Nondestructive testing method, system and equipment for thickness of internal crack of concrete structure and storage medium

Abstract

The invention discloses a nondestructive testing method, system and equipment for the thickness of an internal crack of a concrete structure and a storage medium. The nondestructive testing method comprises the following steps: carrying out SH wave observation to obtain observation waveform data; constructing a concrete structure simulation model, and performing ultrasonic forward modeling to obtain predicted waveform data; calculating a waveform residual error between the concrete structure and the simulation model to obtain a percentage error of the target function; stopping iteration when a preset number of iterations is reached or the percentage error is smaller than a set threshold value; otherwise, updating the transverse wave speed and density of the concrete structure simulation model, updating the current concrete structure simulation model, and repeating iteration; imaging the transverse wave velocity in the current concrete structure simulation model after iteration is finished, and calculating the internal crack thickness of the concrete structure according to the number of lattice points of the transverse wave velocity in a low-value region in the height direction. According to the method, the state of the crack in the bearing platform can be accurately evaluated under the condition that the concrete structure is not damaged.

Description

Technical Field

[0001] The present invention relates to the technical field of nondestructive testing, and in particular to a nondestructive testing method, system, equipment and storage medium for the thickness of cracks inside a concrete structure. Background Art

[0002] The cap of an offshore wind turbine is an important structure that supports the wind turbine generator set. Its safety and reliability directly affect the stable operation of the entire wind farm. However, due to the complex and changeable marine environment, the concrete cap is prone to internal cracks under long-term stress and environmental influences, which affects its bearing capacity and service life. Traditional concrete crack detection methods, such as destructive testing and visual observation, are often unable to fully and accurately evaluate the characteristics of internal cracks in the cap, including the number, size and thickness of cracks. These methods may not only cause damage to the structure, but also have great limitations in the identification and evaluation of deep cracks.

[0003] Therefore, it is urgent to solve the above problems. Summary of the invention

[0004] Purpose of the invention: The first purpose of the present invention is to provide a nondestructive detection method for the thickness of cracks inside a concrete structure, which can accurately evaluate the state of cracks inside a concrete structure without destroying the concrete structure.

[0005] The second object of the present invention is to provide a nondestructive detection system for the thickness of cracks inside a concrete structure.

[0006] A third object of the present invention is to provide an electronic device.

[0007] A fourth object of the present invention is to provide a computer storage medium.

[0008] Technical solution: To achieve the above purpose, the present invention discloses a nondestructive detection method for the thickness of cracks inside a concrete structure, comprising the following steps:

[0009] (1) The concrete structure is divided into data collection grid points, and SH wave observation is performed using an ultrasonic instrument to obtain observed waveform data;

[0010] (2) Construct a simulation model of concrete structure and the attenuation coefficient of waves in concrete structure;

[0011] (3) Using the SH wave equation and the wave attenuation coefficient in the concrete structure, ultrasonic forward modeling is performed on the current concrete structure simulation model to obtain predicted waveform data;

[0012] (4) calculating the waveform residual between the concrete structure and the concrete structure simulation model according to the observed waveform data and the predicted waveform data, and constructing an objective function to obtain a percentage error of the objective function;

[0013] (5) When the preset number of iterations is reached or the percentage error of the objective function is less than the preset percentage error threshold, the iteration is stopped; otherwise, the gradient of the updated shear wave velocity and density in the concrete structure simulation model is calculated, and the shear wave velocity and density of the concrete structure simulation model are updated according to the gradient, the current concrete structure simulation model is updated, and steps (3) to (4) are repeated;

[0014] (6) imaging the shear wave velocity in the current concrete structure simulation model after the iteration, and calculating the internal crack thickness of the concrete structure according to the number of grid points in the low value area of ​​the shear wave velocity in the height direction;

[0015] Optionally, in the step (1), for the collection grid point division of the rectangular concrete structure, a longitudinal straight line is established, starting from the left side of the rectangular concrete structure, and a straight line is drawn at a certain interval along the longitudinal direction, and a transverse straight line is established, starting from the upper side of the rectangular concrete structure, and a straight line is drawn at a certain interval along the transverse direction to complete the arrangement of the collection line of the rectangular concrete structure; for the collection grid point division of the circular rectangular concrete structure, a circumference line is drawn at a certain interval along the radial direction with the center of the circle as the center, and then a straight line is drawn at a certain angle starting from the longitudinal direction to complete the arrangement of the collection line of the circular rectangular concrete structure.

[0016] Optionally, the initial value of the shear wave velocity in the concrete structure simulation model in step (2) is the average value of the shear wave velocities at at least 5 randomly collected points on the concrete structure, and the initial value of the density in the concrete structure simulation model is the concrete density used in the concrete structure.

