Fast calculation method of ultrasonic time delay of anisotropic weld based on slowness conservation

Abstract

The application belongs to the field of ultrasonic nondestructive testing, and particularly relates to a kind of anisotropic weld ultrasonic time delay fast calculation method based on slowness conservation.The method obtains the equivalent anisotropic stiffness matrix of each region according to the grain orientation characteristics of different regions of weld, and solves the relationship between quasi-longitudinal wave phase velocity and group velocity;Then, the mapping relationship between transverse slowness and group velocity component is established by using propagation direction as medium.In the multi-layer parallel partitioned weld model, based on the law of transverse slowness conservation at the interface, the multi-layer refraction path solving is converted into a residual equation about single transverse slowness, and the transverse slowness parameter satisfying the boundary condition is obtained by iterative solving, and then the propagation time delay matrix between transmitting array element, imaging point and receiving array element is quickly calculated.The application solves the problem that various traditional time delay calculation methods are difficult to consider higher positioning accuracy and shorter imaging time;It can also be combined with various traditional imaging algorithms, and has good universality and expansibility.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic nondestructive testing, specifically relating to a method for rapid calculation of ultrasonic time delay of anisotropic welds based on slowness conservation, and the corresponding ultrasonic imaging method, computer program product, and ultrasonic nondestructive testing equipment. Background Technology

[0002] Phased array ultrasonic testing is widely used in weld defect detection. For structures with significant multi-layer anisotropy, such as coarse-grained welds, columnar-grained welds, or austenitic welds, beam deflection, focus drift, and energy scattering easily occur during ultrasonic wave propagation. This makes it difficult for traditional time delay calculation methods based on the isotropic assumption to accurately reflect the actual propagation path, thus affecting defect imaging quality and positioning accuracy.

[0003] Existing imaging methods typically employ constant sound velocity and linear propagation models, calculating propagation time delay through geometric distance. When the weld contains multiple layers of microstructure and significant grain orientation differences, these methods struggle to characterize interlayer refraction and propagation characteristics where phase velocity and group velocity directions are inconsistent, easily leading to positioning errors in deep defect imaging. To improve accuracy, existing techniques use ray tracing or path searching for time delay correction; however, these methods usually require repeated wave velocity interpolation and iterative calculations for numerous propagation paths, resulting in high computational costs and failing to meet the rapid processing requirements of full-matrix ultrasonic imaging. Therefore, designing a rapid ultrasonic time delay calculation method that balances anisotropic propagation accuracy and computational efficiency for welds with significant multilayered anisotropic structures has become a pressing technical challenge for those skilled in the art. Summary of the Invention

[0004] To address the problem that existing methods struggle to balance accuracy and computational efficiency in ultrasonic time delay calculations for welds in multi-layered anisotropic structures, this invention provides a rapid ultrasonic time delay calculation method for anisotropic welds based on slowness conservation, along with a corresponding ultrasonic imaging method for the weld, a computer program product, and ultrasonic non-destructive testing equipment.

[0005] This invention is achieved using the following technical solution: A rapid calculation method for ultrasonic time delay of anisotropic welds based on slowness conservation includes the following steps: The metallographic structure distribution of the weld to be tested is obtained, and the weld to be tested is divided into multiple layers along the depth according to the statistical law of grain orientation; the stiffness and density values ​​of each layer are calibrated; and the equivalent elastic stiffness matrix of the weld region is constructed.

[0006] Multiple discrete propagation directions are selected within the two-dimensional propagation plane. The quasi-longitudinal wave phase velocity in each propagation direction is solved using the Christoffel equation based on the equivalent elastic stiffness matrix and the density values ​​of each layer. and lateral slowness ; and combine the polarization vector of the wave mode with the longitudinal wave phase velocity Decompose to obtain In any one of the weld seams to be tested i Lateral component of layer group velocity and longitudinal components .

[0007] Each discrete propagation direction corresponding , , and As a quadruple, a lookup table representing the mapping relationship between transverse slowness and transverse and longitudinal components is constructed using quadruples under multiple different propagation directions; denoted as: and .

[0008] Based on the condition of lateral slowness conservation at each interface, and combined with the spatial relationship between the transmitting array element and the target point, a lateral displacement residual function along the propagation path is constructed. .

[0009] Within the domain of the lookup table, iteratively solve for the results that enable the current task... Optimal lateral slowness of convergence The optimal lateral slowness is calculated using a lookup table. Corresponding vertical components .

[0010] according to The propagation time of ultrasonic waves in each layer of the weld is calculated and accumulated to obtain the propagation delay between the transmitting array element and any imaging point in the weld to be tested, and then a propagation delay matrix is ​​created.

