A phased array ultrasonic method for wind turbine main shaft crack detection

Abstract

The application discloses a phased array ultrasonic technology for wind turbine main shaft crack detection, which comprises S1 customized block setting parameters, S2 evaluation of wave height method reliability, S3 evaluation of tip diffraction method reliability, S4 scan preparation, S5 segmented scan operation, S6 cyclic scan different segments, S7 final evaluation. In S4, the encoder and the scanning trolley are prepared, the equipment probe system is set and calibrated, the main shaft is cleaned, and four circumferential segmented scanning track lines are marked on the main shaft body. More than 90% of the damage or defects of the in-service wind turbine main shaft are initiated from the surface, mainly manifested as wear, cracks and the like. The disclosure combines a set of comprehensive detection technology of PAUT technology, detects the surface cracking area on the surface of the main shaft, can be operated in the wind turbine cabin, has a better operation environment, has high detection efficiency, and provides a reliable basis for evaluating the safe operation, maintenance and repair plan of the wind turbine.

Description

Technical Field

[0001] This invention relates to the field of wind turbine testing, and more specifically, to a phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine. Background Technology

[0002] As wind turbines become increasingly larger, the main shaft, which forms the drivetrain, experiences various complex operating conditions during service, such as varying speeds, torques, axial loads from wind, and bending moments caused by various factors. These complex loads can lead to premature wear, cracks, and other failures in the wind turbine main shaft. Furthermore, potential defects may be inherent within the main shaft itself during the material smelting and forging processes.

[0003] As a key component of wind turbines, the main shaft has large geometric dimensions and variable diameter (tapered) characteristics: the flange connection to the hub uses a flange structure, with a flange diameter exceeding 2000mm; the other end connects to the hollow shaft of the gearbox, with a diameter ranging from 200mm to 500mm, and a length ranging from 2500mm to over 5000mm. However, most early wear or cracks on the main shaft appear in areas that cannot be observed with the naked eye, such as under the inner ring of the bearing or under the bearing locating ring, making defect detection in these areas extremely difficult. Because wind turbine main shafts are installed at heights of 50 meters or even over 100 meters, inspecting their health becomes difficult and costly.

[0004] Phased-Array Ultrasonic Testing (PAUT) is increasingly being used as a non-destructive testing technique in various fields, such as industrial manufacturing and medicine. It is recognized for its speed, intuitiveness, accuracy, and ease of use. However, quantitative detection of damage to the main shaft of in-service wind turbines remains a challenge. B&V uses Shaft Test technology to detect and assess cracks in the main shaft. However, this technology operates inside the wind turbine hub, in a harsh environment, resulting in low efficiency. Furthermore, this technology can only provide relatively accurate qualitative assessments for severe damage and cannot provide quantitative evaluations of defects. Summary of the Invention

[0005] To address the aforementioned technical challenges, this application proposes a phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine using PAUT technology. This method can detect areas on the shaft surface where surface cracks may exist, thus overcoming the shortcomings of the prior art.

[0006] To achieve the above-mentioned objective, the technical solution of the present invention is implemented as follows: A phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine includes the following steps: S1 Customize sample blocks and set parameters: Customize three sample blocks, including sample block one, sample block two, and sample block three. All three sample blocks are made of the same shaft material and processing technology as the spindle. Sample block one and sample block two are used for calibration of various process parameters. Sample block three is made at a 1:1 scale with the inspection area of ​​the spindle. Several simulated cracks with different depths, the same length, and the same groove are processed on sample block three. The simulated crack area of ​​sample block three corresponds to the inspection area of ​​the spindle. The simulated crack area of ​​sample block three is detected and the signal wave height of each simulated crack is obtained. The sensitivity of the on-site scanning is defined by the signal wave height. S2 Evaluation of the reliability of the wave height method: Using sample block three as a reference sample, the wave height method is used to obtain the calculated values ​​of each simulated crack on sample block three. The calculated values ​​and actual values ​​of the depth dimensions of each simulated crack are compared and the deviation values ​​are recorded. Then, the reliability of the wave height method in detecting the spindle defect and whether the error is accurate to an acceptable range are evaluated by the deviation values ​​corresponding to each simulated crack. S3 Evaluation of the reliability of the tip diffraction method: The measured values ​​of the simulated crack depth dimensions are obtained by using the tip diffraction method, and then the deviation between the measured values ​​of the simulated crack depth dimensions and the actual values ​​is evaluated to verify the reliability of the tip diffraction method and whether the error range is accurate to an acceptable range. S4 Scanning Preparation: First, prepare the encoder and scanning carriage to record data obtained at different scanning positions; then set the scanning range and calibrate the size of the probe system of the equipment, and clean the spindle; finally, measure the axial position of the probe on the spindle and mark four circumferentially segmented scanning trajectory lines on the spindle. S5 Segment Scanning Operation: After selecting a segment that has not yet been scanned, first lock the rotor of the wind turbine, perform an initial scan on the selected segment and record the data; then check and verify the quality of the data, verify whether the wave height of the structural signal meets the requirements, whether there are defect signals in the shaft, and whether the defect signals are saturated; after the data quality is qualified, store the data, and perform several more scans and record the data; if no defect signals are found, skip directly to step S6; if defect signals are found in the target area, increase the scan gain and perform a tip diffraction scan; S6 Cyclicly scan different segments: After completing the scan of the previous segment, unlock the fan impeller, rotate the main shaft 90 degrees, select the next segment that has not yet been scanned, and then repeat step S5 until all the scan lines are scanned. S7 Final Evaluation: After completing the scanning of the scanning trajectory, the data obtained from the scanning is evaluated as a whole, referring to the wave height method mentioned in S2 and the tip diffraction method mentioned in S3.