[0017] Optionally, the specific calculation formula for the wave attenuation coefficient y(r) in the concrete structure in step (2) is:

[0018] y(r)=Ar α

[0019] where r represents the offset between the sensor and receiver in the ultrasonic instrument, and the constant A and the exponent α are determined by minimizing the residual energy of the waveform.

[0020] Optionally, the specific calculation formula of the waveform residual in step (4) is:

[0021] Δd s,r,n =D s,r (m n )-d s,r

[0022] Where m n Represents the current concrete structure simulation model parameters, which include shear wave velocity and density, d s,r represents the ultrasonic waveform data collected on the concrete structure, D s,r (m n ) indicates that the model parameter of the concrete structure simulation model in the forward modeling is m n The waveform data obtained when , the subscripts s and r represent the sth transmitter and the rth receiver; n represents the current iteration number;

[0023] Objective function E(m n ) is as follows:

[0024]

[0025] Where Δd is the waveform residual Δd calculated from the observed waveform data measured by the ultrasonic instrument and the predicted waveform data s,r,n The column vector is composed of, T represents the transpose of the vector;

[0026] The percentage error of the objective function is calculated as:

[0027] e(m n )=E(m n ) / E(m1)

[0028] Where E(m1) is the objective function value corresponding to the initial concrete structure simulation model.

[0029] Optionally, the specific formula for calculating the gradient of the shear wave velocity and density update in the concrete structure simulation model in step (5) is:

[0030]

[0031] Where Gv and Gr represent the gradients of shear wave velocity and density in the concrete structure simulation model, N represents the number of transmitters, and v y represents the particle speed, and represents the shear stress of the forward propagating wave field, and represents the shear stress of the counter-propagating wave field, represents the displacement of the back-propagating wave field, Vs and ρ represent the shear wave velocity and density of the concrete structure simulation model, respectively;

[0032] The updating method is the steepest descent method, and the calculation formula is:

[0033]

[0034] ρ n+1=ρ n -β n G

[0035] Where n represents the current iteration number, α n and β n are the update steps of shear wave velocity and density respectively.

[0036] Optionally, the low-value area in step (6) is an area with a shear wave velocity lower than 500 m / s, and the grid size used is L×L mm; first, the shear wave velocity in the current concrete structure simulation model after the iteration is completed is imaged, and if there is a low-value area in the image, it is determined that there are cracks in the area; if there is no low-value area in the image, it is determined that there are no cracks in the area; when there is a low-value area, the crack thickness H=L×M of the area is calculated according to the number of grid points in the low-value area of ​​the shear wave velocity in the height direction, wherein L is the grid size, and M is the number of grid points in the low-value area of ​​the shear wave velocity in the height direction.

[0037] Based on the same inventive concept, the present invention discloses a nondestructive detection system for the thickness of cracks inside a concrete structure, comprising:

[0038] The observation waveform acquisition module is used to divide the concrete structure into acquisition grid points and use ultrasonic instruments to observe SH waves to obtain observation waveform data;

[0039] The first construction module is used to construct a concrete structure simulation model and an attenuation coefficient of waves in the concrete structure, wherein an initial value of the shear wave velocity in the concrete structure simulation model is an average value of the shear wave velocities at at least 5 points randomly collected on the concrete structure, and an initial value of the density in the concrete structure simulation model is a concrete density used in the concrete structure;

[0040] The prediction waveform simulation module is used to perform ultrasonic forward simulation on the current concrete structure simulation model through the SH wave equation and the attenuation coefficient of the wave in the concrete structure to obtain the prediction waveform data;

[0041] An error calculation module is used to calculate the waveform residual between the concrete structure and the concrete structure simulation model according to the observed waveform data and the predicted waveform data, and to construct an objective function to obtain a percentage error of the objective function;

[0042] An iterative update module is used to stop the iteration when a preset number of iterations is reached or the percentage error of the objective function is less than a set percentage error threshold; otherwise, the gradient of the updated shear wave velocity and density in the concrete structure simulation model is calculated, and the shear wave velocity and density of the concrete structure simulation model are updated according to the gradient, the current concrete structure simulation model is updated, and the waveform simulation module and the error calculation module are repeatedly predicted;

[0043] The crack thickness determination module is used to image the shear wave velocity in the current concrete structure simulation model after the iteration is completed, and calculate the internal crack thickness of the concrete structure according to the number of grid points in the low value area of ​​the shear wave velocity in the height direction.

