Forging flaw detection method and system based on ultrasonic waves

Abstract

The invention provides a forge piece flaw detection method and system based on ultrasonic waves. Full-matrix data collected by scanning of an ultrasonic array on the surface of a forge piece along a preset path is obtained; separating a symmetric mode component and an antisymmetric mode component of the Lamb wave; the method comprises the following steps: establishing a propagation model in a frequency-wavenumber domain by taking a signal reflected from a known geometric structure of a forging as a reference, and determining non-uniform sound velocity distribution in the forging and attenuation coefficient distribution related to frequency; a focusing operator used for compensating signal propagation time and amplitude is constructed for each transmit-receive array element pair for any pixel point of the to-be-imaged area; performing synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component by using a focusing operator to obtain a symmetric mode focused image and an antisymmetric mode focused image; and determining a fusion criterion according to energy and phase information based on pixel points in the two images, and carrying out weighted fusion on the symmetric mode focusing image and the antisymmetric mode focusing image to generate an internal defect image of the forge piece.

Description

Technical Field

[0001] This application belongs to the field of flaw detection, and in particular relates to a method and system for flaw detection of forgings based on ultrasonic waves. Background Technology

[0002] Forgings are core load-bearing components in high-end equipment such as aerospace, nuclear power, and high-speed trains. Therefore, rigorous non-destructive testing of forgings to promptly detect and assess potential internal metallurgical defects (such as inclusions, porosity, and cracks) is crucial. Ultrasonic testing technology, due to its strong penetration, high sensitivity, and harmlessness to humans, has become the primary technique for detecting internal defects in forgings. Traditional ultrasonic testing often uses single-crystal probes for A-scan, B-scan, or C-scan, which suffers from low detection efficiency, low resolution, and strong reliance on operator experience. With technological advancements, ultrasonic phased arrays, by controlling the excitation delay of each element in the array, can achieve beam deflection, scanning, and focusing, significantly improving detection efficiency and flexibility. Building upon this, advanced imaging algorithms based on full matrix data acquisition (FMC), such as Synthetic Aperture Focusing (SAFT) and Total Focusing (TFM), can achieve focusing on every point within the detection area through coherent superposition of the full matrix data, thereby obtaining high-resolution, high signal-to-noise ratio defect images.

[0003] After undergoing complex manufacturing processes such as forging and heat treatment, the internal grain structure of forgings often exhibits non-uniformity and anisotropy, causing the sound velocity and attenuation characteristics of ultrasonic waves to be spatially non-constant. Traditional synthetic aperture focusing algorithms are mostly based on the assumption of a homogeneous medium, that is, assuming that the sound velocity and attenuation are constant, which can cause serious phase errors, leading to problems such as defocusing, artifacts, and inaccurate defect localization and quantification in the imaging results. For forgings of specific shapes, such as plates and shells, using Lamb waves for detection has unique advantages. However, Lamb waves have multi-mode and dispersion characteristics, meaning that multiple waveforms, such as symmetrical and anti-symmetrical modes, exist simultaneously at the same frequency, and their propagation speed varies with frequency. These different modes of signals overlap and interfere with each other, making accurate signal identification and interpretation difficult. If used directly for imaging without differentiation, a large number of mode artifacts will be generated, affecting the defect identification capability. Summary of the Invention

[0004] To address the problem of low defect identification in forging inspection due to signal aliasing and interference, this invention proposes an ultrasonic-based forging inspection method, comprising the following steps: Acquire the full matrix data collected by the ultrasonic array scanning along a preset path on the surface of the forging; perform a two-dimensional Fourier transform on the full matrix data to separate the symmetric mode component and antisymmetric mode component of the Lamb wave in the frequency-wavenumber domain. Using the signal reflected from the known geometry of the forging as a reference, a propagation model is established in the frequency-wavenumber domain, and the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging are determined through model inversion. For any pixel in the imaging region, based on the non-uniform sound velocity distribution and attenuation coefficient distribution, a focusing operator is constructed for each transceiver array element pair to compensate for signal propagation time and amplitude; the focusing operator is used to perform synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component respectively to obtain the symmetric mode focused image and the antisymmetric mode focused image. Based on the energy and phase information of pixels in the two images, a fusion criterion is determined, and the symmetric mode focused image and the antisymmetric mode focused image are weighted and fused to generate an image of internal defects in the forging.

[0005] Optionally, performing a two-dimensional Fourier transform on the full matrix data to separate the symmetric and antisymmetric mode components of the Lamb wave in the frequency-wavenumber domain includes: Perform a two-dimensional fast Fourier transform on the full matrix data along the time and space dimensions to obtain the frequency-wavenumber spectrum; Based on the Young's modulus, Poisson's ratio, and thickness of the forging material, calculate the theoretical dispersion curves of the Lamb wave symmetric mode and the antisymmetric mode; In the frequency-wavenumber spectrum, the first filtering window is constructed with the theoretical dispersion curve of the symmetric mode as the center line to filter the spectral data and obtain the symmetric mode components. In the frequency-wavenumber spectrum, a second filtering window is constructed with the theoretical dispersion curve of the antisymmetric mode as the center line to filter the spectral data and obtain the antisymmetric mode components.