[0007] Furthermore, S1 specifically includes the following process: S101: The first sample block is a standard sample block and adopts the CSK-1A standard, used for sound velocity calibration and wedge delay calibration; the second sample block is customized according to the actual sound path path of the test at a 1:1 scale, used for calibrating the wedge delay and setting or calibrating the ACG and TCG under various focusing rules used in the project scan. S102: Based on the location range and depth of the crack defects in the actual service spindle, several simulated cracks with different depths, the same length and width, and the same tip cross-sectional shape are processed on the sample block three using EDM technology. The depth range of the simulated cracks is 1mm-15mm. In practice, when the crack depth of the simulated crack is less than 6mm, it can be increased in increments of 0.5mm, and when the crack depth of the simulated crack is greater than 6mm, it can be increased in increments of 1mm, depending on the specific situation. S103: Detect the simulated crack on the sample block three and obtain its corresponding signal wave height. Define the sensitivity of the on-site inspection by the signal wave height. The sensitivity includes recording sensitivity and evaluation sensitivity.

[0008] Furthermore, in S103, the method for detecting the simulated crack on the sample block three is to use the surface of the central hole of the spindle as an acoustic wave reflecting surface to reflect the acoustic wave to the simulated crack area of ​​the sample block three, thereby measuring the signal wave height and using it to define the sensitivity of the on-site inspection.

[0009] Furthermore, the number of simulated cracks processed on the standard sample block three is 22.

[0010] Furthermore, the specific process of S2 is as follows: S201: Select the signal wave height of the reference structure corresponding to the main axis on sample block three, and the signal wave height of each simulated crack at different depths on sample block three, and calculate the decibel value (dB) of the signal wave height of each simulated crack relative to the signal wave height of the reference structure. S202: Based on the decibel values ​​(dB) corresponding to each simulated crack signal obtained from S201 and the measured values ​​of each simulated crack depth, the relationship equation between the decibel values ​​(dB) of each simulated crack signal and the measured values ​​of the corresponding simulated crack depth is derived by linear regression. S203: Calculate the depth of each simulated crack using the simulated crack measurement value relationship equation, compare the calculated value with the actual value of each simulated crack depth, and record the deviation values. Use the magnitude of the deviation values ​​to evaluate the accuracy range and reliability of the linear relationship equation obtained by the wave height method, and then evaluate the reliability of the wave height method in detecting the spindle defect and whether the error range is accurate to an acceptable range. S204: Derive the linear function relationship embodied in the simulated crack measurement value relationship equation. Based on the laboratory analysis results of the actual defective spindle and the corresponding PAUT scan defect signal wave height in decibels, replace the linear function relationship with a constant to finally obtain the linear relationship equation for evaluating the crack depth of the actual spindle in the field.

[0011] Furthermore, in step S202, after measuring the depth dimensions of each simulated crack using the wave height method, and verifying through actual calculations, the relationship equation between the simulated crack measurement values ​​and the various signal parameters when the measured depth dimensions of the simulated crack are ≤15mm is as follows: H1 = A1X1 + B1; In the equation relating the simulated crack measurements: H1—Measured value of the simulated crack depth obtained by wave height method, a fixed value, in mm; X1 = 20 1g (crack signal wave height / reference structure signal wave height); X1 is the wave height correction coefficient of the simulated crack relative to the reference structure signal, which is a calculated value and the unit is decibels (dB); where the crack signal wave height and the reference structure signal wave height are both expressed as percentages (%). A1—Linear slope; B1—System constant; Substituting H1 and X1 into the equation relating the simulated crack measurements, we obtain the values ​​of A1 and B1.