[0044] Based on the same inventive concept, the present invention discloses an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement a nondestructive detection method for the thickness of cracks inside a concrete structure as described above.

[0045] Based on the same inventive concept, the present invention discloses a computer-readable storage medium having a computer program stored thereon, characterized in that the computer program is executed by a processor to implement the above-mentioned non-destructive detection method for the thickness of cracks inside a concrete structure.

[0046] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the present invention collects information on the internal structure of concrete through ultrasonic SH waves, obtains information on the internal physical values ​​of the concrete cap by using the full waveform inversion method, selects the accompanying state method as the method for updating the physical value gradient, and adopts the steepest descent method to update the simulation model. When the preset number of iterations is reached or the percentage error is less than the set threshold, the process stops, and finally an image of the two-dimensional shear wave velocity value inside the concrete structure is obtained, and the thickness of the cracks in the area is evaluated by the number of grid points less than 500m / s; the present invention will not destroy the internal structure of the concrete cap being tested, and can be tested without affecting its performance, thereby ensuring the integrity of the material, and can realize a rapid evaluation of the thickness of the cracks on the concrete cap, while traditional destructive testing usually causes damage to the material or structure, limiting subsequent use; the present invention can realize an accurate evaluation of the thickness of the cracks on the concrete cap, and the grid point is set to 0.1mm, and the corresponding simulation accuracy can perform a high-precision, low-error evaluation of millimeter-level cracks, fully meeting engineering requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of the process of the present invention;

[0048] Figure 2 It is a schematic diagram of ultrasonic instrument detection in the present invention;

[0049] Figure 3 It is the arrangement diagram of the rectangular platform collection line in the present invention;

[0050] Figure 4 It is the arrangement diagram of the circular platform collection line in the present invention;

[0051] Figure 5It is a schematic diagram of the simulation of the initial shear wave velocity of a 1 mm horizontal crack of a concrete cap in the present invention;

[0052] Figure 6 It is a schematic diagram of the iterative shear wave velocity simulation of a 1 mm horizontal crack of a concrete cap in the present invention;

[0053] Figure 7 This is the error variation diagram of the 1 mm horizontal crack of the concrete cap in the present invention;

[0054] Figure 8 It is a schematic diagram of the simulation of the initial shear wave velocity of the oblique crack of the concrete cap in the present invention;

[0055] Fig. 9 It is a schematic diagram of the iterative shear wave velocity simulation of the oblique crack of the concrete cap in the present invention;

[0056] Fig.10 is an error variation diagram of the oblique cracks of the concrete cap in the present invention;

[0057] Fig.11 It is a schematic diagram of the framework of the system in the present invention. DETAILED DESCRIPTION

[0058] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0059] Example 1: Figure 1 As shown, the present invention provides a nondestructive detection method for the thickness of cracks inside a concrete structure, comprising the following steps:

[0060] (1) The concrete structure is divided into collection grid points, and the SH wave is observed using an ultrasonic instrument to obtain the observed waveform data; Figure 3 As shown in the figure, for the collection grid point division of the rectangular concrete structure, a longitudinal straight line is set up, starting from the left side of the rectangular concrete structure, and a straight line is drawn every 1 to 10 cm along the longitudinal direction. A transverse straight line is set up, starting from the upper side of the rectangular concrete structure, and a straight line is drawn every 1 to 10 cm along the transverse direction to complete the arrangement of the rectangular concrete structure collection line; as shown in the figure, Figure 4 As shown, for the collection grid point division of the circular rectangular concrete structure, a perimeter line is drawn every 1 to 5 cm along the radial direction with the center of the circle as the center, and then a straight line is drawn every 30° from the longitudinal direction to complete the arrangement of the collection line of the circular rectangular concrete structure;

[0061] (2) Constructing a concrete structure simulation model and a wave attenuation coefficient in the concrete structure, wherein the initial value of the shear wave velocity in the concrete structure simulation model is the average value of the shear wave velocities at at least five points randomly collected on the concrete structure, and the initial value of the density in the concrete structure simulation model is the concrete density used in the concrete structure;

[0062] The specific calculation formula of the wave attenuation coefficient y(r) in the concrete structure is:

[0063] y(r)=Ar α

[0064] Where r represents the offset between the sensor and the receiver in the ultrasonic instrument, the constant A and the exponent α are determined by minimizing the residual energy of the waveform;

[0065] (3) Using the SH wave equation and the wave attenuation coefficient in the concrete structure, ultrasonic forward modeling is performed on the current concrete structure simulation model to obtain predicted waveform data;

[0066] The expression of the SH wave equation is:

[0067]

[0068] where ρ(x,z) represents density, μ(x,z) represents shear modulus, and v y represents the particle velocity, σ xy and σ zy represents the shear stress, f y represents the force in the y direction, t represents the time, x and z represent the coordinates of the particle in the x direction and the z direction respectively.