[0011] As a further improvement of the present invention, the metallographic structure distribution of the weld to be tested is obtained by EBSD detection; if the grain orientation statistical law remains consistent in any thickness range in the depth direction of the weld to be tested, it is divided into one layer, and the weld has the same elastic parameters in the same layer.

[0012] As a further improvement of the present invention, the method for constructing the equivalent elastic stiffness matrix includes: (1) The weld to be tested i The stiffness matrix corresponding to the grain orientation of the layer is denoted as c i The average stiffness matrix is ​​calculated using the following formula. C V :

[0013] In the above formula,N Indicates the number of weld layers.

[0014] (2) Under the assumption of uniform stress, calculate the mean compliance matrix. S R for:

[0015] (2) Combination C V and S R The equivalent elastic stiffness matrix of the weld region was calculated. C eff for:

[0016] As a further improvement of the present invention, the method for solving the phase velocity of quasi-longitudinal waves in any propagation direction includes: Select multiple discrete propagation direction angles within the two-dimensional propagation plane. The eigenvalues ​​and eigenvectors of the Christoffel equation are solved in each discrete propagation direction. A quasi-longitudinal wave mode corresponding to the particle vibration direction and the wave normal direction is selected to obtain the phase velocity of the quasi-longitudinal wave. .

[0017] As a further improvement of the present invention, arbitrary propagation direction lateral slowness on The calculation formula is: .

[0018] As a further improvement of the present invention, the following formula is first used to calculate any number of weld seams to be tested. i Phase velocity of the layer :

[0019] In the above formula, The equivalent elastic stiffness matrix of the anisotropic weld medium in fourth-order tensor form is given. i , j , k , l Corresponding to each level of index; n l The first normal vector of the unit wave represents the... l One component; u j and u k The polarization vectors of the corresponding wave modes are respectively the first and second polarization vectors of the wave modes. j and the k Each component.

[0020] Again Perform orthogonal decomposition to obtain In any one of the weld seams to be tested i Lateral component of layer group velocity and longitudinal components .

[0021] As a further improvement of the present invention, the lateral displacement residual function The expression is:

[0022] In the above formula, m Indicates the number of layers of anisotropic media traversed by the propagation path; z i Indicates the ultrasound in the first... i The propagation thickness in the layer; p x Indicates lateral slowness; X The total lateral distance between the starting and ending points of the propagation; and These represent the transverse and longitudinal components of the group velocity in the i-th layer, respectively.

[0023] As a further improvement to the present invention, the optimal lateral slowness The iterative solution employs the secant method or the quasi-Newton method, and the initial values ​​for iteration are determined based on the geometric positional relationship between the transmitting array elements and the target point.

[0024] As a further improvement of this invention, the formula for calculating the propagation time delay (TOF) between the transmitting array element and any target point in the weld to be tested is as follows:

[0025] The present invention also includes a computer program product comprising a computer program that, when executed by a processor, implements the aforementioned method for rapid calculation of ultrasonic time delay of anisotropic welds based on slowness conservation, in order to generate a propagation time delay matrix characterizing the propagation time delay between the transmitting array element and any target point in the weld to be tested.

[0026] The present invention also includes a method for ultrasonic imaging of weld seams, comprising: (1) The propagation time delay (TOF) between the transmitting array element and any target point in the weld under test is calculated using the fast calculation method of ultrasonic time delay of anisotropic weld based on slowness conservation as described above.

[0027] For emission elements in array imaging T Imaging points P and receiving array elements R Its two-way propagation delay for: ; In the above formula, This represents any imaging point from the transmitting element T to the weld under test. P Propagation delay between; Represents any imaging point in the weld to be tested. P The propagation delay between the receiver array element R and the receiver array element R.

[0028] (2) Acquire the full matrix acquisition data of the weld area, and calculate the pixel points within the imaging area using the following formula. P Imaging values I TFM ( P ):

[0029] In the above formula, N The total number of array elements, s TR For launching array elements T With receiving array elements R The corresponding A-scan signal.

[0030] The present invention also includes an ultrasonic nondestructive testing device, which includes an ultrasonic probe, a data processing module and a display module. The data processing module includes 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 uses the aforementioned ultrasonic imaging method for welds to generate the final imaging result based on the A-scan signal acquired by the ultrasonic probe.

[0031] The technical solution provided by this invention has the following beneficial effects: This invention establishes propagation path constraints based on the transverse slowness conservation condition in multilayer anisotropic media. It can take into account interlayer refraction and the propagation characteristics of inconsistent phase velocity and group velocity directions during time delay calculation, thereby improving the accuracy of ultrasonic propagation path characterization in anisotropic welds and reducing time delay errors and defect location deviations caused by traditional straight-line propagation models.

