Eddy current detection sensor, delamination defect detection system and detection method

Abstract

The present invention provides an eddy current detection sensor, a layered defect detection system and a detection method, wherein the eddy current detection sensor comprises an eddy current detection probe, and the eddy current detection probe comprises an annular excitation coil and a receiving coil; wherein the annular excitation coil is sleeved around a preselected cross section of a product to be detected, and the receiving coil is arranged on the inner side of the annular excitation coil. The eddy current detection sensor, the layered defect detection system and the detection method provided by the present invention can solve the problems of the existing eddy current detection methods having near-surface blind spots or having high costs and low image contrast ratios.

Description

Technical Field

[0001] The present invention relates to the technical field of non-destructive testing (NDT), and more specifically, to an eddy current detection sensor, a delamination defect detection system and a detection method. Background Art

[0002] During the production of sheet metal, such as rolled copper busbars, delamination defects may occur, such as poor connections between different layers, bubbles or inclusions. These defects can affect the performance and reliability of the copper busbar, so effective detection is required.

[0003] Nowadays, eddy current testing is used to detect delamination defects of various materials that are easy to delaminate (such as rolled copper busbars, etc.). Most of them are CFRP, FRP, aluminum sheets and other materials. Most of them use ultrasonic testing and thermal imaging testing.

[0004] However, both detection methods have their own shortcomings in industry. For example, the ultrasonic detection method has a near-surface blind spot, while the thermal imaging detection method has the problems of high cost and low image contrast ratio.

[0005] Based on the above technical problems, there is an urgent need for an eddy current detection method for metal materials with low cost, high image contrast ratio and no near-surface blind spots. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide an eddy current detection sensor, a layered defect detection system and a detection method to solve the problems of existing eddy current detection methods having near-surface blind spots or high costs and low image contrast ratios.

[0007] The eddy current detection sensor provided by the present invention comprises an eddy current detection probe, wherein the eddy current detection probe comprises a ring-shaped excitation coil and a receiving coil; wherein,

[0008] The annular excitation coil is sleeved around a preselected cross section of the product to be detected, and the receiving coil is arranged on the inner side of the annular excitation coil.

[0009] In addition, a preferred solution is that at least two receiving coils are arranged inside the annular excitation coil; and

[0010] The receiving coils are distributed in a matrix pattern inside the annular excitation coil.

[0011] In addition, a preferred solution is that the eddy current detection sensor includes at least two eddy current detection probes, and the eddy current detection probes are distributed in a matrix along the extension direction of the product to be detected; and

[0012] The annular excitation coils in each eddy current detection probe are respectively arranged around different preselected cross sections of the product to be detected.

[0013] In addition, a preferred solution is that the eddy current detection sensor further includes a transmission mechanism arranged along the extension direction of the product to be detected, and the eddy current detection probe is connected to the transmission mechanism; and,

[0014] The eddy current detection probe is driven by the transmission mechanism to perform eddy current scanning detection on different cross sections of the product to be detected.

[0015] On the other hand, the present invention also provides a delamination defect detection system, comprising: a signal generator, a conditioning circuit, a host computer and the aforementioned eddy current detection sensor; wherein,

[0016] The signal generator is used to input an excitation signal to the excitation coil in the eddy current detection sensor;

[0017] The eddy current detection sensor is used to perform eddy current detection on the product to be detected based on the excitation signal and generate a receiving signal in the receiving coil;

[0018] The conditioning circuit is used to process the received signal and send it to the host computer;

[0019] The host computer is used to display the processed received signal.

[0020] In addition, a preferred solution is that if there is a distorted signal in the processed received signal displayed on the host computer; then,

[0021] The host computer is also used to analyze the distortion signal to determine the specific position and width of the delamination defect in the product to be inspected.

[0022] In another aspect, the present invention further provides a delamination defect detection method, wherein the delamination defect detection method uses the above-mentioned delamination defect detection system for detection; the method comprises:

[0023] Inputting an excitation signal to an excitation coil in the eddy current detection sensor through the signal generator;

[0024] generating an induced eddy current in the product to be detected based on the excitation signal by the excitation coil;

[0025] generating a receiving signal based on the induced eddy current by the receiving coil;

[0026] Processing the received signal through the conditioning circuit and sending it to the host computer;

[0027] The processed received signal is displayed by the host computer.

[0028] In addition, a preferred solution is that if there is a distorted signal in the processed received signal displayed on the host computer; then,

[0029] The distortion signal is analyzed by the host computer to determine the specific position and width of the delamination defect in the product to be inspected.