[0069] (4) Calculating the waveform residual between the concrete structure and the concrete structure simulation model based on the observed waveform data and the predicted waveform data, constructing the objective function of the full waveform inversion method, and calculating the error of the objective function;

[0070] The specific calculation formula of the waveform residual is:

[0071] Δd s,r,n =D s,r (m n )-d s,r

[0072] Where m n Represents the current concrete structure simulation model parameters, which include shear wave velocity and density, d s,r represents the ultrasonic waveform data collected on the concrete structure, D s,r (m n ) indicates that the model parameter of the concrete structure simulation model in the forward modeling is m n The waveform data obtained when , the subscripts s and r represent the sth transmitter and the rth receiver; n represents the current iteration number;

[0073] The objective function E(m n ) is as follows:

[0074]

[0075] Where Δd is the waveform residual Δd calculated from the observed waveform data measured by the ultrasonic instrument and the predicted waveform data s,r,n The column vector is composed of, T represents the transpose of the vector;

[0076] The percentage error of the objective function is calculated as:

[0077] e(m n )=E(m n ) / E(m1)

[0078] Where E(m1) is the objective function value corresponding to the initial concrete structure simulation model; for example, the value of the objective function E(m1) obtained for the first time is 200, e(m1) is set to 100%, and the value of the objective function E(m2) obtained for the second time is 100, then e(m2) is 50%;

[0079] (5) When the preset number of iterations is reached or the percentage error of the objective function is less than the preset percentage error threshold, the iteration is stopped; otherwise, the gradient of the updated shear wave velocity and density in the concrete structure simulation model is calculated, and the shear wave velocity and density of the concrete structure simulation model are updated according to the gradient, the current concrete structure simulation model is updated, and steps (3) to (4) are repeated; the preset number of iterations is 50 times, and the percentage error threshold of the objective function is set to 1%;

[0080] The specific formula for calculating the gradient of shear wave velocity and density update in the concrete structure simulation model is:

[0081]

[0082] Where Gv and Gr represent the gradients of shear wave velocity and density in the concrete structure simulation model, N represents the number of transmitters, and v y represents the particle speed, and represents the shear stress of the forward propagating wave field, and represents the shear stress of the counter-propagating wave field, represents the displacement of the back-propagating wave field, Vs and ρ represent the shear wave velocity and density of the concrete structure simulation model, respectively;

[0083] The updating method is the steepest descent method, and the calculation formula is:

[0084]

[0085] ρ n+1 =ρ n -βn G

[0086] Where n represents the current iteration number, α n and β n are the update steps of shear wave velocity and density respectively;

[0087] (6) Imaging the shear wave velocity in the current concrete structure simulation model after the iteration, and evaluating the crack thickness inside the concrete structure by the number of grid points in the low-value area of ​​the shear wave velocity in the height direction; the low-value area is the area with a shear wave velocity lower than 500 m / s, and the grid point size used is L×L mm, for example, 0.1×0.1 mm;

[0088] Firstly, the shear wave velocity in the current concrete structure simulation model after the iteration is completed is imaged. If there is a low-value area in the image, it is determined that there is a crack in the area. If there is no low-value area in the image, it is determined that there is no crack in the area.

[0089] When there is a low-value area, the crack thickness of the area is evaluated according to the number of grid points in the low-value area of ​​the shear wave velocity in the height direction, and is H = L × M, where L is the grid point size, and M is the number of grid points in the low-value area of ​​the shear wave velocity in the height direction. For example, the number of grid points in the low-value area in the height direction at 1 cm is 15. If the grid point size used is 0.1 × 0.1 mm, the crack thickness of the area is considered to be 1.5 mm.