[0032] This invention pre-constructs a lookup table between lateral slowness and group velocity components, and transforms the solution of multi-layer propagation paths into a scalar residual function solution problem with respect to lateral slowness. By combining the secant method and vectorized batch implementation, it avoids repeatedly performing complex wave velocity calculations and path-by-path search operations for each propagation path, which can significantly reduce the amount of computation and improve the time delay solution efficiency, thus meeting the rapid processing requirements of full-matrix ultrasound imaging.

[0033] This invention balances the accuracy of anisotropic propagation modeling with the efficiency of numerical implementation. It can shorten the preprocessing time of full-matrix ultrasonic imaging while ensuring the accuracy of propagation delay calculation, making it suitable for rapid detection and engineering applications of anisotropic weld defects. Furthermore, the propagation delay obtained by this invention can be used as an independent delay correction result, combined with specific imaging algorithms, and is applicable to full-focus imaging, delay-product summation imaging, synthetic aperture focusing imaging, and other ultrasonic imaging methods based on propagation delay, exhibiting good versatility and scalability. Attached Figure Description

[0034] Figure 1 This is a flowchart of the steps in the rapid calculation method for ultrasonic time delay of anisotropic welds based on slowness conservation provided in Embodiment 1 of the present invention.

[0035] Figure 2 This is a simulation model for ultrasonic phased array detection of weld defects.

[0036] Figure 3 Imaging results of different schemes in the test experiment.

[0037] Figure 4 This is a comparison chart of the signal-to-noise ratios of various schemes for the three types of defects in the test experiment.

[0038] Figure 5 This is a comparison chart of the positioning errors of various schemes for the three types of defects in the test experiment.

[0039] Figure 6 This is a comparison chart of the imaging times for different schemes in the test experiment. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0041] Example 1 To address the problems of inaccurate propagation path characterization, high computational cost, and difficulty in meeting the requirements of rapid full-matrix ultrasonic imaging in existing ultrasonic time delay calculations for various irregular weld seams, this embodiment provides a rapid calculation method for ultrasonic time delay of anisotropic weld seams based on the conservation of latitude. This method first constructs the equivalent anisotropic stiffness matrix for each region based on the grain orientation characteristics of different regions of the weld seam, and solves the relationship between the quasi-longitudinal wave phase velocity and the group velocity. Then, using the propagation direction as a medium, a mapping relationship is established between the transverse latitude and the transverse and longitudinal components of the group velocity. Next, in a multi-layer parallel partitioned weld seam model, based on the property of conserved transverse latitude at the interface, this embodiment transforms the solution of the multi-layer refraction path into a residual equation for a single transverse latitude, and obtains the optimal transverse latitude parameter that satisfies the boundary conditions through iterative solution. Finally, the propagation time delay matrix between the transmitting element, the imaging point, and the receiving element is rapidly calculated based on the longitudinal component of the group velocity corresponding to the optimal transverse latitude. The time delay matrix generated in this embodiment can be combined with methods such as full-focus imaging and time delay product summation for imaging anisotropic coarse-grained weld defects. Compared with the traditional linear propagation model and the ray tracing method based on Fermat's principle, the technical solution provided in this embodiment significantly reduces the imaging time while maintaining high positioning accuracy.

[0042] In detail, such as Figure 1 As shown, the rapid calculation method for ultrasonic time delay of anisotropic welds based on slowness conservation provided in this embodiment includes the following steps: 1. Obtain the metallographic structure distribution of the weld to be tested, and divide the weld to be tested into multiple layers along the depth according to the statistical law of grain orientation; calibrate the stiffness and density values ​​of each layer; and construct the equivalent elastic stiffness matrix of the weld region.

[0043] In this embodiment, the weld region is divided into multiple layers along its depth, and the physical properties of the weld under test are characterized using a multi-layer parallel partition weld model. In the multi-layer parallel partition weld model, the grain orientation statistical regularity within each weld region is relatively consistent, thus the discrete grain structure can be macroscopically equivalent to anisotropic continuous media with different elastic parameters.

[0044] In practical applications, grain orientation information in the weld seam is derived from electron backscatter diffraction (EBSD) data, material microstructure statistical results, or a pre-established material parameter database. To more accurately create the required multi-layered parallel partitioned weld seam model, this embodiment can perform EBSD detection on the weld seam region, and then divide the weld seam into multiple regions along the depth direction based on the metallographic characteristics, EBSD orientation distribution characteristics, or depth-direction microstructure differences in the detection results. In practical applications, at least two anisotropic media can be defined within any weld seam region.