[0030] In addition, a preferred solution is to configure the frequency and amplitude of the excitation signal according to the pre-detection depth of the product to be detected.

[0031] In addition, a preferred solution is that the upper computer analyzes the distortion signal to determine the specific position and width of the delamination defect in the product to be inspected, including:

[0032] Analyzing the received signal to extract characteristic parameters related to the delamination defect in the received signal;

[0033] The characteristic parameters are classified using a preset recognition algorithm to achieve automatic recognition of the delamination defects in the product to be inspected.

[0034] Compared with the prior art, the eddy current detection sensor, delamination defect detection system and detection method according to the present invention have the following beneficial effects:

[0035] The eddy current detection sensor, layered defect detection system and detection method provided by the present invention adopt array eddy current detection technology. By setting an eddy current detection probe including a ring-shaped excitation coil and a receiving coil, the deficiencies of ultrasonic detection and thermal imaging detection are compensated. The large ring-shaped coil is used for excitation and the receiving coil is used for reception, so that it can adapt to the detection needs of large copper busbars in industrial scenarios. In addition, by arranging the ring-shaped excitation coil outside the product, an inserted detection design can be realized, which can simplify the operation of the product during the detection process and make it more efficient and convenient.

[0036] In order to achieve the above and related purposes, one or more aspects of the present invention include features that will be described in detail later and are particularly pointed out in the claims. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all of these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] By referring to the following description in conjunction with the accompanying drawings, and with a more comprehensive understanding of the present invention, other objects and results of the present invention will become more apparent and easy to understand. In the accompanying drawings:

[0038] Figure 1A structural principle diagram of the eddy current detection sensor provided by the present invention;

[0039] Figure 2 A side view of the eddy current detection sensor provided by the present invention;

[0040] Figure 3 A logical framework diagram of the layered defect detection system provided by the present invention;

[0041] Figure 4 A graph showing the relationship between the voltage amplitude of the receiving coil and the scanning distance during the simulation of the delamination defect detection method provided by the present invention.

[0042] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0043] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, many specific details are set forth. However, it is apparent that these embodiments may also be implemented without these specific details. In other examples, for ease of describing one or more embodiments, known structures and devices are shown in the form of block diagrams.

[0044] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] Figure 1 The three-dimensional structure of the eddy current detection sensor provided by the present invention is shown. Figure 2 The side view structure of the eddy current detection sensor provided by the present invention is shown, combined with Figure 1 and Figure 2It can be seen that the high-sensitivity eddy current detection sensor provided by the present invention is used to detect delamination defects in a product to be detected (such as a rolled copper bar). The product to be detected may include one or more eddy current detection probes as eddy current detection units, wherein the eddy current detection probe includes multiple eddy current coils, and the eddy current coils are divided into annular excitation coils and receiving coils, and each eddy current detection probe has an independent excitation coil and receiving coil; in actual use, by reasonably designing the geometric parameters and probe spacing of the probe array composed of multiple eddy current detection probes, the detection resolution and sensitivity of the entire eddy current detection sensor can be effectively improved.

[0046] Specifically, for an eddy current detection probe, the annular excitation wire needs to be set around a preselected cross section of the product to be detected, and the receiving coil is set inside the annular excitation coil; for example, for a plate product (such as a rolled copper bar, such as Figure 1 As shown), the annular excitation coil needs to surround a preselected cross section of the product to be inspected, so as to detect delamination defects of different depths in a preselected cross section of the product to be inspected.

[0047] It should be noted that one eddy current detection probe needs to be equipped with one annular excitation coil, and at least two receiving coils are configured for the annular excitation coil, wherein two receiving coils form a group, and multiple groups can be set (such as Figure 1 As shown, three groups of receiving coils are provided); and, in order to improve the receiving effect of the receiving coils, the receiving coils are distributed in a matrix on the inner side of the annular excitation coil.

[0048] Furthermore, in order to improve the detection effect, the eddy current detection sensor may include multiple (at least two) eddy current detection probes, each of which is distributed in a matrix along the extension direction of the product to be detected; and the annular excitation coils in each eddy current detection probe are respectively set around different pre-selected cross-sections of the product to be detected, and array eddy current non-destructive testing can be achieved by setting multiple eddy current detection probes. In array eddy current non-destructive testing, multiple eddy current detection probes distributed in an array can generate multiple eddy currents at the same time, and each eddy current corresponds to an independent detection area on the product to be detected; this can greatly improve the efficiency of detection.

