Metal component defect depth detection system and method based on sweep frequency pulsed eddy current

Abstract

The invention relates to a metal component defect depth detection system and method based on sweep frequency pulsed eddy current. The system comprises a pulse eddy current probe module, a pulse signal excitation module, a current amplification module, a voltage amplification module, a band-pass filtering module and a signal acquisition module. The pulsed eddy current probe module comprises an excitation probe and a receiving probe which are respectively used for transmitting excitation signal pulsed eddy current and receiving sampling data; the pulse signal excitation module is connected with the upper computer module and the current amplification module, and is used for receiving the control command and exciting pulse signal current to control probe detection; the current amplification module is used for amplifying the pulse current; the voltage amplification module is connected with the receiving probe and the band-pass filtering module and is used for amplifying the induced voltage; the band-pass filtering module is used for frequency screening; and the signal acquisition module is responsible for performing format conversion on the sampling data and uploading the sampling data to an upper computer. The system can realize excitation and signal acquisition for different depth areas, and accurately determine the characteristic frequency of defect depth.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of pulsed eddy current nondestructive testing, in particular to a metal component defect depth detection system and method based on swept-frequency pulsed eddy current. BACKGROUND

[0002] Eddy current testing technology, as an important nondestructive testing method, plays a key role in metal component quality evaluation and defect detection. Based on electromagnetic induction principle, the technology measures the change of induced eddy current to determine the internal structure state of the material. Studies have shown that the penetration ability of eddy current in a conductor can be approximately described by the skin depth, which is inversely proportional to the square root of the excitation signal frequency, providing a theoretical basis for the detection of defects of different depths. On this basis, existing technologies have developed various detection methods such as single-frequency eddy current, multi-frequency eddy current, and pulsed eddy current.

[0003] Among them, pulsed eddy current detection technology is a kind of transient eddy current detection technology developed to overcome the limitations of conventional eddy current detection, such as limited detection depth and significant influence of probe lift-off effect. Compared with traditional single-frequency or multi-frequency excitation methods, pulsed eddy current uses a square wave signal with a certain duty cycle for excitation, which has a wide frequency spectrum and rich time-domain information, and has advantages such as large detection depth, multiple characteristic parameters, and easy quantification, especially suitable for detection and evaluation of ferromagnetic metal components.

[0004] Although pulsed eddy current technology is relatively mature in metal thickness measurement, it still faces many challenges in quantitatively evaluating the depth of internal defects (such as cracks, corrosion, etc.) of components. Specifically, existing methods rely heavily on time-domain signal analysis, but the complex time-frequency characteristics of pulsed square waves may make it difficult to determine the specific frequency of a certain defect; using a single frequency to quantitatively explore the depth of defects in metal components may require several changes in frequency to determine the corresponding frequency of the defect, which is tedious, inefficient, and may lead to inaccurate detection results due to improper frequency selection SUMMARY

[0005] The purpose of the present application is to provide a metal component defect depth detection system and method based on swept-frequency pulsed eddy current, which can solve the problems of low efficiency and insufficient accuracy in the quantitative evaluation of defect depth in existing pulsed eddy current detection technology; realize targeted excitation and signal acquisition in different depth regions, quickly and accurately determine the characteristic frequency reflecting the depth of a specific defect, and significantly improve the quantitative identification ability and detection reliability of defect depth.

[0006] To achieve the above purpose, the technical solution provided by the present application is as follows:

[0007] In a first aspect, the present invention provides a defect depth detection system for metal components based on swept-frequency pulsed eddy currents, the system comprising:

[0008] A pulsed eddy current probe module includes an excitation probe and a receiving probe. The excitation probe is used to emit an excitation signal pulsed eddy current to the metal component under test; the receiving probe is used to receive sampled data.

[0009] A pulse signal excitation module, which is connected to a host computer module and a current amplification module, is used to receive control commands issued by the host computer module and control the pulse eddy current probe module to detect the metal component under test by exciting the pulse signal current;

[0010] A current amplification module is connected to the excitation probe in the pulsed eddy current probe module and the pulse signal excitation module, and is used to amplify the pulse signal current and provide deformation current to the excitation probe.

[0011] A voltage amplification module, which is connected to the receiving probe and the bandpass filter module, is used to amplify the induced voltage detected by the receiving probe;

[0012] A bandpass filter module, wherein the input terminal of the bandpass filter module is connected to the voltage amplification module and the output terminal is connected to the signal acquisition module, and the bandpass filter module is used for frequency filtering;

[0013] The signal acquisition module is used to convert the analog signal format of the sampling data acquired by the pulse eddy current probe module into a digital signal format and transmit the sampling data to the host computer module.