[0006] Optionally, the step of using the signal reflected from the known geometry of the forging as a reference to establish a propagation model in the frequency-wavenumber domain, and determining the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging through model inversion, includes: Echo signals from the bottom or side surfaces of the forging are extracted from the full matrix data, and the echo signals are separated into symmetric mode reference signals and antisymmetric mode reference signals. Initial homogeneous medium propagation models are established for both the symmetric and antisymmetric modes. The reference signals predicted by each model are compared with the reference signals of the corresponding modes measured in actual operation, and the root mean square error of the two in phase and amplitude is calculated as the objective function. The gradient descent optimization algorithm is adopted to minimize the objective function corresponding to each mode. The sound velocity and attenuation coefficient values ​​in each propagation model are updated independently and iteratively until the root mean square error is lower than the preset threshold. The non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the symmetric mode and the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the antisymmetric mode are determined respectively.

[0007] Optionally, for any pixel in the region to be imaged, based on the non-uniform sound velocity distribution and attenuation coefficient distribution, a focusing operator is constructed for each transceiver array element pair to compensate for signal propagation time and amplitude, including: The area to be imaged is divided into a pixel grid; For any pixel P(x,z) in the grid, and the emitted array elements and receiving array elements The send / receive pair consists of: Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the aforementioned symmetric mode, the propagation time is calculated using the ray tracing method. Total attenuation Constructing a symmetric mode focusing operator ; Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the antisymmetric mode, the propagation time is calculated using the ray tracing method. Total attenuation Constructing antisymmetric mode focusing operators ; in, ω is the angular frequency, m is the number of the transmitting element in the ultrasonic array, n is the number of the receiving element in the ultrasonic array, and j is the imaginary unit.

[0008] Optionally, the step of using the focusing operator to perform synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component respectively to obtain the symmetric mode focused image and the antisymmetric mode focused image includes: For the separated symmetric mode components, the signal of each transmit / receive pair in the frequency domain is represented as follows: ; For each pixel P(x,z) in the region to be imaged, the symmetric mode focusing operator is used. Coherently superimpose the symmetric mode components of all transmit and receive pairs and calculate their pixel values. ; The calculation results of all pixels are combined to form a complete symmetrical pattern focused image. ; Using the same processing flow, the antisymmetric mode focusing operator is employed. Signal with antisymmetric mode components in the frequency domain Perform overlay calculations to obtain an antisymmetric mode focused image. .

[0009] Optionally, the step of determining a fusion criterion based on the energy and phase information of pixels in the two images, and performing weighted fusion of the symmetric mode focused image and the antisymmetric mode focused image to generate an image of internal defects in the forging, includes: For pixels with the same position (x, z) in two focused images and ; Calculate symmetric mode weights ; Calculate antisymmetric mode weights ; Calculate the phase consistency factor ; Pixel values ​​of merged images .

[0010] In a second aspect, the present invention proposes an ultrasonic-based forging flaw detection system, comprising the following modules: The decomposition module is used to acquire the full matrix data collected by the ultrasonic array scanning along a preset path on the surface of the forging; and to perform a two-dimensional Fourier transform on the full matrix data to separate the symmetric mode component and antisymmetric mode component of the Lamb wave in the frequency-wavenumber domain. The inversion module is used to establish a propagation model in the frequency-wavenumber domain using the signal reflected from the known geometry of the forging as a reference, and to determine the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging through model inversion. The generation module is used to construct a focusing operator for each transceiver array element pair to compensate for signal propagation time and amplitude based on the non-uniform sound velocity distribution and attenuation coefficient distribution for any pixel point in the imaging area; and to use the focusing operator to perform synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component respectively to obtain the symmetric mode focused image and the antisymmetric mode focused image. The fusion module is used to determine the fusion criteria based on the energy and phase information of pixels in two images, and to perform weighted fusion on the symmetric mode focused image and the antisymmetric mode focused image to generate an image of internal defects in the forging.

[0011] Optionally, performing a two-dimensional Fourier transform on the full matrix data to separate the symmetric and antisymmetric mode components of the Lamb wave in the frequency-wavenumber domain includes: Perform a two-dimensional fast Fourier transform on the full matrix data along the time and space dimensions to obtain the frequency-wavenumber spectrum; Based on the Young's modulus, Poisson's ratio, and thickness of the forging material, calculate the theoretical dispersion curves of the Lamb wave symmetric mode and the antisymmetric mode; In the frequency-wavenumber spectrum, the first filtering window is constructed with the theoretical dispersion curve of the symmetric mode as the center line to filter the spectral data and obtain the symmetric mode components. In the frequency-wavenumber spectrum, a second filtering window is constructed with the theoretical dispersion curve of the antisymmetric mode as the center line to filter the spectral data and obtain the antisymmetric mode components.

[0012] Optionally, the step of using the signal reflected from the known geometry of the forging as a reference to establish a propagation model in the frequency-wavenumber domain, and determining the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging through model inversion, includes: Echo signals from the bottom or side surfaces of the forging are extracted from the full matrix data, and the echo signals are separated into symmetric mode reference signals and antisymmetric mode reference signals. Initial homogeneous medium propagation models are established for both the symmetric and antisymmetric modes. The reference signals predicted by each model are compared with the reference signals of the corresponding modes measured in actual operation, and the root mean square error of the two in phase and amplitude is calculated as the objective function. The gradient descent optimization algorithm is adopted to minimize the objective function corresponding to each mode. The sound velocity and attenuation coefficient values ​​in each propagation model are updated independently and iteratively until the root mean square error is lower than the preset threshold. The non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the symmetric mode and the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the antisymmetric mode are determined respectively.

