Laser-EMAT guided wave evaluation system for micro damage of high-temperature alloy sheet in high-temperature environment

Abstract

The invention discloses a Laser-EMAT guided wave evaluation system for micro damage of a high-temperature alloy sheet in a high-temperature environment, which comprises a Laser-EMAT system, and the Laser-EMAT system comprises a laser transmitter, a cylindrical lens, an electromagnetic ultrasonic Lamb guided wave receiving probe, an impedance matching network, a pre-filter amplifier, a data acquisition card and Labview software. The Laser-EMAT guided wave evaluation system for the tiny damage of the high-temperature alloy sheet in the high-temperature environment is used for executing the Laser-EMAT guided wave evaluation method for the tiny damage of the high-temperature alloy sheet in the high-temperature environment. The laser-EMAT system is used for carrying out damage detection on the alloy plate, the non-contact electromagnetic ultrasonic technology is adopted, defects are recognized through Lamb guided wave imaging, the effects of high resolution and high detection sensitivity are achieved, and tiny damage can be accurately recognized. The invention further provides a method for performing temperature compensation on imaging, and the detection sensitivity is improved.

Description

Technical Field

[0001] The invention relates to the technical field of ultrasonic detection of alloy materials, and in particular to a Laser-EMAT guided wave evaluation system for micro-damage of a high-temperature alloy thin plate under a high-temperature environment. Background Art

[0002] Alloy materials are widely used in transportation, construction, electromechanical and other industries due to their good casting properties and plastic processing properties. They also play an important role in the aerospace field due to their advantages such as lightness and corrosion resistance. However, with the continuous advancement of technology, the demand for high-temperature alloy parts is also increasing. Since medium and high-strength alloys have characteristics such as high thermal conductivity, laser reflectivity and a wide solidification temperature range, how to monitor defects such as thermal cracks generated by alloys in high-temperature environments has become an important issue.

[0003] Since the Lamb wave excited by the pulsed laser has a wide bandwidth and multiple guided wave modes, it is very easy to have wave packet aliasing. After interacting with the crack, the guided wave dispersion is serious, the spatial resolution is poor, and the detection sensitivity decreases. The most critical thing is that it is difficult to distinguish the defect wave packets and it is impossible to effectively detect minor damage. Therefore, it is necessary to develop a system and method for detecting minor damage to alloys. Summary of the invention

[0004] In view of the above-mentioned prior art, the present invention provides a Laser-EMAT guided wave evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment, mainly to solve the technical problems existing in the above-mentioned background technology.

[0005] To achieve the above purpose, the technical solution of the embodiment of the present invention is implemented as follows:

[0006] The Laser-EMAT waveguide evaluation system for micro-damage of a high-temperature alloy sheet under a high-temperature environment comprises a Laser-EMAT system, wherein the Laser-EMAT system comprises: a laser transmitter, a cylindrical lens, an electromagnetic ultrasonic Lamb waveguide receiving probe, an impedance matching network, a pre-filter amplifier, a data acquisition card, and Labview software. The Laser-EMAT waveguide evaluation system for micro-damage of a high-temperature alloy sheet under a high-temperature environment is used to perform a Laser-EMAT waveguide evaluation method for micro-damage of a high-temperature alloy sheet under a high-temperature environment. The method comprises the following steps:

[0007] Step 1: The laser emitter is projected onto the alloy plate through a cylindrical lens, and the plate excites Lamb guided waves propagating along the length direction of the plate based on the thermoelastic mechanism;

[0008] Step 2: When the Lamb waveguide encounters a tiny damage defect in the alloy, a defect reflection echo is generated, which is received by the electromagnetic ultrasonic Lamb waveguide receiving probe, amplified by the pre-filter amplifier, and input into the computer through the data acquisition card. The signal is collected using Labview software to obtain the alloy plate detection echo signal;