[0014] The host computer module is used to receive, process, and analyze the sampled data, and generate and issue probe operation control commands.

[0015] As a preferred embodiment of the present invention, the excitation pulse signal current type sent by the pulse signal excitation module to the pulse eddy current probe module is specifically a rectangular pulse or a half-wave sine pulse.

[0016] As a preferred embodiment of the present invention, the probe operation control commands include a probe excitation frequency sub-command, a sweep frequency start frequency sub-command, an interval frequency sub-command, and a termination frequency sub-command.

[0017] As a preferred embodiment of the present invention, the host computer module includes a manual input unit, host computer software, and a display unit; the manual input unit is used to transmit user input commands to the host computer software; the host computer software is used for parameter setting, sampling data analysis, and probe operation control command generation; the display unit is used to visually display the user input commands, parameter types and values, sampling data analysis results, and probe operation control commands.

[0018] As a preferred embodiment of the present invention, both the excitation probe and the receiving probe are provided with a working coil. The structural types of the working coil include, but are not limited to, the following: cylindrical coil, conical focusing coil, and ingot-shaped coil.

[0019] As a preferred embodiment of the present invention, the host computer module and the pulse signal excitation module are electrically connected via a USB connector.

[0020] Secondly, the present invention provides a method for detecting the defect depth of metal components based on swept-frequency pulsed eddy currents, the method comprising:

[0021] S01, set the excitation signal frequency to the critical frequency calculated based on the wall thickness of the metal component under test, and use a rectangular pulse signal to scan the metal component under test; locate the defect area by comparing the extreme value of the received signal in the sampled data with the defect-free reference signal;

[0022] S02, the host computer module sets the sweep frequency start frequency, interval frequency and end frequency, and generates probe working control command; the pulse signal excitation module receives the probe working control command and sends a half-wave sine pulse signal to the pulse eddy current probe module, and the pulse eddy current probe module detects the non-defect area and defect area of ​​the metal component under test respectively.

[0023] S03, the host computer module receives the sampled data and records the voltage response extreme value corresponding to each scanning frequency;

[0024] S04, The host computer module extracts the voltage extreme values ​​corresponding to each frequency point from the sampled data; calculates the difference between the voltage signal extreme values ​​of the defective area and the non-defective area to obtain multiple frequency-extreme value difference data points;

[0025] S05, based on the frequency-extreme difference data points, draw a detection relationship curve, identify the inflection point with the largest slope in the detection relationship curve, and determine the characteristic frequency value corresponding to the inflection point; input the characteristic frequency value into the skin depth calculation model to calculate and obtain the defect penetration depth value of the tested metal component.

[0026] As a preferred embodiment of the present invention, the skin depth calculation model is as follows:

[0027] δ = 1 /

[0028] Where δ is the defect penetration depth; f c σ is the characteristic frequency value; μ is the magnetic permeability of the tested metal component; σ is the electrical conductivity of the tested metal component.

[0029] In summary, the present invention has the following beneficial effects:

[0030] This invention effectively solves the problems of low efficiency and insufficient accuracy in existing technologies by combining a two-step detection method that integrates "single-frequency initial screening and localization" with "precise quantification using frequency sweep mode." First, it uses a critical frequency to quickly determine the defect location, avoiding blind scanning. Then, it acquires wideband response data in one go through controllable frequency sweep excitation. This method eliminates the cumbersome process of repeatedly changing a single frequency for trial and error, allowing depth calculation to be completed in a single frequency sweep, greatly improving detection efficiency. Furthermore, this invention also calculates defect depth values ​​based on a defined physical model (skin effect) and objective curve characteristics (inflection points), reducing subjective interference and significantly improving the accuracy and reliability of quantitative assessment. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a system structure block diagram of the present invention;

[0033] Figure 2 This is a flowchart of the method of the present invention;

[0034] Figure 3 This is a graph showing the relationship between the difference between the extreme values ​​of the signal in the defective region and the extreme values ​​of the voltage signal in the non-defective region at the same frequency in an embodiment of the present invention and the defect penetration depth. Detailed Implementation

[0035] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed merely to enable those skilled in the art to better understand and implement the subject matter described herein, and are not intended to limit the scope, applicability, or examples set forth in the claims. The function and arrangement of the elements discussed may be changed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the various examples. For example, the described methods may be performed in a different order than described, and steps may be added, omitted, or combined. Furthermore, features described in some examples may be combined in other examples.