[0013] Optionally, for any pixel in the region to be imaged, based on the non-uniform sound velocity distribution and attenuation coefficient distribution, a focusing operator is constructed for each transceiver array element pair to compensate for signal propagation time and amplitude, including: The area to be imaged is divided into a pixel grid; For any pixel P(x,z) in the grid, and the emitted array elements and receiving array elements The send / receive pair consists of: Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the aforementioned symmetric mode, the propagation time is calculated using the ray tracing method. Total attenuation Constructing a symmetric mode focusing operator ; Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the antisymmetric mode, the propagation time is calculated using the ray tracing method. Total attenuation Constructing antisymmetric mode focusing operators ; in, ω is the angular frequency, m is the number of the transmitting element in the ultrasonic array, n is the number of the receiving element in the ultrasonic array, and j is the imaginary unit.

[0014] Optionally, the step of using the focusing operator to perform synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component respectively to obtain the symmetric mode focused image and the antisymmetric mode focused image includes: For the separated symmetric mode components, the signal of each transmit / receive pair in the frequency domain is represented as follows: ; For each pixel P(x,z) in the region to be imaged, the symmetric mode focusing operator is used. Coherently superimpose the symmetric mode components of all transmit and receive pairs and calculate their pixel values. ; The calculation results of all pixels are combined to form a complete symmetrical pattern focused image. ; Using the same processing flow, the antisymmetric mode focusing operator is employed. Signal with antisymmetric mode components in the frequency domain Perform overlay calculations to obtain an antisymmetric mode focused image. .

[0015] Optionally, the step of determining a fusion criterion based on the energy and phase information of pixels in the two images, and performing weighted fusion of the symmetric mode focused image and the antisymmetric mode focused image to generate an image of internal defects in the forging, includes: For pixels with the same position (x, z) in two focused images and ; Calculate symmetric mode weights ; Calculate antisymmetric mode weights ; Calculate the phase consistency factor ; Pixel values ​​of merged images .

[0016] Compared with existing technologies, this invention utilizes the echo signal from the forging's own structure to establish a propagation model of non-uniform sound velocity and attenuation, and constructs a focusing operator accordingly. This model can compensate for the phase and amplitude distortions caused by ultrasonic waves propagating in complex grain structures, overcoming image defocusing, artifacts, and positioning errors caused by the invalidation of the medium homogeneity assumption. Furthermore, this invention separates and independently images the symmetric and antisymmetric modes of the Lamb wave in the frequency-wavenumber domain, eliminating crosstalk and interference between different mode signals and avoiding mode artifacts. By weighted fusion of two high-quality mode images, complementary defect information carried by different modes is integrated, enhancing the real defect features while suppressing random noise. This results in defect images with higher signal-to-noise ratio and clearer details, improving the reliability of internal defect detection in forgings. Attached Figure Description

[0017] Figure 1 A flowchart of the first embodiment; Figure 2 Schematic diagrams of wavenumber and frequency in symmetric and antisymmetric models; Figure 3 This is a schematic diagram of synthetic aperture focusing. Figure 4 This is a schematic diagram of weighted fusion. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] The terminology used in the implementation section of this application is for the purpose of explaining specific embodiments of this application only, and is not intended to limit this application.

[0020] Figure 1 The flowchart of the first embodiment of the present invention is as follows: Figure 1 As shown, it includes the following steps: S1, acquire the full matrix data collected by the ultrasonic array scanning along a preset path on the surface of the forging; perform a two-dimensional Fourier transform on the full matrix data to separate the symmetric mode component and antisymmetric mode component of the Lamb wave in the frequency-wavenumber domain. A one-dimensional linear ultrasonic phased array probe is attached to the surface of a forging using an acoustic coupling agent. A mechanical scanning device controls the probe to move at a constant speed along a straight path along the length of the forging. At each location searched, each element in the array is excited once as a transmitting unit, while all elements receive the echo signal. This process continues until all elements have completed one transmission cycle. The resulting set of time-domain signals constitutes the full matrix data, which is a three-dimensional matrix that records the change in echo signal amplitude over time for each transmit-receive element pair.

[0021] For each transmitting element, the two-dimensional spatiotemporal data matrix composed of time-domain signals recorded by all receiving elements is transformed into the frequency-wavenumber domain by performing a two-dimensional Fourier transform along the time and space dimensions. In the frequency-wavenumber coordinate system, the energy concentration regions of symmetric modes (S0 mode) and antisymmetric modes (A0 mode) are determined based on the Lamb wave theory dispersion curve calculated according to the forging material and thickness. Two independent filters are used: one filter passes through the energy region of the symmetric mode, and the other filter passes through the energy region of the antisymmetric mode. These two filters are applied to the frequency-wavenumber domain data, and a two-dimensional inverse Fourier transform is performed on the filtered results to obtain the symmetric mode signal components and antisymmetric mode signal components that are separated in the spatiotemporal domain.

[0022] In an optional embodiment, performing a two-dimensional Fourier transform on the full matrix data to separate the symmetric and antisymmetric mode components of the Lamb wave in the frequency-wavenumber domain includes: Perform a two-dimensional fast Fourier transform on the full matrix data along the time and space dimensions to obtain the frequency-wavenumber spectrum; Based on the Young's modulus, Poisson's ratio, and thickness of the forging material, calculate the theoretical dispersion curves of the Lamb wave symmetric mode and the antisymmetric mode; In the frequency-wavenumber spectrum, the first filtering window is constructed with the theoretical dispersion curve of the symmetric mode as the center line to filter the spectral data and obtain the symmetric mode components. In the frequency-wavenumber spectrum, a second filtering window is constructed with the theoretical dispersion curve of the antisymmetric mode as the center line to filter the spectral data and obtain the antisymmetric mode components.