[0045] After layering the weld region, areas with consistent grain orientation statistics across any thickness along the weld depth direction are grouped into the same layer. Within the same layer, the weld exhibits the same density and elastic parameters. Therefore, this embodiment calibrates the density and stiffness values ​​of each layer within the weld. Based on this, for a given weld region, it is assumed that the region contains… N Groups of grain orientation samples located in different layers, the stiffness matrix corresponding to each grain orientation is denoted as... c i The average stiffness matrix can then be calculated using the following formula. C V :

[0046] In the above formula, N Indicates the number of weld layers.

[0047] Under the assumption of uniform stress, the Reuss mean compliance matrix can be calculated. S R for:

[0048] The equivalent elastic stiffness matrix of this region is obtained by using Voigt-Reuss-Hill averaging. Then, combined with... C V and S R The equivalent elastic stiffness matrix of the weld region was calculated. C eff for:

[0049] This equivalent stiffness matrix can be used to characterize the macroscopic anisotropic elastic characteristics of different regions of the weld.

[0050] In practical applications, an equivalent elastic stiffness matrix is ​​created based on EBSD test data. C eff In this case, the stiffness matrix in the local crystal coordinate system can be constructed first based on the intrinsic elastic constant of the crystal. Then, by combining the Euler angle and coordinate transformation relationship, the crystal stiffness matrix can be transformed into the global coordinate system to obtain the stiffness matrix corresponding to different grain orientations.

[0051] II. Selecting multiple discrete propagation directions within a two-dimensional propagation plane The quasi-longitudinal wave phase velocity in each propagation direction is solved using the Christoffel equation based on the equivalent elastic stiffness matrix and the density values ​​of each layer. and lateral slowness ; and combine the polarization vector of the wave mode with the longitudinal wave phase velocity Decompose to obtain In any one of the weld seams to be tested i Lateral component of the layer and longitudinal components .

[0052] In ultrasonic imaging of the weld area, the propagation path and direction of the ultrasonic waves are... Regarding this, for each layer of anisotropic medium, this embodiment selects angles for multiple discrete propagation directions within the two-dimensional propagation plane, such as... The eigenvalues ​​and eigenvectors of the Christoffel equation are solved in each discrete propagation direction. Then, a quasi-longitudinal wave mode corresponding to the particle vibration direction and the wave normal direction is selected to obtain the required quasi-longitudinal wave phase velocity. .

[0053] Specifically, for the unit wave normal vector n, this embodiment first constructs the Christoffel tensor. : ; In the above formula, The equivalent elastic stiffness matrix of the anisotropic weld medium in fourth-order tensor form is given. i , j , k , l Corresponding to each order index; in this embodiment, the values ​​of the four are all 1, 2, and 3, that is, the equivalent elastic stiffness matrix has a total of 81 components; n l The first normal vector of the unit wave represents the... l One component; n j The first normal vector of the unit wave represents the... j Each component.

[0054] Then, the current propagation direction is calculated using the following formula. The corresponding quasi-longitudinal wave phase velocity :

[0055] In the above formula, For the weld area i The material density of the anisotropic medium in the layer; For Kronecker symbols.

[0056] Based on propagation direction angle The corresponding quasi-longitudinal wave phase velocity This embodiment can calculate the lateral slowness in the corresponding propagation direction. The calculation formula is: .

[0057] Next, combining the propagation direction angle Quasi-longitudinal wave phase velocity This embodiment can further calculate the transverse and longitudinal components of the group velocity; the calculation process includes: First, calculate any number of welds to be tested using the following formula. i Phase velocity of the layer :

[0058] In the above formula, The equivalent elastic stiffness matrix of the anisotropic weld medium in fourth-order tensor form is given. i , j , k , l Corresponding to each level of index; n l The first normal vector of the unit wave represents the... l One component; u j and u k The polarization vectors of the corresponding wave modes are respectively the first and second polarization vectors of the wave modes. j and the k Each component.

[0059] Again Perform orthogonal decomposition to obtain In any one of the weld seams to be tested i Lateral component of group velocity of layer and longitudinal components .

[0060] III. Each discrete propagation direction The corresponding quasi-longitudinal wave phase velocity lateral slowness transverse component of group velocity Longitudinal component of group velocity As a quadruple, a lookup table representing the mapping relationship between transverse slowness and transverse and longitudinal components is constructed using quadruples under multiple different propagation directions; denoted as: and .

