Defect positioning method and system based on ultrasonic guided wave dispersion characteristics

Abstract

This invention discloses a method and system for locating ultrasonic guided wave defects based on helical dispersion characteristics. The method includes: calculating the helical angle based on the phase equation and wavefront theory of helical guided waves; calculating the helical group velocity and helical phase velocity based on the helical angle, axial group velocity, and axial phase velocity; plotting helical angle dispersion curves and helical group velocity dispersion curves using the helical angle and helical group velocity, respectively; optimizing the parameters of a helical sensing network based on the helical angle, the helical group velocity, and the helical phase velocity; mapping several mode-frequency pairs that meet preset conditions from the helical angle dispersion curve to the helical group velocity dispersion curve to obtain a mapping result; and obtaining an ultrasonic guided wave defect location map based on the mapping result and the parameter-optimized helical sensing network, thus completing the ultrasonic guided wave defect location method based on helical dispersion characteristics.

Description

Technical Field

[0001] This invention relates to the field of high-precision defect location technology, specifically to an ultrasonic guided wave defect location method and system based on helical dispersion characteristics. Background Technology

[0002] For pipeline structures in large, critical structural components of high-end equipment, achieving high-precision defect localization is crucial. Currently, most ultrasonic guided wave defect localization methods for pipeline structures are based on axisymmetric longitudinal modes and helical Lamb wave theory. Axisymmetric longitudinal modes are suitable for inspecting pipes with small diameter-to-thickness ratios, as their propagation paths are all along the axisymmetric direction and the sensing paths are parallel, enabling axial defect localization, but with lower accuracy in the circumferential direction. Helical Lamb waves propagate in a helical pattern, with intersecting sensing paths, achieving high-precision circumferential-axial defect localization; however, the approximate Lamb wave dispersion curve limits its application in pipes with small diameter-to-thickness ratios, making it more suitable for pipes with large diameter-to-thickness ratios. Summary of the Invention

[0003] To achieve high-precision defect location in pipe structures with small diameter-to-thickness ratios, engineers overcame the limitations of the helical Lamb wave plate wave approximation theory, derived the helical dispersion curve, and proposed an ultrasonic guided wave defect location method based on the helical dispersion characteristics. This method achieves high-precision defect location across the entire frequency domain for pipe structures with different diameter-to-thickness ratios. The method includes:

[0004] The helix angle is calculated based on the phase equation of the helical guided wave and the wavefront theory of the helical guided wave.

[0005] Calculate the helical group velocity and helical phase velocity based on the helical angle, axial group velocity, and axial phase velocity;

[0006] Plot the helix angle dispersion curve and the helix group velocity dispersion curve using the helix angle and the helix group velocity respectively;

[0007] The parameters of the spiral sensing network are optimized based on the spiral angle, the spiral group velocity, and the spiral phase velocity.

[0008] Several mode-frequency pairs that meet preset conditions are mapped from the helical angle dispersion curve to the helical group velocity dispersion curve to obtain the mapping result;

[0009] Based on the mapping results and the optimized helical sensing network, an ultrasonic guided wave defect localization map is obtained, thus completing the ultrasonic guided wave defect localization method based on helical dispersion characteristics.

[0010] Optionally, the formula for calculating the helix angle is:

[0011]

[0012] Where N is the circumferential order, f is the frequency, and R a C is the outer diameter. pz denoted as axial phase velocity.

[0013] Optionally, the calculation process for the spiral group velocity is as follows:

[0014]

[0015] Among them, C pz Where ω is the axial phase velocity, ω is the angular frequency, and C is the angular frequency. gz For axial group velocity.

[0016] Optionally, the calculation process for the helical phase velocity is as follows:

[0017]

[0018] Where i represents the i-th iteration, and Δω represents the frequency step in each iteration.

[0019] Optionally, the spiral sensing network includes an excitation sensor group and a receiving sensor group;

[0020] The excitation sensor group consists of two symmetrically distributed linear loads with helical angles.

[0021] The receiving sensor group is composed of circular piezoelectric elements.

[0022] This invention also discloses an ultrasonic guided wave defect localization system based on helical dispersion characteristics, the system comprising:

[0023] The helix angle calculation module is used to calculate the helix angle based on the phase equation of the helix guided wave and the wavefront theory of the helix guided wave.