[0009] Step 3, adjusting the impedance matching network to achieve impedance matching between the electromagnetic ultrasonic Lamb waveguide receiving probe and the input impedance of the pre-filter amplifier;

[0010] Step 4, keeping the laser point position unchanged, moving the electromagnetic ultrasonic Lamb waveguide receiving probe in a direction away from the defect, and collecting echo signals at different positions;

[0011] Step 5, processing and imaging the detection echo signal, and judging whether the alloy plate has micro damage defects according to the imaging image;

[0012] Step 6, control the mode of Lamb wave by controlling the laser wavelength, use specific mode Lamb wave to detect different types of defects, and select the best mode for detection of different defects to improve the detection sensitivity of minor damages.

[0013] Furthermore, the electromagnetic ultrasonic Lamb waveguide receiving probe includes a permanent magnet, a linear coil, a yoke and a brass shell. The permanent magnet is a pair of samarium cobalt high-temperature resistant magnets with opposite polarities and is placed in the brass shell. The linear coil is made of silk-covered wire wound on a ceramic block. The linear coil is placed in the middle of the permanent magnet, and the yoke is placed above the permanent magnet.

[0014] Furthermore, the permanent magnet has a width of 5-20 mm, a length of 5-20 mm, a height of 5-20 mm, an outer diameter of the silk-covered wire of 0.1-0.5 mm, and a thickness of the magnetic track of 3-5 mm.

[0015] Furthermore, in step 1, the laser transmitter uses a solid-state laser Nd:YAG laser, and the pulse width is adjusted to 8-12ns and the laser energy is 590-650V.

[0016] Furthermore, in step 1, the focal length of the cylindrical lens is 400 mm, and the laser emitter is focused into a sheet light source with a length of 8-10 mm and a width of 1-1.5 mm after passing through the cylindrical lens.

[0017] Furthermore, in step 4, the electromagnetic ultrasonic Lamb waveguide receiving probe is moved in a step length of 2-5 mm in a direction away from the defect to collect echo signals at different positions, and at least 50 groups of detection echo signals are collected in total.

[0018] Furthermore, in step 5, the detection echo signal is processed and imaged, and the method steps are as follows:

[0019] Step S1, preprocessing the collected signal, including filtering and denoising, to improve signal quality;

[0020] Step S2, performing Hilbert transform on the preprocessed signal to generate an analytical signal, and extracting instantaneous characteristics including instantaneous amplitude and instantaneous phase from the analytical signal;

[0021] Step S3, analyzing the law of instantaneous characteristics changing with temperature, and establishing a mathematical model describing the relationship between temperature and instantaneous amplitude and phase;

[0022] Step S4, using LM algorithm to optimize the relationship model parameters between temperature and transient characteristics;

[0023] Step S5, establishing a regression model using the least squares method;

[0024] Step S6, bringing the experimental waveguide signal into the regression model, calculating the compensation parameters, and applying the compensation parameters to adjust the original signal to obtain a compensated signal;

[0025] Step S7, using a validation set or a cross-algorithm validation method to evaluate the accuracy of the temperature compensation model, and adjusting model parameters or optimizing the algorithm according to the validation results;

[0026] Step S8, importing the compensated waveguide signal and frequency-wavenumber data into MATLAB software, performing a two-dimensional Fourier transform, forming a frequency-wavenumber domain imaging spectrum, analyzing the imaging spectrum, and evaluating the detection results of micro-damage;

[0027] Step S9, use Disperse to calculate the corresponding relationship between the frequency and wave number data of each mode of Lamb waveguide, import 50 groups of detection echo signals and each mode frequency-waveguide data into matlab for two-dimensional Fourier transform and imaging. The imaging difference between defects and non-defects can be clearly seen from the imaging image, realizing the rapid detection of minor damages of alloy plates and thin plates.

[0028] Furthermore, the step S4 specifically includes defining a temperature compensation model, including temperature and other related variables; collecting performance data at different temperatures, establishing an objective function, calculating a residual vector and a Jacobian matrix; initializing parameters, selecting an adjustment parameter λ; iteratively solving, and updating parameter estimates until convergence conditions are met.

