Differential signal feature-based micro-defect pulsed eddy current response signal analysis method and system

Abstract

The invention discloses a differential signal characteristic-based micro-defect pulsed eddy current response signal analysis method and system, and relates to the technical field of nondestructive testing, and the method comprises the following steps: classifying test pieces with processing defects according to defect widths, and selecting a plurality of test pieces in each class to form a sample group with defect-free reference pieces of the same type; and carrying out pulsed eddy current detection on the sample group to obtain a time-domain or frequency-domain signal curve so as to obtain a corresponding difference peak value. And finally, constructing a material defect parameter inversion model, and calculating defect parameters by using a signal difference peak value. According to the invention, the conversion from the detection signal to the defect parameter is realized, the micro defect can be efficiently and accurately analyzed, the precision and efficiency of the micro defect detection and evaluation based on the differential signal characteristics can be improved, and an effective technical means is provided for the detection and analysis of the micro defect.

Description

Technical Field

[0001] The present invention relates to the technical field of non-destructive testing, and more specifically, to a method and system for analyzing the pulsed eddy current response signal of micro-defects based on differential signal characteristics. Background Art

[0002] Currently, in industrial production and equipment maintenance, the detection of micro-defects inside materials is of great importance. Traditional eddy current detection methods often face problems such as insufficient sensitivity and susceptibility to signal interference when detecting micro-defects. Pulse eddy current technology can provide rich time-domain information to a certain extent, improving the detection effect. However, for the weak response signals generated by micro-defects, how to accurately analyze and extract effective features remains a challenge. Existing signal analysis methods may not be able to effectively distinguish noise and defect signals when processing the pulsed eddy current micro-defect response signals, resulting in inaccurate detection results.

[0003] Therefore, how to improve the accuracy of the detection results of micro-defects inside materials is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a method and system for analyzing the pulsed eddy current response signal of micro-defects based on differential signal characteristics to solve the problems existing in the background art.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for analyzing the pulsed eddy current response signal of micro-defects based on differential signal characteristics includes:

[0007] Obtain a number of test pieces with processing defects, classify the test pieces according to the defect width and defect depth; then select a number of test pieces in each category, and select a non-defective test piece of the same type as a reference piece for comparison; take each test piece and the reference piece with a comparison relationship as a sample group;

[0008] Perform pulsed eddy current detection on the samples in each of the sample groups in sequence, obtain the time-domain signal curve or frequency-domain signal curve of the test signal, and obtain the time-domain signal differential peak value or frequency-domain signal fundamental frequency differential peak value between the test signal and the reference signal;

[0009] Construct an inversion model for the defect parameters of the material to be tested, and calculate the defect parameters according to the signal differential peak value of the material to be tested.

[0010] Optionally, the obtaining of several test pieces with processing defects specifically includes: the samples with a control relationship in each sample group are two workpieces with the same structure and material, and the only difference is that one contains defects and the other does not; or the samples with a control relationship in each sample group are two regions in one workpiece, one containing defects and the other not containing defects.

[0011] Optionally, the defects contained in the samples in each sample group have different depths.

[0012] Optionally, the performing of pulsed eddy current testing specifically includes:

[0013] Generating a pulsed excitation signal with adjustable frequency and duty cycle;

[0014] Exciting the probe coil to generate an excitation magnetic field, generating eddy currents inside the test piece, and thus obtaining a test signal;

[0015] Extracting the test signal to obtain the time-domain signal curve or frequency-domain signal curve of the test signal;

[0016] Performing differential processing on the time-domain signal curve of the test signal and the time-domain signal curve of the reference signal to obtain the time-domain signal differential peak value.

[0017] Optionally, it further includes performing differential processing on the frequency-domain signal curve of the test signal and the frequency-domain signal curve of the reference signal to extract the fundamental frequency peak value, and obtaining the frequency-domain signal fundamental frequency differential peak value.

[0018] Optionally, the constructing of the inversion model for the defect parameters of the material to be tested is specifically expressed as:

[0019] H = kh + c;

[0020] Where H is the extracted differential peak value, h is the surface defect depth or width corresponding to it, k is the slope of the straight line, and c is the intercept.

[0021] Optionally, it further includes when the surface defect width changes solely, using the time-domain signal differential peak value as the input of the inversion model for the defect parameters of the material to be tested to realize the quantitative analysis of the unknown defect width;

[0022] When the surface defect depth changes solely, using the frequency-domain signal fundamental frequency differential peak value as the input of the inversion model for the defect parameters of the material to be tested to realize the quantitative analysis of the unknown defect depth.

