A metal crack detection device and method based on a slow-wave structure of split-ring resonators

Abstract

The present application relates to a metal crack detection device and method based on an open resonator slow-wave structure. The device includes a dielectric substrate, a microstrip transmission line, and a resonant unit group. The resonant unit group includes a plurality of resonant units periodically interwoven and distributed on both sides of the central axis of the dielectric substrate. The resonant unit group is used to excite its own resonance in a coupling manner through the plurality of resonant units and generate a uniform magnetic field of a slow-wave structure to generate a passband. The metal crack detection device uses a plurality of resonant units periodically interwoven and distributed on both sides of the central axis of the dielectric substrate to achieve the ability to adjust the coverage area of the metal crack detection device to meet demand and to detect metal cracks in a larger range. During the electromagnetic wave transmission process, the individual resonant units in the resonant unit group are excited by magnetic field coupling to generate a slow-wave structure and a relatively uniform magnetic field. This makes the metal crack detection device insensitive to the location of the metal crack in metal crack detection applications and has a high sensitivity.

Description

Technical Field

[0001] The present application relates to the technical field of metal crack detection, and in particular to a metal crack detection device and method based on an open resonator slow-wave structure. Background Art

[0002] Metal materials are widely used in infrastructure today, such as railways, pipelines, and spacecraft. However, these structures are often exposed to outdoor environments and operate for long periods of time. Due to the effects of extreme weather and stress-induced metal fatigue, cracks inevitably develop on the metal surface, leading to overall structural failure. Failure to promptly detect and repair these cracks could result in serious safety incidents or significant economic losses. Therefore, health monitoring of these metal structures is essential.

[0003] Currently, the more widely used non-destructive detection methods for metal cracks include ultrasonic testing, eddy current testing, magnetic particle testing and other technologies. However, these non-destructive testing methods all have problems such as complex wiring installation, high maintenance costs, and the equipment is not easy to carry. Resonant electromagnetic sensors have the characteristics of small size, light weight, and easy engineering installation and deployment. In addition, the current PCB process is relatively mature, which can reduce the overall maintenance cost to a certain extent. The resonant electromagnetic sensor is deployed on the metal surface, and the resonant frequency of the sensor can be obtained through the detection equipment. When a crack appears on the metal, the resonant frequency of the sensor will shift, and the size of the metal crack is characterized by the shift in the resonant frequency.

[0004] The resonant electromagnetic sensors currently used for metal crack detection have a small coverage area and a relatively limited range of detectable metal cracks. When detecting large-area metal cracks, multiple scanning tests or the deployment of multiple resonant electromagnetic sensors are required, and the detection sensitivity is low. Summary of the Invention

[0005] The embodiments of the present application provide a metal crack detection device and method based on an open resonator slow-wave structure, which is used to solve the technical problems that existing metal crack detection devices usually need to deploy multiple sensors or multiple scanning detections when detecting within a large area, and the metal crack detection devices have low detection sensitivity.

[0006] In order to achieve the above objectives, the embodiments of the present application provide the following technical solutions:

[0007] A metal crack detection device based on an open resonator slow-wave structure includes a dielectric substrate, a microstrip transmission line, and a resonant unit group arranged on the dielectric substrate. The input end of the resonant unit group is arranged between a first microstrip transmission line and a second microstrip transmission line. The resonant unit group includes a plurality of resonant units periodically interwoven and distributed on both sides of the central axis of the dielectric substrate. The first microstrip transmission line is used to transmit energy excited by the resonant units adjacent to the first microstrip transmission line through coupling, and the second microstrip transmission line is used to receive and transmit energy output by the resonant units adjacent to the second microstrip transmission line through coupling. The resonant unit group is used to excite self-resonance through coupling of the plurality of resonant units and generate a uniform magnetic field of the slow-wave structure to generate a passband.

[0008] Preferably, the resonance unit comprises a resonant ring in the form of a microstrip opening.

[0009] Preferably, the resonant ring is an annular component consisting of a continuous thick edge and a thin edge in the form of a microstrip opening.

[0010] Preferably, the plurality of resonant units on both sides of the central axis of the dielectric substrate are periodically and equidistantly interwoven.