[0024] The spiral waveguide parameter calculation module is used to calculate the spiral group velocity and spiral phase velocity based on the spiral angle, axial group velocity, and axial phase velocity.

[0025] The dispersion curve calculation module is used to plot the helical angle dispersion curve and the helical group velocity dispersion curve using the helical angle and the helical group velocity, respectively.

[0026] The sensor network parameter optimization module is used to optimize the parameters of the spiral sensor network based on the spiral angle, spiral group velocity, and spiral phase velocity.

[0027] The group mapping module is used to map several mode-frequency pairs that meet preset conditions from the helical angular dispersion curve to the helical group velocity dispersion curve to obtain the mapping result;

[0028] The defect localization module is used to obtain an ultrasonic guided wave defect localization map based on the mapping results and the optimized helical sensing network, thus completing the ultrasonic guided wave defect localization method based on helical dispersion characteristics. Optionally, the calculation process of the helical angle is as follows:

[0029]

[0030] Where N is the circumferential order, f is the frequency, and R a C is the outer diameter. pz denoted as axial phase velocity.

[0031] Optionally, the calculation process for the spiral group velocity is as follows:

[0032]

[0033] Among them, C pz Where ω is the axial phase velocity, ω is the angular frequency, and C is the angular frequency. gz For axial group velocity.

[0034] Optionally, the calculation process for the helical phase velocity is as follows:

[0035]

[0036] Where i represents the i-th iteration, and Δω represents the frequency step in each iteration.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] This invention overcomes the application limitations of helical Lamb waves in structures with small diameter-to-thickness ratios and low-frequency excitation by acquiring the dispersion characteristics of helical guided waves under the actual propagation path. Furthermore, by utilizing the dispersion characteristics of the helical wave and selecting appropriate frequency-mode pairs, it enables high-precision defect positioning of large key tubular structural components in high-end equipment. Attached Figure Description

[0039] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of a spiral sensing network for an ultrasonic guided wave defect localization method based on spiral dispersion characteristics, according to an embodiment of the present invention. Figure 1 a is a three-dimensional schematic diagram of a spiral sensor network in a pipe; Figure 1 b is a two-dimensional schematic diagram of the spiral sensing network unfolded circumferentially; Figure 1 c is a schematic diagram of the single-sensor path imaging principle in the elliptic imaging algorithm; Figure 1 Schematic diagram of the imaging principle of the d-elliptic imaging algorithm under a spiral sensor network;

[0041] Figure 2 This is a schematic diagram of the experimental sample in an embodiment of the present invention;

[0042] Figure 3 This is a comparison diagram of the dispersion curves of the helical group velocity and the axial group velocity in an embodiment of the present invention, wherein, Figure 3 a is a comparison diagram of the dispersion curves of the spiral group velocity and the axial group velocity. Figure 3 b is a magnified comparison of the dispersion curves F(n,1) of the spiral group velocity and the axial group velocity modes. Figure 3 c is a magnified comparison of the dispersion curves F(n,2) of the spiral group velocity and the axial group velocity modes. Figure 3 d is a magnified comparison of the dispersion curves of the spiral group velocity and the axial group velocity F(n,3) modes;

[0043] Figure 4 This is a comparison diagram of the dispersion curves of the helical phase velocity and the axial phase velocity in an embodiment of the present invention. Figure 4 a is a comparison diagram of the dispersion curves of the helical phase velocity and the axial phase velocity. Figure 4 b is a magnified comparison of the dispersion curves F(n,2) of the helical phase velocity and axial phase velocity modes. Figure 4 c is a magnified comparison diagram of the dispersion curves of the helical phase velocity and the axial phase velocity F(n,1) modes; Figure 4 d is a magnified comparison diagram of the dispersion curves of the helical phase velocity and the axial phase velocity F(n,3) modes;

[0044] Figure 5 This is a graph showing the helical angle dispersion curves of different circumferential orders according to the present invention;

[0045] Figure 6 This is a schematic diagram of a mode-frequency pair group satisfying a preset helix angle on the velocity dispersion curve of a helical group according to an embodiment of the present invention, wherein, Figure 6 a is the overall diagram of the mode-frequency pair group that satisfies the preset helical angle on the velocity dispersion curve of the helical group; Figure 6 b is a magnified view of the mode-frequency pair group that satisfies the preset helical angle on the velocity dispersion curve of the helical group;