[0036] As used herein, the term "comprising" and its variations are open terms meaning "including but not limited to". The term "based on" means "at least partially based on". The terms "one embodiment" and "an embodiment" mean "at least one embodiment". The term "another embodiment" means "at least one other embodiment". The terms "first", "second", etc., may refer to different or the same objects. Other definitions, whether explicit or implicit, may be included below. Unless explicitly indicated by the context, the definition of a term shall remain consistent throughout the specification.

[0037] This embodiment provides a defect depth detection system for metal components based on swept-frequency pulse eddy currents. The system includes:

[0038] The pulsed eddy current probe module includes an excitation probe and a receiving probe. The excitation probe is used to transmit an excitation signal pulsed eddy current to the metal component under test; the receiving probe is used to receive the sampled data.

[0039] The pulse signal excitation module is connected to the host computer module and the current amplification module. It is used to receive control commands issued by the host computer module and control the pulse eddy current probe module to detect the metal component under test by exciting the pulse signal current.

[0040] The current amplification module is connected to the excitation probe and pulse signal excitation module in the pulse eddy current probe module, and is used to amplify the pulse signal current and provide deformation current for the excitation probe.

[0041] The voltage amplification module is connected to the receiving probe and the bandpass filter module and is used to amplify the induced voltage detected by the receiving probe.

[0042] The bandpass filter module has its input connected to the voltage amplifier module and its output connected to the signal acquisition module. The bandpass filter module is used for frequency filtering.

[0043] The signal acquisition module is used to convert the analog signal format of the sampling data acquired by the pulse eddy current probe module into a digital signal format and transmit the sampling data to the host computer module.

[0044] The host computer module is used to receive, process, and analyze the sampled data, and generate and issue probe operation control commands.

[0045] like Figure 1 As shown, this system adopts a modular design, consisting of a host computer module, a pulse signal excitation module, a current amplification module, a pulse eddy current probe module, a voltage amplification module, a bandpass filter module, and a signal acquisition module. Each module forms a complete detection closed loop through signal and control flow. Its core processing and control system is the host computer module.

[0046] The host computer module, serving as the system's highest-level control command issuing and data signal processing terminal, has a built-in software unit that acts as the system's "brain." This software unit integrates a parameter setting unit. Before detection begins, the operator presets all detection parameters and generates probe operation control commands in this unit. Specific configurable parameters include, but are not limited to: excitation signal parameters: the start frequency, interval frequency, and end frequency of the half-wave sine wave signal required for frequency sweep detection; and hardware module parameters: the gain value of the voltage amplification module, the selection of the power amplifier unit in the current amplification module, the amplification factor, number of sampling points, and sampling frequency of the signal acquisition module, etc. After parameter settings are completed, the host computer module directly sends digital control commands containing the above parameters to the pulse signal excitation module via a USB communication interface.

[0047] The pulse signal excitation module is used for command parsing and signal generation. It includes a host computer control command parsing unit and a waveform excitation unit. After receiving instructions from the host computer via USB, the command parsing unit parses the instructions and executes the corresponding operations to drive the waveform excitation unit to generate the required excitation signal. Subsequently, the module converts the digital control signal into an analog signal output and sends it to subsequent related modules.

[0048] The current amplification module and the pulsed eddy current probe module are responsible for signal driving and eddy current excitation. The current amplification module receives the analog signal from the pulse signal excitation module and amplifies the current of the pulse signal to the required level to effectively drive the excitation probe in the pulsed eddy current probe module. In addition, this module is also responsible for providing a drive signal with a specific waveform (such as deformation current) to the excitation probe. The pulsed eddy current probe module is the front-end sensor of the system. Its core is a customized coil, mainly including cylindrical coils, conical focusing coils, and ingot-shaped coils. The probe body can be precisely shaped using 3D printing technology, and the number of turns can be determined according to the detection requirements. The most suitable combination of excitation and receiving probes can be flexibly selected according to specific detection requirements and environment to optimize the detection effect. When the amplified pulse wave signal is applied to the excitation probe, a primary magnetic field is generated around it. This magnetic field acts on the surface of the adjacent ferromagnetic metal component, inducing eddy currents. When the eddy currents propagate in the component and encounter surface or internal defects, their distribution changes. This change triggers a secondary magnetic field, which is detected by the receiving probe and converted into an induced voltage signal.