[0023] A fully collected matrix of data, for example, 1024×64 dimensions, where 1024 represents the number of time sampling points and 64 represents the number of spatial array elements, is processed using a two-dimensional Fast Fourier Transform algorithm to convert it into a frequency-wavenumber spectrum. The frequency-wavenumber spectrum is plotted with frequency on the vertical axis and wavenumber on the horizontal axis, showing the distribution of wave energy at different frequencies and wavenumbers.

[0024] Based on the known physical parameters of the forging material, such as Young's modulus of 210 GPa, Poisson's ratio of 0.3, and thickness of 20 mm, the theoretical wavenumbers of the Lamb wave symmetric S0 mode and antisymmetric A0 mode at different frequencies are calculated by solving the Rayleigh-Lamb wave equation, and two theoretical dispersion curves are plotted, as follows: Figure 2 As shown. The core of calculating the theoretical dispersion curve of the Lamb wave is solving the Rayleigh-Lamb equation. Using the material's Young's modulus (E), Poisson's ratio (ν), and density (ρ), the P-wave velocity and S-wave velocity are calculated. The numerical solution process involves defining a frequency range and using a numerical root-finding algorithm to search for wave numbers that satisfy the equations for both the symmetric and antisymmetric modes for each frequency value within that range. All the solved (frequency, wavenumber) data points are plotted on a coordinate system to obtain the theoretical dispersion curves for the symmetric mode (S0, S1, S2...) and the antisymmetric mode (A0, A1, A2...).

[0025] On the frequency-wavenumber spectrum, a two-dimensional Gaussian filter window with a bandwidth of 0.2 radians per millimeter is constructed with the theoretical dispersion curve of the symmetric mode as the center line. Data falling within this window in the spectrum is retained, while data outside the window is set to zero, thereby extracting the symmetric mode components. Using the same method, a second filter window is constructed with the theoretical dispersion curve of the antisymmetric mode as the center to extract the antisymmetric mode components.

[0026] S2, using the signal reflected from the known geometry of the forging as a reference, a propagation model is established in the frequency-wavenumber domain, and the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging are determined through model inversion; The bottom echo of the forging is selected as the reflected signal of the known geometry. The bottom echo signals corresponding to all transmit / receive array element pairs are extracted from the full matrix data, and their transit time and amplitude at different frequencies are measured. The imaging section of the forging is discretized into a pixel grid, and a propagation model mapping sound velocity and attenuation coefficient to signal transit time and amplitude is established. Tomographic imaging algorithms such as simultaneous iterative reconstruction are used for model inversion. Using the measured transit time and amplitude as targets, the sound velocity and attenuation coefficient values ​​of each pixel in the grid are continuously adjusted through iterative optimization until the error between the model-calculated transit time and amplitude and the actual measured values ​​is minimized. This yields a non-uniform sound velocity field and a frequency-dependent attenuation coefficient field that reflect changes in the internal grain structure of the forging.

[0027] S3, for any pixel in the imaging area, based on the non-uniform sound velocity distribution and attenuation coefficient distribution, construct a focusing operator for each transceiver array element pair to compensate for signal propagation time and amplitude; use the focusing operator to perform synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component respectively to obtain the symmetric mode focused image and the antisymmetric mode focused image. The imaging region is divided into a pixel grid consistent with the sound velocity distribution grid. For any pixel in the grid, using ray tracing algorithms such as the fast travel method, the sound wave propagation path and shortest propagation time from each transmitting element to that pixel and from that pixel to each receiving element are calculated in the determined non-uniform sound velocity field. The propagation times of the transmitting and receiving paths are added together to obtain the focusing delay time of the transmitting / receiving element pair for that pixel. Simultaneously, a line integral is performed along the calculated propagation path on the frequency-dependent attenuation coefficient field to calculate the cumulative signal attenuation; its reciprocal is the amplitude compensation weight. The focusing delay times of all transmitting / receiving element pairs and the amplitude compensation weight together constitute the focusing operator for that pixel.

[0028] Two blank images, the same size as the area to be imaged, are created, corresponding to the symmetric and antisymmetric modes, respectively. Each pixel in the imaging area is traversed; for the current pixel, all transmit-receive array element pairs are then traversed. Based on the calculated focusing operator, the amplitude of the sampling point specified by the focusing delay time is extracted from the separated symmetric mode signal data, multiplied by the corresponding amplitude compensation weight, and the result is accumulated at the position of that pixel in the symmetric mode image. Similarly, the corresponding amplitude is extracted and weighted from the antisymmetric mode signal data and accumulated at the corresponding pixel in the antisymmetric mode image. After traversing all array element pairs, the focusing calculation for the pixel is complete. This process is repeated for all pixels to generate complete symmetric mode focused images and antisymmetric mode focused images, as shown below. Figure 3 .

[0029] S4. Based on the energy and phase information of pixels in the two images, a fusion criterion is determined, and the symmetric mode focused image and the antisymmetric mode focused image are weighted and fused to generate an image of internal defects in the forging.

