Ultrasonic guided wave defect positioning method and system based on spiral dispersion characteristic

Abstract

The invention discloses an ultrasonic guided wave defect positioning method and system based on spiral dispersion characteristics. The method comprises the following steps: calculating a spiral angle based on a phase equation of a spiral guided wave and a wavefront theory of the spiral guided wave; calculating a spiral group velocity and a spiral phase velocity based on the spiral angle, the axial group velocity and the axial phase velocity; respectively drawing a helical angle dispersion curve and a helical group velocity dispersion curve by using the helical angle and the helical group velocity; optimizing parameters of the spiral sensing network based on the spiral angle, the spiral group velocity and the spiral phase velocity; mapping a plurality of modal-frequency pairs meeting preset conditions into the spiral group velocity frequency dispersion curve from the spiral angle frequency dispersion curve to obtain a mapping result; and obtaining an ultrasonic guided wave defect positioning map based on the mapping result and the spiral sensing network after parameter optimization, and completing the ultrasonic guided wave defect positioning method based on the spiral frequency dispersion characteristic.

Description

Technical Field

[0001] The present invention relates to the technical field of high-precision defect positioning, and in particular to an ultrasonic guided wave defect positioning method and system based on spiral dispersion characteristics. Background Art

[0002] For pipeline structures in large key structural parts of high-end equipment, it is crucial to achieve high-precision defect positioning. At present, most ultrasonic guided wave defect positioning methods for pipeline structures are based on axisymmetric longitudinal modes and spiral Lamb wave theory. Axisymmetric longitudinal modes are suitable for the detection of small diameter-thickness ratio pipelines. Their propagation paths are all along the axisymmetric direction, and the sensing paths are parallel to each other, which can achieve axial defect positioning, but the circumferential positioning accuracy is low. The propagation path of spiral Lamb waves is spiral, and the sensing paths intersect with each other, which can achieve high-precision circumferential-axial defect positioning, but its Lamb wave dispersion curve approximation theory limits its application in small diameter-thickness ratio pipelines, and is more suitable for large diameter-thickness ratio pipelines. Summary of the invention

[0003] In order to achieve high-precision defect location of pipeline structures with small thickness-to-diameter ratio, technicians broke through the limitations of spiral Lamb wave plate wave approximation theory, derived the spiral dispersion curve, and proposed an ultrasonic guided wave defect location method based on the spiral dispersion characteristics. This method has achieved a high-precision defect location method in the full frequency domain for pipeline structures with different diameter-to-thickness ratios. The method includes:

[0004] The spiral angle is calculated based on the phase equation of spiral guided waves and the wavefront theory of spiral guided waves;

[0005] Calculating a helical group velocity and a helical phase velocity based on the helix angle, the axial group velocity, and the axial phase velocity;

[0006] Use the spiral angle and spiral group velocity to draw the spiral angle dispersion curve and spiral group velocity dispersion curve respectively;

[0007] Optimizing parameters of a spiral sensing network based on the spiral angle, the spiral group velocity, and the spiral phase velocity;

[0008] Mapping a number of mode-frequency pairs that meet preset conditions from the spiral angle dispersion curve to the spiral group velocity dispersion curve to obtain a mapping result;

[0009] Based on the mapping results and the spiral sensing network after parameter optimization, an ultrasonic guided wave defect locating map is obtained, and an ultrasonic guided wave defect locating method based on spiral dispersion characteristics is completed.

[0010] Optionally, the helix angle calculation formula is:

[0011]

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

[0013] Optionally, the calculation process of the spiral group velocity is:

[0014]

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

[0016] Optionally, the calculation process of the spiral phase velocity is:

[0017]

[0018] Where i is the i-th iteration and Δω is the frequency step of each iteration.