[0046] Figure 7 This is a map showing the location of the maximum damage probability under different threshold parameters in an embodiment of the present invention;

[0047] Figure 8 This is a flowchart illustrating the steps of an ultrasonic guided wave defect localization method based on helical dispersion characteristics, according to an embodiment of the present invention. Detailed Implementation

[0048] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] Example 1

[0050] Ultrasonic guided wave defect localization method based on helical dispersion characteristics, such as Figure 8 As shown, the method includes:

[0051] The formula for calculating the helix angle is derived based on the phase equation of helical guided waves and the wavefront theory of helical guided waves.

[0052] Based on the phase equation and wavefront theory of helical guided waves, the relationship between the helix angle (β) and the axial phase velocity (C) of the helical guided wave is obtained. pz )relation:

[0053]

[0054] Where N is the circumferential order, f is the frequency, and R a C is the outer diameter. pz denoted as axial phase velocity.

[0055] Formulas for calculating helical group velocity and helical phase velocity are based on helix angle, axial group velocity, and axial phase velocity.

[0056] Using axial group velocity (C) gz ) and spiral group velocity (C gs Given the same flight time and using the helix angle formula, the formula for calculating the velocity of the helix group can be obtained:

[0057]

[0058] Among them, C pz Let ω be the axial phase velocity and ω be the angular frequency, i.e., 2πf.

[0059] Based on the spiral group velocity (C) gs ) and spiral phase velocity (C ps From the relationship, obtain the iterative formula for the spiral phase velocity:

[0060]

[0061] Where i represents the i-th iteration, Δω represents the frequency step of each iteration, and Δω=ω(i+1)-ω(i).

[0062] Use the formulas for calculating the helix angle and the helix group velocity to plot the helix angle dispersion curve and the helix group velocity dispersion curve, respectively.

[0063] Based on the helix angle formula, helix angle dispersion curves for different circumferential orders are plotted; based on the helix group velocity calculation formula, helix group velocity dispersion curves are plotted; based on the helix phase velocity calculation formula, helix phase velocity dispersion curves are plotted.

[0064] The parameters of the helical sensor network are optimized based on the aforementioned formulas for calculating the helical angle, helical group velocity, and helical phase velocity.

[0065] Based on the propagation characteristics of helical guided waves, a helical sensing network is established, such as... Figure 1 As shown, Figure 1 a is a three-dimensional schematic diagram of a spiral sensor network in a pipe. Figure 1 b is a schematic diagram after unfolding circumferentially. The helical sensing network consists of two parts: an excitation sensor group and a receiving sensor group. The excitation sensor group is composed of two symmetrically distributed linear loads with helical angles (thick black solid lines and thick black dashed lines), and the receiving sensor group is composed of circular piezoelectric sheets. Each linear load corresponds to 11 receiving sensors for receiving helical guided wave signals, for a total of 22 receiving sensors. The excitation sensor group and the receiving sensor group form 22 helical sensing paths (thin black solid lines and thin black dashed lines), constituting the helical sensing network.

[0066] Analyzing the relationship between the helix angle of the helical sensor network and the area to be detected, the larger the helix angle, the denser the coverage of the sensing path at the center of the area to be detected, and the larger the uncovered area near the excitation load ends on the upper and lower sides; the smaller the helix angle, the stronger the coverage of the sensing path at the excitation load ends on the upper and lower sides, but the lower the crossing ability of the sensing path; when the helix angle is too small, the sensing path will be approximately parallel and propagate along the axial direction, degenerating into an axisymmetric mode excitation mode, and the positioning accuracy will be greatly reduced.

[0067] The helix angle is determined by taking into account the size of the area to be inspected and the location where defects are likely to occur.

[0068] If the defect-prone area is unknown, routine inspection of the area to be inspected is required. In this case, the helix angle should be minimized as much as possible while ensuring the sensor path crosses, so as to increase the coverage area of ​​the sensor path.

[0069] If the defect-prone area is known, then to increase the positioning accuracy, the helix angle should be increased as much as possible while ensuring that the sensing path can cover the defect-prone area. This will increase the sensing path coverage density at the center of the area to be detected and improve the positioning accuracy.

