Self-adaptive bolt defect ultrasonic detection method

Abstract

The invention discloses a self-adaptive bolt defect ultrasonic detection method, which comprises the following steps: S1, acquiring attribute data of bolts of different material models, the attribute data comprising material types, lengths and diameters; s2, based on the detection depth and width of the probe at different angles, combining with the attribute data of the bolt, and fitting to establish a probe angle adjustment model; s3, establishing a defect sensitivity model based on the reflection time and the reflection amplitude of probe scanning; the reflection time and the reflection amplitude scanned by the probe are obtained through the bolt experiment block, and an amplitude-time reference curve is established; the method comprises the following steps: scanning a defective bolt through a probe to obtain an actual reflection amplitude of the bolt, and establishing an amplitude-time actual curve; compared with the prior art, by dynamically adjusting the angle of the probe and combining a temperature compensation mechanism, the method can effectively improve the detection precision, is suitable for bolts of various different specifications, and is wide in temperature application range.

Description

Technical Field

[0001] The present invention relates to the field of bolt defect detection, and in particular to an adaptive bolt defect ultrasonic detection method. Background Art

[0002] Bolts are critical fasteners in pressure-bearing equipment, and fatigue cracks can lead to catastrophic accidents. Traditional inspection requires disassembly of the bolts followed by magnetic particle or penetrant testing. Disassembly at high altitudes is highly risky, and reassembly can increase the clearance (>0.1mm), accelerating bolt failure. Bolts used for extended periods of time are prone to rust at the thread root, which is difficult to remove, resulting in a missed inspection rate exceeding 30%.

[0003] Existing ultrasonic technology for detecting bolt defects mostly performs in-situ testing, which has limitations. The probe has a fixed angle and cannot adapt to bolts of different specifications, resulting in a deep defect detection rate of less than 50%. Moreover, most bolts that need to be inspected often serve in high-temperature environments, which can affect ultrasonic testing and lead to errors. Summary of the Invention

[0004] The purpose of the present invention is to propose an adaptive ultrasonic detection method for bolt defects, which is aimed at addressing the existing ultrasonic detection of bolts, which is mostly in-situ detection with a fixed probe angle and has limitations. It is also affected by temperature, resulting in errors.

[0005] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0006] An adaptive ultrasonic detection method for bolt defects includes the following specific steps:

[0007] S1. Obtaining attribute data of bolts of different materials and models, wherein the attribute data includes material type, length L and diameter D, and obtaining an aspect ratio r=L / D;

[0008] S2. Based on the detection depth and width of the probe at different angles and combined with the bolt property data, a probe angle adjustment model is fitted and established;

[0009] S3. Establish a defect sensitivity model based on the reflection time and reflection amplitude of the probe scan. Obtain the reflection time and reflection amplitude of the probe scan through the bolt test block and establish an amplitude-time reference curve. Obtain the actual reflection amplitude of the bolt by scanning the defective bolt with the probe and establish an actual amplitude-time curve. Compare the actual curve with the reference curve to determine whether a defect exists.

[0010] S4. Place the probe at the same angle and scan the bolt end face to be tested at a constant speed; obtain the probe scanning time, probe angle, and actual temperature;

[0011] S5. Calculate the defect depth based on the sound velocity, probe scanning time, probe angle, and actual temperature corresponding to the bolt material type;

[0012] S6. When scanning, the probe rotates at a constant step. The probe rotation angle position is recorded by the probe rotary encoder to obtain the real-time rotation angle of the probe. Combined with the bolt diameter, probe scanning time, the sound velocity corresponding to the bolt material type, and the probe placement angle, the radial position and circumferential angular position of the defect are calculated.

[0013] As a further preferred embodiment of the present invention, S2 specifically includes:

[0014] S21. Using carbon steel as a benchmark, calibrate the effects of different materials on sound wave propagation through experiments to form a calibration coefficient k;

[0015] S22. Obtaining optimal probe placement angle data for bolts with different aspect ratios, and grouping the obtained data into two groups: a training set and a test set.

[0016] S23, performing multiple fitting on the test set to obtain a probe angle adjustment model;

[0017] S24. Use a practical test set to test and verify the probe angle adjustment model, and update and optimize the probe angle adjustment model.

[0018] As a further preference of the present invention, a quadratic polynomial or a linear formula is used for fitting, preferably a quadratic polynomial.