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

[0020] The excitation sensor group is composed of two symmetrically distributed line loads with a helical angle;

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

[0022] The present invention also discloses an ultrasonic guided wave defect locating system based on spiral dispersion characteristics, the system comprising:

[0023] A spiral angle calculation module is used to calculate the spiral angle based on the phase equation of spiral guided waves and the wavefront theory of spiral guided waves;

[0024] A spiral waveguide parameter calculation module, used for calculating the spiral group velocity and the spiral phase velocity based on the spiral angle, the axial group velocity and the axial phase velocity;

[0025] A dispersion curve calculation module, used to draw a spiral angle dispersion curve and a spiral group velocity dispersion curve respectively using the spiral angle and the spiral group velocity;

[0026] A sensor network parameter optimization module, used for optimizing the parameters of the spiral sensor network based on the spiral angle, spiral group velocity and spiral phase velocity;

[0027] A pair group mapping module, used to map a number of mode-frequency pairs that meet preset conditions from the spiral angle dispersion curve to the spiral group velocity dispersion curve to obtain a mapping result;

[0028] The defect location module is used to obtain an ultrasonic guided wave defect location map based on the mapping result and the spiral sensor network after parameter optimization, and complete the ultrasonic guided wave defect location method based on the spiral dispersion characteristics. Optionally, the calculation process of the spiral angle is:

[0029]

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

[0031] Optionally, the calculation process of the spiral group velocity is:

[0032]

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

[0034] Optionally, the calculation process of the spiral phase velocity is:

[0035]

[0036] Where i is the i-th iteration and Δω is the frequency step of each iteration.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention overcomes the application limitations of spiral Lamb waves in small diameter-to-thickness ratio structures and low-frequency excitation by obtaining the dispersion characteristics of spiral guided waves in the actual propagation path, and utilizes the spiral dispersion characteristics to select appropriate frequency-mode pairs to achieve high-precision defect positioning of large key tubular structural parts of high-end equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] Figure 1 Schematic diagram of a spiral sensing network of an ultrasonic guided wave defect location method based on spiral dispersion characteristics according to an embodiment of the present invention, wherein: Figure 1 a is a three-dimensional schematic diagram of the spiral sensor network in the pipeline; Figure 1 b is a two-dimensional schematic diagram of the spiral sensor network unfolded along the circumferential direction; Figure 1 c is the imaging principle diagram of a single sensing path in the elliptical imaging algorithm; Figure 1 d Imaging principle diagram of elliptical imaging algorithm under spiral sensor network;

[0041] Figure 2 A schematic diagram of an experimental sample of an embodiment of the present invention;

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

[0043] Figure 4 : is a comparison diagram of the dispersion curves of the spiral phase velocity and the axial phase velocity in the embodiment of the present invention, wherein: Figure 4 a is the overall comparison diagram of the helical phase velocity and axial phase velocity dispersion curves, Figure 4 b is the comparison diagram of the helical phase velocity and axial phase velocity dispersion curves F(n,2) modal enlargement. Figure 4 c is the comparison diagram of the modal enlargement of the helical phase velocity and axial phase velocity dispersion curves F(n,1); Figure 4 d is the comparison diagram of the modal enlargement of the helical phase velocity and axial phase velocity dispersion curves F(n,3);

[0044] Figure 5 It is a spiral angle dispersion curve diagram of the present invention under different circumferential orders;

[0045] Figure 6 Schematic diagram of mode-frequency pairs satisfying a preset spiral angle on a spiral group velocity dispersion curve according to an embodiment of the present invention, wherein: Figure 6 a is the total diagram of the mode-frequency pairs that meet the preset spiral angle on the spiral group velocity dispersion curve; Figure 6 b is a local enlarged view of the mode-frequency pair group that meets the preset spiral angle on the spiral group velocity dispersion curve;

[0046] Figure 7 It is a maximum damage probability position diagram under different threshold parameters of an embodiment of the present invention;

[0047] Figure 8 This is a method step diagram of an ultrasonic guided wave defect locating method based on spiral dispersion characteristics according to an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] Embodiment 1

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

[0051] The calculation formula of the spiral angle is obtained based on the phase equation of spiral waveguide and the wavefront theory of spiral waveguide.