[0070] The mapping result is obtained by mapping several mode-frequency pairs that satisfy the preset helical angle condition from the helical angle dispersion curve to the helical group velocity dispersion curve.

[0071] Based on the characteristics of the area to be detected, a helical waveguide helix angle value (preset helix angle) is selected; based on the helix angle dispersion curves at different circumferential orders, mode-frequency pairs satisfying the preset helix angle are obtained; the mode-frequency pairs satisfying the preset helix angle are plotted on the velocity dispersion curve of the helical group to obtain the mapping result.

[0072] Based on the mapping results, the mode-frequency pairs used for detection are determined.

[0073] Based on the mode-frequency pair mapping results of the spiral group velocity dispersion curve, the mode-frequency pair used for detection is determined according to the selection principle of weak dispersion characteristics; at the same time, according to the spiral group velocity dispersion curve, the spiral group velocity of the selected mode at the selected excitation frequency is determined.

[0074] Based on the determined mode-frequency pairs used for detection and the helical sensing network, an ultrasonic guided wave defect localization map is obtained, thus completing the ultrasonic guided wave defect localization method based on helical dispersion characteristics.

[0075] The region to be detected is discretized. Based on the determined spiral group velocity of the mode-frequency pair used for detection, the flight time (τ) of the spiral guided wave from the excitation point through the discrete point (x,y) in the region to the receiving point is calculated. k ):

[0076]

[0077] in, This represents the excitation point on the k-th sensing path; τ represents the receiving point on the k-th sensing path; k This represents the flight time over the discrete point (x, y).

[0078] Based on the selected helix angle value, a helical sensing network is established, the mode for detection is excited, and the sensor is used to receive non-destructive and lossy signals under different sensing paths, and the difference signal is calculated.

[0079] like Figure 1 As shown in (b), for the difference signal, a suitable threshold β is selected to reduce noise interference;

[0080] Using the noise-reduced detection signal S, the damage probability I(x,y) at the discrete point (x,y) in the detection area is calculated:

[0081]

[0082] Among them, S k The received guided wave signal on the k-th sensing path has undergone thresholding.

[0083] Based on the damage probability at each discrete point in the area to be detected, a defect location map is drawn, and the location error is calculated.

[0084] By changing different thresholds β, a series of localization results and localization errors are obtained, and a map of the location of maximum damage probability is plotted.

[0085] Example 2

[0086] Figure 2 The test specimen for the pipe structure exhibiting internal corrosion defects was made of #304 steel, with an outer diameter of 500 mm, a wall thickness of 10 mm, a length of 1500 mm, and a density of 7800 kg / m³. 3 The elastic modulus is 210 GPa and the Poisson's ratio is 0.28. The internal corrosion damage was prepared using an electrolytic etching machine, resulting in an uneven etched surface with a maximum depth of 2.11 mm and a diameter of approximately 10 mm.

[0087] according to Figure 2 For the experimental specimens, the ultrasonic guided wave defect localization method based on the spiral dispersion characteristics was used to locate and quantitatively analyze the internal corrosion defects of the specimens.

[0088] Obtain the spiral dispersion curve:

[0089] First, the axial phase velocity and axial group velocity are obtained from the material and geometric parameters of the sample. Then, the helical group velocity is calculated according to the formula (2) for calculating the helical group velocity. Figure 3 This is a comparison of the velocity dispersion curves of the helical group and the axial group for circumferential orders 1-8 and modules 1-8. Solid lines represent the helical group velocity dispersion curves for each mode, while dashed lines represent the axial group velocity dispersion curves for each mode. The arrows on the solid lines indicate the variation of the circumferential order *n* of the modes represented by each curve in the helical group velocity dispersion curve cluster, and the arrows on the dashed lines indicate the variation of the circumferential order *n* of the modes represented by each curve in the axial group velocity dispersion curve cluster. The comparison of the dispersion curves shows that the difference between the helical group velocity and the axial group velocity is mainly in the low-frequency region, and primarily concentrated in the bending modes of modes 1 to 3.