[0029] Furthermore, the step S5 specifically includes defining the form of the regression model, including dependent variables, independent variables and model parameters; collecting the observed values ​​of all independent variables and dependent variables; preprocessing the data, removing outliers and missing values; establishing the objective function, defining the residual sum of squares, and estimating the model parameters by the least squares method.

[0030] The beneficial effects of the present invention are:

[0031] The present invention provides a Laser-EMAT waveguide evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment. Its electromagnetic ultrasonic Lamb waveguide receiving probe adopts a linear coil wound with silk-wrapped wire, combined with a high-temperature resistant samarium cobalt permanent magnet and a magnetic yoke to form a unique probe configuration, and the brass shell can greatly protect the probe from the influence of the external environment and improve the energy conversion efficiency. It adopts non-contact electromagnetic ultrasonic technology, does not need to carry coupling agents, can quickly detect micro-damage in high-temperature environment, and improves the detection efficiency while ensuring the detection quality.

[0032] The use of two-dimensional Fourier transform technology combined with Lamb waveguide modal information can intuitively identify whether there are defects, which is suitable for online non-destructive testing of alloy thin plates and can achieve long-distance rapid testing. A method of establishing a regression model is proposed to perform temperature compensation on images in a high-temperature environment to improve detection sensitivity. By changing the Laser-EMAT system parameters and selecting the optimal parameters based on the dispersion curve, the effect of damage changes on waveguide dispersion is more significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the principle of the laser transmitter exciting ultrasonic waves in the Laser-EMAT waveguide evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment in the embodiment of the present application;

[0034] Figure 2 This is an internal structure diagram of the electromagnetic ultrasonic Lamb guided wave receiving probe in the Laser-EMAT guided wave evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment in the embodiment of the present application;

[0035] Figure 3 This is a diagram of the detection method of the alloy plate by the Laser-EMAT system in the Laser-EMAT guided wave evaluation system for micro-damage of a high-temperature alloy thin plate under a high-temperature environment in an embodiment of the present application;

[0036] Figure 4 This is a schematic diagram of the detection principle of the alloy plate by the Laser-EMAT system in the Laser-EMAT guided wave evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment in an embodiment of the present application;

[0037] Figure 5 This is a signal imaging flow chart of the Laser-EMAT guided wave evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment in an embodiment of the present application;

[0038] Figure 6This is a detection echo signal diagram of the alloy plate without defects in the Laser-EMAT waveguide evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment in the embodiment of the present application;

[0039] Figure 7 This is a detection echo signal diagram of the alloy plate with defects in the Laser-EMAT waveguide evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment in the embodiment of the present application;

[0040] Figure 8 This is a frequency-wave number diagram obtained after two-dimensional Fourier transform of 50 groups of detection echo signals in the Laser-EMAT waveguide evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment in the embodiment of the present application when the alloy plate has no defects;

[0041] Fig. 9 This is a frequency-wave number diagram obtained by performing two-dimensional Fourier transform on 50 groups of detection echo signals in the Laser-EMAT waveguide evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment in the embodiment of the present application when the alloy plate has defects;

[0042] Fig.10 This is a non-defect detection echo signal diagram of the Laser-EMAT waveguide evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment in the embodiment of the present application when the laser transmitter parameters are changed;

[0043] Fig.11 This is a defect detection echo signal diagram of the Laser-EMAT waveguide evaluation system for micro-damage of a high-temperature alloy thin plate under a high-temperature environment in an embodiment of the present application when the laser transmitter parameters are changed;

[0044] Fig.12 The frequency-wave number diagram obtained by performing two-dimensional Fourier transform on 50 groups of defect-free detection echo signals in the Laser-EMAT waveguide evaluation system for micro-damage of high-temperature alloy thin plates under high-temperature environment in the embodiment of the present application when the laser transmitter parameters are changed;