[0090] The nondestructive testing method of Example 1 was used to evaluate the 1mm horizontal cracks inside the concrete foundation. First, a rectangular concrete test block with a size of 50cm×20cm×20cm was made, and a foam sheet with a size of 3cm×3cm×1mm was pre-buried at a depth of 10cm. The shear wave velocity of the foam sheet was generally not more than 500m / s after measurement, which is similar to the shear wave velocity of the crack, so it was used to simulate the crack. Collection grid points were set on the surface of the formed rectangular concrete. The spacing of the grid points in the horizontal direction was 1cm, and in the vertical direction was 1cm. An ultrasonic instrument was used to collect ultrasonic data according to the set collection grid points. Figure 2 As shown in the figure, it is a schematic diagram of using ultrasonic instruments to measure and collect data. Before the inversion begins, the ultrasonic instrument is used to randomly select 10 locations of the concrete structure to measure the shear wave velocity. After measurement, the average shear wave velocity is 2500m / s, so this value is selected as the initial value of the shear wave velocity in the inverted concrete structure simulation model, as shown in Figure 5 As shown. The selected initial values ​​are input into the programming software MATLAB to implement the entire inversion process. At the beginning, it can be seen that the initial concrete structure simulation model simulates only concrete and no horizontal cracks can be seen. After the pre-set 50 iterations (the total time is about 10 minutes), the final shear wave velocity result is as follows Figure 6 As shown in the figure, it can be clearly seen that there is a low-value area of ​​about 3 cm in length at a depth of about 10 cm. After measurement, it can be found that the thickness of this low-value area is about 1 mm, which is consistent with the actual width of the foam board. The results of the concrete crack thickness at several grid points at every 1 cm length are shown in Table 1. It can be seen that the maximum error obtained by this method does not exceed 0.3 mm, and the average error is only 0.2 mm. Figure 7 As shown, it can be seen intuitively that the percentage error of the objective function gradually decreases from the initial 100% to about 5%, indicating that this method has accurately inverted the internal structure of concrete and horizontal cracks.

[0091] Table 11mm horizontal crack thickness assessment

[0092]

[0093] The nondestructive testing method of Example 1 was used to evaluate the oblique cracks inside the concrete foundation. First, a circular concrete test block with a radius of 10 cm was made, and an oblique foam sheet with a size of 10 cm×6 cm×2 mm was pre-embedded in the test block. The surface of the formed circular concrete was divided into collection grid points. With the center of the circle as the center, a circumference line was drawn every 1 cm along the radial direction, and then a straight line was drawn every 30° from the longitudinal direction. An ultrasonic instrument was used to collect ultrasonic data according to the set collection grid points. Before the inversion began, an ultrasonic instrument was used to randomly select 10 locations on the concrete structure to measure the shear wave velocity. The average shear wave velocity was measured to be 2500 m / s, so this value was selected as the initial value of the shear wave velocity in the concrete structure simulation model. Figure 8 As shown. The selected initial values ​​are input into the MATLAB software to implement the entire inversion process. At the beginning, it can be seen that the initial concrete structure simulation model simulates only concrete and no oblique cracks can be seen. After the pre-set 50 iterations, the total time is about 10 minutes, and the final shear wave velocity results are as follows Fig. 9 As shown in the figure, there is an obvious inclined low-value area, which proves the existence of cracks. Then, the results of the concrete crack thickness at several grid points at every 1 cm length are shown in Table 2. It can be seen that the maximum error obtained by this method does not exceed 0.3 mm, and the average error is only 0.15 mm. Fig.10 As shown, it can be seen intuitively that the percentage error of the objective function gradually decreases from the initial 100% to about 5%, indicating that this method has accurately inverted the internal structure of concrete and oblique cracks.

[0094] Table 2 Evaluation of diagonal crack thickness

[0095]

[0096] Example 2

[0097] like Fig.11 As shown, the present invention discloses a nondestructive detection system for the thickness of cracks inside a concrete structure, comprising:

[0098] The observation waveform acquisition module is used to divide the collection grid points of the concrete structure and use an ultrasonic instrument to observe the SH wave to obtain the observation waveform data; for the collection grid point division of the rectangular concrete structure, a longitudinal straight line is set up, starting from the left side of the rectangular concrete structure, and a straight line is drawn every 1 to 10 cm along the longitudinal direction, and a transverse straight line is set up, starting from the upper side of the rectangular concrete structure, and a straight line is drawn every 1 to 10 cm along the transverse direction to complete the arrangement of the collection line of the rectangular concrete structure; for the collection grid point division of the circular rectangular concrete structure, a perimeter line is drawn every 1 to 5 cm along the radial direction with the center of the circle as the center, and then a straight line is drawn every 30° starting from the longitudinal direction to complete the arrangement of the collection line of the circular rectangular concrete structure.

[0099] The first construction module is used to construct a concrete structure simulation model and an attenuation coefficient of waves in the concrete structure, wherein an initial value of the shear wave velocity in the concrete structure simulation model is an average value of the shear wave velocities at at least 5 points randomly collected on the concrete structure, and an initial value of the density in the concrete structure simulation model is a concrete density used in the concrete structure;

[0100] The specific calculation formula of the wave attenuation coefficient y(r) in the concrete structure is:

[0101] y(r)=Ar α

[0102] where r represents the offset between the sensor and receiver in the ultrasonic instrument, and the constant A and the exponent α are determined by minimizing the residual energy of the waveform.