[0030] A Hilbert transform is applied to the two focused images to obtain a complex image containing amplitude and phase information. For each pixel in the image, its energy (the square of the complex amplitude) in the symmetric and antisymmetric complex images is calculated. A fusion weight is set based on the energy value; for example, the higher the energy of a pixel in a certain image, the greater its fusion weight at that point. Simultaneously, the phase difference between the two complex images at that pixel is calculated. If the phase difference is less than a preset threshold, it indicates strong coherence between the two modes at that point, possibly originating from the same defect, thus increasing its fusion weight; otherwise, it is decreased. The pixel values ​​of the two complex images are weighted and summed according to the calculated fusion weights to obtain the fused complex image. Its amplitude is taken as the defect image, such as... Figure 4 .

[0031] In an optional embodiment, the step of using the signal reflected from the known geometry of the forging as a reference to establish a propagation model in the frequency-wavenumber domain, and determining the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging through model inversion, includes: Echo signals from the bottom or side surfaces of the forging are extracted from the full matrix data, and the echo signals are separated into symmetric mode reference signals and antisymmetric mode reference signals. Initial homogeneous medium propagation models are established for both the symmetric and antisymmetric modes. The reference signals predicted by each model are compared with the reference signals of the corresponding modes measured in actual operation, and the root mean square error of the two in phase and amplitude is calculated as the objective function. The gradient descent optimization algorithm is adopted to minimize the objective function corresponding to each mode. The sound velocity and attenuation coefficient values ​​in each propagation model are updated independently and iteratively until the root mean square error is lower than the preset threshold. The non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the symmetric mode and the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the antisymmetric mode are determined respectively.

[0032] Specifically, the echo signal reflected from the bottom surface along the thickness direction of the forging is located and extracted from the full matrix data. For example, for a 20 mm thick steel part, the signal appears within a time window of approximately 13 microseconds. Using the aforementioned mode separation method, this bottom surface echo signal is decomposed into a symmetric mode reference signal and an antisymmetric mode reference signal. Initial propagation models are established for the symmetric and antisymmetric modes respectively. In one embodiment, models are established for the symmetric and antisymmetric modes respectively, and each model mainly consists of two parameters: uniform phase velocity and frequency-related attenuation coefficient. The initial uniform phase velocity value can be directly found from the calculated theoretical dispersion curve, and the phase velocity value corresponding to the center frequency of the ultrasonic probe is preferentially selected as the initial value for the symmetric and antisymmetric modes. For the attenuation coefficient, the approximate attenuation value of the forging material in the corresponding frequency band can be found in the material handbook, and a frequency-related function is set, for example... 'a' is a coefficient, or a small empirical constant. For example, assume the symmetric mode sound velocity is uniformly 5000 m / s throughout the forging region, with an attenuation coefficient of 0.1 dB / mm. Similarly, assume the antisymmetric mode sound velocity is 3000 m / s, with an attenuation of 0.2 dB / mm. Based on the initial model, the predicted reference signals for the symmetric and antisymmetric modes are simulated and calculated. The model-predicted reference signals are compared one by one with the actual separated reference signals, and the root mean square error (RMSE) of the phase and amplitude differences between the two is calculated. This error is used as the objective function. The gradient descent algorithm is used to iteratively adjust the sound velocity and attenuation values ​​at each grid point in the symmetric mode model, with the goal of reducing the RMSE of the symmetric mode. Independently, the same optimization process is performed on the antisymmetric mode until the RMSE of both models is reduced to a preset threshold, such as below 0.01, resulting in a non-uniform sound velocity and attenuation distribution.

[0033] In an optional embodiment, for any pixel in the region to be imaged, based on the non-uniform sound velocity distribution and attenuation coefficient distribution, a focusing operator is constructed for each transceiver array element pair to compensate for signal propagation time and amplitude, including: The area to be imaged is divided into a pixel grid; For any pixel P(x,z) in the grid, and the emitted array elements and receiving array elements The send / receive pair consists of: Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the aforementioned symmetric mode, the propagation time is calculated using the ray tracing method. Total attenuation Constructing a symmetric mode focusing operator ; Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the antisymmetric mode, the propagation time is calculated using the ray tracing method. Total attenuation Constructing antisymmetric mode focusing operators ; in, denoted as angular frequency, m as the number of the transmitting element in the ultrasonic array, n as the number of the receiving element in the ultrasonic array, and j as the imaginary unit. .

[0034] The internal region of the forging to be imaged, for example, a 100 mm × 20 mm area, is divided into a pixel grid, such as a 200 × 40 grid, with each pixel measuring 0.5 mm × 0.5 mm. For any pixel P in the grid, its coordinates are x, z, and any coordinates determined by the transmitting array element... and receiving array elements For the sent / receive pairs, perform the following calculations: For the symmetric mode, using the previously obtained non-uniform sound velocity and attenuation distributions, the ray tracing algorithm is used to calculate the sound velocity from the transmitting array element. From pixel P(x,z), then from pixel P(x,z) to the receiving array element Shortest propagation time and total attenuation accumulated along the path A symmetric mode focusing operator is constructed based on the above formula.

[0035] For antisymmetric modes, the propagation time along the same path can be calculated using ray tracing by utilizing their corresponding non-uniform sound velocity and attenuation distribution. Total attenuation And based on the above formula, a focusing operator for the antisymmetric mode is constructed.

[0036] This process will be repeated for all pixels and all transmit / receive pairs in the grid to generate a complete database of focusing operators.