[0045] Fig.13 The frequency-wave number diagram obtained by performing two-dimensional Fourier transform on 50 groups of defective detection echo signals when the laser transmitter parameters are changed in the Laser-EMAT waveguide evaluation system for micro-damage of a high-temperature alloy thin plate under a high-temperature environment in an embodiment of the present application;

[0046] Fig.14 This is a dispersion characteristic curve of an aluminum alloy with a thickness of 2 mm in the Laser-EMAT waveguide evaluation system for micro-damage of a high-temperature alloy thin plate under a high-temperature environment in an embodiment of the present application.

[0047] Description of Figure Numbers:

[0048] 1. Permanent magnet; 2. Linear coil; 3. Yoke; 4. Brass shell; 5. Alloy plate. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further elaborated in detail below in conjunction with the drawings and specific embodiments of the specification. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In the following description, the expression "some embodiments" is related to a subset of all possible embodiments, but it should be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0050] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

[0051] It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments proposed herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and the scope of the present invention will be fully conveyed to those skilled in the art. And the purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present invention. When used herein, the singular forms of "one", "one" and "said / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "compose" and / or "include" when used in this specification determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0052] It should also be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "inside", "outside", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0053] In order to fully understand the present invention, a detailed structure will be proposed in the following description to illustrate the technical solution proposed by the present invention. The optional embodiments of the present invention are described in detail as follows, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0054] In order to make the above technical solutions and features of the present invention more intuitive and easy to understand, the following is a detailed explanation in conjunction with the accompanying drawings and specific embodiments. The embodiments described in the accompanying drawings are only exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0055] like Figure 2 The figure shows the configuration of the electromagnetic ultrasonic Lamb waveguide receiving probe of the present invention. The electromagnetic ultrasonic Lamb waveguide receiving probe comprises a permanent magnet 1, a linear coil 2, a yoke 3 and a brass shell 4. The permanent magnet 1 is a pair of samarium cobalt high temperature resistant magnets with opposite polarities and is placed in the brass shell 4. The linear coil 2 is made of a silk-covered wire wound on a ceramic block. The linear coil 2 is placed in the middle of the permanent magnet 1, and the yoke 3 is placed above the permanent magnet 1.

[0056] Exemplarily, the permanent magnet 1 has a width of 5-20 mm, a length of 5-20 mm, a height of 5-20 mm, an outer diameter of the wire cover is 0.1-0.5 mm, and a thickness of the magnetic track 3 is 3-5 mm.

[0057] like Figure 3 , Figure 4 As shown, the present application provides a Laser-EMAT waveguide evaluation system for micro-damage of a high-temperature alloy thin plate under a high-temperature environment, characterized in that it includes a Laser-EMAT system, the Laser-EMAT system includes: a laser transmitter, a cylindrical lens, an electromagnetic ultrasonic Lamb waveguide receiving probe, an impedance matching network, a pre-filter amplifier, a data acquisition card, and Labview software. The Laser-EMAT system is used for a Laser-EMAT waveguide evaluation method for micro-damage of a high-temperature alloy thin plate under a high-temperature environment, and the method steps are as follows:

[0058] Step 1, the laser emitter is projected onto the alloy plate 5 through a cylindrical lens, and the plate excites Lamb guided waves propagating along the length direction of the plate based on the thermoelastic mechanism;

[0059] Exemplarily, the laser emitter uses a solid-state laser Nd:YAG laser, and the pulse width is adjusted to 8-12ns and the laser energy is 590-650V; the focal length of the cylindrical lens is 400mm, and the laser emitter is focused into a sheet light source with a length of 8-10mm and a width of 1-1.5mm after passing through the cylindrical lens.