[0012] Furthermore, the specific process of deriving the linear relationship equation in S203 is as follows: S2031: Using the linear function relationship of the simulated crack measurement value relationship equation obtained in S202, referring to the constants A1 and B1 in the linear function relationship, and based on the laboratory analysis results of the main shaft of the actual failure fracture and the defect signal wave height decibel of PAUT scan, the constants A2 and B2 are obtained. S2032: Substitute A2 and B2 obtained in S2031 into the linear function relationship to obtain the linear relationship equation required for practical application: H2 = A2 X2+B2; In the linear relationship equation: H2—Calculated value of the crack depth dimension to be evaluated, in mm; X2 = 20 1g(A defect / Aref), the value is expressed in decibels (dB); A defect —Signal wave height of the crack, expressed as a percentage; Aref—Signal wave height of the reference structure, expressed as a percentage; A2—A constant derived from laboratory analysis of the actual failed fracture of the spindle and the decibel level of the defect signal wave from PAUT scanning, used to replace A1; B2—A constant derived from laboratory analysis of the actual failed fracture of the spindle and the decibel level of the defect signal wave from PAUT scanning, used to replace B1.

[0013] Furthermore, in step S3, the specific process of the tip diffraction method is as follows: S301 Check for diffraction signals in defects: If a crack is found in a selected area, perform a tip diffraction scan on the selected area and evaluate the data obtained from the scan to check for diffraction signals in the data. S302 outputs the following values: If a diffraction signal is detected, then the cursor is used to read the values ​​of the location of the strongest point of the crack opening acoustic wave and the location of the strongest point of the diffraction signal. S303 Calculation Results: Finally, the measured value H is calculated using the following formula; H = Uref - Umea; In the formula: H—Measured crack depth, in mm; Uref—The numerical value of the location of the strongest sound wave at the crack opening, used as a reference position for calculation, in mm; Umea—The numerical value of the location of the strongest diffraction signal, used as the measurement position for calculation, in mm.

[0014] Furthermore, in S3, the PAUT probe used in the tip diffraction method has a minimum number of 32 elements, a minimum excitation aperture greater than 19.2 mm, and uses the central hole of the spindle as the acoustic wave reflecting surface.

[0015] Further, S4 includes the following steps: S401: First, prepare the encoder and the scanning carriage, and set and calibrate the probe system of the device, and calibrate the encoder of the scanning carriage; S402: Clean the surface of the spindle to remove foreign objects and ensure good coupling between the wedge and the spindle; S403: Measure the axial position of the probe on the shaft of the main shaft, and mark each of the scanning trajectory lines on the shaft; at the same time, mark the scanning starting point, which is the 12 o'clock position on the cross section of the main shaft when a selected blade of the wind turbine is vertically downward.

[0016] Furthermore, in S403, the selected blade of the wind turbine can be determined according to actual needs, preferably blade A.

[0017] Furthermore, during the S403 process, an auxiliary scanning alignment fixture can be installed on the spindle bearing as needed. The fixture fits against the spindle shaft and is positioned axially to ensure that the distance between the probe and the reference surface is constant. Additionally, a plane perpendicular to the taper of the shaft fits against the front plane of the wedge block, ensuring that the probe can scan at a fixed angle, reducing data quality instability caused by probe deflection. The fixture minimizes the impact of human factors on the quality of the scanning results.

[0018] Further, S5 includes the following steps: S501: After selecting a segment that has not yet been scanned, lock the impeller of the wind turbine and use a brake to stop the impeller from rotating, so as to avoid affecting the scanning effect; S502: Scan the selected segment; in addition, ensure that the scanning start line of the selected segment and the wedge center line are aligned for each probe scanning operation; S503: Use standard sensitivity for scanning. The scanning gain is controlled within ±3dB of the scanning sensitivity defined in S1. After one scan, check the data quality on the screen and verify whether the waveform height of the structural signal meets the requirements, whether there are defective signals, and whether the defective signals are saturated. If either the structural signal or the defective signal is saturated, reduce the scanning sensitivity and rescan. If neither the structural signal nor the defective signal is saturated, but the waveform height of the structural signal is not up to the requirements, increase the scanning sensitivity to make the structural signal have a qualified waveform height and rescan. Finally, record and store the qualified data, and repeat the scan three times while maintaining the scanning gain and recording the data. S504 High-gain scanning operation: If no defect signal is found, skip directly to step S6; if a defect signal is found in the target area, increase the scanning gain and perform tip diffraction scanning; the set value of the scanning gain = the gain value when the full-screen waveform height of the defect signal is 80% + (18~23) dB; scan three times and store the scanning data; S505: Repeat steps S503 and S504 three times; S506: Scan the next segment and repeat steps S501 to S505.

[0019] The beneficial effects of this invention: Over 90% of damage or defects in the main shaft of in-service wind turbines originate from the surface, mainly manifested as wear and cracks. This disclosure utilizes the hollow structure of the wind turbine main shaft as a sound wave reflecting surface to detect surface defects in the large-diameter main shaft, thus covering the vast majority of damage or defects in the main shaft. Based on this, this disclosure can quantitatively assess the crack depth and crack length on the surface of in-service wind turbine main shafts with high accuracy.

[0020] This disclosure utilizes a comprehensive testing method incorporating PAUT technology to inspect areas on the main shaft surface that may exhibit surface cracks. The method allows for operation within the wind turbine nacelle, providing a favorable working environment and high testing efficiency. The quantitative results provided by this disclosure offer a reliable basis for evaluating the safe operation, maintenance, and repair plans for wind turbines. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be 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.