[0023] Optionally, it further includes performing amplification and filtering processing on the test signal.

[0024] A pulsed eddy current response signal analysis system for micro-defects based on differential signal characteristics, comprising:

[0025] A preparation module, which obtains a number of test pieces with processing defects, classifies the test pieces according to the defect width and defect depth; then selects a number of test pieces from each category and selects a defect-free test piece of the same type as a reference piece for comparison; and takes each test piece and the reference piece with a control relationship as a sample group.

[0026] A pulsed eddy current detection module, which sequentially performs pulsed eddy current detection on the samples in each of the above sample groups, obtains the time-domain signal curve or frequency-domain signal curve of the test signal, and obtains the time-domain signal differential peak value or frequency-domain signal fundamental frequency differential peak value between the test signal and the reference signal.

[0027] A defect parameter calculation module, which constructs an inversion model for defect parameters of the material to be measured and calculates the defect parameters according to the signal differential peak value of the material to be measured.

[0028] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a method and system for analyzing the pulsed eddy current response signal of micro defects based on the characteristics of differential signals. First, the test pieces with processing defects are classified according to the defect width, and several test pieces are selected from each category and combined with a defect-free reference piece of the same type to form a sample group. This grouping method can effectively compare the defective and defect-free situations and has strong pertinence. Secondly, pulsed eddy current detection is performed on the sample group, and the time-domain or frequency-domain signal curve can be obtained, and then the corresponding differential peak value can be obtained. Through this detection and calculation, the difference characteristics of the defective samples relative to the defect-free samples in the signal can be accurately extracted, providing reliable data for subsequent analysis. Finally, an inversion model for defect parameters of the material is constructed, and the defect parameters are calculated using the signal differential peak value, realizing the conversion from the detection signal to the defect parameters, which can efficiently and accurately analyze micro defects, helping to improve the accuracy and efficiency of the detection and evaluation of micro defects based on the characteristics of differential signals, and providing an effective technical means for the detection and analysis of micro defects. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained according to the provided drawings without creative efforts.

[0030] Figure 1 It is the flowchart of the method provided by the present invention. Detailed Embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] An embodiment of the present invention discloses a method for analyzing the pulsed eddy current response signal of a micro defect based on the differential signal feature, as Figure 1 shown, including:

[0033] Obtain a number of test pieces with processing defects, and classify the test pieces according to the defect width and defect depth; then select a number of test pieces in each category, and select a same-type test piece without defects as a reference piece for comparison; take each test piece and the reference piece with a comparison relationship as a sample group;

[0034] Perform pulsed eddy current detection on the samples in each sample group in turn, obtain the time-domain signal curve or frequency-domain signal curve of the test signal, and obtain the time-domain signal differential peak or frequency-domain signal fundamental frequency differential peak between the test signal and the reference signal;

[0035] Construct an inversion model for the defect parameters of the material to be measured, and calculate the defect parameters according to the signal differential peak of the material to be measured.

[0036] In a specific embodiment, obtaining a number of test pieces with processing defects specifically includes: the samples with a comparison relationship in each sample group are two workpieces with the same structure and material, and the only difference is that one contains defects and the other does not contain defects. Or the samples with a comparison relationship in each sample group are two regions in a workpiece, one containing defects and the other not containing defects.

[0037] In the solution of this embodiment, each defective test piece to be detected requires a defect-free test piece as a reference for the signal; only in this way can the signal of the defective part be obtained through the differential processing of the detection signals of the two. Therefore, the test piece and the reference piece in the sample group should be workpieces that are exactly the same except for the defects, so as to exclude the influence of other factors such as structure or material on the obtained detection signal.

[0038] In actual detection applications, a completely qualified workpiece can be used as a reference piece, and a workpiece with defects can be used as a test piece. The two together form a sample group. In other embodiments, for workpieces with symmetric structures, two regions with a symmetric relationship in the workpiece, one containing defects and the other not, can also be used as a sample group. The performance consistency of the same batch or the same workpiece is usually good; therefore, setting the sample group in this way has a better control effect on excluding interference factors. At the same time, in order to obtain information about workpieces with different defect depths, the defects contained in the samples in each selected sample group have different depths.