[0037] In an optional embodiment, the step of using the focusing operator to perform synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component respectively to obtain a symmetric mode focused image and an antisymmetric mode focused image includes: For the separated symmetric mode components, the signal of each transmit / receive pair in the frequency domain is represented as follows: ; For each pixel P(x,z) in the region to be imaged, the symmetric mode focusing operator is used. Coherently superimpose the symmetric mode components of all transmit and receive pairs and calculate their pixel values. ; The calculation results of all pixels are combined to form a complete symmetrical pattern focused image. ; Using the same processing flow, the antisymmetric mode focusing operator is employed. Signal with antisymmetric mode components in the frequency domain Perform overlay calculations to obtain an antisymmetric mode focused image. .

[0038] A one-dimensional Fourier transform is performed on the previously separated symmetric mode time-domain signal components, i.e., the signals of each transmit / receive pair mn, to obtain their frequency domain representation. A function of frequency ω. To calculate the pixel value of a given pixel P at coordinates x, z in a symmetrically focused image. This requires coherent superposition of the signals from all transmit and receive pairs. For each transmit and receive pair mn, its frequency domain signal... Symmetric mode focusing operator corresponding to the previously constructed pixel P Multiply the results and integrate them over the entire frequency bandwidth. Sum the integrals of all transmit and receive pairs to obtain the final intensity value of the pixel. Arrange the calculated results of all pixels within the grid according to their spatial positions to form a complete symmetrical mode focused image. .

[0039] Similarly, the frequency domain signal components of the antisymmetric mode It also executes the exact same processing flow. It utilizes the focusing operator of the antisymmetric mode. By focusing and coherently superimposing the signals from all transmit and receive pairs, the value of each pixel is calculated, and finally, a complete antisymmetric mode focused image is generated. .

[0040] In an optional embodiment, the step of determining a fusion criterion based on the energy and phase information of pixels in the two images, and performing weighted fusion of the symmetric mode focused image and the antisymmetric mode focused image to generate an image of internal defects in the forging includes: For pixels with the same position (x, z) in two focused images and ; Calculate symmetric mode weights ; Calculate antisymmetric mode weights ; Calculate the phase consistency factor ; Pixel values ​​of merged images .

[0041] This embodiment is performed pixel-by-pixel. For pixels located at the same coordinates x and z in two focused images, their complex values ​​are respectively and For example, the pixel value at a certain point. It is 3+4j. It is 5-12j. The square of the modulus is 25. If the square of the modulus is 169, then... Approximately 0.129. Weights of the antisymmetric mode. Approximately 0.871. The sum of the complex numbers is 8-8j, and its modulus is approximately 11.31. The sum of the moduli is 18. Factors. It is approximately 0.628. Approximately 7.516. Repeat this calculation for all pixels in the image to generate the final defect image.

[0042] The second embodiment is an ultrasonic-based forging flaw detection system, comprising the following modules: The decomposition module is used to acquire the full matrix data collected by the ultrasonic array scanning along a preset path on the surface of the forging; and to perform a two-dimensional Fourier transform on the full matrix data to separate the symmetric mode component and antisymmetric mode component of the Lamb wave in the frequency-wavenumber domain. The inversion module is used to establish a propagation model in the frequency-wavenumber domain using the signal reflected from the known geometry of the forging as a reference, and to determine the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging through model inversion. The generation module is used to construct a focusing operator for each transceiver array element pair to compensate for signal propagation time and amplitude based on the non-uniform sound velocity distribution and attenuation coefficient distribution for any pixel point in the imaging area; and to use the focusing operator to perform synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component respectively to obtain the symmetric mode focused image and the antisymmetric mode focused image. The fusion module is used to determine the fusion criteria based on the energy and phase information of pixels in two images, and to perform weighted fusion on the symmetric mode focused image and the antisymmetric mode focused image to generate an image of internal defects in the forging.

[0043] In an optional embodiment, performing a two-dimensional Fourier transform on the full matrix data to separate the symmetric and antisymmetric mode components of the Lamb wave in the frequency-wavenumber domain includes: Perform a two-dimensional fast Fourier transform on the full matrix data along the time and space dimensions to obtain the frequency-wavenumber spectrum; Based on the Young's modulus, Poisson's ratio, and thickness of the forging material, calculate the theoretical dispersion curves of the Lamb wave symmetric mode and the antisymmetric mode; In the frequency-wavenumber spectrum, the first filtering window is constructed with the theoretical dispersion curve of the symmetric mode as the center line to filter the spectral data and obtain the symmetric mode components. In the frequency-wavenumber spectrum, a second filtering window is constructed with the theoretical dispersion curve of the antisymmetric mode as the center line to filter the spectral data and obtain the antisymmetric mode components.

[0044] In an optional embodiment, the step of using the signal reflected from the known geometry of the forging as a reference to establish a propagation model in the frequency-wavenumber domain, and determining the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging through model inversion, includes: Echo signals from the bottom or side surfaces of the forging are extracted from the full matrix data, and the echo signals are separated into symmetric mode reference signals and antisymmetric mode reference signals. Initial homogeneous medium propagation models are established for both the symmetric and antisymmetric modes. The reference signals predicted by each model are compared with the reference signals of the corresponding modes measured in actual operation, and the root mean square error of the two in phase and amplitude is calculated as the objective function. The gradient descent optimization algorithm is adopted to minimize the objective function corresponding to each mode. The sound velocity and attenuation coefficient values ​​in each propagation model are updated independently and iteratively until the root mean square error is lower than the preset threshold. The non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the symmetric mode and the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the antisymmetric mode are determined respectively.