[0022] Figure 1 This is a front view of the spindle described in this invention.

[0023] Figure 2 These are cross-sectional and perspective views of the spindle described in this invention.

[0024] Figure 3 This is a schematic diagram of the structure of sample block one described in this invention.

[0025] Figure 4 This is a schematic diagram of the structure of sample block two described in this invention.

[0026] Figure 5 This is a schematic diagram of the structure of sample block three described in this invention.

[0027] Figure 6 These refer to the segments, scanning lines, and scanning start points on the main shaft as described in this invention.

[0028] Figure 7 This is a sound wave path diagram for using the central hole of the main shaft as the sound wave reflecting surface in this invention.

[0029] Figure 8 This is a screenshot of the software interface for the acoustic wave path diagram of the main shaft center hole used as the acoustic wave reflecting surface in this invention.

[0030] Figure 9 This is a schematic diagram illustrating an example of the tooling used to assist in scanning alignment in this invention. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. The embodiments of the present invention are given only for illustrating the present invention, and are not intended to limit the present invention. Therefore, any improvements to the present invention under the premise of the method of the present invention are within the scope of protection of the present invention.

[0032] To facilitate understanding of the above technical solutions of the present invention, the following detailed description of the above technical solutions of the present invention will be provided through specific usage methods.

[0033] A phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine includes the following steps: S1 Customize sample blocks and set parameters: Customize three sample blocks, including sample block one, sample block two, and sample block three. All three sample blocks are made of the same shaft material and processing technology as the spindle. Sample block one and sample block two are used for calibration of various process parameters. Sample block three is made at a 1:1 scale with the inspection area of ​​the spindle. Several simulated cracks with different depths, the same length, and the same groove are processed on sample block three. The simulated crack area of ​​sample block three corresponds to the inspection area of ​​the spindle. The simulated crack area of ​​sample block three is detected and the signal wave height of each simulated crack is obtained. The sensitivity of the on-site scanning is defined by the signal wave height. S2 Evaluation of the reliability of the wave height method: Using sample block three as a reference sample, the wave height method is used to obtain the calculated values ​​of each simulated crack on sample block three. The calculated values ​​and actual values ​​of the depth dimensions of each simulated crack are compared and the deviation values ​​are recorded. Then, the reliability of the wave height method in detecting the spindle defect and whether the error is accurate to an acceptable range are evaluated by the deviation values ​​corresponding to each simulated crack. S3 Evaluation of the reliability of the tip diffraction method: The measured values ​​of the simulated crack depth dimensions are obtained by using the tip diffraction method, and then the deviation between the measured values ​​of the simulated crack depth dimensions and the actual values ​​is evaluated to verify the reliability of the tip diffraction method and whether the error range is accurate to an acceptable range. S4 Scanning Preparation: First, prepare the encoder and scanning carriage to record data obtained at different scanning positions; then set the scanning range and calibrate the size of the probe system of the equipment, and clean the spindle; finally, measure the axial position of the probe on the spindle and mark four circumferentially segmented scanning trajectory lines on the spindle. S5 Segment Scanning Operation: After selecting a segment that has not yet been scanned, first lock the rotor of the wind turbine, perform an initial scan on the selected segment and record the data; then check and verify the quality of the data, verify whether the wave height of the structural signal meets the requirements, whether there are defect signals in the shaft, and whether the defect signals are saturated; after the data quality is qualified, store the data, and perform several more scans and record the data; if no defect signals are found, skip directly to step S6; if defect signals are found in the target area, increase the scan gain and perform a tip diffraction scan; S6 Cyclicly scan different segments: After completing the scan of the previous segment, unlock the fan impeller, rotate the main shaft 90 degrees, select the next segment that has not yet been scanned, and then repeat step S5 until all the scan lines are scanned. S7 Final Evaluation: After completing the scanning of the scanning trajectory, the data obtained from the scanning is evaluated as a whole, referring to the wave height method mentioned in S2 and the tip diffraction method mentioned in S3.

[0034] In a specific embodiment of the present invention, S1 specifically includes the following process: S101: The first sample block is a standard sample block and adopts the CSK-1A standard, used for sound velocity calibration and wedge delay calibration; the second sample block is customized according to the actual sound path path of the test at a 1:1 scale, used for calibrating the wedge delay and setting or calibrating the ACG and TCG under various focusing rules used in the project scan. S102: Based on the location range and depth of the crack defects in the actual service spindle, several simulated cracks with different depths, the same length and width, and the same tip cross-sectional shape are processed on the sample block three using EDM technology. The depth range of the simulated cracks is 1mm-15mm. In practice, when the crack depth of the simulated crack is less than 6mm, it can be increased in increments of 0.5mm, and when the crack depth of the simulated crack is greater than 6mm, it can be increased in increments of 1mm, depending on the specific situation. S103: Detect the simulated crack on the sample block three and obtain its corresponding signal wave height. Define the sensitivity of the on-site inspection by the signal wave height. The sensitivity includes recording sensitivity and evaluation sensitivity.