[0060] Step 2: When the Lamb waveguide encounters a tiny damage defect in the alloy, a defect reflection echo is generated. The defect reflection echo is received by the electromagnetic ultrasonic Lamb waveguide receiving probe, amplified by the pre-filter amplifier, and input into the computer through the data acquisition card. The signal is collected using Labview software to obtain the detection echo signal of the alloy plate 5.

[0061] Step 3, adjusting the impedance matching network to achieve impedance matching between the electromagnetic ultrasonic Lamb waveguide receiving probe and the input impedance of the pre-filter amplifier.

[0062] Step 4, keeping the laser point position unchanged, moving the electromagnetic ultrasonic Lamb waveguide receiving probe in a direction away from the defect, and collecting echo signals at different positions;

[0063] Exemplarily, the electromagnetic ultrasonic Lamb waveguide receiving probe is moved in a step length of 2-5 mm in a direction away from the defect to collect echo signals at different positions, and at least 50 groups of detection echo signals are collected in total.

[0064] Step 5: Process and image the detection echo signal, and determine whether the alloy plate 5 has micro damage defects based on the image.

[0065] Step 6, the mode of Lamb wave is controlled by controlling the laser wavelength. For different types of defects, Lamb wave with a specific mode is used for detection, and the best mode is selected for detection of different defects to improve the detection sensitivity of minor damages.

[0066] For example, the Laser-EMAT system parameters are changed to change the laser radius from 1.5 mm to 5 mm. Figures 5 to 12 It can be seen that after changing the spot radius, the damage change has a significant impact on the waveguide dispersion. The waveguide wavelength calculation formula λ=v p / f, where λ is the wavelength, v p is the propagation speed of the guided wave in the solid, and f is the frequency of the wave. Based on the formula, the wavelength λ is the slope of the slope of the origin in the phase velocity dispersion curve of the fixed thickness thin plate. The slope will have an intersection with the dispersion curves of multiple guided wave modes in the phase velocity dispersion curve, indicating that the Laser-EMAT system using the corresponding wavelength can excite the target mode guided wave signal at the frequency corresponding to the intersection. Fig.14As shown in the figure, the wavelength of the waveguide corresponding to the oblique line is 3.5mm, and there are intersections with the A0, S0, A1, S1, A2 and S2 modes at frequencies of 0.7MHz, 1.1MHz, 1.6MHz, 1.8MHz, 2.4MHz and 2.5MHz respectively. Therefore, the mode of the Lamb wave can be controlled by controlling the wavelength, and then the specific mode Lamb wave is used to detect different types of defects, and the sensitivity of different types of defects to different waveguide modes is obtained. The best mode is selected for detection of different types of defects to improve the detection sensitivity of minor damage.

[0067] like Figure 5 As shown, the detection echo signal is processed and imaged in step 5, including the following steps:

[0068] Step S1, preprocessing the signals collected by the Laser-EMAT system, including filtering and denoising, to improve signal quality.

[0069] Step S2, performing Hilbert transform on the preprocessed signal to generate an analytical signal, and extracting instantaneous characteristics including instantaneous amplitude and instantaneous phase from the analytical signal;

[0070] For example, the increase in temperature will increase the expansion coefficient of the material, reduce the material density, and reduce the elastic modulus. This is manifested as a decrease in signal amplitude and a shift in phase. Therefore, the temperature effect can be described by the change in the amplitude and phase of the Lamb wave signal;

[0071] Perform Hilbert transform on the preprocessed signal. Through Hilbert transform, the real signal x(t) can be expanded into a complex signal X a (t) = x(t) + i*y(t), where X(t) is the analytical signal, the real part x(t) is the original signal, the imaginary part y(t) is the original signal generated by Hilbert transform, and i is the imaginary unit. Instantaneous characteristics such as instantaneous amplitude (envelope) and instantaneous phase are extracted from the analytical signal. The instantaneous amplitude can be obtained by calculating the modulus of the analytical signal, and the instantaneous phase is the argument of the analytical signal.