[0049] On the other hand, the eddy current detection sensor also includes a transmission mechanism arranged along the extension direction of the product to be detected, and the eddy current detection probe is connected to the transmission mechanism; and the eddy current detection probe, driven by the transmission mechanism, performs eddy current scanning detection of different cross-sections of the product to be detected. The eddy current detection sensor provided by the present invention can detect multiple areas at the same time by setting multiple eddy current detection probes, or quickly detect a large area in one scanning process; this has great advantages in some complex application scenarios, such as the detection of aircraft skins, composite materials and nuclear power plant pipelines. In general, array eddy current nondestructive testing inherits the advantages of eddy current nondestructive testing, such as no contact, no consumables, online real-time detection, etc., and at the same time, through array probe technology, the efficiency and capability of detection are improved.

[0050] To further illustrate the specific use of the eddy current detection sensor provided by the present invention in the detection of delamination defects of the product to be detected, Figure 3 The logical framework of the layered defect detection system provided by the present invention is shown; Figure 3 It can be seen that the present invention also provides a delamination defect detection system, which comprises: a signal generator, a conditioning circuit, a host computer and the aforementioned eddy current detection sensor; wherein,

[0051] The signal generator is used to input an excitation signal to the excitation coil in the eddy current detection sensor;

[0052] The eddy current detection sensor is used to perform eddy current detection on the product to be detected based on the excitation signal, and generate a receiving signal in the receiving coil;

[0053] The conditioning circuit is used to process the received signal and send it to the host computer;

[0054] The host computer is used to display the processed received signal.

[0055] Furthermore, if there is a distorted signal in the processed received signal displayed on the host computer, the host computer is also used to analyze the distorted signal to determine the specific position and stratification width of the delamination defect in the product to be inspected.

[0056] Furthermore, in order to illustrate the working principle of the delamination defect detection system provided by the present invention, the present invention also provides a delamination defect detection method, which uses the above-mentioned delamination defect detection system for detection; the delamination defect detection method includes:

[0057] Pre-design of eddy current detection sensors, including determining the type of eddy current detection probe, probe size, operating frequency, array structure, probe circuit, probe structure fixation, etc.;

[0058] Then, the product to be inspected is inspected, including inputting an excitation signal to the excitation coil in the eddy current detection sensor through the signal generator, and generating an induced eddy current in the product to be inspected based on the excitation signal through the excitation coil; and then generating a receiving signal based on the induced eddy current through the receiving coil (mainly used to characterize the change of eddy current signal caused by delamination defects in the induced eddy current, which is essentially an induced electromotive force);

[0059] Then, the received signal is processed by the conditioning circuit (including amplification, filtering and demodulation of the received signal) and sent to the host computer;

[0060] Finally, the processed received signal is displayed through the host computer.

[0061] In addition, if there is a distorted signal in the processed received signal displayed on the host computer, the host computer evaluates and analyzes the distorted signal to determine the specific location and width of the delamination defect in the product to be tested, and provides delamination defect information of the product to be tested. Of course, the evaluation and analysis of the distorted signal can also be performed on other equipment or manually.

[0062] It should be noted that, in actual operation, the frequency and amplitude of the excitation signal can be configured according to the pre-detection depth of the product to be detected (the corresponding relationship between the pre-detection depth and the frequency and amplitude of the excitation signal can be obtained through multiple tests), and then the annular excitation coil is used to excite the product to be detected to generate induced eddy currents. The other coils (i.e., receiving coils) in the eddy current detection probe are used as induction coils and are affected by the alternating magnetic field generated by the alternating current of the excitation coil, thereby inducing an induced electromotive force. The induced electromotive force of the array coil is collected to obtain the corresponding receiving signal, which is then processed by the conditioning circuit and sent to the host computer.

[0063] Furthermore, for the received signal processing design, the analog circuit can be used to amplify, filter and demodulate the signal according to the signal frequency of different receiving coils, so as to facilitate display on the host computer. For determining the delamination defect position of the product to be tested, the received signal after signal processing can be put on the host computer for display, and observe whether it has a distorted signal. If a distorted signal is generated, the defect exists directly below the eddy current detection probe, and then the specific position and delamination width of the delamination defect of the product to be tested are calculated and analyzed according to the position and amplitude of the distorted signal displayed by the host computer.

[0064] It should be noted that the eddy current detection sensor provided by the present invention requires an excitation signal to drive the annular excitation coil to generate an alternating magnetic field. A multi-frequency or broadband excitation signal generated by a signal generator can be used here to adapt to the detection of layered defects at different depths; the signal generated by the receiving coil needs to be amplified, filtered, and processed by a preprocessing circuit (i.e., a conditioning circuit); then, the processed received signal is input into a data acquisition card for subsequent signal analysis.