[0039] In a specific embodiment, the pulsed eddy current detection specifically includes:

[0040] Generating a pulsed excitation signal with adjustable frequency and duty cycle;

[0041] Exciting the probe coil to generate an excitation magnetic field, generating eddy currents inside the workpiece to be tested, and thus obtaining a test signal;

[0042] Extracting the test signal to obtain the time-domain signal curve or frequency-domain signal curve of the test signal;

[0043] Performing differential processing on the time-domain signal curve of the test signal and the time-domain signal curve of the reference signal to obtain the time-domain signal differential peak value.

[0044] It also includes performing differential processing on the frequency-domain signal curve of the test signal and the frequency-domain signal curve of the reference signal by extracting the fundamental frequency peak value to obtain the frequency-domain signal fundamental frequency differential peak value.

[0045] Since when the defect depth remains unchanged and the width is the single variable, the relationship curve between the obtained time-domain signal differential peak value and the surface defect width has good linearity, and there is no need to perform differential processing on the frequency-domain signal anymore. When the surface defect width changes alone, the time-domain signal differential peak value is used as the input of the defect parameter inversion model of the material to be tested to realize the quantitative analysis of the unknown defect width; while when the defect width remains unchanged and the depth is the single variable, the relationship curve between the frequency-domain signal fundamental frequency differential peak value and the surface defect depth has better linearity than the relationship curve between the time-domain signal differential peak value and the surface defect depth. Therefore, when the surface defect depth changes alone, the frequency-domain signal fundamental frequency differential peak value is used as the input of the defect parameter inversion model of the material to be tested to realize the quantitative analysis of the unknown defect width.

[0046] In a specific embodiment, a test piece containing known defects with the same width but different depths is selected. At a certain detection speed, the signals for detecting defects with the same width but different depths in the horizontal and / or vertical directions are measured, and the sensor installation position and the corresponding linear slope and intercept parameters are determined, so as to construct the defect parameter inversion model of the material to be tested, which is specifically expressed as:

[0047] H = kh + c;

[0048] Where H is the extracted differential peak value, h is the corresponding surface defect depth or width, k is the slope of the straight line, and c is the intercept.

[0049] Based on the differential peak value of the material to be measured, the defect parameter information is inversely retrieved, and the defect parameters of the material to be measured are calculated, specifically expressed as:

[0050] h = (H - c) / k

[0051] Substitute the differential peak value H into the above formula to perform the inverse retrieval of the defect parameter information, and the value of the defect parameter h can be obtained, thus realizing the quantitative identification of the material to be measured.

[0052] In a specific embodiment, since the excitation magnetic field is relatively weak, the voltage signal output by the Hall sensor is also relatively small, often only a few dozen millivolts, and there are also many high-frequency interference signals mixed in it. Therefore, it is necessary to perform amplification and filtering processing on the signal output by the sensor probe, that is, to perform amplification and filtering processing on the obtained reference signal, detection signal, and test signal, filter out the clutter interference signals in the signal and amplify it to make it reach the measurement range of the subsequent data acquisition module. To achieve this function, in the embodiment of the present invention, an amplification circuit with the instrumentation amplifier AD620 as the core can be used to amplify the signal, and a second-order low-pass filter composed of the high-precision operational amplifier OP07 is used to filter out the interference signals.

[0053] In a specific embodiment, an experimental system is built, which mainly includes three parts: an excitation signal generating device composed of a pulse signal generator and a power amplifier, a pulsed eddy current detection probe composed of an excitation coil and a magnetic field sensor, and a data acquisition device; the excitation coil is connected to the excitation signal generating device, and the magnetic field sensor at the center of the bottom of the excitation coil is connected to the data acquisition device; first, the pulse signal generator generates a pulsed excitation time-domain signal, which is obtained from the above analysis. The power amplifier is used to amplify the pulsed excitation time-domain signal and transmit it to the excitation coil. At the same time, the magnetic field sensor detects the magnetic field magnitude on the surface of the test piece, and the detected signal is collected through the data acquisition device.

[0054] A pulsed eddy current response signal analysis system based on differential signal characteristics, comprising:

[0055] A preparation module, which obtains a number of test pieces with processing defects, classifies the test pieces according to the defect width and defect depth; then selects a number of test pieces in each category, and selects a defect-free same-type test piece as a reference piece for comparison; each test piece and the reference piece with a comparison relationship form a sample group;

[0056] The pulsed eddy current detection module sequentially performs pulsed eddy current detection on the samples in each sample group to obtain the time-domain signal curve or frequency-domain signal curve of the test signal, and obtains the time-domain signal differential peak or frequency-domain signal fundamental frequency differential peak between the test signal and the reference signal.