[0072] Step S3, analyzing the law of the instantaneous characteristic changing with temperature, and establishing a mathematical model describing the relationship between temperature and instantaneous amplitude and phase.

[0073] Step S4, using LM algorithm to optimize the relationship model parameters between temperature and transient characteristics;

[0074] Exemplarily, the step S4 specifically includes defining a temperature compensation model, including temperature and other related variables; collecting performance data at different temperatures, establishing an objective function, calculating a residual vector and a Jacobian matrix; initializing parameters, selecting an adjustment parameter λ; iteratively solving, and updating parameter estimates until convergence conditions are met.

[0075] The steps for model parameter optimization using the LM algorithm are:

[0076] (1) Define the model and collect data: Establish a mathematical model of the amplitude and phase of the guided wave with respect to the number of sampling points at different temperatures and collect data.

[0077] (2) Establishing the objective function: Define an objective function related to temperature T and number of sampling points N:

[0078]

[0079] Among them (r i )p is the actual detection signal y at temperature T i The signal reconstructed by the model and the actual signal acquired multiple times The residual p between is the parameter vector, and N is the number of sampling points. The estimation of compensation parameters is converted into the problem of finding the optimal solution of parameters through the formula.

[0080] (3) Initialization parameters: Select an initial parameter estimate p (0) .

[0081] (4) Calculate the residual and construct the Jacobian matrix: Calculate the residual vector (r)p between the predicted value of the temperature compensation model and the actual observed value, and construct the Jacobian J relative to the parameters.

[0082] (5) Calculate the cost function: Calculate the cost function:

[0083] Cost function = 1 / 2r(p) T r(p)

[0084] The cost function is half of the sum of squared residuals.

[0085] (6) Select tuning parameter: Select a tuning parameter λ, which controls the balance between gradient descent and Gauss-Newton steps.

[0086] (7) Iterative solution: In each iteration, the parameter estimates are updated by solving the following linear equations:

[0087] (J T J+λI)Δp=-J T r

[0088] Among them, Δp is the parameter update amount, I is the identity matrix, r is the residual vector, and J is the Jacobian matrix.

[0089] (8) Update parameters: Update parameter estimates using the update amount: p (k+1) =p (k) +Δp, where k is the number of iterations.

[0090] (9) Evaluation update: Evaluate the performance of the cost function under the new parameter value. If the stopping criterion is met (such as the parameter change is less than a certain threshold or the maximum number of iterations is reached), the iteration is stopped.

[0091] (10) Adjust the tuning parameter: Adjust the tuning parameter λ according to the improvement of the cost function. If the cost function improves, then reduce λ; if there is no improvement, then increase λ.

[0092] (11) Check convergence conditions: Check whether the convergence conditions are met, such as whether the parameter change is less than a certain threshold or whether the preset maximum number of iterations is reached.

[0093] (12) Output results: If the convergence condition is met, the iteration is stopped and the final parameter estimation value is output, and the optimal estimation value of the amplitude and phase of the guided wave at different temperatures is obtained.

[0094] Step S5, establishing a regression model using the least squares method;

[0095] Exemplarily, the step S5 specifically includes: defining the regression model form, including dependent variables, independent variables and model parameters; collecting the observed values ​​of all independent variables and dependent variables; preprocessing the data, removing outliers and missing values; establishing the objective function, defining the residual sum of squares, and estimating the model parameters by the least squares method.

[0096] The steps to build a regression model using the least squares method are:

[0097] (1) Define the model and collect data: Determine the form of the regression model

[0098] y=aT+b

[0099] Where y is the dependent variable; T is the independent variable; a and b are model parameters. Collect data: including observations of all independent and dependent variables. Ensure the quality and integrity of the data.

[0100] (2) Data preprocessing: Check data distribution and remove outliers and missing values.