[0065] Of course, corresponding to the aforementioned implementation method of setting the eddy current detection probe on the transmission mechanism, the present invention can also design a scanning platform to realize the automatic scanning of the eddy current detection sensor along the product to be detected. During the scanning process, the signal data is collected and analyzed in real time, and the detection results are visualized so that the operator can quickly understand the layered defects of the product to be detected.

[0066] In order to further verify the use effect of the delamination defect detection method provided by the present invention, the present invention further simulates and verifies it on the simulation software. In the simulation verification process, firstly, the center point of the defect is used as the origin to perform a uniform scanning at a distance of 20 mm before and after in the simulation. In the simulation software, when the coil scans from far away from the defect to directly above the defect, and then scans from directly above the defect to far away, a one-dimensional plot of the scanning distance and the corresponding receiving coil amplitude change is obtained as shown in FIG. Figure 4 As shown, it can be observed that when there is a defect directly below the probe during the scanning process, its peak-to-peak value can reach 19mv, and its amplitude change can be observed on the oscilloscope (a host computer). Secondly, the depth and size of the defect can be determined by the amplitude information of the signal. The size and duration of the amplitude distortion during the uniform scanning process can be used to preliminarily evaluate the size of the defect and its specific location.

[0067] Then, a series of standard samples containing delamination defects of different depths and sizes are made for calibration and performance evaluation of the array eddy current testing system. By analyzing the test results of the system on these standard samples, its detection capability, resolution and sensitivity can be evaluated, and then the system parameters can be optimized to improve the detection performance.

[0068] To further illustrate how to specifically analyze the location of the delamination defect of the product to be inspected according to the eddy current detection sensor provided by the present invention, the working principle of the eddy current detection sensor provided by the present invention is introduced in detail below.

[0069] According to the eddy current testing principle, the electromagnetic numerical analysis of the product to be tested is based on Maxwell's equations. The eddy current testing model is as follows: Figure 1As shown. The flow detection model includes the product to be detected, the annular excitation coil and the receiving coil. The excitation current density in the annular excitation coil is J. The coil area and the conductor area in the numerical solution domain are denoted as Ωs and Ωt respectively, and the air domain is represented by Ωr. The electromagnetic field equations in each solution domain can be written in the following differential equation form:

[0070] In the conductor region Ωt, the behavior of the electromagnetic field is described by the following equation:

[0071]

[0072] Where H is the magnetic field intensity, J is the current density, D is the electric displacement, E is the electric field intensity, B is the magnetic induction intensity, and t is time.

[0073] Due to the eddy current effect, an excitation current will be generated in the coil area Ωs, and its electromagnetic field formula is similar to that in the conductor area.

[0074] In the air region Ωr, since air is non-conductive, the current density J is 0, and the electromagnetic field behavior can also be expressed by the following equation:

[0075]

[0076] These equations are the forms of Maxwell's equations in different media, which can provide a theoretical basis for eddy current detection. In the above equations, E and H represent the electric field intensity and magnetic field intensity respectively; B and J represent the magnetic induction intensity and eddy current density respectively; D represents the charge density. The normal vector of the magnetic induction intensity and the tangent vectors of E and H are continuous on the boundary.

[0077] However, since eddy current decays rapidly in the depth direction of the conductor, eddy current testing is only applicable to damage on the surface and near the surface of the conductor. The eddy current intensity is the largest on the surface of the test piece and decays exponentially with increasing depth. The depth at which the eddy current decays to 1 / e times the surface is usually defined as the skin depth δ of the eddy current, and the formula is:

[0078]

[0079] Where f is the current frequency, μ is the magnetic permeability, is the conductivity.

[0080] Therefore, when the excitation frequency is 2000, the maximum penetration depth of the eddy current is 4.6mm. Therefore, the defect depth is set to 2.5mm in the Comsol simulation model. When the excitation coil inputs the excitation signal, induced eddy currents are generated near the surface of the product to be inspected. When the eddy current signal encounters defects and is distorted, the impedance of the induction coil will be affected, and this influence will be converted into a change in the voltage amplitude of the induction coil, which can be observed by the inspector on the oscilloscope.

[0081] In a preferred embodiment of the present invention, the distortion signal can be analyzed by artificial intelligence (such as machine learning), such as: the distortion signal is analyzed by the host computer to determine the specific position and width of the delamination defect in the product to be inspected, including:

[0082] The received signal is analyzed to extract characteristic parameters related to the delamination defect in the received signal; the characteristic parameters are classified using a preset recognition algorithm to achieve automatic recognition of the delamination defect in the product to be detected.