[0052] Based on the phase equation and wavefront theory of spiral waveguide, the spiral angle (β) and axial phase velocity (C pz )relation:

[0053]

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

[0055] The helical group velocity calculation formula and the helical phase velocity calculation formula are calculated based on the helix angle, axial group velocity and axial phase velocity.

[0056] Using the axial group velocity (C gz ) and spiral group velocity (C gs ) satisfies the same flight time, and combined with the spiral angle formula, the spiral group velocity calculation formula is obtained:

[0057]

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

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

[0060]

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

[0062] The spiral angle calculation formula and the spiral group velocity calculation formula are used to draw the spiral angle dispersion curve and the spiral group velocity dispersion curve respectively.

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

[0064] The parameters of the spiral sensor network are optimized based on the spiral angle calculation formula, the spiral group velocity calculation formula and the spiral phase velocity calculation formula.

[0065] Based on the propagation characteristics of spiral guided waves, a spiral sensor network is established, such as Figure 1 As shown, Figure 1 a is a three-dimensional schematic diagram of the spiral sensor network in the pipeline. Figure 1 b is a schematic diagram after circumferential expansion. The spiral sensor network consists of an excitation sensor group and a receiving sensor group; the excitation sensor group is composed of two symmetrically distributed line loads with a spiral angle (black thick solid line and black thick dashed line), and the receiving sensor group is composed of a circular piezoelectric piece; each line load corresponds to 11 receiving sensors for receiving spiral waveguide signals, a total of 22 receiving sensors; the excitation sensor group and the receiving sensor group form 22 spiral sensing paths (black thin solid line and black thin dashed line), forming a spiral sensor network.

[0066] The relationship between the spiral angle of the spiral sensor network and the area to be detected is analyzed. The larger the spiral angle, the denser the coverage of the sensor path in the center of the area to be detected, and the larger the uncovered area near the ends of the upper and lower excitation loads. The smaller the spiral angle, the stronger the coverage ability of the sensor path at the ends of the upper and lower excitation loads, but the lower the crossing ability of the sensor path. When the spiral angle is too small, the sensor path will be approximately parallel and propagate along the axial direction, degenerating into an axisymmetric modal excitation mode, and the positioning accuracy will be greatly reduced.

[0067] The size of the helix angle is determined by comprehensively considering 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 and routine inspection is required for the inspection area, the spiral angle should be reduced as much as possible under the premise of ensuring the intersection of the sensing paths, so as to increase the coverage area of ​​the sensing paths;

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

[0070] A plurality of mode-frequency pairs satisfying a preset spiral angle condition are mapped from the spiral angle dispersion curve to the spiral group velocity dispersion curve to obtain a mapping result.

[0071] According to the characteristics of the area to be detected, the spiral waveguide helical angle value (preset spiral angle) is selected; based on the spiral angle dispersion curves under different circumferential orders, the mode-frequency pair group that meets the preset spiral angle is obtained; the mode-frequency pair group that meets the preset spiral angle is plotted on the spiral group velocity dispersion curve to obtain the mapping result

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

[0073] According to the mode-frequency pair mapping result of the spiral group velocity dispersion curve, the mode-frequency pair used for detection is determined based on the weak dispersion characteristic. 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 pair for detection and the spiral sensing network, an ultrasonic guided wave defect locating map is obtained, and an ultrasonic guided wave defect locating method based on spiral dispersion characteristics is completed.

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

[0076]

[0077] in, represents the excitation point on the kth sensing path; represents the receiving point on the kth sensing path; τ k Represents the flight time through a discrete point (x,y).