[0019] As a further preferred embodiment of the present invention, when 3≤aspect ratio r≤25, the probe angle adjustment model is:

[0020] When the temperature is between -20℃ and 80℃:

[0021]

[0022] When the temperature is >80℃:

[0023] θ 高 =θ 常 +0.2°, every 40°C increase, θ 高 Increase 0.2°

[0024] When the temperature is less than 20℃:

[0025] θ 低 =θ 常 -0.1°, for every 20°C decrease, θ 低 Decrease by 0.05°.

[0026] As a further preferred embodiment of the present invention, when the aspect ratio r<3 or the aspect ratio r>25, a dual-angle probe combination is used for detection.

[0027] As a further preferred embodiment of the present invention, S3 specifically includes:

[0028] S31, making a bolt test block, and opening a plurality of grooves in a stepped manner on the bolt test block;

[0029] S32, the probe is scanned at the optimal placement angle to obtain reflection time and reflection amplitude;

[0030] S33, pre-processing the reflection time and reflection amplitude, and grouping them according to whether there is a groove, to form data of the non-grooved area and data of the grooved area;

[0031] S34, calculating the mean value C of the reflection amplitude in the data of the non-grooving area;

[0032] S35. Perform attenuation compensation on the reflection amplitude in the data of the grooved area through weighted processing; then perform normalization processing; and obtain an amplitude-time reference curve S(t) by fitting, S(t)=A×e^(-B×t)+C;

[0033] Where A is the initial amplitude coefficient, B is the material attenuation coefficient, and t is the ultrasonic propagation time;

[0034] Since the depth of each groove is different, the acoustic wave signal has a certain attenuation. Through weighted processing, the attenuation of the acoustic wave signal is compensated, effectively improving the measurement accuracy.

[0035] S36. Scan the defective bolt with a probe to obtain the actual reflection amplitude of the bolt and establish an actual amplitude-time curve;

[0036] S37. Compare the actual curve with the reference curve and perform fitting to obtain defect judgment conditions;

[0037] The defect judgment condition is: when the actual curve > the reference curve + 6, it is judged that a defect exists at that location.

[0038] As a further preferred embodiment of the present invention, in said S4, calibration is required before and during scanning; calibration is performed every 10 minutes during scanning;

[0039] A process hole is opened on the end face of the bolt, and calibration is performed by measuring the reflection time of the process hole.

[0040] As a further preferred embodiment of the present invention, the defect depth d is

[0041] d=(v×t×cosθ×(1+kΔT)) / 2,

[0042] Where v is the material sound velocity, t is the peak time of the defect signal, that is, the reflection time, θ is the probe placement angle, k is the temperature compensation coefficient, and ΔT is the temperature deviation, that is, the actual temperature is -20°C.

[0043] As a further preferred embodiment of the present invention, the defect radial position u is

[0044] The circumferential angular position of the defect α=β, where β is the real-time rotation angle of the probe.

[0045] The adaptive ultrasonic detection method for bolt defects proposed in the present invention has the following beneficial effects compared with the prior art:

[0046] 1. The present invention can effectively improve detection accuracy by dynamically adjusting the probe angle and combining it with a temperature compensation mechanism. It is suitable for bolts of various specifications and a wide temperature range.

[0047] 2. By setting the reference curve, the sensitivity of defect judgment is improved, the interference of thread structure is reduced, the accuracy is improved, and the defect splashing rate can be increased;

[0048] 3. The present invention establishes a gradient weight compensation mechanism to eliminate measurement errors and improve accuracy;

[0049] 4. The detection method and calibration method of the present invention are simple, the detection time is short, and the calculation speed is fast;

[0050] 5. Improve engineering reliability through temperature compensation. DETAILED DESCRIPTION

[0051] The present invention is described in detail with reference to the following specific examples.

[0052] An adaptive ultrasonic detection method for bolt defects includes the following specific steps:

[0053] S1. Obtaining attribute data of bolts of different materials and models, wherein the attribute data includes material type, length L and diameter D, and obtaining an aspect ratio r=L / D.

[0054] S2. Based on the detection depth and width of the probe at different angles and combined with the property data of the bolt, a probe angle adjustment model is fitted and established.

[0055] The S2 specifically includes:

[0056] S21. Taking carbon steel as the benchmark, the effects of different materials on sound wave propagation are calibrated through experiments to form a calibration coefficient k.

[0057] S22. Obtain optimal probe placement angle data for bolts with different aspect ratios, and group the obtained data into two groups: one group is a training set, and the other group is a test set.

[0058] S23. Perform multiple fitting on the test set to obtain a probe angle adjustment model. A quadratic polynomial or a linear formula is used for fitting, preferably a quadratic polynomial.