[0090] Calculate the helical phase velocity according to the formula (3) for calculating the helical phase velocity. Figure 4 This is a comparison diagram of helical phase velocity dispersion curves and axial phase velocity dispersion curves with circumferential orders of 1-8 and modules of 1-5. Solid lines represent the helical phase velocity dispersion curves for each mode, while dashed lines represent the axial phase velocity dispersion curves for each mode. The arrows on the solid lines indicate the variation of the circumferential order n of the modes represented by each curve in the helical phase velocity dispersion curve cluster, and the arrows on the dashed lines indicate the variation of the circumferential order n of the modes represented by each curve in the axial phase velocity dispersion curve cluster.

[0091] Determine the helix angle of the helix sensor network:

[0092] The internal corrosion defects of the test specimen were pre-positioned at the center of the area to be detected. Taking into account both the positioning accuracy and the size of the area to be covered, the helix angle tangent was determined to be around 0.6, that is, the angle between the two intersecting sensing paths was approximately 60°.

[0093] Determine the mode-frequency pair of the helical waveguide:

[0094] According to the helix angle formula (1), the dispersion curves of helix angles with circumferential orders of 1-8 are plotted, as follows: Figure 5 As shown in the figure. The solid arrows in the figure indicate the changes in the circumferential order n of the F(n,1) mode cluster, F(n,2) mode cluster, F(n,3) mode cluster, F(n,4) mode cluster, and F(n,5) mode cluster; the thick black horizontal dashed line indicates that the helix angle tangent is 0.6; the intersection of the black dashed line and the helix angle dispersion curve indicates the helix guided wave mode-frequency pair that satisfies the preset helix angle.

[0095] The mode-frequency pairs that satisfy the preset helix angle are mapped onto the velocity dispersion curve of the helical group, such as... Figure 6 As shown, the black circle symbol represents the modal-frequency point that satisfies the helix angle tangent value of approximately 0.6.

[0096] Depend on Figure 6 It can be seen that the dispersion curves of mode-frequency pairs with moduli of 2 and 3 and circumferential order greater than 2 have relatively gentle slopes, which characterize weak dispersion. Harmonics at these frequencies are less prone to distortion during propagation, so they can all be selected as excitation frequencies and modes for damage localization. In this example, the F(3,3) mode with a circumferential order of 3 and a mode of 3 is selected as the guided wave mode for detecting defects, with a corresponding excitation frequency of 20kHz.

[0097] Defect location:

[0098] For experimental specimens with internal corrosion damage, according to Figure 1 The displayed helical sensing network is loaded with two sets of helical excitation line loads on the left to excite the F(3,3) mode. Eleven corresponding sensors on the right simultaneously receive these signals, acquiring two sets of guided wave signals. Each set contains eleven parallel sensing paths, for a total of twenty-two sensing path signals. The same data excitation acquisition is performed in a non-destructive pipeline structure to obtain baseline data, and the difference between the damage signal and the baseline signal is calculated to obtain the difference signal.

[0099] A series of thresholds β are taken at 5μs intervals from 30μs to 60μs to denoise the difference signal, and a series of denoised detection signals S are obtained.

[0100] The area to be inspected is discretized with a spatial interval of (0.5 mm, 0.5 mm). Based on the detection signal S, the damage probability at each discrete point in the area to be inspected is calculated using formulas (4) and (5) to obtain the defect location results under different thresholds.

[0101] The maximum damage probability location map under different threshold parameters is shown below. Figure 7 As shown in the figure, the solid black lines and dashed black lines on the left represent symmetrically distributed excitation loads, while the hollow black circles and hollow black rhombuses on the right represent the receiving sensors corresponding to the two excitation loads. The solid black circles represent the actual defect locations, and the solid black triangles represent the localization results under different thresholds. The figure shows that under different threshold parameters, most detection results approach the actual defect locations, forming the clusters of damage locations with the highest probability. By setting a series of thresholds and selecting damage location clusters, the randomness of the threshold parameters can be eliminated, improving the reliability of defect identification.

[0102] Example 3

[0103] An ultrasonic guided wave defect localization system based on helical dispersion characteristics, the system comprising:

[0104] The helix angle calculation module is used to derive the helix angle calculation formula based on the phase equation and wavefront theory of helix guided waves.

[0105] Based on the phase equation and wavefront theory of helical guided waves, the relationship between the helix angle (β) and the axial phase velocity (C) of the helical guided wave is obtained. pz )relation:

[0106]

[0107] Where N is the circumferential order, f is the frequency, and R a It is the outer diameter.