[0078] Based on the selected spiral angle value, a spiral sensing network is established to excite the mode used for detection, and the sensor is used to receive the lossless and lossy signals under different sensing paths to calculate the difference signal;

[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 detection signal S after noise reduction, calculate the damage probability I(x,y) at the discrete point (x,y) in the detection area:

[0081]

[0082] Among them, S k is the waveguide signal received on the kth sensing path after threshold processing.

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

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

[0085] Embodiment 2

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

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

[0088] Obtain a spiral dispersion curve:

[0089] First, the axial phase velocity and axial group velocity are obtained from the material and geometric parameters of the sample, and the spiral group velocity is calculated according to the spiral group velocity calculation formula (2). Figure 3 The figure shows the comparison of the spiral group velocity dispersion curve and the axial group velocity dispersion curve for circumferential order 1-8 and modulus 1-8. The solid line represents the spiral group velocity dispersion curve of each mode, the dotted line represents the axial group velocity dispersion curve of each mode, the solid arrow points to the change of the modal circumferential order n represented by each curve in the spiral group velocity dispersion curve cluster, and the dotted arrow points to the change of the modal circumferential order n represented by each curve in the axial group velocity dispersion curve cluster. It can be seen from the dispersion curve comparison that the difference between the spiral group velocity and the axial group velocity is mainly reflected in the low-frequency region, and is mainly concentrated in the bending modes with modes 1 to 3.

[0090] According to the spiral phase velocity calculation formula (3), the spiral phase velocity is calculated: Figure 4 The figure is a comparison of the spiral phase velocity dispersion curve and the axial phase velocity dispersion curve with circumferential order of 1-8 and modulus of 1-5. The solid line represents the spiral phase velocity dispersion curve of each mode, the dotted line represents the axial phase velocity dispersion curve of each mode, the solid arrow points to the change of the modal circumferential order n represented by each curve in the spiral phase velocity dispersion curve cluster, and the dotted arrow points to the change of the modal circumferential order n represented by each curve in the axial phase velocity dispersion curve cluster.

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

[0092] The preset position of the internal corrosion defect of the experimental sample is located at the center of the area to be detected. Taking into account the positioning accuracy and the size of the coverable area, the tangent value of the spiral angle is determined to be around 0.6, that is, the angle between the two cross-sensing paths is approximately 60°.

[0093] Determine the helical guided wave mode-frequency pairs:

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

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

[0096] Depend on Figure 6 It can be seen that the dispersion curve slope of the mode-frequency pair with modulus 2 and 3 and circumferential order greater than 2 is relatively gentle, which represents weak dispersion characteristics. Harmonics at this frequency are not easily distorted during propagation, so they can be selected as the excitation frequency and mode for damage location. In this example, the F(3,3) mode with circumferential order 3 and mode 3 is selected as the guided wave mode for defect detection, and its corresponding excitation frequency is 20kHz.

[0097] Defect location:

[0098] For the test specimens with internal corrosion damage, according to Figure 1 The spiral sensor network shown is loaded with two sets of spiral excitation line loads on the left to excite the F(3,3) mode. The corresponding eleven sensors on the right receive synchronously to obtain two sets of guided wave signals. Each set of signals contains eleven parallel sensing paths, totaling twenty-two sensing path signals. The same data excitation acquisition work is carried out in the lossless pipeline structure to obtain the benchmark data, and the difference between the damage signal and the benchmark signal is calculated to obtain the difference signal.

[0099] A series of threshold values ​​β are taken from 30 μs to 60 μs at intervals of 5 μs, and the difference signal is subjected to noise reduction processing to obtain a series of noise-reduced detection signals S.

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

[0101] The maximum damage probability position diagram under different threshold parameters is shown in Figure 7 As shown in the figure, the black solid line and the black dotted line on the left represent the symmetrically distributed excitation loads, the black hollow circle and the black hollow diamond on the right represent the receiving sensors corresponding to the above two excitation loads, the black solid circle represents the actual defect position, and the black solid triangle represents the positioning results under different thresholds. It can be seen from the figure that under different threshold parameters, most of the detection results are close to the actual defect position, forming a damage location cluster with the highest probability. By setting a series of thresholds and taking damage location clusters, the randomness of the threshold parameters can be eliminated and the reliability of defect identification can be improved.