[0035] In a specific embodiment of the present invention, in step S103, the method for detecting the simulated crack on the sample block three is to use the surface of the central hole of the spindle as an acoustic wave reflecting surface to reflect the acoustic wave to the simulated crack area of ​​the sample block three, thereby measuring the signal wave height and using it to define the sensitivity of the on-site inspection.

[0036] In one specific embodiment of the present invention, the number of simulated cracks processed on the standard sample block three is 22.

[0037] In a specific embodiment of the present invention, the specific process of S2 is as follows: S201: Select the signal wave height of the reference structure corresponding to the main axis on sample block three, and the signal wave height of each simulated crack at different depths on sample block three, and calculate the decibel value (dB) of the signal wave height of each simulated crack relative to the signal wave height of the reference structure. S202: Based on the decibel values ​​(dB) corresponding to each simulated crack signal obtained from S201 and the measured values ​​of each simulated crack depth, the relationship equation between the decibel values ​​(dB) of each simulated crack signal and the measured values ​​of the corresponding simulated crack depth is derived by linear regression. S203: Calculate the depth of each simulated crack using the simulated crack measurement value relationship equation, compare the calculated value with the actual value of each simulated crack depth, and record the deviation values. Use the magnitude of the deviation values ​​to evaluate the accuracy range and reliability of the linear relationship equation obtained by the wave height method, and then evaluate the reliability of the wave height method in detecting the spindle defect and whether the error range is accurate to an acceptable range. S204: Derive the linear function relationship embodied in the simulated crack measurement value relationship equation. Based on the laboratory analysis results of the actual defective spindle and the corresponding PAUT scan defect signal wave height in decibels, replace the linear function relationship with a constant to finally obtain the linear relationship equation for evaluating the crack depth of the actual spindle in the field.

[0038] In a specific embodiment of the present invention, in step S202, after measuring the depth dimensions of each simulated crack using the wave height method, and verifying through actual calculation, the relationship equation between the simulated crack measurement values ​​and the various signal parameters when the measured depth dimensions of the simulated crack are ≤15mm is as follows: H1 = A1X1 + B1; In the equation relating the simulated crack measurements: H1—Measured value of the simulated crack depth obtained by wave height method, a fixed value, in mm; X1 = 20 1g (crack signal wave height / reference structure signal wave height); X1 is the wave height correction coefficient of the simulated crack relative to the reference structure signal, which is a calculated value and the unit is decibels (dB); where the crack signal wave height and the reference structure signal wave height are both expressed as percentages (%). A1—Linear slope; B1—System constant; Substituting H1 and X1 into the equation relating the simulated crack measurements, we obtain the values ​​of A1 and B1.

[0039] In a specific embodiment of the present invention, the specific process of obtaining the linear relationship equation in step S203 is as follows: S2031: Using the linear function relationship of the simulated crack measurement value relationship equation obtained in S202, referring to the constants A1 and B1 in the linear function relationship, and based on the laboratory analysis results of the main shaft of the actual failure fracture and the defect signal wave height decibel of PAUT scan, the constants A2 and B2 are obtained. S2032: Substitute A2 and B2 obtained in S2031 into the linear function relationship to obtain the linear relationship equation required for practical application: H2 = A2 X2+B2; In the linear relationship equation: H2—Calculated value of the crack depth dimension to be evaluated, in mm; X2 = 20 1g(A defect / Aref), the value is expressed in decibels (dB); A defect —Signal wave height of the crack, expressed as a percentage; Aref—Signal wave height of the reference structure, expressed as a percentage; A2—A constant derived from laboratory analysis of the actual failed fracture of the spindle and the decibel level of the defect signal wave from PAUT scanning, used to replace A1; B2—A constant derived from laboratory analysis of the actual failed fracture of the spindle and the decibel level of the defect signal wave from PAUT scanning, used to replace B1.

[0040] In a specific embodiment of the present invention, the specific process of the tip diffraction method in step S3 is as follows: S301 Check for diffraction signals in defects: If a crack is found in a selected area, perform a tip diffraction scan on the selected area and evaluate the data obtained from the scan to check for diffraction signals in the data. S302 outputs the following values: If a diffraction signal is detected, then the cursor is used to read the values ​​of the location of the strongest point of the crack opening acoustic wave and the location of the strongest point of the diffraction signal. S303 Calculation Results: Finally, the measured value H is calculated using the following formula; H = Uref - Umea; In the formula: H—Measured crack depth, in mm; Uref—The numerical value of the location of the strongest sound wave at the crack opening, used as a reference position for calculation, in mm; Umea—The numerical value of the location of the strongest diffraction signal, used as the measurement position for calculation, in mm.

[0041] Furthermore, in S3, the PAUT probe used in the tip diffraction method has a minimum number of 32 elements, a minimum excitation aperture greater than 19.2 mm, and uses the central hole of the spindle as the acoustic wave reflecting surface.