[0061] In actual testing, the propagation direction through the weld is restricted to a specified angular range, namely: In this embodiment, after discretizing the angle range and obtaining several angle values, the corresponding propagation direction can be obtained by solving the Christoffel equation for each angle value. Quasi-longitudinal wave phase velocity lateral slowness and the transverse component of the group velocity and longitudinal components Based on the direction of propagation The values ​​of the four parameters associated can form a quadruple, denoted as: { , , , Each quadruple is considered a data point, and multiple quadruples propagating in different directions constitute multiple data points. Based on these data points, this embodiment can further construct a representation of lateral slowness. transverse component of group velocity and longitudinal components A lookup table for mapping relationships; denoted as: and .

[0062] In this embodiment, with For example, the construction method of this lookup table is as follows: first extract the lateral slowness from each quadruple. and horizontal components The value of is used to obtain the corresponding binary tuple; each binary tuple constitutes a two-dimensional parametric coordinate; in By marking the data points corresponding to each pair in the parameter plane, we can obtain... and The mapping relationship between the two can be represented by a discrete lookup table or by a fitted function curve. In order to improve data processing efficiency in subsequent applications, this embodiment uses a discrete lookup table to represent the mapping relationship between the two.

[0063] In practical applications, the data density of the constructed lookup table mainly depends on the number of angle values ​​obtained during the discretization phase of the propagation direction. To improve the accuracy of propagation delay calculation, this embodiment should encrypt the lookup table as much as possible. For example, the interval between adjacent angle values ​​in the discretization phase can be reduced to increase the number of discretized angle values, thereby increasing the number of final generated quadruples. Considering the large computational load of solving the Christoffel equation for each angle value to obtain the corresponding quadruples, this embodiment can also use an interpolation algorithm to interpolate adjacent data pairs in the lookup table, provided that the accuracy requirements are met, to improve the data density of the lookup table.

[0064] IV. Based on the condition of lateral slowness conservation at each interface, and combined with the spatial relationship between the transmitting array element and the target point, construct the lateral displacement residual function along the propagation path. .

[0065] In the multi-layer parallel partitioned weld model of this embodiment, the tangential component of the wave vector is continuous at the interface when the ultrasonic wave passes through different regions. Therefore, the transverse slowness remains conserved at each layer interface. Assuming the propagation path passes through m regions, the transverse slowness satisfies:

[0066] in, For the first i Phase velocity direction angle in the layer; This represents the phase velocity of the corresponding layer.

[0067] Traditional ray tracing methods based on Fermat's principle typically treat the coordinates of refraction points at each interface as unknowns, searching for the shortest propagation path through multidimensional optimization. While these methods achieve high accuracy, they incur significant computational overhead when the number of layers increases or when solving for a large number of array elements and pixel combinations point by point. In this embodiment, however, the lateral slowness conservation relation is utilized to transform the multi-layer propagation path problem from a multivariate optimization problem of refraction point coordinates into a scalar problem of solving for a single lateral slowness parameter, thereby significantly simplifying the computation process.

[0068] Specifically, let the ultrasound be in the... The propagation thickness in the layer is The transverse and longitudinal components of the group velocity are respectively and The lateral displacement caused by propagation in this layer is:

[0069] The sum of displacements obtained by adding up all layers should equal the total lateral displacement, which should also equal the total lateral distance between the propagation start and end points. X The residual between the two can be expressed by the following lateral displacement residual function. express:

[0070] In the above formula, m Indicates the number of layers of anisotropic media traversed by the propagation path; z i Indicates the ultrasound in the first... i The propagation thickness in the layer; p x Indicates lateral slowness; X The total lateral distance between the starting and ending points of the propagation; and These represent the transverse and longitudinal components of the group velocity in the i-th layer, respectively.

[0071] Therefore, when When the lateral slowness is such that the propagation path solution satisfies the geometric boundary conditions, the corresponding lateral slowness is the solution.

[0072] 5. Within the domain of the lookup table, iteratively solve for the results that enable the current task... Optimal lateral slowness of convergence The optimal lateral slowness is calculated using a lookup table. Corresponding vertical components .

[0073] In this embodiment, the optimal lateral slowness The iterative solution employs the secant method or the quasi-Newton method, and the initial values ​​for iteration are determined based on the geometric positional relationship between the transmitting array elements and the target point.

[0074] Specifically, taking the secant method as an example, its iterative form is as follows:

[0075] in, For the number of iterations, , and These are the lateral slowness values ​​determined in the (k+1), k, and (k-1)th iterations, respectively; These represent the values ​​of the lateral displacement residual function in the (k-1)th and kth iterations, respectively.

