A resonant structure, a metal non-destructive testing sensor, a detection system and a method

Abstract

The present invention relates to the field of microwave sensing technology, in particular to a resonant structure, a metal non-destructive testing sensor, a detection system and a method. Among them, the metal non-destructive testing sensor includes a reference ground, and the reference ground includes a resonant structure; a dielectric substrate disposed on the reference ground; a microstrip line disposed on the dielectric substrate, and the microstrip line extends along the axial direction of the dielectric substrate. When using the metal non-destructive testing system to detect metal surface defects according to the present invention, any form of defects on the metal surface will increase the overall equivalent inductance, and the resonant frequency of the metal non-destructive testing sensor will decrease. It will not cause missed detection for cracks in any direction, length, width and depth on the metal surface, and the detection sensitivity is relatively high, and cracks at the sub-millimeter level can be detected.

Description

Technical Field

[0001] The present invention relates to the field of microwave sensing technology, and in particular to a resonant structure, a metal non-destructive testing sensor, a detection system and a method. Background Art

[0002] During the actual application process of various structures made of metal materials in fields such as construction and transportation, defects such as scratches, cracks and rust will be generated due to factors such as scratching, fatigue load and external erosion. The initially generated fatigue cracks are generally very small and difficult to be intuitively and timely detected. As the service time increases, the fatigue cracks will continuously increase, which will pose a great threat to the safety of engineering structures. Therefore, it is very necessary to conduct periodic inspections on materials and timely detect the initial stage of metal defects.

[0003] Traditional methods for non-destructive testing of materials, such as ultrasonic testing, eddy current testing, magnetic flux leakage testing, etc., cannot give timely warnings for millimeter-scale cracks that have just occurred. In recent years, various sensors based on radio frequency resonant structures have been proposed for detecting damage on the metal surface. For example, sub-wavelength split-ring resonators (SRRs), complementary split-ring resonators (CSRRs) and other structures derived from them are often used as basic units of metamaterials. However, due to the good electromagnetic field localization characteristics of these resonant structures, they can be used for microwave non-destructive testing and sensing.

[0004] The fatigue cracks on the metal surface will affect the near-field distribution of the sensor. The change in the electromagnetic field distribution is directly manifested as the change in the resonant frequency of the sensor, which can be used to characterize the metal surface cracks. This is the mechanism of using a resonant near-field sensor to detect metal cracks. Compared with other microwave technologies for crack detection, CSRR sensors have the advantages of low operating frequency, high sensitivity, can detect sub-millimeter-scale metal cracks, relatively low manufacturing cost, and can be used to detect metal damage covered with a dielectric coating. And due to its small size, it is beneficial to more accurately determine the crack position.

[0005] The metal non-destructive testing sensor composed of the traditional CSRR structure has extremely low sensitivity in some directions, and even misses the detection of cracks on the metal surface. Moreover, it has been found through research that when using the sensor composed of the traditional CSRR structure to detect cracks on the metal surface, for shallow cracks, the width is the main influencing factor, and the equivalent capacitance decreases, which will cause the resonant frequency of the sensor to shift to a higher frequency; for narrow cracks, the depth is the main influencing factor, and the equivalent inductance increases, which will cause the resonant frequency of the sensor to shift to a lower frequency; if the crack is neither shallow nor narrow, the influences of both width and depth cannot be ignored, and the frequency shift to a higher frequency and the frequency shift to a lower frequency will cancel each other out, resulting in an insignificant frequency shift phenomenon and leading to missed detection. During the actual crack detection process, all existing crack defects should be detected, otherwise missed detection will occur, which is unacceptable for microwave non-destructive testing. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a resonant structure, a metal non-destructive testing sensor, a detection system and a method, aiming to overcome the deficiencies in the prior art.

[0007] To achieve the above object, a first aspect of the present invention provides a resonant structure, comprising: a metal ring provided with an opening; a first metal branch and a second metal branch, the first metal branch and the second metal branch are respectively disposed on the metal ring and located at both ends of the opening; a part of the first metal branch and the second metal branch is located inside the metal ring. The resonant structure proposed by the present invention designs the metal disc at the center of the traditional CSRR structure into two metal branches, and increases the equivalent inductance of the CSRR by increasing the path of the resonant structure, reduces its resonant frequency, and realizes miniaturization to a certain extent.