[0011] Preferably, the plurality of resonant units on both sides of the central axis of the dielectric substrate are distributed in a periodic and non-equidistant interlaced manner.

[0012] Preferably, the microstrip openings of the resonance units on both sides of the central axis of the dielectric substrate are arranged opposite to each other.

[0013] The present application also provides a metal crack detection method based on an open resonator slow-wave structure, which is applied to the above-mentioned metal crack detection device based on an open resonator slow-wave structure, also referred to as a metal crack detection device. The metal crack detection method includes the following steps:

[0014] Placing a metal crack detection device on a metal sample to be tested, and connecting the metal crack detection device to a network analyzer, wherein the network analyzer is respectively connected to a first microstrip transmission line and a second microstrip transmission line of the metal crack detection device through cables;

[0015] Obtaining, by means of the network analyzer and the metal crack detection device, the passband data of the metal sample to be tested in a cracked state and the passband threshold of the metal sample to be tested in a healthy state under the same characteristic frequency band conditions;

[0016] Comparing the passband data with the passband threshold to obtain a frequency change of the metal sample to be tested;

[0017] The crack size of the metal sample to be tested is determined according to the frequency variation.

[0018] Preferably, before obtaining the passband data of the metal sample to be tested in a cracked state and the passband threshold of the metal sample to be tested in a healthy state under the same characteristic frequency band conditions through the network analyzer and the metal crack detection device, the metal crack detection method includes: the first microstrip transmission line of the metal crack detection device is connected to the energy output end of the network analyzer through a cable, and the second microstrip transmission line of the metal crack detection device is connected to the energy receiving end of the network analyzer through a cable.

[0019] Preferably, the characteristic frequency band is a forward transmission coefficient of a -40dB passband.

[0020] Preferably, comparing the passband data with the passband threshold to obtain the frequency variation of the metal sample to be tested includes: the frequency variation is the difference between the passband data and the passband threshold.

[0021] It can be seen from the above technical solution that the embodiments of the present application have the following advantages: the metal crack detection device and method based on the open resonator slow-wave structure, the device includes a dielectric substrate, a microstrip transmission line and a resonance unit group, the resonance unit group is arranged between the first microstrip transmission line and the second microstrip transmission line, the resonance unit group includes several resonance units periodically interwoven and distributed on both sides of the central axis of the dielectric substrate; the first microstrip transmission line is used to transmit energy that excites the resonance unit adjacent to the first microstrip transmission line to excite its own resonance through coupling, the second microstrip transmission line is used to receive and transmit the energy output by the resonance unit adjacent to the second microstrip transmission line through coupling, and the resonance unit group is used to excite its own resonance through a coupling manner through several resonance units and generate a uniform magnetic field of the slow-wave structure to generate a passband. The metal crack detection device based on the open resonator slow-wave structure realizes that the coverage area of the metal crack detection device can be adjusted according to demand by periodically interweaving several resonant units on both sides of the central axis of the dielectric substrate, and can realize metal crack detection over a larger range. During the electromagnetic wave transmission process, each resonant unit in the resonant unit group is excited by magnetic field coupling to generate a slow-wave structure and a relatively uniform magnetic field. As a result, the metal crack detection device is not sensitive to the location of the metal crack in the metal crack detection application and has high sensitivity. This solves the technical problems that existing metal crack detection devices usually need to deploy multiple sensors or multiple scanning tests when detecting over a large area, and the metal crack detection devices have low detection sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1 Schematic diagram of a top view of a metal crack detection device based on an open resonator slow-wave structure according to an embodiment of the present application;

[0024] Figure 2 Schematic diagram of the three-dimensional structure of the metal crack detection device based on the open resonator slow-wave structure according to an embodiment of the present application;

[0025] Figure 3 Schematic diagram of the magnetic field of the resonant unit of the metal crack detection device based on the open resonator slow-wave structure according to an embodiment of the present application;

[0026] Figure 4 This is a flowchart of the steps of the metal crack detection method based on the open resonator slow-wave structure according to an embodiment of the present application;

[0027] Figure 5 This is a passband diagram of the metal crack detection method based on the open resonator slow-wave structure described in an embodiment of the present application;

[0028] Figure 6 This is a diagram showing the frequency variation and crack depth of the metal crack detection method based on the open resonator slow-wave structure described in an embodiment of the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0030] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0032] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this application.