[0083] It should be noted that how to set a preset recognition algorithm based on artificial intelligence is a common technical means in the field of artificial intelligence. The present invention here only uses artificial intelligence to analyze distorted signals. Therefore, the specific process of setting a preset recognition algorithm based on artificial intelligence will not be repeated here.

[0084] It can be seen from the above specific embodiments that the eddy current detection sensor, delamination defect detection system and detection method provided by the present invention have at least the following advantages:

[0085] 1. A larger annular excitation coil is used for excitation, which increases the intensity of the induced eddy current and makes the amplitude change of the signal received by the receiving coil more obvious. The annular structure probe is more conducive to the automation of industrial detection and can scan the four sides of the copper busbar at the same time.

[0086] 2. The excitation coil is perpendicular to the delamination defect, which causes greater disturbance of the eddy current in the defect area, making the detection signal more obvious and improving the detection sensitivity and signal-to-noise ratio.

[0087] 3. The use of array-distributed receiving coils is conducive to more accurate detection of eddy current changes generated in the defect area, thereby further improving the sensitivity and resolution of detection. Multiple receiving coils can simultaneously receive eddy current signals in multiple areas, achieving one-time large-scale detection and greatly improving the detection speed.

[0088] As above Figures 1 to 4 The eddy current detection sensor, delamination defect detection system and detection method according to the present invention are described by way of example. However, those skilled in the art should understand that various improvements can be made to the eddy current detection sensor, delamination defect detection system and detection method proposed by the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the attached claims.

Claims

1. An eddy current detection sensor, characterized in that: It includes an eddy current detection probe, which includes a ring-shaped excitation coil and a receiving coil; wherein, The annular excitation coil is set around a preselected cross section of the plate-like product to be tested, and the receiving coil is set inside the annular excitation coil; wherein, At least two receiving coils are arranged inside the annular excitation coil, and the receiving coils are distributed in a matrix inside the annular excitation coil; and The eddy current detection sensor includes at least two eddy current detection probes, each of which is distributed in a matrix along the extension direction of the product to be detected; the annular excitation coil in each eddy current detection probe is respectively arranged around different preselected cross-sections of the product to be detected.

2. The eddy current detection sensor according to claim 1, characterized in that: The eddy current detection sensor further includes a transmission mechanism arranged along the extension direction of the product to be detected, and the eddy current detection probe is connected to the transmission mechanism; and The eddy current detection probe is driven by the transmission mechanism to perform eddy current scanning detection on different cross sections of the product to be detected.

3. A layered defect detection system, characterized in that: include: A signal generator, a conditioning circuit, a host computer and an eddy current detection sensor as claimed in claim 1 or 2; wherein: The signal generator is used to input an excitation signal to the excitation coil in the eddy current detection sensor; The eddy current detection sensor is used to perform eddy current detection on the product to be detected based on the excitation signal and generate a receiving signal in the receiving coil; The conditioning circuit is used to process the received signal and send it to the host computer; The host computer is used to display the processed received signal.

4. The delamination defect detection system according to claim 3, characterized in that: If there is a distorted signal in the processed received signal displayed on the host computer; then, The host computer is also used to analyze the distortion signal to determine the specific position and width of the delamination defect in the product to be inspected.

5. A delamination defect detection method, characterized in that: The delamination defect detection method is performed using the delamination defect detection system according to claim 3 or 4; comprising: Inputting an excitation signal to an excitation coil in the eddy current detection sensor through the signal generator; generating an induced eddy current in a plate-like product to be inspected based on the excitation signal by means of the excitation coil; generating a receiving signal based on the induced eddy current by the receiving coil; Processing the received signal through the conditioning circuit and sending it to the host computer; The processed received signal is displayed by the host computer.

6. The delamination defect detection method according to claim 5, characterized in that: If there is a distorted signal in the processed received signal displayed on the host computer; then, The distortion signal is analyzed by the host computer to determine the specific position and width of the delamination defect in the product to be inspected.

7. The delamination defect detection method according to claim 6, characterized in that: The frequency and amplitude of the excitation signal are configured according to the pre-detection depth of the product to be detected.

8. The delamination defect detection method according to claim 6, characterized in that: The analyzing the distortion signal by the host computer to determine the specific position and width of the delamination defect in the product to be inspected includes: Analyzing the received signal to extract characteristic parameters related to the delamination defect in the received signal; The characteristic parameters are classified using a preset recognition algorithm to achieve automatic recognition of the delamination defects in the product to be inspected.

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