[0008] Optionally, the first metal branch further includes the remaining part located outside the metal ring. By extending the remaining part of the first metal branch in a direction away from the metal ring, the present invention can further increase the path of the resonant structure.

[0009] Optionally, the metal ring includes a metal circular ring or a metal elliptical ring. The resonant structure proposed by the present invention can select and adjust the shape of the metal ring according to the actual detection situation, and can be applied to a variety of detection scenarios.

[0010] A second aspect of the present invention further provides a metal non-destructive testing sensor, comprising: a reference ground including the resonant structure described in the first aspect of the present invention; a dielectric substrate disposed on the reference ground; a microstrip line disposed on the dielectric substrate and extending along the axial direction of the dielectric substrate. With the metal non-destructive testing sensor having a novel resonant structure, the present invention designs the metal disc at the center of the traditional CSRR structure into two metal branches, and realizes that any form of crack on the metal surface will increase the overall equivalent inductance of the sensor, and intuitively shows that the resonant frequency of the metal non-destructive testing sensor decreases. And the bending direction of the metal branch can be the same as the direction of the connection bridge between the resonant structure and the reference ground, so as to increase the detection sensitivity.

[0011] Optionally, the reference ground is a metal reference ground, and the metal reference ground includes an intermediate region and other regions, and the resonant structure is disposed in the intermediate region. The present invention can obtain the resonant structure by using an etching process in the intermediate region of the metal reference ground, which is beneficial to actual production and manufacturing.

[0012] The third aspect of the present invention also provides a metal non-destructive testing system, comprising: a metal to be tested; a metal non-destructive testing sensor disposed on the metal to be tested, the metal non-destructive testing sensor being used to detect defects of the metal to be tested and generate a resonance frequency; a vector network analyzer for receiving the resonance frequency generated by the metal non-destructive testing sensor; the metal non-destructive testing sensor being as described in the second aspect of the present invention. The metal non-destructive testing system proposed by the present invention adopts a metal non-destructive testing sensor with a novel resonance structure, which can operate at a lower frequency without increasing the size, has the advantage of miniaturization, and is more conducive to integration. When using the metal non-destructive testing system to detect metal surface defects, any form of defect on the metal surface will increase the overall equivalent inductance, and the resonance frequency of the metal non-destructive testing sensor will decrease. Cracks in any direction, length, width, and depth on the metal surface will not be missed, and the detection sensitivity is relatively high, and cracks at the sub-millimeter level can be detected.

[0013] Optionally, the metal non-destructive testing system further comprises: a protective coating coated on the surface of the metal to be tested. The present invention can effectively avoid accidental scratching of the metal surface during the detection process by coating the protective coating.

[0014] Optionally, the metal non-destructive testing system further comprises: a first SMA connector and a second SMA connector, the first SMA connector and the second SMA connector are respectively welded to both ends of the microstrip line; the metal non-destructive testing sensor is communicatively connected to the vector network analyzer through the first SMA connector and the second SMA connector. The present invention realizes a stable connection between the metal non-destructive testing sensor and the vector network analyzer by adopting SMA connectors, ensuring the accuracy of detection data transmission.

[0015] The fourth aspect of the present invention also provides a method for non-destructive testing of metals, comprising the following steps: providing a metal to be tested; providing a non-destructive metal testing sensor, setting the non-destructive metal testing sensor on the metal to be tested, the non-destructive metal testing sensor being used to detect defects of the metal to be tested and generate a resonant frequency; providing a vector network analyzer, the vector network analyzer being used to receive the resonant frequency generated by the non-destructive metal testing sensor; the non-destructive metal testing sensor being as described in the second aspect of the present invention. The method for non-destructive testing of metals proposed by the present invention adopts a non-destructive metal testing sensor with a novel resonant structure, can operate at a lower frequency without increasing the size, has the advantage of miniaturization, and is more conducive to integration. Any form of defect on the metal surface will increase the overall equivalent inductance, and the resonant frequency of the non-destructive metal testing sensor will decrease. Cracks in any direction, length, width, and depth on the metal surface will not be missed in detection, and the detection sensitivity is relatively high, and cracks at the sub-millimeter level can be detected. Moreover, the detection method has simple steps and is easy to operate.