[0108] The helical waveguide parameter calculation module is used to calculate the helical group velocity and helical phase velocity based on the helical angle, axial group velocity, and axial phase velocity.

[0109] Using axial group velocity (C) gz ) and spiral group velocity (C gs Given the same flight time and using the helix angle formula, the formula for calculating the velocity of the helix group can be obtained:

[0110]

[0111] Among them, C pz Let ω be the axial phase velocity and ω be the angular frequency, i.e., 2πf.

[0112] Based on the spiral group velocity (C) gs ) and spiral phase velocity (Cps From the relationship, obtain the formula for calculating the spiral phase velocity:

[0113]

[0114] Where i represents the i-th iteration, Δω represents the frequency step of each iteration, and Δω=ω(i+1)-ω(i).

[0115] The dispersion curve calculation module is used to draw the dispersion curves of the helical angle under different circumferential orders based on the helical angle formula; to draw the dispersion curves of the helical group velocity based on the helical group velocity calculation formula; and to draw the dispersion curves of the helical phase velocity based on the helical phase velocity calculation formula.

[0116] The sensor network parameter optimization module is used to optimize the parameters of the spiral sensor network based on the spiral angle calculation formula, the spiral group velocity calculation formula, and the spiral phase velocity calculation formula.

[0117] Based on the propagation characteristics of helical guided waves, a helical sensing network is established, such as... Figure 1 As shown, Figure 1 a is a three-dimensional schematic diagram of a spiral sensor network in a pipe. Figure 1 b is a schematic diagram after unfolding circumferentially. The helical sensing network consists of two parts: an excitation sensor group and a receiving sensor group. The excitation sensor group is composed of two symmetrically distributed linear loads with helical angles (thick black solid lines and thick black dashed lines), and the receiving sensor group is composed of circular piezoelectric sheets. Each linear load corresponds to 11 receiving sensors for receiving helical guided wave signals, for a total of 22 receiving sensors. The excitation sensor group and the receiving sensor group form 22 helical sensing paths (thin black solid lines and thin black dashed lines), constituting the helical sensing network.

[0118] Analyzing the relationship between the helix angle of the helical sensor network and the area to be detected, the larger the helix angle, the denser the coverage of the sensing path at the center of the area to be detected, and the larger the uncovered area near the excitation load ends on the upper and lower sides; the smaller the helix angle, the stronger the coverage of the sensing path at the excitation load ends on the upper and lower sides, but the lower the crossing ability of the sensing path; when the helix angle is too small, the sensing path will be approximately parallel and propagate along the axial direction, degenerating into an axisymmetric mode excitation mode, and the positioning accuracy will be greatly reduced.

[0119] The helix angle is determined by taking into account the size of the area to be inspected and the location where defects are likely to occur.

[0120] If the defect-prone area is unknown, routine inspection of the area to be inspected is required. In this case, the helix angle should be minimized as much as possible while ensuring the sensor path crosses, so as to increase the coverage area of ​​the sensor path.

[0121] If the defect-prone area is known, then to increase the positioning accuracy, the helix angle should be increased as much as possible while ensuring that the sensing path can cover the defect-prone area. This will increase the sensing path coverage density at the center of the area to be detected and improve the positioning accuracy.

[0122] The group mapping module is used to map several mode-frequency pairs that satisfy the preset helical angle condition from the helical angle dispersion curve to the helical group velocity dispersion curve to obtain the mapping result.

[0123] Based on the characteristics of the area to be detected, a helical waveguide helix angle value (preset helix angle) is selected; based on the helix angle dispersion curves at different circumferential orders, mode-frequency pairs satisfying the preset helix angle are obtained; the mode-frequency pairs satisfying the preset helix angle are plotted on the velocity dispersion curve of the helical group to obtain the mapping result.

[0124] Based on the mapping results, the mode-frequency pairs used for detection are determined.

[0125] Based on the mode-frequency pair mapping results of the spiral group velocity dispersion curve, the mode-frequency pair used for detection is determined according to the selection principle of weak dispersion characteristics; at the same time, according to the spiral group velocity dispersion curve, the spiral group velocity of the selected mode at the selected excitation frequency is determined.

[0126] The defect localization module is used to obtain an ultrasonic guided wave defect localization map based on the determined mode-frequency pair for detection and the spiral sensing network, thereby completing the ultrasonic guided wave defect localization method based on spiral dispersion characteristics.