[0102] Embodiment 3

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

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

[0105] Based on the phase equation and wavefront theory of spiral waveguide, the spiral angle (β) and axial phase velocity (C pz )relation:

[0106]

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

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

[0109] Using the axial group velocity (C gz ) and spiral group velocity (C gs ) satisfies the same flight time, and combined with the spiral angle formula, the spiral group velocity calculation formula is obtained:

[0110]

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

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

[0113]

[0114] Wherein, 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 spiral angle dispersion curve under different circumferential orders based on the spiral angle formula; draw the spiral group velocity dispersion curve based on the spiral group velocity calculation formula; draw the spiral phase velocity dispersion curve based on the spiral 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 spiral guided waves, a spiral sensor network is established, such as Figure 1 As shown, Figure 1 a is a three-dimensional schematic diagram of the spiral sensor network in the pipeline. Figure 1 b is a schematic diagram after circumferential expansion. The spiral sensor network consists of an excitation sensor group and a receiving sensor group; the excitation sensor group is composed of two symmetrically distributed line loads with a spiral angle (black thick solid line and black thick dashed line), and the receiving sensor group is composed of a circular piezoelectric piece; each line load corresponds to 11 receiving sensors for receiving spiral waveguide signals, a total of 22 receiving sensors; the excitation sensor group and the receiving sensor group form 22 spiral sensing paths (black thin solid line and black thin dashed line), forming a spiral sensor network.

[0118] The relationship between the spiral angle of the spiral sensor network and the area to be detected is analyzed. The larger the spiral angle, the denser the coverage of the sensor path in the center of the area to be detected, and the larger the uncovered area near the ends of the upper and lower excitation loads. The smaller the spiral angle, the stronger the coverage ability of the sensor path at the ends of the upper and lower excitation loads, but the lower the crossing ability of the sensor path. When the spiral angle is too small, the sensor path will be approximately parallel and propagate along the axial direction, degenerating into an axisymmetric modal excitation mode, and the positioning accuracy will be greatly reduced.

[0119] The size of the helix angle is determined by comprehensively considering 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 and routine inspection is required for the inspection area, the spiral angle should be reduced as much as possible under the premise of ensuring the intersection of the sensing paths, so as to increase the coverage area of ​​the sensing paths;

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

[0122] The pair group mapping module is used to map a plurality of mode-frequency pairs that meet a preset spiral angle condition from the spiral angle dispersion curve to the spiral group velocity dispersion curve to obtain a mapping result.

[0123] According to the characteristics of the area to be detected, the spiral waveguide helical angle value (preset spiral angle) is selected; based on the spiral angle dispersion curves under different circumferential orders, the mode-frequency pair group that meets the preset spiral angle is obtained; the mode-frequency pair group that meets the preset spiral angle is plotted on the spiral group velocity dispersion curve to obtain the mapping result

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

[0125] According to the mode-frequency pair mapping result of the spiral group velocity dispersion curve, the mode-frequency pair used for detection is determined based on the weak dispersion characteristic. 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 location module is used to obtain an ultrasonic guided wave defect location map based on the determined mode-frequency pair for detection and the spiral sensing network, and complete the ultrasonic guided wave defect location method based on the spiral dispersion characteristics.

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

[0128]

[0129] in, represents the excitation point on the kth sensing path; represents the receiving point on the kth sensing path; τ k Represents the flight time through a discrete point (x,y).

[0130] Based on the selected spiral angle value, a spiral sensing network is established to excite the mode used for detection, and the sensor is used to receive the lossless and lossy signals under different sensing paths to calculate the difference signal;

[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 detection signal S after noise reduction, calculate the damage probability I(x, y) at the discrete point (x, y) in the area to be detected:

[0133]

[0134] Among them, S k is the waveguide signal received on the kth sensing path after threshold processing.