[0057] The defect parameter calculation module constructs an inversion model for the defect parameters of the material to be tested and calculates the defect parameters according to the signal differential peak of the material to be tested.

[0058] In the present specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference can be made to the description in the method part.

[0059] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for analyzing pulsed eddy current response signals of tiny defects based on differential signal characteristics, characterized in that: include: Obtain a number of test pieces with processing defects, and classify the test pieces according to defect width and defect depth; Then select several test pieces in each category and select a test piece of the same type without defects as a reference piece for comparison; each test piece and the reference piece with a comparison relationship are a sample group; Performing pulsed eddy current testing on the samples in each sample group in turn, obtaining a time domain signal curve or a frequency domain signal curve of the test signal, and obtaining a time domain signal difference peak value or a frequency domain signal fundamental frequency difference peak value between the test signal and a reference signal; Construct a defect parameter inversion model for the material to be tested, and calculate the defect parameters based on the signal differential peak value of the material to be tested.

2. The method for analyzing pulsed eddy current response signals of tiny defects based on differential signal characteristics according to claim 1 is characterized in that: The obtaining of a plurality of test pieces with processing defects specifically includes: the samples with a control relationship in each sample group are two workpieces with the same structure and material, the only difference being that one of them contains defects and the other does not; or the samples with a control relationship in each sample group are two regions with defects and two regions without defects in a workpiece.

3. The method for analyzing pulsed eddy current response signals of tiny defects based on differential signal characteristics according to claim 2 is characterized in that: The samples in each of the sample groups contain defects with different depths.

4. The method for analyzing pulsed eddy current response signals of tiny defects based on differential signal characteristics according to claim 1 is characterized in that: The pulsed eddy current detection specifically comprises: Generate a pulse excitation signal with adjustable frequency and duty cycle; The probe coil is excited to generate an exciting magnetic field, which generates eddy currents inside the test piece, thereby obtaining a test signal; Extracting the test signal to obtain a time domain signal curve or a frequency domain signal curve of the test signal; The time domain signal curve of the test signal and the time domain signal curve of the reference signal are differentially processed to obtain the time domain signal differential peak value.

5. The method for analyzing pulsed eddy current response signals of tiny defects based on differential signal characteristics according to claim 4 is characterized in that: The method also includes extracting the fundamental frequency peak value of the frequency domain signal curve of the test signal and the frequency domain signal curve of the reference signal and performing differential processing to obtain the fundamental frequency difference peak value of the frequency domain signal.

6. The method for analyzing pulsed eddy current response signals of tiny defects based on differential signal characteristics according to claim 1 is characterized in that: The construction of the defect parameter inversion model of the material to be tested is specifically expressed as follows: H = kh + c; Where H is the extracted differential peak, h is the corresponding surface defect depth or width, k is the slope of the straight line, and c is the intercept.

7. The method for analyzing pulsed eddy current response signals of tiny defects based on differential signal characteristics according to claim 1 is characterized in that: It also includes the use of the time domain signal difference peak as the input of the defect parameter inversion model of the material to be tested when the width of the surface defect changes in a single way, so as to achieve quantitative analysis of the unknown defect width; When the depth of the surface defect changes in a single way, the peak value of the fundamental frequency difference of the frequency domain signal is used as the input of the defect parameter inversion model of the material to be tested to achieve quantitative analysis of the unknown defect depth.

8. The method for analyzing pulsed eddy current response signals of tiny defects based on differential signal characteristics according to claim 1 is characterized in that: The method also includes amplifying and filtering the test signal.

9. A system for analyzing pulsed eddy current response signals of tiny defects based on differential signal characteristics, characterized in that: A method for analyzing a pulsed eddy current response signal of a tiny defect based on differential signal characteristics as described in any one of claims 1 to 8 comprises: A preparation module is provided to obtain a number of test pieces with processing defects, and classify the test pieces according to defect width and defect depth; then a number of test pieces are selected in each category, and a test piece of the same type without defects is selected as a reference piece for comparison; each test piece and the reference piece having a comparison relationship are regarded as a sample group; A pulsed eddy current detection module performs pulsed eddy current detection on each sample in the sample group in turn, obtains a time domain signal curve or a frequency domain signal curve of the test signal, and obtains a time domain signal difference peak value or a frequency domain signal fundamental frequency difference peak value between the test signal and the reference signal; The defect parameter calculation module constructs a defect parameter inversion model for the material to be tested and calculates the defect parameters according to the signal differential peak value of the material to be tested.

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