[0103] The prediction waveform simulation module is used to perform ultrasonic forward simulation on the current concrete structure simulation model through the SH wave equation and the attenuation coefficient of the wave in the concrete structure to obtain the prediction waveform data;

[0104] The expression of the SH wave equation is:

[0105]

[0106] where ρ(x,z) represents density, μ(x,z) represents shear modulus, and v y represents the particle velocity, σ xy and σ zy represents the shear stress, f yrepresents the force in the y direction, t represents the time, x and z represent the coordinates of the particle in the x direction and the z direction respectively.

[0107] The error calculation module is used to calculate the waveform residual between the concrete structure and the concrete structure simulation model according to the observed waveform data and the predicted waveform data, and to construct an objective function to obtain a percentage error of the objective function.

[0108] The specific calculation formula of the waveform residual is:

[0109] Δd s,r,n =D s,r (mn)-d s,r

[0110] Where m n Represents the current concrete structure simulation model parameters, which include shear wave velocity and density, d s,r represents the ultrasonic waveform data collected on the concrete structure, D s,r (m n ) indicates that the model parameter of the concrete structure simulation model in the forward modeling is m n The waveform data obtained when , the subscripts s and r represent the sth transmitter and the rth receiver; n represents the current iteration number;

[0111] The objective function E(m n ) is as follows:

[0112]

[0113] Where Δd is the waveform residual Δd calculated from the observed waveform data measured by the ultrasonic instrument and the predicted waveform data s,r,n The column vector is composed of, T represents the transpose of the vector;

[0114] The percentage error of the objective function is calculated as:

[0115] e(m n )=E(m n ) / E(m1)

[0116] Wherein E(m1) is the objective function value corresponding to the initial concrete structure simulation model; for example, the value of the objective function E(m1) obtained for the first time is 200, e(m1) is set to 100%, and the value of the objective function E(m2) obtained for the second time is 100, then e(m2) is 50%.

[0117] The iterative update module is used to stop the iteration when the preset number of iterations is reached or the percentage error of the objective function is less than the set percentage error threshold; otherwise, the gradient of the shear wave velocity and density update in the concrete structure simulation model is calculated, the shear wave velocity and density of the concrete structure simulation model are updated according to the gradient, the current concrete structure simulation model is updated, and the waveform simulation module and the error calculation module are repeatedly predicted; the preset number of iterations is 50 times, and the percentage error threshold of the objective function is set to 1%.

[0118] The specific formula for calculating the gradient of shear wave velocity and density update in the concrete structure simulation model is:

[0119]

[0120] Where Gv and Gr represent the gradients of shear wave velocity and density in the concrete structure simulation model, N represents the number of transmitters, and v y represents the particle speed, and represents the shear stress of the forward propagating wave field, and represents the shear stress of the counter-propagating wave field, represents the displacement of the back-propagating wave field, Vs and ρ represent the shear wave velocity and density of the concrete structure simulation model, respectively;

[0121] The updating method is the steepest descent method, and the calculation formula is:

[0122]

[0123] ρ n+1 =ρ n -β n G

[0124] Where n represents the current iteration number, α n and β n are the update steps of shear wave velocity and density respectively.

[0125] The crack thickness determination module is used to image the shear wave velocity in the current concrete structure simulation model after the iteration, and calculate the crack thickness inside the concrete structure according to the number of grid points in the low value area of ​​the shear wave velocity in the height direction. The low value area is the shear wave velocity area below 500m / s, and the grid size used is L×Lmm, for example 0.1×0.1mm;

[0126] Firstly, the shear wave velocity in the current concrete structure simulation model after the iteration is completed is imaged. If there is a low-value area in the image, it is determined that there is a crack in the area. If there is no low-value area in the image, it is determined that there is no crack in the area.

[0127] When there is a low-value area, the crack thickness of the area is evaluated according to the number of grid points in the low-value area of ​​the shear wave velocity in the height direction, and is H = L × M, where L is the grid point size, and M is the number of grid points in the low-value area of ​​the shear wave velocity in the height direction. For example, the number of grid points in the low-value area in the height direction at 1 cm is 15. If the grid point size used is 0.1 × 0.1 mm, the crack thickness of the area is considered to be 1.5 mm.

[0128] Embodiment 3: Another embodiment of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement a nondestructive detection method for the thickness of cracks inside a concrete structure as described above.