[0101] (3) Establishing the objective function: This patent performs a linear regression analysis on y and T, and lets RSS be the weighted sum of squares of the residual of the measured value y, then:

[0102]

[0103] The regression coefficients a and b at different temperatures are calculated by using the least squares curve fitting method. The change rates of a and b at different temperatures are calculated by using the least squares curve fitting method. The average values ​​of the change rates of a and b are calculated by multiple samplings. Through the regression model, the compensation algorithm for different temperatures is established as: y=aT+b, thereby obtaining the compensation signal from the current temperature to the reference temperature.

[0104] Step S6, bringing the experimental waveguide signal into the regression model, calculating the compensation parameters, and applying the compensation parameters to adjust the original signal to obtain a compensated signal;

[0105] Step S7, using a validation set or a cross-algorithm validation method to evaluate the accuracy of the temperature compensation model, and adjusting model parameters or optimizing the algorithm according to the validation results;

[0106] Step S8, importing the compensated waveguide signal and frequency-wavenumber data into MATLAB software, performing a two-dimensional Fourier transform, forming a frequency-wavenumber domain imaging spectrum, analyzing the imaging spectrum, and evaluating the detection results of micro-damage;

[0107] Step S9, use Disperse to calculate the corresponding relationship between the frequency and wave number data of each mode of Lamb waveguide, import 50 groups of detection echo signals and each mode frequency-waveguide data into matlab for two-dimensional Fourier transform and imaging, observe the imaging difference of defects based on the imaging image, and realize the rapid detection of minor damage of alloy plate and thin plate.

[0108] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. The protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. Laser-EMAT guided wave evaluation system for micro damage of high temperature alloy thin plates under high temperature environment, characterized by: The invention comprises a Laser-EMAT system, which comprises: a laser transmitter, a cylindrical lens, an electromagnetic ultrasonic Lamb waveguide receiving probe, an impedance matching network, a pre-filter amplifier, a data acquisition card, and Labview software. The Laser-EMAT waveguide evaluation system for micro-damage of a high-temperature alloy sheet under a high-temperature environment is used to perform a Laser-EMAT waveguide evaluation method for micro-damage of a high-temperature alloy sheet under a high-temperature environment. The method comprises the following steps: Step 1: The laser emitter is projected onto the alloy plate through a cylindrical lens, and the plate excites Lamb guided waves propagating along the length direction of the plate based on the thermoelastic mechanism; Step 2: When the Lamb waveguide encounters a tiny damage defect in the alloy, a defect reflection echo is generated, which is received by the electromagnetic ultrasonic Lamb waveguide receiving probe, amplified by the pre-filter amplifier, and input into the computer through the data acquisition card. The signal is collected using Labview software to obtain the alloy plate detection echo signal; Step 3, adjusting the impedance matching network to achieve impedance matching between the electromagnetic ultrasonic Lamb waveguide receiving probe and the input impedance of the pre-filter amplifier; Step 4, keeping the laser point position unchanged, moving the electromagnetic ultrasonic Lamb waveguide receiving probe in a direction away from the defect, and collecting echo signals at different positions; Step 5, processing and imaging the detection echo signal, and judging whether the alloy plate has micro damage defects according to the imaging image; Step 6, control the mode of Lamb wave by controlling the laser wavelength, use specific mode Lamb wave to detect different types of defects, and select the best mode for detection of different defects to improve the detection sensitivity of minor damages.

2. The Laser-EMAT guided wave evaluation system for micro damage of high temperature alloy thin plates under high temperature environment according to claim 1 is characterized in that: The electromagnetic ultrasonic Lamb guided wave receiving probe includes a permanent magnet, a linear coil, a yoke and a brass shell. The permanent magnet adopts a pair of samarium cobalt high-temperature resistant magnets with opposite polarities and is placed in the brass shell. The linear coil is made of silk-covered wire wound on a ceramic block. The linear coil is placed in the middle of the permanent magnet, and the yoke is placed above the permanent magnet.