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

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

[0137] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. An ultrasonic guided wave defect location method based on spiral dispersion characteristics, characterized in that: The method comprises: The spiral angle is calculated based on the phase equation of spiral guided waves and the wavefront theory of spiral guided waves; Calculating a helical group velocity and a helical phase velocity based on the helix angle, the axial group velocity, and the axial phase velocity; Use the spiral angle and spiral group velocity to draw the spiral angle dispersion curve and spiral group velocity dispersion curve respectively; Optimizing parameters of a spiral sensing network based on the spiral angle, the spiral group velocity, and the spiral phase velocity; Mapping a number of mode-frequency pairs that meet preset conditions from the spiral angle dispersion curve to the spiral group velocity dispersion curve to obtain a mapping result; Based on the mapping results and the spiral sensing network after parameter optimization, an ultrasonic guided wave defect locating map is obtained, and an ultrasonic guided wave defect locating method based on spiral dispersion characteristics is completed.

2. The ultrasonic guided wave defect location method based on spiral dispersion characteristics according to claim 1 is characterized in that: The helix angle calculation formula is: Where N is the circumferential order, f is the frequency, R a is the outer diameter, C pz is the axial phase velocity.

3. The ultrasonic guided wave defect location method based on spiral dispersion characteristics according to claim 2 is characterized in that: The calculation process of the spiral group velocity is: Where ω is the angular frequency, C gz is the axial group velocity.

4. The ultrasonic guided wave defect location method based on spiral dispersion characteristics according to claim 3 is characterized in that: The calculation process of the spiral phase velocity is: Where i is the i-th iteration and Δω is the frequency step of each iteration.

5. The ultrasonic guided wave defect location method based on spiral dispersion characteristics according to claim 1 is characterized in that: The spiral sensor network includes an excitation sensor group and a receiving sensor group; The excitation sensor group is composed of two symmetrically distributed line loads with a helical angle; The receiving sensor group is composed of circular piezoelectric sheets.

6. An ultrasonic guided wave defect location system based on spiral dispersion characteristics, the system being used to implement the method described in any one of claims 1 to 5, characterized in that the system include: A spiral angle calculation module is used to calculate the spiral angle based on the phase equation of spiral guided waves and the wavefront theory of spiral guided waves; A spiral waveguide parameter calculation module, used for calculating the spiral group velocity and the spiral phase velocity based on the spiral angle, the axial group velocity and the axial phase velocity; A dispersion curve calculation module, used to draw a spiral angle dispersion curve and a spiral group velocity dispersion curve respectively using the spiral angle and the spiral group velocity; A sensor network parameter optimization module, used for optimizing the parameters of the spiral sensor network based on the spiral angle, spiral group velocity and spiral phase velocity; A pair group mapping module, used to map a number of mode-frequency pairs that meet preset conditions from the spiral angle dispersion curve to the spiral group velocity dispersion curve to obtain a mapping result; The defect location module is used to obtain an ultrasonic guided wave defect location map based on the mapping result and the spiral sensing network after parameter optimization, and complete the ultrasonic guided wave defect location method based on the spiral dispersion characteristics.

7. The ultrasonic guided wave defect location system based on spiral dispersion characteristics according to claim 6 is characterized in that: The calculation process of the helix angle is: Where N is the circumferential order, f is the frequency, R a is the outer diameter, C pz is the axial phase velocity.

8. The ultrasonic guided wave defect location system based on spiral dispersion characteristics according to claim 7 is characterized in that: The calculation process of the spiral group velocity is: Where ω is the angular frequency, C gz is the axial group velocity.

9. The ultrasonic guided wave defect location system based on spiral dispersion characteristics according to claim 8, characterized in that: The calculation process of the spiral phase velocity is: Where i is the i-th iteration and Δω is the frequency step of each iteration.

Images