[0076] It is important to emphasize that the precision of the lookup table may affect the optimal lateral slowness. To improve computational accuracy, and considering the limited data density of the lookup table, this embodiment can pre-calculate the phase velocity curves and group velocity curves of quasi-P-waves in different regions offline. Subsequent time delay calculations only require calling the lookup table and performing interpolation, eliminating the need to repeatedly solve the Christoffel equation, thereby reducing online computation costs.

[0077] VI. According to The propagation time of ultrasonic waves in each layer of the weld is calculated and accumulated to obtain the propagation delay between the transmitting array element and any imaging point in the weld to be tested, and then a propagation delay matrix is ​​created.

[0078] In this embodiment, the formula for calculating the Time-of-Flight (TOF) propagation between the transmitting array element and any target point in the weld to be tested is as follows:

[0079] In practical applications, to further improve computational efficiency, all imaging points and array element combinations can be vectorized and parallelized, and batch delay calculations can be achieved by combining them with a pre-established lookup table. This significantly shortens the computation time while ensuring the accuracy of propagation delay calculation, and finally obtains the required propagation delay matrix.

[0080] Example 2 Based on the scheme in Example 1, this embodiment further provides a weld ultrasonic imaging method, which includes: (1) The propagation time delay (TOF) between the transmitting array element and any target point in the weld to be tested is calculated using the fast calculation method of ultrasonic time delay of anisotropic weld based on slowness conservation as described in Example 1.

[0081] For emission elements in array imaging T Imaging points P and receiving array elements R Its two-way propagation delay for: ; In the above formula, This represents any imaging point from the transmitting element T to the weld under test. P Propagation delay between; Represents any imaging point in the weld to be tested. P The propagation delay between the receiver array element R and the receiver array element R.

[0082] (2) Acquire the full matrix acquisition data of the weld area, and calculate the pixel points within the imaging area using the following formula. P Imaging values I TFM ( P ):

[0083] In the above formula, N The total number of array elements, s TR For launching array elements T With receiving array elements R The corresponding A-scan signal.

[0084] In this embodiment, the input data required for imaging is the full matrix acquisition data (FMC) obtained during the array ultrasound detection process. The full matrix acquisition data can be obtained by transmitting element by element and receiving all elements of the array probe. That is, under the condition that only one transmitting element is excited at a time, all receiving elements synchronously acquire the response signal. After the transmission process of all elements is completed in sequence, a complete transmitting element-receiving element signal matrix is ​​formed.

[0085] In practical applications, the data acquisition object can be a weld test block, a welded component, or a corresponding finite element simulation model. For experimental data, FMC data can be acquired through a phased array ultrasonic testing system; for simulation data, array excitation and reception conditions consistent with or corresponding to the actual probe parameters can be set in the numerical model, and simulated FMC data can be generated through element-by-element excitation and full-element reception. The acquired FMC data, along with array probe parameters, workpiece geometric information, and weld partition material parameters, serve as the inputs for the propagation delay calculation and imaging reconstruction of this invention.

[0086] Furthermore, in the actual imaging stage, the DMAS imaging method can also be used to multiply and accumulate the delayed signals pairwise to enhance spatial coherence and suppress structural noise. In this embodiment, a correction based on propagation delay conserved by slowness is introduced. Different imaging methods can further improve the accuracy of defect location reconstruction while maintaining a high signal-to-noise ratio.

[0087] Example 3 Based on the scheme in Embodiment 1, this embodiment further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, it implements the fast calculation method for ultrasonic time delay of anisotropic welds based on slowness conservation as in Embodiment 1, so as to generate a propagation time delay matrix characterizing the propagation time delay between the transmitting array element and any target point in the weld to be tested.

[0088] This embodiment also includes an ultrasonic non-destructive testing device, which includes an ultrasonic probe, a data processing module and a display module. The data processing module includes 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 adopts the weld ultrasonic imaging method as in Embodiment 2 to generate the final imaging result based on the A-scan signal collected by the ultrasonic probe.

[0089] Performance verification To verify the technical effectiveness of the rapid calculation method and imaging method for ultrasonic time delay of anisotropic welds based on slowness conservation provided by this invention, technicians conducted comparative tests with other traditional methods under specified scenarios. To facilitate differentiation between different imaging methods, this experiment refers to the full-focusing imaging and time delay product summation method based on the assumption of uniform sound speed and linear propagation as the "TFM" method and the "DMAS" method, respectively; the ray tracing correction full-focusing imaging and time delay product summation method based on Fermat's principle as the "FSRT-TFM" method and the "FSRT-DMAS" method, respectively; and the full-focusing imaging and time delay product summation method based on the propagation time delay calculation method of this invention as the "SCFRT-TFM" method and the "SCFRT-DMAS" method, respectively. The experimental procedure is as follows: I. Implementation process of the present invention The present invention first divides the 800HT alloy weld into sections based on the metallographic and EBSD characterization results, and constructs a two-dimensional columnar crystal finite element model based on the Voronoi method; then, by combining grain orientation data and coordinate transformation relationships, the equivalent elastic parameters of each section are determined, thereby establishing an anisotropic ultrasonic propagation model for the coarse-grained weld, such as... Figure 2 As shown in the figure. Side-drilled defects with diameters of 2 mm and depths of 10 mm, 15 mm, and 20 mm were set in the model, denoted as SDH1, SDH2, and SDH3, respectively. Then, simulation FMC data was acquired in the numerical model using a per-element transmission and full-element reception method.