[0127] The region to be detected is discretized. Based on the determined spiral group velocity of the mode-frequency pair used for detection, the flight time (τ) of the spiral guided wave from the excitation point through the discrete point (x,y) in the region to the receiving point is calculated. k ):

[0128]

[0129] in, This represents the excitation point on the k-th sensing path; τ represents the receiving point on the k-th sensing path; k This represents the flight time over the discrete point (x, y).

[0130] Based on the selected helix angle value, a helical sensing network is established, the mode for detection is excited, and the sensor is used to receive non-destructive and lossy signals under different sensing paths, and the difference signal is calculated.

[0131] like Figure 1 As shown in (b), for the difference signal, a suitable threshold β is selected to reduce noise interference;

[0132] Using the noise-reduced detection signal S, calculate the damage probability I(x,y) at the discrete point (x,y) in the detection area:

[0133]

[0134] Among them, S k The received guided wave signal on the k-th sensing path has undergone thresholding.

[0135] Based on the damage probability at each discrete point in the area to be detected, a defect location map is drawn, and the location error is calculated.

[0136] By changing different thresholds β, a series of localization results and localization errors are obtained, and a map of the location of maximum damage probability is plotted.

[0137] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for locating ultrasonic guided wave defects based on helical dispersion characteristics, characterized in that, The method includes: The helix angle is calculated based on the phase equation of the helical guided wave and the wavefront theory of the helical guided wave. The formula for calculating the helix angle is: ； in, For the circumferential order, For frequency, outer diameter The axial phase velocity; Calculate the helical group velocity and helical phase velocity based on the helical angle, axial group velocity, and axial phase velocity; The calculation process for the velocity of the spiral group is as follows: ； in, Angular frequency, For axial group velocity; The calculation process for the spiral phase velocity is as follows: ； in, i For the first i iteration The frequency step size for each iteration; Plot the helix angle dispersion curve and the helix group velocity dispersion curve using the helix angle and the helix group velocity respectively; The parameters of the spiral sensing network are optimized based on the spiral angle, the spiral group velocity, and the spiral phase velocity. Several mode-frequency pairs that meet preset conditions are mapped from the helical angle dispersion curve to the helical group velocity dispersion curve to obtain the mapping result; Based on the mapping results and the optimized helical sensing network, an ultrasonic guided wave defect localization map is obtained, thus completing the ultrasonic guided wave defect localization method based on helical dispersion characteristics.

2. The ultrasonic guided wave defect localization method based on helical dispersion characteristics according to claim 1, characterized in that, The spiral sensing network includes an excitation sensor group and a receiving sensor group; The excitation sensor group consists of two symmetrically distributed linear loads with helical angles. The receiving sensor group is composed of circular piezoelectric elements.

3. An ultrasonic guided wave defect localization system based on helical dispersion characteristics, said system being used to implement the method described in any one of claims 1-2, characterized in that the system include: The helix angle calculation module is used to calculate the helix angle based on the phase equation of the helix guided wave and the wavefront theory of the helix guided wave. The calculation process for the helix angle is as follows: ； in, For the circumferential order, For frequency, outer diameter The axial phase velocity; The spiral waveguide parameter calculation module is used to calculate the spiral group velocity and spiral phase velocity based on the spiral angle, axial group velocity, and axial phase velocity. The calculation process for the velocity of the spiral group is as follows: ； in, Angular frequency, For axial group velocity; The calculation process for the spiral phase velocity is as follows: ； in, i For the first i iteration The frequency step size for each iteration; The dispersion curve calculation module is used to plot the helical angle dispersion curve and the helical group velocity dispersion curve using the helical angle and the helical group velocity, respectively. The sensor network parameter optimization module is used to optimize the parameters of the spiral sensor network based on the spiral angle, spiral group velocity, and spiral phase velocity. The group mapping module is used to map several mode-frequency pairs that meet preset conditions from the helical angular dispersion curve to the helical group velocity dispersion curve to obtain the mapping result; The defect localization module is used to obtain an ultrasonic guided wave defect localization map based on the mapping results and the optimized helical sensing network, thus completing the ultrasonic guided wave defect localization method based on helical dispersion characteristics.

Images