[0042] In one specific embodiment of the present invention, step S4 includes the following steps: S401: First, prepare the encoder and the scanning carriage, and set and calibrate the probe system of the device, and calibrate the encoder of the scanning carriage; S402: Clean the surface of the spindle to remove foreign objects and ensure good coupling between the wedge and the spindle; S403: Measure the axial position of the probe on the shaft of the main shaft, and mark each of the scanning trajectory lines on the shaft; at the same time, mark the scanning starting point, which is the 12 o'clock position on the cross section of the main shaft when a selected blade of the wind turbine is vertically downward.

[0043] In one specific embodiment of the present invention, the blade of the wind turbine selected in S403 can be determined according to actual needs, preferably blade A.

[0044] In a specific embodiment of the present invention, during the process of S403, an auxiliary scanning alignment fixture can be installed on the bearing of the spindle as needed. The fixture fits against the shaft of the spindle and is positioned axially to ensure that the distance between the probe and the reference surface is constant. Furthermore, a plane perpendicular to the taper of the shaft fits against the front plane of the wedge block to ensure that the probe can scan at a fixed angle, reducing the instability of data quality caused by probe deflection. The fixture minimizes the impact of human factors on the data quality of the scanning results.

[0045] In one specific embodiment of the present invention, step S5 includes the following steps: S501: After selecting a segment that has not yet been scanned, lock the impeller of the wind turbine and use a brake to stop the impeller from rotating, so as to avoid affecting the scanning effect; S502: Scan the selected segment; in addition, ensure that the scanning start line of the selected segment and the wedge center line are aligned for each probe scanning operation; S503: Use standard sensitivity for scanning. The scanning gain is controlled within ±3dB of the scanning sensitivity defined in S1. After one scan, check the data quality on the screen and verify whether the waveform height of the structural signal meets the requirements, whether there are defective signals, and whether the defective signals are saturated. If either the structural signal or the defective signal is saturated, reduce the scanning sensitivity and rescan. If neither the structural signal nor the defective signal is saturated, but the waveform height of the structural signal is not up to the requirements, increase the scanning sensitivity to make the structural signal have a qualified waveform height and rescan. Finally, record and store the qualified data, and repeat the scan three times while maintaining the scanning gain and recording the data. S504 High-gain scanning operation: If no defect signal is found, skip directly to step S6; if a defect signal is found in the target area, increase the scanning gain and perform tip diffraction scanning; the set value of the scanning gain = the gain value when the full-screen waveform height of the defect signal is 80% + (18~23) dB; scan three times and store the scanning data; S505: Repeat steps S503 and S504 three times; S506: Scan the next segment and repeat steps S501 to S505.

[0046] Specific working principle: In step S1, sample block 1, sample block 2, and sample block 3 are fabricated as auxiliary samples. Several simulated cracks are then created on sample block 3 to compare with the actual crack defects of the operating spindle. Sample block 1 can be used to calibrate the acoustic velocity of the spindle and the delay of the probe wedge. Sample block 2 is made of the same material as the spindle under test and can be used to calibrate the TCG curves and ACG calibrations of various focusing methods, as well as the probe sensitivity. Two mature existing technologies, the wave height method mentioned in step S2 and the tip diffraction method mentioned in step S3, are used to verify the reliability of the simulated cracks and derive a linear relationship equation applicable to actual detection. Steps S2 and S3 can be used to verify the reliability of the overall method. Subsequently, steps S4, S5, and S6 are used to scan the operating spindle, obtaining various scan data. These scan data are then verified using the wave height method mentioned in S2 and the tip diffraction method mentioned in S3. Through dual verification and evaluation using the wave height method and the tip diffraction method, the actual defect situation of the operating spindle is finally accurately determined. The wave height method used in S2 and the tip diffraction method used in S3 of this invention are both mature methods commonly used in the detection field.