3. The Laser-EMAT guided wave evaluation system for micro damage of high temperature alloy thin plates under high temperature environment according to claim 2 is characterized in that: The permanent magnet has a width of 5-20 mm, a length of 5-20 mm, and a height of 5-20 mm. The outer diameter of the silk-covered wire is 0.1-0.5 mm, and the thickness of the magnetic track is 3-5 mm.

4. The Laser-EMAT guided wave evaluation system for micro damage of high temperature alloy thin plates under high temperature environment according to claim 1, characterized in that: In the step 1, the laser transmitter is a solid-state laser Nd:YAG laser, and the pulse width is adjusted to 8-12ns and the laser energy is 590-650V.

5. The Laser-EMAT guided wave evaluation system for micro damage of high temperature alloy thin plates under high temperature environment according to claim 4, characterized in that: In step 1, the focal length of the cylindrical lens is 400 mm, and the laser emitter is focused through the cylindrical lens to form a sheet-shaped light source with a length of 8-10 mm and a width of 1-1.5 mm.

6. The Laser-EMAT guided wave evaluation system for micro damage of high temperature alloy thin plates under high temperature environment according to claim 1, characterized in that: In the step 4, the electromagnetic ultrasonic Lamb waveguide receiving probe is moved in a step length of 2-5 mm in a direction away from the defect to collect echo signals at different positions, and at least 50 groups of detection echo signals are collected in total.

7. The Laser-EMAT guided wave evaluation system for micro damage of high temperature alloy thin plates under high temperature environment according to claim 1, characterized in that: In step 5, the detection echo signal is processed and imaged, and the method steps are as follows: Step S1, preprocessing the collected signal, including filtering and denoising, to improve signal quality; Step S2, performing Hilbert transform on the preprocessed signal to generate an analytical signal, and extracting instantaneous characteristics including instantaneous amplitude and instantaneous phase from the analytical signal; Step S3, analyzing the law of instantaneous characteristics changing with temperature, and establishing a mathematical model describing the relationship between temperature and instantaneous amplitude and phase; Step S4, using LM algorithm to optimize the relationship model parameters between temperature and transient characteristics; Step S5, establishing a regression model using the least squares method; Step S6, bringing the experimental waveguide signal into the regression model, calculating the compensation parameters, and applying the compensation parameters to adjust the original signal to obtain a compensated signal; Step S7, using a validation set or a cross-algorithm validation method to evaluate the accuracy of the temperature compensation model, and adjusting model parameters or optimizing the algorithm according to the validation results; Step S8, importing the compensated waveguide signal and frequency-wavenumber data into MATLAB software, performing a two-dimensional Fourier transform, forming a frequency-wavenumber domain imaging spectrum, analyzing the imaging spectrum, and evaluating the detection results of micro-damage; Step S9, use Disperse to calculate the corresponding relationship between the frequency and wave number data of each mode of Lamb waveguide, import 50 groups of detection echo signals and each mode frequency-waveguide data into matlab for two-dimensional Fourier transform and imaging. The imaging difference between defects and non-defects can be clearly seen from the imaging image, realizing the rapid detection of minor damages of alloy plates and thin plates.

8. The Laser-EMAT guided wave evaluation system for micro damage of high temperature alloy thin plates under high temperature environment according to claim 7, characterized in that: The step S4 specifically includes defining a temperature compensation model, including temperature and other related variables; collecting performance data at different temperatures, establishing an objective function, calculating a residual vector and a Jacobian matrix; initializing parameters, and selecting an adjustment parameter λ; Iterate the solution and update the parameter estimates until the convergence conditions are met.

9. The Laser-EMAT guided wave evaluation system for micro damage of high temperature alloy thin plates in high temperature environment according to claim 7, characterized in that: The step S5 specifically includes defining the regression model form, including dependent variables, independent variables and model parameters; collecting the observed values ​​of all independent variables and dependent variables; preprocessing the data to remove outliers and missing values; establishing the objective function and defining the residual sum of squares. The model parameters are estimated by the least squares method.

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