[0059] S24. Use a practical test set to test and verify the probe angle adjustment model, and update and optimize the probe angle adjustment model.

[0060] When 3≤ aspect ratio r≤25, the probe angle adjustment model is:

[0061] When the temperature is between -20℃ and 80℃:

[0062]

[0063] When the temperature is >80℃:

[0064] θ 高 =θ 常 +0.2°, every 40°C increase, θ 高 Increase 0.2°

[0065] When the temperature is less than 20℃:

[0066] θ 低 =θ 常 -0.1°, for every 20°C decrease, θ 低 Decrease by 0.05°.

[0067] When the aspect ratio r<3 or the aspect ratio r>25, a dual-angle probe combination is used for detection.

[0068] S3. Establish a defect sensitivity model based on the reflection time and reflection amplitude of the probe scan. Obtain the reflection time and reflection amplitude of the probe scan through the bolt test block and establish an amplitude-time reference curve. Scan the bolt with the defect through the probe to obtain the actual reflection amplitude of the bolt and establish an actual amplitude-time curve. Compare the actual curve with the reference curve to determine whether there is a defect.

[0069] The S3 specifically includes:

[0070] S31. Make a bolt test block, and open a plurality of grooves on the bolt test block in a stepped manner.

[0071] S32. The probe is scanned at an optimal placement angle to obtain reflection time and reflection amplitude.

[0072] S33 , pre-processing the reflection time and reflection amplitude, and grouping them according to whether there is a groove or not, to form data of a non-grooved area and data of a grooved area.

[0073] S34. Calculate the mean value C of the reflection amplitude in the data of the non-grooved area.

[0074] S35. Perform attenuation compensation on the reflection amplitude in the grooved area data by weighted processing; then perform normalization processing; and obtain the amplitude-time reference curve S(t) by fitting, S(t) = A×e^(-B×t)+C.

[0075] Where A is the initial amplitude coefficient, B is the material attenuation coefficient, and t is the ultrasonic propagation time.

[0076] Since the depth of each groove is different, the acoustic wave signal has a certain attenuation. Through weighted processing, the attenuation of the acoustic wave signal is compensated, effectively improving the measurement accuracy.

[0077] S36. Scan the defective bolt with a probe to obtain the actual reflection amplitude of the bolt and establish an actual amplitude-time curve.

[0078] S37. By comparing the actual curve with the reference curve, fitting is performed to obtain defect judgment conditions.

[0079] The defect judgment condition is: when the actual curve > the reference curve + 6, it is judged that a defect exists at that location.

[0080] S4. Place the probe at the same angle and scan the bolt end face to be tested at a constant speed; obtain the probe scanning time, probe angle, and actual temperature.

[0081] Calibration is required before and during scanning; calibration is done every 10 minutes during scanning;

[0082] A process hole is opened on the end face of the bolt, and calibration is performed by measuring the reflection time of the process hole.

[0083] As a further preferred embodiment of the present invention, the defect depth d is

[0084] d=(v×t×cosθ×(1+kΔT)) / 2,

[0085] Where v is the material sound velocity, t is the peak time of the defect signal, that is, the reflection time, θ is the probe placement angle, k is the temperature compensation coefficient, and ΔT is the temperature deviation, that is, the actual temperature is -20°C.

[0086] S5. Calculate the defect depth based on the sound velocity, probe scanning time, probe angle, and actual temperature corresponding to the bolt material type.

[0087] S6. When scanning, the probe rotates at a constant step. The probe rotation angle position is recorded by the probe rotary encoder to obtain the real-time rotation angle of the probe. Combined with the bolt diameter, probe scanning time, the sound velocity corresponding to the bolt material type, and the probe placement angle, the radial position and circumferential angular position of the defect are calculated.

[0088] Defect radial position u,

[0089] The circumferential angular position of the defect α=β, where β is the real-time rotation angle of the probe.

[0090] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of protection of the present invention.