[0049] The voltage amplification module is directly connected to the receiving probe, responsible for initially amplifying the weak induced voltage signal detected by the probe. The input of the bandpass filter module is connected to the voltage amplification module, and the output is connected to the signal acquisition module. This module is used for frequency filtering, allowing only signals within a specific frequency band to pass through, effectively suppressing noise interference.

[0050] The signal acquisition module is responsible for converting the amplified and filtered analog voltage signal into a digital signal format via A / D conversion, and then uploading the sampled data back to the host computer module for further analysis via the USB interface.

[0051] In another possible embodiment, a method for detecting the defect depth of metal components based on swept-frequency pulsed eddy currents is also provided, the method comprising:

[0052] S01, set the excitation signal frequency to the critical frequency calculated based on the wall thickness of the metal component under test, and use a rectangular pulse signal to scan the metal component under test; locate the defect area by comparing the extreme value of the received signal in the sampled data with the defect-free reference signal;

[0053] S02, the host computer module sets the sweep frequency start frequency, interval frequency and end frequency, and generates probe working control command; the pulse signal excitation module receives the probe working control command and sends a half-wave sine pulse signal to the pulse eddy current probe module, and the pulse eddy current probe module detects the non-defect area and defect area of ​​the metal component under test respectively.

[0054] S03, the host computer module receives the sampled data and records the voltage response extreme value corresponding to each scanning frequency;

[0055] S04, The host computer module extracts the voltage extreme values ​​corresponding to each frequency point from the sampled data; calculates the difference between the signal extreme values ​​of the defective area and the non-defective area, and obtains multiple frequency-extreme value difference data points;

[0056] S05. Based on the frequency-extreme difference data points, draw the detection relationship curve, identify the inflection point with the largest slope in the detection relationship curve, and determine the characteristic frequency value corresponding to the inflection point; input the characteristic frequency value into the skin depth calculation model to calculate and obtain the defect depth value of the tested metal component.

[0057] Specifically, this method combines single-frequency scanning localization with frequency sweep detection analysis to efficiently and accurately quantify defect depth. The method flow is as follows: Figure 2 As shown. First, the excitation signal frequency is set to the critical frequency f calculated based on the wall thickness of the metal component being measured. c The probe uses a rectangular pulse signal to perform a preliminary scan of the component under test. By comparing the voltage extreme value of the received signal in the sampled data with the pre-calibrated defect-free reference signal, when the probe scans to a certain area, if the received voltage response extreme value is significantly greater than the defect-free reference value, it can be determined that there is a defect in the area where the probe is located, thus completing the preliminary location of the defect area.

[0058] Next, after defect localization, the system switches to frequency sweep detection mode. The host computer module sets the starting frequency f of the frequency sweep in the parameter setting unit. start Interval frequency Δf and termination frequency f end The system generates probe operation control commands. Upon receiving these commands, the pulse signal excitation module parses and generates a corresponding half-wave sinusoidal pulse sequence signal, which is then sent to the pulse eddy current probe module. Subsequently, the pulse eddy current probe module performs precise frequency sweep detection on the confirmed defect area and the known defect-free reference area. Simultaneously, the signal acquisition module acquires and uploads the voltage response signals of both areas. Then, the host computer module receives and processes the sampled data, recording the extreme values ​​of the voltage response signals in the defect area and the defect-free area corresponding to each scanning frequency point. It then extracts the voltage extreme values ​​corresponding to each scanning frequency point and calculates the difference between the extreme values ​​of the signal in the defect area and the voltage signal in the defect-free area at the same frequency, thus obtaining multiple frequency-extreme value difference data points characterizing the relationship between frequency and signal difference. Next, based on the obtained frequency-extreme value difference data points, a detection relationship curve is plotted. By analyzing this curve, the inflection point with the largest slope is identified, and the characteristic frequency value f corresponding to this inflection point is determined. c .

[0059] Finally, the obtained feature frequency values ​​f c Substituting the preferred skin depth calculation model of this invention:

[0060] δ = 1 /

[0061] Where δ is the defect penetration depth; f c σ represents the characteristic frequency; μ represents the magnetic permeability of the tested metal component; and σ represents the electrical conductivity of the tested metal component. This model allows for the calculation and final determination of the defect penetration depth of the tested metal component.

[0062] like Figure 3 As shown, the characteristic frequency value f corresponding to the inflection point can be determined. c The depth of the defect at that location.

[0063] This method uses a host computer module to control a pulse signal excitation module to generate a half-wave sinusoidal pulse sequence with precisely adjustable frequency, thus achieving frequency sweep detection. Compared with single-frequency pulse excitation, it can excite multiple controllable frequency excitation signals at one time, providing a rich data foundation for accurately extracting single feature frequencies. This enables efficient and accurate quantitative assessment of the depth of minute defects, significantly improving the accuracy and efficiency of detection.