[0045] In an optional embodiment, for any pixel in the region to be imaged, based on the non-uniform sound velocity distribution and attenuation coefficient distribution, a focusing operator is constructed for each transceiver array element pair to compensate for signal propagation time and amplitude, including: The area to be imaged is divided into a pixel grid; For any pixel P(x,z) in the grid, and the emitted array elements and receiving array elements The send / receive pair consists of: Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the symmetric mode, the propagation time and total attenuation are calculated using the ray tracing method, and a symmetric mode focusing operator is constructed. ; Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the antisymmetric mode, the propagation time and total attenuation are calculated using the ray tracing method, and an antisymmetric mode focusing operator is constructed. ; in, Let A be the propagation time, and A be the total attenuation. ω is the angular frequency.

[0046] In an optional embodiment, the step of using the focusing operator to perform synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component respectively to obtain a symmetric mode focused image and an antisymmetric mode focused image includes: For the separated symmetric mode components, the signal of each transmit / receive pair in the frequency domain is represented as follows: ; For each pixel P(x,z) in the region to be imaged, the symmetric mode focusing operator is used. Coherently superimpose the symmetric mode components of all transmit and receive pairs and calculate their pixel values. ; The calculation results of all pixels are combined to form a complete symmetrical pattern focused image. ; Using the same processing flow, the antisymmetric mode focusing operator is employed. Signal with antisymmetric mode components in the frequency domain Perform overlay calculations to obtain an antisymmetric mode focused image. .

[0047] In an optional embodiment, the step of determining a fusion criterion based on the energy and phase information of pixels in the two images, and performing weighted fusion of the symmetric mode focused image and the antisymmetric mode focused image to generate an image of internal defects in the forging includes: For pixels with the same position (x, z) in two focused images and ; Calculate symmetric mode weights ; Calculate antisymmetric mode weights ; Calculate the phase consistency factor ; Pixel values ​​of merged images .

[0048] In an exemplary embodiment, a non-transitory computer-readable storage medium including instructions is also provided, such as a memory including instructions that can be executed by a processor of a device to perform the method provided in this disclosure. For example, the non-transitory computer-readable storage medium may be a ROM, random access memory (RAM), CD-ROM, magnetic tape, floppy disk, and optical data storage device, etc.

[0049] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0050] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0051] The method and electronic device for providing product object information provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and its core ideas. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for flaw detection of forgings based on ultrasound, characterized in that, Includes the following steps: Acquire the full matrix data collected by the ultrasonic array scanning along a preset path on the surface of the forging; perform a two-dimensional Fourier transform on the full matrix data to separate the symmetric mode component and antisymmetric mode component of the Lamb wave in the frequency-wavenumber domain. Using the signal reflected from the known geometry of the forging as a reference, a propagation model is established in the frequency-wavenumber domain, and the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging are determined through model inversion. For any pixel in the imaging region, based on the non-uniform sound velocity distribution and attenuation coefficient distribution, a focusing operator is constructed for each transceiver array element pair to compensate for signal propagation time and amplitude; the focusing operator is used to perform synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component respectively to obtain the symmetric mode focused image and the antisymmetric mode focused image. Based on the energy and phase information of pixels in the two images, a fusion criterion is determined, and the symmetric mode focused image and the antisymmetric mode focused image are weighted and fused to generate an image of internal defects in the forging.

2. The method according to claim 1, characterized in that, The step of performing a two-dimensional Fourier transform on the full matrix data to separate the symmetric and antisymmetric mode components of the Lamb wave in the frequency-wavenumber domain includes: Perform a two-dimensional fast Fourier transform on the full matrix data along the time and space dimensions to obtain the frequency-wavenumber spectrum; Based on the Young's modulus, Poisson's ratio, and thickness of the forging material, calculate the theoretical dispersion curves of the Lamb wave symmetric mode and the antisymmetric mode; In the frequency-wavenumber spectrum, the first filtering window is constructed with the theoretical dispersion curve of the symmetric mode as the center line to filter the spectral data and obtain the symmetric mode components. In the frequency-wavenumber spectrum, a second filtering window is constructed with the theoretical dispersion curve of the antisymmetric mode as the center line to filter the spectral data and obtain the antisymmetric mode components.

3. The method according to claim 1, characterized in that, The process of using the signal reflected from the known geometry of the forging as a reference to establish a propagation model in the frequency-wavenumber domain, and determining the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging through model inversion, includes: Echo signals from the bottom or side surfaces of the forging are extracted from the full matrix data, and the echo signals are separated into symmetric mode reference signals and antisymmetric mode reference signals. Initial homogeneous medium propagation models are established for both the symmetric and antisymmetric modes. The reference signals predicted by each model are compared with the reference signals of the corresponding modes measured in actual operation, and the root mean square error of the two in phase and amplitude is calculated as the objective function. The gradient descent optimization algorithm is adopted to minimize the objective function corresponding to each mode. The sound velocity and attenuation coefficient values ​​in each propagation model are updated independently and iteratively until the root mean square error is lower than the preset threshold. The non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the symmetric mode and the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the antisymmetric mode are determined respectively.

4. The method according to claim 1, characterized in that, For any pixel in the region to be imaged, based on the non-uniform sound velocity distribution and attenuation coefficient distribution, a focusing operator is constructed for each transceiver array element pair to compensate for signal propagation time and amplitude, including: The area to be imaged is divided into a pixel grid; For any pixel P(x,z) in the grid, and the emitted array elements and receiving array elements The send / receive pair consists of: Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the aforementioned symmetric mode, the propagation time is calculated using the ray tracing method. Total attenuation Constructing a symmetric mode focusing operator ; Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the antisymmetric mode, the propagation time is calculated using the ray tracing method. Total attenuation Constructing antisymmetric mode focusing operators ; in, ω is the angular frequency, m is the number of the transmitting element in the ultrasonic array, n is the number of the receiving element in the ultrasonic array, and j is the imaginary unit.