[0047] In summary, by utilizing the above-described technical solution of this invention, compared to the prior art, this disclosure provides a comprehensive testing method that incorporates PAUT technology to inspect areas on the main shaft surface where surface cracks may exist. This method allows for operation inside the wind turbine nacelle, providing a better working environment and high testing efficiency. The quantitative results provided by this disclosure offer a reliable basis for evaluating the safe operation, maintenance, and repair plans for wind turbines.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine generator, comprising the following steps: S1 Customize sample blocks and set parameters: Customize three sample blocks, including sample block one, sample block two, and sample block three. All three sample blocks are made of the same shaft material and processing technology as the spindle. Sample block one and sample block two are used for calibration of various process parameters. Sample block three is made at a 1:1 scale with the inspection area of ​​the spindle. Several simulated cracks with different depths, the same length, and the same groove are processed on sample block three. The simulated crack area of ​​sample block three corresponds to the inspection area of ​​the spindle. The simulated crack area of ​​sample block three is detected and the signal wave height of each simulated crack is obtained. The sensitivity of the on-site scanning is defined by the signal wave height. S2 Evaluation of the reliability of the wave height method: Using sample block three as a reference sample, the wave height method is used to obtain the calculated values ​​of each simulated crack on sample block three. The calculated values ​​and actual values ​​of the depth dimensions of each simulated crack are compared and the deviation values ​​are recorded. Then, the reliability of the wave height method in detecting the spindle defect and whether the error is accurate to an acceptable range are evaluated by the deviation values ​​corresponding to each simulated crack. S3 Evaluation of the reliability of the tip diffraction method: The measured values ​​of the simulated crack depth dimensions are obtained by using the tip diffraction method, and then the deviation between the measured values ​​of the simulated crack depth dimensions and the actual values ​​is evaluated to verify the reliability of the tip diffraction method and whether the error range is accurate to an acceptable range. S4 Scanning Preparation: First, prepare the encoder and scanning carriage to record data obtained at different scanning positions; then set the scanning range and calibrate the size of the probe system of the equipment, and clean the spindle; finally, measure the axial position of the probe on the spindle and mark four circumferentially segmented scanning trajectory lines on the spindle. S5 Segment Scanning Operation: After selecting a segment that has not yet been scanned, first lock the rotor of the wind turbine, perform an initial scan on the selected segment and record the data; then check and verify the quality of the data, verify whether the wave height of the structural signal meets the requirements, whether there are defect signals in the shaft, and whether the defect signals are saturated; after the data quality is qualified, store the data, and perform several more scans and record the data; if no defect signals are found, skip directly to step S6; if defect signals are found in the target area, increase the scan gain and perform a tip diffraction scan; S6 Cyclicly scan different segments: After completing the scan of the previous segment, unlock the fan impeller, rotate the main shaft 90 degrees, select the next segment that has not yet been scanned, and then repeat step S5 until all the scan lines are scanned. S7 Final Evaluation: After completing the scanning of the scanning trajectory, the data obtained from the scanning is evaluated as a whole, referring to the wave height method mentioned in S2 and the tip diffraction method mentioned in S3.

2. The phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine generator according to claim 1, characterized in that, The S1 specifically The process includes the following: S101: The first sample block is a standard sample block and adopts the CSK-1A standard, used for sound velocity calibration and wedge delay calibration; the second sample block is customized according to the actual sound path path of the test at a 1:1 scale, used for calibrating the wedge delay and setting or calibrating the ACG and TCG under various focusing rules used in the project scan. S102: Based on the location range and depth of the crack defects of the spindle in actual service, several simulated cracks with different depths, the same length and width, and the same tip cross-sectional shape are processed on the sample block three using EDM process. The depth range of the simulated cracks is 1mm-15mm. S103: Detect the simulated crack on the sample block three and obtain its corresponding signal wave height. Define the sensitivity of the on-site inspection by the signal wave height. The sensitivity includes recording sensitivity and evaluation sensitivity.

3. The phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine generator according to claim 2, characterized in that, In step S103, the method for detecting the simulated crack on the sample block three is to use the surface of the central hole of the spindle as an acoustic wave reflecting surface to reflect the acoustic wave to the simulated crack area of ​​the sample block three, thereby measuring the signal wave height and using it to define the sensitivity of the on-site inspection.

4. The phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine generator according to claim 1, characterized in that, The specific process of S2 is as follows: S201: Select the signal wave height of the reference structure corresponding to the main axis on sample block three, and the signal wave height of each simulated crack at different depths on sample block three, and calculate the decibel value (dB) of the signal wave height of each simulated crack relative to the signal wave height of the reference structure. S202: Based on the decibel values ​​(dB) corresponding to each simulated crack signal obtained from S201 and the measured values ​​of each simulated crack depth, the relationship equation between the decibel values ​​(dB) of each simulated crack signal and the measured values ​​of the corresponding simulated crack depth is derived by linear regression. S203: Calculate the depth of each simulated crack using the simulated crack measurement value relationship equation, compare the calculated value with the actual value of each simulated crack depth, and record the deviation values. Use the magnitude of the deviation values ​​to evaluate the accuracy range and reliability of the linear relationship equation obtained by the wave height method, and then evaluate the reliability of the wave height method in detecting the spindle defect and whether the error range is accurate to an acceptable range. S204: Derive the linear function relationship embodied in the simulated crack measurement value relationship equation. Based on the laboratory analysis results of the actual defective spindle and the corresponding PAUT scan defect signal wave height in decibels, replace the linear function relationship with a constant to finally obtain the linear relationship equation for evaluating the crack depth of the actual spindle in the field.