[0016] Optionally, the method for non-destructive testing of metals further comprises: coating a protective coating on the surface of the metal to be tested. By coating the protective coating, the present invention can effectively avoid situations such as accidental scratching of the metal surface during the detection process. Description of the Drawings

[0017] Figure 1 Schematic diagram of the resonant structure of the present invention;

[0018] Figure 2 Comparison diagram of the resonant frequencies of the resonant structure of the present invention and the traditional CSRR structure of the same size;

[0019] Figure 3 Schematic diagram of the metal reference ground of the present invention;

[0020] Figure 4 Top view of the non-destructive metal testing sensor of the present invention;

[0021] Figure 5 Side view of the non-destructive metal testing sensor of the present invention;

[0022] Figure 6 Physical photo of the non-destructive metal testing sensor of the present invention;

[0023] Figure 7 Variation diagram of the resonant frequency of the sensor of the present invention with the expansion of the crack width;

[0024] Figure 8 Variation diagram of the resonant frequency of the sensor of the present invention with the expansion of the crack depth;

[0025] Figure 9 Schematic diagram of the non-destructive metal testing system of the present invention;

[0026] Figure 10 Schematic diagram when the metal nondestructive testing system of the present invention performs testing;

[0027] Figure 11 Flowchart of the metal nondestructive testing method of the present invention. Detailed implementation manners

[0028] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described here are only for illustrative purposes and are not used to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that the present invention does not have to be practiced with these specific details. In other instances, well-known circuits, software, or methods have not been specifically described to avoid obscuring the present invention.

[0029] Throughout the specification, the reference to "an embodiment", "embodiments", "an example" or "examples" means that the specific features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment of the present invention. Thus, the phrases "in an embodiment", "in embodiments", "an example" or "examples" appearing throughout the specification do not necessarily all refer to the same embodiment or example. In addition, the specific features, structures, or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. Moreover, those of ordinary skill in the art should understand that the diagrams provided herein are for illustrative purposes only and the diagrams are not necessarily drawn to scale.

[0030] Please refer to Figure 1 , an embodiment of the present invention shows a resonant structure, including a metal ring 11, and an opening is provided on the metal ring 11; wherein, the shape of the metal ring 11 can be selected according to actual detection needs; in one embodiment, the metal ring 11 can be a metal circular ring; in another embodiment, the metal ring 11 can also be a metal elliptical ring.

[0031] The resonant structure further includes a first metal stub 12 and a second metal stub 13, the first metal stub 12 and the second metal stub 13 are respectively arranged on the metal ring 11 and are located at both ends of the opening; in one embodiment, the first metal stub 12 and the second metal stub 13 can adopt a columnar design, and the first metal stub 12 and the second metal stub 13 are arranged parallel to each other. Further, part of the first metal stub 12 and all of the second metal stub 13 are located inside the metal ring 11; the first metal stub 12 further includes the remaining part located outside the metal ring 11.

[0032] Please refer toFigure 2 , in an alternative embodiment of the present invention, the radius R of the designed resonant structure is 2.2 mm. Compared with the prior art, the working frequency of the resonant structure shown in this embodiment is reduced by 39% compared with the traditional CSRR structure with the same radius.