Claims

1. An adaptive ultrasonic detection method for bolt defects, characterized in that: The specific steps include: S1. Obtaining attribute data of bolts of different materials and models, wherein the attribute data includes material type, length L and diameter D, and obtaining an aspect ratio r=L / D; S2. Based on the detection depth and width of the probe at different angles and combined with the bolt attribute data, a probe angle adjustment model is fitted and established; S3. Establish a defect sensitivity model based on the reflection time and reflection amplitude of the probe scan. Obtain the reflection time and reflection amplitude of the probe scan through the bolt test block and establish an amplitude-time reference curve. Obtain the actual reflection amplitude of the bolt by scanning the defective bolt with the probe and establish an actual amplitude-time curve. Compare the actual curve with the reference curve to determine whether a defect exists. S4. Place the probe at the same angle and scan the bolt end face to be tested at a constant speed; obtain the probe scanning time, probe angle, and actual temperature; S5. Calculate the defect depth based on the sound velocity, probe scanning time, probe angle, and actual temperature corresponding to the bolt material type; S6. When scanning, the probe rotates at a constant step. The probe rotation angle position is recorded by the probe rotary encoder to obtain the real-time rotation angle of the probe. Combined with the bolt diameter, probe scanning time, the sound velocity corresponding to the bolt material type, and the probe placement angle, the radial position and circumferential angular position of the defect are calculated.

2. The method for adaptive ultrasonic detection of bolt defects according to claim 1, characterized in that: The S2 specifically includes: S21. Using carbon steel as a benchmark, calibrate the effects of different materials on sound wave propagation through experiments to form a calibration coefficient k; S22. Obtaining optimal probe placement angle data for bolts with different aspect ratios, and grouping the obtained data into two groups: a training set and a test set. S23, performing multiple fitting on the test set to obtain a probe angle adjustment model; S24. Use a practical test set to test and verify the probe angle adjustment model, and update and optimize the probe angle adjustment model.

3. The method for adaptive ultrasonic detection of bolt defects according to claim 2, characterized in that: A quadratic polynomial or a linear formula is used for fitting, with the quadratic polynomial being preferred.

4. The method for adaptive ultrasonic detection of bolt defects according to claim 2, characterized in that: When 3≤ aspect ratio r≤25, the probe angle adjustment model is: When the temperature is between -20℃ and 80℃: When the temperature is >80℃: θ 高 =θ 常 +0.2°, every 40°C increase, θ 高 Increase 0.2° When the temperature is less than 20℃: θ 低 =θ 常 -0.1°, for every 20°C decrease, θ 低 Decrease by 0.05°.

5. The method for adaptive ultrasonic detection of bolt defects according to claim 2, characterized in that: When the aspect ratio r<3 or the aspect ratio r>25, a dual-angle probe combination is used for detection.

6. The method for adaptive ultrasonic detection of bolt defects according to claim 1, characterized in that: The S3 specifically includes: S31, making a bolt test block, and opening a plurality of grooves in a stepped manner on the bolt test block; S32, the probe is scanned at the optimal placement angle to obtain reflection time and reflection amplitude; S33, pre-processing the reflection time and reflection amplitude, and grouping them according to whether there is a groove, to form data of the non-grooved area and data of the grooved area; S34, calculating the mean value C of the reflection amplitude in the data of the non-grooving area; S35. Perform attenuation compensation on the reflection amplitude in the data of the grooved area through weighted processing; then perform normalization processing; and obtain an amplitude-time reference curve S(t) by fitting, S(t)=A×e^(-B×t)+C; Where A is the initial amplitude coefficient, B is the material attenuation coefficient, and t is the ultrasonic propagation time; Since the depth of each groove is different, the acoustic wave signal has a certain attenuation. Through weighted processing, the attenuation of the acoustic wave signal is compensated, effectively improving the measurement accuracy. S36. Scan the defective bolt with a probe to obtain the actual reflection amplitude of the bolt and establish an actual amplitude-time curve; S37. Compare the actual curve with the reference curve and perform fitting to obtain defect judgment conditions; The defect judgment condition is: when the actual curve > the reference curve + 6, it is judged that a defect exists at that location.

7. The method for adaptive ultrasonic detection of bolt defects according to claim 1, characterized in that: In S4, calibration is required before and during scanning; calibration is performed every 10 minutes during scanning; A process hole is opened on the end face of the bolt, and calibration is performed by measuring the reflection time of the process hole.

8. The method for adaptive ultrasonic detection of bolt defects according to claim 1, characterized in that: The defect depth d is determined by d=(v×t×cosθ×(1+kΔT)) / 2, Where v is the material sound velocity, t is the peak time of the defect signal, that is, the reflection time, θ is the probe placement angle, k is the temperature compensation coefficient, and ΔT is the temperature deviation, that is, the actual temperature is -20°C.

9. The method for adaptive ultrasonic detection of bolt defects according to claim 1, characterized in that: The radial position u of the defect, The circumferential angular position of the defect α=β, where β is the real-time rotation angle of the probe.

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