[0090] Based on the input simulated FMC data, this invention calculates the relationship between phase velocity and group velocity by combining the equivalent stiffness matrix of each zone of the weld, and establishes a lookup table for lateral slowness. Subsequently, the propagation delay from the transmitting element to the pixel and from the pixel to the receiving element are solved for each pixel in the imaging area, and the propagation delay is substituted into the TFM and DMAS imaging framework to complete the defect reconstruction.

[0091] II. Imaging Comparison of Different Schemes

[0092] The imaging effects of the present invention and the control group are as follows: Figure 3 As shown, Figure 3 Part (a) shows the imaging effect of the TFM scheme. Figure 3 Part (b) shows the imaging results of the DMAS scheme. Figure 3 Part (c) shows the imaging effect of the FSRT-TFM scheme. Figure 3 The middle (d) section shows the imaging results of the FSRT-DMAS scheme. Figure 3 The middle (e) section shows the imaging effect of the SCFRT-TFM scheme. Figure 3 The middle (f) section shows the imaging effect of the SCFRT-DMAS scheme.

[0093] Analysis of the data in the figure shows that, compared with the traditional TFM and DMAS methods that use uniform sound velocity, the defect imaging positions of FSRT-TFM, FSRT-DMAS, SCFRT-TFM and SCFRT-DMAS after time delay correction are closer to the actual defect positions (white circles in the figure).

[0094] Performance comparison between the present invention and the control group scheme, for example Figures 4-6 As shown. Among them, Figure 4 A comparison chart of the signal-to-noise ratios of various schemes for the three types of defects; Figure 5 A comparison chart of the positioning errors of various schemes for the three types of defects; Figure 6 This is a comparison chart of the imaging times for each scheme.

[0095] Analysis of the data in the figure shows that the FSRT-DMAS and SCFRT-DMAS methods with propagation delay correction have higher signal-to-noise ratios and significantly reduced localization errors compared to traditional TFM and DMAS imaging. Specifically, the localization error of defect 1 was reduced by 72%. However, under the same computational resource configuration, FSRT-like methods take more than 60 seconds to compute, while the proposed SCFRT-DMAS and SCFRT-TFM methods take approximately 1 second to image, approaching the computational efficiency of traditional imaging methods without time delay correction. Therefore, this invention can effectively reduce defect localization errors in anisotropic welds. Furthermore, compared to the ray tracing correction FSRT method based on Fermat's principle, this invention significantly reduces imaging time while maintaining high imaging accuracy.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fast computation method of anisotropic weld ultrasonic time delay based on slowness conservation, characterized in that, It includes: The metallographic structure distribution of the weld to be tested is obtained, and the weld to be tested is divided into multiple layers along the depth according to the statistical law of grain orientation; Calibrate the stiffness and density values ​​of each layer; And construct the equivalent elastic stiffness matrix of the weld region; Multiple discrete propagation directions are selected within the two-dimensional propagation plane. The quasi-longitudinal wave phase velocity in each propagation direction is solved using the Christoffel equation based on the equivalent elastic stiffness matrix and the density values ​​of each layer. and lateral slowness ; and combine the polarization vector of the wave mode with the longitudinal wave phase velocity Decompose to obtain In any one of the weld seams to be tested i Lateral component of layer group velocity and longitudinal components ;Including: First, calculate any number of welds to be tested using the following formula. i Phase velocity of the layer : ； In the above formula, The equivalent elastic stiffness matrix of the anisotropic weld medium in fourth-order tensor form is given. i , j , k , l Corresponding to each level of index; n l The first normal vector of the unit wave represents the... l One component; u j and u k The polarization vectors of the corresponding wave modes are respectively the first and second polarization vectors. j and the k One component; Again on Orthogonal decomposition is performed to obtain In the weld to be tested, the arbitrary first i The lateral component and longitudinal component of the group velocity each discrete propagation direction corresponding , , and As a four-tuple, a lookup table representing the mapping between the transverse slowness and the transverse and longitudinal components is constructed using the four-tuples at multiple different propagation directions; denoted as: and ; According to the condition of transverse slowness conservation at the interface of each layer, combined with the spatial position relationship between the transmitting array element and the target point, a transverse displacement residual function along the propagation path is constructed , and the expression is: ； In the above formula, m represents the number of anisotropic media layers traversed by the propagation path; z i Indicates the ultrasound in the first... i The propagation thickness in the layer; p x Indicates lateral slowness; X The total lateral distance between the starting and ending points of the propagation; and These represent the transverse and longitudinal components of the group velocity in the i-th layer, respectively; within the definition domain of the look-up table, iteratively solving for the optimal lateral slowness that enables convergence in the current task ; and computing the optimal lateral slowness corresponding longitudinal component ; According to The propagation time of ultrasonic wave in each layer of the weld is calculated and accumulated to obtain the propagation time delay between the transmitting array element and any imaging point in the weld to be measured, and further a propagation time delay matrix is created.