5. The method according to claim 4, characterized in that, The step of using the focusing operator to perform synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component respectively to obtain the symmetric mode focused image and the antisymmetric mode focused image includes: For the separated symmetric mode components, the signal of each transmit / receive pair in the frequency domain is represented as follows: ; For each pixel P(x,z) in the region to be imaged, the symmetric mode focusing operator is used. Coherently superimpose the symmetric mode components of all transmit and receive pairs and calculate their pixel values. ; The calculation results of all pixels are combined to form a complete symmetrical pattern focused image. ; Using the same processing flow, the antisymmetric mode focusing operator is employed. Signal with antisymmetric mode components in the frequency domain Perform overlay calculations to obtain an antisymmetric mode focused image. .

6. The method according to claim 1, characterized in that, The step of determining a fusion criterion based on the energy and phase information of pixels in two images, and performing weighted fusion of the symmetric mode focused image and the antisymmetric mode focused image to generate an image of internal defects in the forging includes: For pixels with the same position (x, z) in two focused images and ; Calculate symmetric mode weights ; Calculate antisymmetric mode weights ; Calculate the phase consistency factor ; Pixel values ​​of merged images .

7. An ultrasonic-based forging flaw detection system, characterized in that, Includes the following modules: The decomposition module is used to acquire the full matrix data collected by the ultrasonic array scanning along a preset path on the surface of the forging; and to perform a two-dimensional Fourier transform on the full matrix data to separate the symmetric mode component and antisymmetric mode component of the Lamb wave in the frequency-wavenumber domain. The inversion module is used to establish a propagation model in the frequency-wavenumber domain using the signal reflected from the known geometry of the forging as a reference, and to determine the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging through model inversion. The generation module is used to construct a focusing operator for each transceiver array element pair to compensate for signal propagation time and amplitude based on the non-uniform sound velocity distribution and attenuation coefficient distribution for any pixel point in the imaging area; and to use the focusing operator to perform synthetic aperture focusing on the symmetric mode component and the antisymmetric mode component respectively to obtain the symmetric mode focused image and the antisymmetric mode focused image. The fusion module is used to determine the fusion criteria based on the energy and phase information of pixels in two images, and to perform weighted fusion on the symmetric mode focused image and the antisymmetric mode focused image to generate an image of internal defects in the forging.

8. The system according to claim 7, characterized in that, The step of performing a two-dimensional Fourier transform on the full matrix data to separate the symmetric and antisymmetric mode components of the Lamb wave in the frequency-wavenumber domain includes: Perform a two-dimensional fast Fourier transform on the full matrix data along the time and space dimensions to obtain the frequency-wavenumber spectrum; Based on the Young's modulus, Poisson's ratio, and thickness of the forging material, calculate the theoretical dispersion curves of the Lamb wave symmetric mode and the antisymmetric mode; In the frequency-wavenumber spectrum, the first filtering window is constructed with the theoretical dispersion curve of the symmetric mode as the center line to filter the spectral data and obtain the symmetric mode components. In the frequency-wavenumber spectrum, a second filtering window is constructed with the theoretical dispersion curve of the antisymmetric mode as the center line to filter the spectral data and obtain the antisymmetric mode components.

9. The system according to claim 7, characterized in that, The process of using the signal reflected from the known geometry of the forging as a reference to establish a propagation model in the frequency-wavenumber domain, and determining the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution inside the forging through model inversion, includes: Echo signals from the bottom or side surfaces of the forging are extracted from the full matrix data, and the echo signals are separated into symmetric mode reference signals and antisymmetric mode reference signals. Initial homogeneous medium propagation models are established for both the symmetric and antisymmetric modes. The reference signals predicted by each model are compared with the reference signals of the corresponding modes measured in actual operation, and the root mean square error of the two in phase and amplitude is calculated as the objective function. The gradient descent optimization algorithm is adopted to minimize the objective function corresponding to each mode. The sound velocity and attenuation coefficient values ​​in each propagation model are updated independently and iteratively until the root mean square error is lower than the preset threshold. The non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the symmetric mode and the non-uniform sound velocity distribution and frequency-related attenuation coefficient distribution of the antisymmetric mode are determined respectively.

10. The system according to claim 7, characterized in that, For any pixel in the region to be imaged, based on the non-uniform sound velocity distribution and attenuation coefficient distribution, a focusing operator is constructed for each transceiver array element pair to compensate for signal propagation time and amplitude, including: The area to be imaged is divided into a pixel grid; For any pixel P(x,z) in the grid, and the emitted array elements and receiving array elements The send / receive pair consists of: Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the aforementioned symmetric mode, the propagation time is calculated using the ray tracing method. Total attenuation Constructing a symmetric mode focusing operator ; Based on the non-uniform sound velocity distribution and attenuation coefficient distribution of the antisymmetric mode, the propagation time is calculated using the ray tracing method. Total attenuation Constructing antisymmetric mode focusing operators ; in, ω is the angular frequency, m is the number of the transmitting element in the ultrasonic array, n is the number of the receiving element in the ultrasonic array, and j is the imaginary unit.

Images