5. The phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine generator according to claim 4, characterized in that, In step S202, after measuring the depth dimensions of each simulated crack using the wave height method, and verifying through actual calculations, the relationship equation between the simulated crack measurement values ​​and the various signal parameters when the measured depth dimensions of the simulated crack are ≤15mm is as follows: H1 = A1X1 + B1; In the equation relating the simulated crack measurements: H1—Measured value of the simulated crack depth obtained by wave height method, a fixed value, in mm; X1 = 20 lg(crack signal wave height / reference structure signal wave height); X1 is the wave height correction coefficient of the simulated crack relative to the reference structure signal, which is a calculated value and the unit is decibels (dB); where the wave height of the crack signal and the wave height of the reference structure signal are both expressed as percentages (%). A1—Linear slope; B1—System constant; Substituting H1 and X1 into the equation relating the simulated crack measurements, we obtain the values ​​of A1 and B1.

6. The phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine generator according to claim 5, characterized in that, The specific process by which S203 derives the linear relationship equation is as follows: S2031: Using the linear function relationship of the simulated crack measurement value relationship equation obtained in S202, referring to the constants A1 and B1 in the linear function relationship, and based on the laboratory analysis results of the main shaft of the actual failure fracture and the defect signal wave height decibel of PAUT scan, the constants A2 and B2 are obtained. S2032: Substitute A2 and B2 obtained in S2031 into the linear function relationship to obtain the linear relationship equation required for practical application: H2 = A2 X2+B2; In the linear relationship equation: H2 – The calculated value of the crack depth dimension to be evaluated, in mm; X2 = 20 lg(A defect / Aref), the value is expressed in decibels (dB); A defect - The signal wave height of the crack, expressed as a percentage; Aref – Signal height of the reference structure, expressed as a percentage; A2 – A constant derived from the laboratory analysis results of the actual failed fracture of the spindle and the decibel level of the defect signal wave from PAUT scanning, used to replace A1; B2 – A constant derived from laboratory analysis of the actual failed fracture of the spindle and the decibel level of the defect signal wave from PAUT scanning, used to replace B1.

7. The phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine according to claim 1, characterized in that, In step S3, the specific process of the tip diffraction method is as follows: S301 Check for diffraction signals in defects: If a crack is found in a selected area, perform a tip diffraction scan on the selected area and evaluate the data obtained from the scan to check for diffraction signals in the data. S302 outputs the following values: If a diffraction signal is detected, then the cursor is used to read the values ​​of the location of the strongest point of the crack opening acoustic wave and the location of the strongest point of the diffraction signal. S303 Calculation Results: Finally, the measured value H is calculated using the following formula; H = Uref - Umea; In the formula: H—Measured crack depth, in mm; Uref—The numerical value of the location of the strongest sound wave at the crack opening, used as a reference position for calculation, in mm; Umea—The numerical value of the location of the strongest diffraction signal, used as the measurement location for calculation, in mm.

8. The phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine according to claim 1, characterized in that, In S3, the PAUT probe used in the tip diffraction method has a minimum number of 32 elements, a minimum excitation aperture greater than 19.2 mm, and uses the central hole of the spindle as the acoustic wave reflecting surface.

9. The phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine generator according to claim 1, characterized in that, S4 includes the following steps: S401: First, prepare the encoder and the scanning carriage, and set and calibrate the probe system of the device, and calibrate the encoder of the scanning carriage; S402: Clean the surface of the spindle to remove foreign objects and ensure good coupling between the wedge and the spindle; S403: Measure the axial position of the probe on the shaft of the main shaft, and mark each of the scanning trajectory lines on the shaft; at the same time, mark the scanning starting point, which is the 12 o'clock position on the cross section of the main shaft when a selected blade of the wind turbine is vertically downward.

10. The phased array ultrasonic method for detecting cracks in the main shaft of a wind turbine according to claim 1, characterized in that, S5 includes the following steps: S501: After selecting a segment that has not yet been scanned, lock the impeller of the wind turbine and use a brake to stop the impeller from rotating, so as to avoid affecting the scanning effect; S502: Scan the selected segment; in addition, ensure that the scanning start line of the selected segment and the wedge center line are aligned for each probe scanning operation; S503: Use standard sensitivity for scanning. The scanning gain is controlled within ±3dB of the scanning sensitivity defined in S1. After one scan, check the data quality on the screen and verify whether the waveform height of the structural signal meets the requirements, whether there are defective signals, and whether the defective signals are saturated. If either the structural signal or the defective signal is saturated, reduce the scanning sensitivity and rescan. If neither the structural signal nor the defective signal is saturated, but the waveform height of the structural signal is not up to the requirements, increase the scanning sensitivity to make the structural signal have a qualified waveform height and rescan. Finally, record and store the qualified data, and repeat the scan three times while maintaining the scanning gain and recording the data. S504 High-gain scanning operation: If no defect signal is found, skip directly to step S6; if a defect signal is found in the target area, increase the scanning gain and perform tip diffraction scanning; the set value of the scanning gain = the gain value when the full-screen waveform height of the defect signal is 80% + (18~23) dB; scan three times and store the scanning data; S505: Repeat steps S503 and S504 three times; S506: Scan the next segment and repeat steps S501 to S505.

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