[0033] Please refer to Figures 3 to 5 , an embodiment of the present invention shows a metal non-destructive testing sensor, including a reference ground 1. The reference ground 1 includes a resonant structure, which is as described in the related embodiments of the resonant structure of the present invention. For the sake of brevity, it will not be elaborated here. Further, the reference ground 1 can be a metal reference ground, and the metal reference ground includes an intermediate region and other regions, and the resonant structure is arranged in the intermediate region. The metal non-destructive testing sensor 5 further includes a dielectric substrate 2, and the dielectric substrate 2 is arranged on the reference ground 1; wherein, the dielectric substrate 2 can adopt existing materials, and its shape and size can match the metal reference ground 1. The metal non-destructive testing sensor 5 further includes a microstrip line 3, and the microstrip line 3 is arranged on the dielectric substrate 2, and the microstrip line 3 extends along the axial direction of the dielectric substrate 2; further, the microstrip line 3 can adopt a two-port microstrip line 3. Please refer to Figure 6 , in an alternative embodiment, the dielectric substrate 2 can adopt an FR4 board.

[0034] In an alternative embodiment, the metal non-destructive testing sensor 5 designed by the present invention is composed of a reference ground 1 etched with a resonant structure, a dielectric substrate 2 and a microstrip line 3; in an alternative embodiment, the resonant structure on the reference ground 1 can be engraved by a laser engraving machine, and the microstrip line 3 is a 50-ohm microstrip line 3. The width of the microstrip line 3 is related to the thickness and dielectric constant of the dielectric substrate 2. The present invention can refer to the approximate formula of a zero-thickness microstrip line 3:

[0035] When

[0036]

[0037]

[0038] When

[0039]

[0040]

[0041] Among them, ε r is the dielectric constant of the dielectric substrate 2, h is the thickness of the dielectric substrate 2, W is the width of the microstrip line 3, Z0 is the characteristic impedance of the microstrip line 3, and ε reis the effective dielectric constant. Within ε r <16, the accuracy of the above formula is 1%.

[0042] As Figure 7 shown, in an alternative embodiment, the performance of the metal non-destructive testing sensor formed by the novel resonant structure designed by the present invention for crack width detection is evaluated through simulation by the three-dimensional electromagnetic simulation software CST. The crack depth is maintained at 1 mm and the length is long enough, taken as 20 mm in this embodiment. The crack width increases from 0 mm to 0.2 mm in steps of 0.01 mm, and the resonant frequency of the metal non-destructive testing sensor keeps decreasing, which is different from the traditional CSRR sensor. When the crack width is 0.01 mm, the frequency shift is 24 MHz. Usually, a frequency shift of 10 MHz is taken as the standard for whether it can be detected. Therefore, it can be concluded that the metal non-destructive testing sensor 5 can detect sub-millimeter cracks.

[0043] As Figure 8 shown, in an alternative embodiment, the performance of the metal non-destructive testing sensor formed by the novel resonant structure designed by the present invention for crack depth detection is evaluated through simulation by the three-dimensional electromagnetic simulation software CST. The crack width is maintained at 0.2 mm and the length is long enough, taken as 20 mm in this embodiment. The crack depth increases from 0 mm to 3 mm in steps of 0.2 mm, and the detection sensitivity of the metal non-destructive testing sensor to the crack depth decreases as the depth increases.

[0044] In summary, the novel resonant structure designed by the present invention is applied to the metal non-destructive testing sensor, and cracks in any direction, length, width, and depth on the metal surface can mainly disturb the equivalent inductance of the sensor, that is, all will disturb the decrease of the resonant frequency of the sensor, solving the problem of missed detection of the traditional CSRR sensor. In addition, the present invention has a lower operating frequency than the traditional CSRR structure of the same size and has the advantage of miniaturization.

[0045] Please refer to Figure 9 , an embodiment of the present invention shows a metal non-destructive testing system, including: a metal 8 to be tested; a metal non-destructive testing sensor 5, the metal non-destructive testing sensor 5 is arranged on the metal 8 to be tested, and the metal non-destructive testing sensor 5 is used to detect a defect 7 of the metal 8 to be tested and generate a resonant frequency; the metal non-destructive testing sensor 5 is as described in the embodiment of the relevant metal non-destructive testing sensor 5 of the present invention; a vector network analyzer, the vector network analyzer is communicatively connected to the metal non-destructive testing sensor 5, and the vector network analyzer is used to receive the resonant frequency signal generated by the metal non-destructive testing sensor 5.