[0129] The electronic device may include: a processor, a memory, a bus and a communication interface, wherein the processor, the communication interface and the memory are connected via a bus; the memory stores a computer program that can be run on the processor, and when the processor runs the computer program, it executes a nondestructive detection method for the thickness of cracks inside a concrete structure provided by any of the aforementioned embodiments of the present invention.

[0130] The memory may include high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk memory. The communication connection between the device network element and at least one other network element is realized through at least one communication interface (which may be wired or wireless), and the Internet, wide area network, local area network, metropolitan area network, etc. may be used.

[0131] The bus may be an ISA bus, a PCI bus or an EISA bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. The memory is used to store a program, and the processor executes the program after receiving an execution instruction. The nondestructive detection method for the thickness of cracks inside a concrete structure disclosed in any implementation of the above-mentioned embodiment of the present invention may be applied to the processor or implemented by the processor.

[0132] The processor may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method can be completed by an integrated logic circuit of hardware in the processor or an instruction in the form of software. The above processor may be a general-purpose processor, which may include a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The methods, steps and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The steps of the method disclosed in conjunction with the embodiments of the present invention can be directly embodied as a hardware decoding processor to be executed, or a combination of hardware and software modules in the decoding processor to be executed. The software module may be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory, and the processor reads the information in the memory and completes the steps of the above method in conjunction with its hardware.

[0133] The electronic device provided in the embodiment of the present application and the method provided in the embodiment of the present application are based on the same inventive concept and have the same beneficial effects as the method adopted, operated or implemented by them.

[0134] Embodiment 4: Another embodiment of the present invention provides a computer-readable storage medium, on which a computer program is stored, and the computer program is executed by a processor to implement the method of any of the above-mentioned embodiments. The computer-readable storage medium shown is an optical disk, on which a computer program (i.e., a program product) is stored, and when the computer program is executed by the processor, the method provided by any of the above-mentioned embodiments will be executed.

[0135] It should be noted that examples of computer-readable storage media may also include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other optical or magnetic storage media, which are not listed here one by one.

[0136] The computer-readable storage medium provided in the above-mentioned embodiments of the present application and the method provided in the embodiments of the present application are based on the same inventive concept and have the same beneficial effects as the method adopted, run or implemented by the application program stored therein.

Claims

1. A nondestructive testing method for the thickness of cracks inside a concrete structure, characterized in that: The steps include: (1) The concrete structure is divided into data collection grid points, and SH wave observation is performed using an ultrasonic instrument to obtain observed waveform data; (2) Construct a simulation model of concrete structure and the attenuation coefficient of waves in concrete structure; (3) Using the SH wave equation and the wave attenuation coefficient in the concrete structure, ultrasonic forward modeling is performed on the current concrete structure simulation model to obtain predicted waveform data; (4) calculating the waveform residual between the concrete structure and the concrete structure simulation model according to the observed waveform data and the predicted waveform data, and constructing an objective function to obtain a percentage error of the objective function; (5) When the preset number of iterations is reached or the percentage error of the objective function is less than the set percentage error threshold, the iteration is stopped; Otherwise, the gradient of the updated shear wave velocity and density in the concrete structure simulation model is calculated, and the shear wave velocity and density of the concrete structure simulation model are updated according to the gradient, the current concrete structure simulation model is updated, and steps (3) to (4) are repeated; (6) After the iteration, the shear wave velocity in the current concrete structure simulation model is imaged, and the thickness of the cracks inside the concrete structure is calculated based on the number of grid points in the low-value area of ​​the shear wave velocity in the height direction.

2. A nondestructive testing method for the thickness of cracks inside a concrete structure according to claim 1, characterized in that: In the step (1), for the collection grid point division of the rectangular concrete structure, a longitudinal straight line is set up, starting from the left side of the rectangular concrete structure, and a straight line is drawn at a certain interval along the longitudinal direction; a transverse straight line is set up, starting from the upper side of the rectangular concrete structure, and a straight line is drawn at a certain interval along the transverse direction to complete the arrangement of the collection line of the rectangular concrete structure; for the collection grid point division of the circular rectangular concrete structure, a perimeter line is drawn at a certain interval along the radial direction with the center of the circle as the center, and then a straight line is drawn at a certain angle starting from the longitudinal direction to complete the arrangement of the collection line of the circular rectangular concrete structure.

3. The nondestructive testing method for the thickness of cracks inside a concrete structure according to claim 1, characterized in that: In the step (2), the initial value of the shear wave velocity in the concrete structure simulation model is the average value of the shear wave velocities at at least 5 points randomly collected on the concrete structure, and the initial value of the density in the concrete structure simulation model is the concrete density used in the concrete structure.