[0064] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0065] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A system for detecting the depth of defects in metal components based on swept-frequency pulsed eddy currents, characterized in that the system... include: A pulsed eddy current probe module includes an excitation probe and a receiving probe. The excitation probe is used to emit an excitation signal pulsed eddy current to the metal component under test; the receiving probe is used to receive sampled data. A pulse signal excitation module, which is connected to a host computer module and a current amplification module, is used to receive control commands issued by the host computer module and control the pulse eddy current probe module to detect the metal component under test by exciting the pulse signal current; A current amplification module is connected to the excitation probe in the pulsed eddy current probe module and the pulse signal excitation module, and is used to amplify the pulse signal current and provide deformation current to the excitation probe. A voltage amplification module, which is connected to the receiving probe and the bandpass filter module, is used to amplify the induced voltage detected by the receiving probe; A bandpass filter module, wherein the input terminal of the bandpass filter module is connected to the voltage amplification module and the output terminal is connected to the signal acquisition module, and the bandpass filter module is used for frequency filtering; The signal acquisition module is used to convert the analog signal format of the sampling data acquired by the pulse eddy current probe module into a digital signal format, and transmit the sampling data to the host computer module. The host computer module is used to receive, process, and analyze the sampled data, and generate and issue probe operation control commands.

2. The metal component defect depth detection system based on swept-frequency pulse eddy current according to claim 1, characterized in that, The excitation pulse signal current type sent by the pulse signal excitation module to the pulse eddy current probe module is specifically a rectangular pulse or a half-wave sine pulse.

3. The metal component defect depth detection system based on swept-frequency pulse eddy current according to claim 2, characterized in that, The probe operation control commands include probe excitation frequency sub-command, sweep start frequency sub-command, interval frequency sub-command, and termination frequency sub-command.

4. The metal component defect depth detection system based on swept-frequency pulse eddy current according to claim 3, characterized in that, The host computer module includes a manual input unit, host computer software, and a display unit; the manual input unit is used to transmit user input commands to the host computer software; the host computer software is used for parameter setting, sampling data analysis, and probe operation control command generation; the display unit is used to visually display the user input commands, parameter types and values, sampling data analysis results, and probe operation control commands.

5. The metal component defect depth detection system based on swept-frequency pulse eddy current according to claim 4, characterized in that, Both the excitation probe and the receiving probe are equipped with a working coil. The structural types of the working coil include, but are not limited to, the following: cylindrical coil, conical focusing coil, and ingot-shaped coil.

6. The metal component defect depth detection system based on swept-frequency pulse eddy current according to claim 5, characterized in that, The host computer module and the pulse signal excitation module are electrically connected via a USB connector.

7. A method for detecting defect depth in metal components based on swept-frequency pulsed eddy currents, characterized in that, The methods include: S01, set the excitation signal frequency to the critical frequency calculated based on the wall thickness of the metal component under test, and use a rectangular pulse signal to scan the metal component under test; locate the defect area by comparing the extreme value of the received signal in the sampled data with the defect-free reference signal; S02, the host computer module sets the sweep frequency start frequency, interval frequency and end frequency, and generates probe working control command; the pulse signal excitation module receives the probe working control command and sends a half-wave sine pulse signal to the pulse eddy current probe module, and the pulse eddy current probe module detects the non-defect area and defect area of ​​the metal component under test respectively. S03, the host computer module receives the sampled data and records the voltage response extreme value corresponding to each scanning frequency; S04, The host computer module extracts the voltage extreme values ​​corresponding to each frequency point from the sampled data; calculates the difference between the voltage signal extreme values ​​of the defective area and the non-defective area to obtain multiple frequency-extreme value difference data points; S05, based on the frequency-extreme difference data points, draw a detection relationship curve, identify the inflection point with the largest slope in the detection relationship curve, and determine the characteristic frequency value corresponding to the inflection point; input the characteristic frequency value into the skin depth calculation model to calculate and obtain the defect penetration depth value of the tested metal component.

8. The method for detecting the defect depth of metal components based on swept-frequency pulse eddy current according to claim 7, characterized in that, The skin depth calculation model is as follows: δ= 1 / , Where δ is the defect penetration depth; f c σ is the characteristic frequency value; μ is the magnetic permeability of the tested metal component; σ is the electrical conductivity of the tested metal component.

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