscale values ​​of all pixels in the sound velocity distribution image, and define the regions with grayscale values ​​less than the segmentation threshold as the steel reinforcement corrosion damage areas.

10. A steel reinforcement corrosion damage assessment system based on ultrasonic tomography, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1-9.

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