4. The nondestructive testing method for the thickness of cracks inside a concrete structure according to claim 1, characterized in that: The specific calculation formula of the wave attenuation coefficient y(r) in the concrete structure in step (2) is: y(r)=On α where r represents the offset between the sensor and receiver in the ultrasonic instrument, and the constant A and the exponent α are determined by minimizing the residual energy of the waveform.

5. The nondestructive testing method for the thickness of cracks inside a concrete structure according to claim 1, characterized in that: The specific calculation formula of the waveform residual in step (4) is: Δd s,r,n =D s,r (m n )-d s,r Where m n Represents the current concrete structure simulation model parameters, which include shear wave velocity and density, d s,r represents the ultrasonic waveform data collected on the concrete structure, D s,r (m n ) indicates that the model parameter of the concrete structure simulation model in the forward modeling is m n The waveform data obtained when , the subscripts s and r represent the sth transmitter and the rth receiver; n represents the current iteration number; Objective function E(m n ) is as follows: Where Δd is the waveform residual Δd calculated from the observed waveform data measured by the ultrasonic instrument and the predicted waveform data s,r,n The column vector is composed of, T represents the transpose of the vector; The percentage error of the objective function is calculated as: e(m n )=E(m n ) / E(m1) Where E(m1) is the objective function value corresponding to the initial concrete structure simulation model.

6. The nondestructive testing method for the thickness of cracks inside a concrete structure according to claim 1, characterized in that: The specific formula for calculating the gradient of the shear wave velocity and density update in the concrete structure simulation model in step (5) is: Where Gv and Gr represent the gradients of shear wave velocity and density in the concrete structure simulation model, N represents the number of transmitters, and v y represents the particle speed, and represents the shear stress of the forward propagating wave field, and represents the shear stress of the counter-propagating wave field, represents the displacement of the back-propagating wave field, Vs and ρ represent the shear wave velocity and density of the concrete structure simulation model, respectively; The updating method is the steepest descent method, and the calculation formula is: v n+1 =ρ n -β n Gr Where n represents the current iteration number, α n and β n are the update steps of shear wave velocity and density respectively.

7. The nondestructive testing method for the thickness of cracks inside a concrete structure according to claim 1, characterized in that: In the step (6), the low-value area is an area with a shear wave velocity lower than 500 m / s, and the grid size used is L×L mm; first, the shear wave velocity in the current concrete structure simulation model after the iteration is completed is imaged, and if there is a low-value area in the image, it is determined that there are cracks in the area, and if there is no low-value area in the image, it is determined that there are no cracks in the area; When there is a low-value area, the crack thickness H=L×M in the area is calculated according to the number of grid points in the low-value area of ​​the shear wave velocity in the height direction, where L is the grid point size and M is the number of grid points in the low-value area of ​​the shear wave velocity in the height direction.

8. A nondestructive testing system for the thickness of cracks inside a concrete structure, characterized in that: include: The observation waveform acquisition module is used to divide the concrete structure into acquisition grid points and use ultrasonic instruments to observe SH waves to obtain observation waveform data; The first construction module is used to construct a concrete structure simulation model and an attenuation coefficient of waves in the concrete structure, wherein an initial value of the shear wave velocity in the concrete structure simulation model is an average value of the shear wave velocities at at least 5 points randomly collected on the concrete structure, and an initial value of the density in the concrete structure simulation model is a concrete density used in the concrete structure; The prediction waveform simulation module is used to perform ultrasonic forward simulation on the current concrete structure simulation model through the SH wave equation and the attenuation coefficient of the wave in the concrete structure to obtain the prediction waveform data; An error calculation module is used to calculate the waveform residual between the concrete structure and the concrete structure simulation model according to the observed waveform data and the predicted waveform data, and to construct an objective function to obtain a percentage error of the objective function; An iterative update module, used to stop iteration when a preset number of iterations is reached or when the percentage error of the objective function is less than a set percentage error threshold; Otherwise, the gradient of the updated shear wave velocity and density in the concrete structure simulation model is calculated, the shear wave velocity and density of the concrete structure simulation model are updated according to the gradient, the current concrete structure simulation model is updated, and the waveform simulation module and the error calculation module are repeatedly predicted; The crack thickness determination module is used to image the shear wave velocity in the current concrete structure simulation model after the iteration is completed, and calculate the internal crack thickness of the concrete structure according to the number of grid points in the low value area of ​​the shear wave velocity in the height direction.

9. An electronic device, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement a nondestructive detection method for the thickness of cracks inside a concrete structure as claimed in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: The computer program is executed by a processor to implement a nondestructive detection method for the thickness of cracks inside a concrete structure according to any one of claims 1 to 7.

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