[0046] In an alternative embodiment, the metal nondestructive testing system further includes: a protective coating 6 coated on the surface of the metal 8 to be tested. Among them, the material of the protective coating 6 can be selected as polytetrafluoroethylene. In another one or some embodiments, the protective coating 6 can also be selected from other materials, which will not be listed one by one here.

[0047] In an alternative embodiment, the metal nondestructive testing system further includes an SMA connector 4. The SMA connector 4 may further include a first SMA connector and a second SMA connector, and the first SMA connector and the second SMA connector are respectively welded to both ends of the microstrip line 3; the metal nondestructive testing sensor 5 is communicatively connected to the vector network analyzer through the first SMA connector and the second SMA connector.

[0048] Please refer to Figure 10 , in a specific embodiment, the metal 8 to be tested can be an aluminum plate with a thickness of 5 mm, and a polytetrafluoroethylene film with a thickness of 0.1 mm is coated on the aluminum plate; then the metal nondestructive testing sensor 5 is placed on the aluminum plate, and detection can be carried out by scanning; finally, the simulated value of the resonant frequency of the metal nondestructive testing sensor 5 designed by the present invention is 3.9915 GHz.

[0049] Please refer to Figure 11 , a metal nondestructive testing method, characterized by comprising the following steps:

[0050] S1. Provide the metal to be tested;

[0051] S2. Coat a protective coating on the surface of the metal to be tested;

[0052] S3. A metal nondestructive testing sensor is provided. The metal nondestructive testing sensor is disposed on the metal to be tested, and the metal nondestructive testing sensor is used to detect defects of the metal to be tested and generate a resonant frequency;

[0053] S4. Provide a vector network analyzer. The vector network analyzer is communicatively connected to the metal nondestructive testing sensor, and the vector network analyzer is used to receive the resonant frequency signal generated by the metal nondestructive testing sensor.

[0054] It should be noted that the specific composition of components such as the metal nondestructive testing sensor involved in this embodiment, as well as descriptions of beneficial effects, etc. can refer to the foregoing embodiments of the present invention. For the sake of brevity in writing, they will not be repeated here. In addition, the detection and analysis of surface defects of the metal to be tested by using a vector network analyzer according to the resonant frequency signal can refer to the prior art. Since the relevant steps of the detection and analysis are not the core inventive points of the present invention, they are not recorded in the text of this application.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention, and they should all be covered within the scope of the claims and the description of the present invention.

Claims

1. A metal non-destructive testing sensor, characterized in that Comprising: A reference ground, the reference ground comprising a resonant structure; A dielectric substrate, the dielectric substrate being disposed on the reference ground; A microstrip line, the microstrip line being disposed on the dielectric substrate and extending along the axial direction of the dielectric substrate; The reference ground is a metal reference ground, the metal reference ground comprising an intermediate region and other regions, and the resonant structure is disposed within the intermediate region; Wherein, the resonant structure comprises: A metal ring, the metal ring being provided with an opening; A first metal branch and a second metal branch, the first metal branch and the second metal branch being respectively disposed on the metal ring and located at both ends of the opening, the first metal branch and the second metal branch being designed in a columnar shape and being parallel to each other at both ends of the opening; Portions of the first metal branch and the second metal branch are located inside the metal ring; The first metal branch further comprises the remaining portion located outside the metal ring; The remaining portion extends in a direction away from the metal ring; The metal ring comprises a metal circular ring or a metal elliptical ring.

2. A metal non-destructive testing system, characterized in that, Comprising: A metal to be measured; A metal non-destructive testing sensor, the metal non-destructive testing sensor being disposed on the metal to be measured, and the metal non-destructive testing sensor being used to detect defects of the metal to be measured and generate a resonant frequency; A vector network analyzer, the vector network analyzer being used to receive the resonant frequency generated by the metal non-destructive testing sensor; The metal non-destructive testing sensor is as described in claim 1; A protective coating, the protective coating being coated on the surface of the metal to be measured; A first SMA connector and a second SMA connector, the first SMA connector and the second SMA connector being respectively welded to both ends of the microstrip line; The metal non-destructive testing sensor is communicatively connected to the vector network analyzer through the first SMA connector and the second SMA connector.

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