2. The method for fast calculation of anisotropic weld ultrasonic time delay based on slowness conservation as claimed in claim 1, characterized in that: The metallographic distribution of the weld under test was obtained by EBSD detection; if the statistical law of grain orientation remains consistent in any thickness range along the depth direction of the weld under test, it is divided into one layer, and the weld has the same elastic parameters in the same layer. And / or, the method for constructing the equivalent elastic stiffness matrix includes: (1) the to-be-tested weld joint is a first weld joint i The stiffness matrix corresponding to the grain orientation of the layer is denoted as c i The average stiffness matrix is calculated by the following formula C V : ； In the above formula, N represents the number of layers of the weld. (2) Calculate the average compliance matrix under the assumption of uniform stress S R is: ； (2) combined C V and S R The equivalent elastic stiffness matrix of the weld region is calculated C eff is: 。 3. The fast calculation method of slowness-conserved anisotropic weld ultrasonic time delay according to claim 2, characterized in that, Methods for solving the phase velocity of quasi-longitudinal waves in any propagation direction include: selecting a plurality of discrete propagation direction angles in a two-dimensional propagation plane and solving the eigenvalues and eigenvectors of the Christoffel equation in each of the discrete propagation directions, selecting a quasi-longitudinal wave mode corresponding to a particle vibration direction and a wave normal direction to obtain the quasi-longitudinal wave phase velocity ; and / or, any direction of propagation the transverse slowness is given by 。 4. The method of claim 1, wherein: the optimal transverse slowness The iterative solution of the equation employs a secant method or a quasi-Newton method, and the initial value of iteration is determined according to the geometric relationship between the transmitting element and the target point.

5. The fast calculation method of slowness-conserved anisotropic weld ultrasonic time delay according to claim 1, characterized in that: The formula for calculating the Time-of-Flight (TOF) propagation delay between the transmitting array element and any target point in the weld to be tested is as follows: ； In the above formula, z i represents the propagation thickness of the ultrasonic wave in the first i layer.

6. A computer program product comprising a computer program, characterised in that, When the computer program is executed by the processor, it implements the fast calculation method for ultrasonic time delay of anisotropic welds based on slowness conservation as described in any one of claims 1-5, so as to generate a propagation time delay matrix characterizing the propagation time delay between the transmitting array element and any target point in the weld to be tested.

7. A method of weld ultrasonic imaging, characterized by, It includes: (1) First, the propagation time delay (TOF) between the transmitting array element and any target point in the weld to be tested is calculated using the fast calculation method for ultrasonic time delay of anisotropic weld based on slowness conservation as described in any one of claims 1-5; For transmitting array elements in array imaging T , imaging points P and receiving array elements R , their two-way propagation delay is: ； In the above formulae, denotes the propagation time delay between the transmitting array element T and an arbitrary imaging point in the weld under test P denotes the propagation time delay between the receiving array element R and an arbitrary imaging point in the weld under test P denotes the propagation time delay between the receiving array element R and an arbitrary imaging point in the weld under test​ (2) Obtain the full matrix acquisition data of the weld area, and calculate the imaging value of any pixel point in the imaging area by the following formula P I TFM ( P )​ ； In the above formula, N is the total number of array elements, s TR is the transmitting array element T and the receiving array element R corresponding A-scan signal.

8. An ultrasonic nondestructive testing device, comprising an ultrasonic probe, a data processing module, and a display module, wherein the data processing module comprises a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, it employs the ultrasonic imaging method for welds as described in claim 7 to generate a final imaging result based on the A-scan signal acquired by the ultrasonic probe.

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