[0033] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0034] Explanation of terms in this application:

[0035] A microwave filter is a two-port network that controls the frequency response of a microwave system by providing signal transmission within the filter's passband and attenuation within the filter's stopband. Typical frequency responses include low-pass, high-pass, band-pass, and band-stop characteristics.

[0036] Slow wave refers to the situation when the propagation constant β of electromagnetic wave is greater than the propagation constant k0 of electromagnetic wave in free space during the propagation process.

[0037] Magnetic field coupling refers to the phenomenon whereby a change in current in one coil induces an electromotive force in an adjacent coil according to Maxwell's equations. These coils are electrically independent of each other, but their mutual influence is linked by a magnetic field.

[0038] Shape perturbation theory refers to the subtle perturbations caused by changing the shape or size of a cavity. For example, changing the cavity shape through an adjustable screw or changing the cavity size through a movable wall, without changing the fundamental characteristics of the system, can cause the resonant frequency of the resonant cavity to shift.

[0039] The embodiments of the present application provide a metal crack detection device and method based on an open resonator slow-wave structure, which is used to solve the technical problems that existing metal crack detection devices usually need to deploy multiple sensors or multiple scanning detections when detecting within a large area, and the metal crack detection devices have low detection sensitivity.

[0040] Example 1:

[0041] Figure 1 Schematic diagram of the top view of the metal crack detection device based on the open resonator slow-wave structure according to the embodiment of the present application, Figure 2 This is a schematic diagram of the three-dimensional structure of a metal crack detection device based on an open resonator slow-wave structure described in an embodiment of the present application.

[0042] like Figure 1 and Figure 2 As shown, an embodiment of the present application provides a metal crack detection device based on an open resonator slow-wave structure, including a dielectric substrate 10 and a microstrip transmission line and a resonant unit group arranged on the dielectric substrate 10. The resonant unit group is arranged between a first microstrip transmission line 21 and a second microstrip transmission line 22. The resonant unit group includes a plurality of resonant units 31 periodically interwoven and distributed on both sides of the central axis of the dielectric substrate 10; the first microstrip transmission line 21 is used to transmit energy of the resonant unit 31 adjacent to the first microstrip transmission line 21 to excite its own resonance through coupling, and the second microstrip transmission line 22 is used to receive and transmit energy output by the resonant unit 31 adjacent to the second microstrip transmission line 22 through coupling. The resonant unit group is used to excite its own resonance through coupling through the plurality of resonant units 31 and generate a uniform magnetic field of the slow-wave structure to generate a passband.

[0043] like Figure 1 and Figure 2 As shown, in the embodiment of the present application, the dielectric substrate 10 is a low-profile substrate made of a flexible material, so that the dielectric substrate 10 is thin, so that the dielectric substrate 10 can better fit the metal sample to be tested and can better adapt to the strain of the metal sample to be tested.

[0044] It should be noted that the metal crack detection device based on the open resonator slow-wave structure adopts a thin and flexible dielectric substrate 10, which can realize the function of conforming the metal crack detection device based on the open resonator slow-wave structure to the metal sample to be tested.

[0045] like Figure 1 and Figure 2 As shown, in the embodiment of the present application, the microstrip transmission line can be used to excite the resonant unit and receive the energy transmitted to the end. The microstrip transmission line is used to connect to the network analyzer. The microstrip transmission line is provided at both ends of the upper surface of the dielectric substrate 10, as shown in FIG. Figure 1As shown, the first microstrip transmission line 21 is arranged at the left end of the upper surface of the dielectric substrate 10, the second microstrip transmission line 22 is arranged at the right end of the upper surface of the dielectric substrate 10, and the resonant unit group is arranged between the first microstrip transmission line 21 and the second microstrip transmission line 22. The resonant unit 31 adjacent to the first microstrip transmission line 21 is non-contact connected and transfers energy through coupling, and the resonant unit 31 adjacent to the second microstrip transmission line 22 is non-contact connected and transfers energy through coupling.

[0046] In the embodiment of the present application, the resonant unit group includes a plurality of resonant units 31 that are periodically interwoven and distributed on both sides of the central axis of the dielectric substrate 10. The resonant units 31 are resonant rings with microstrip openings.

[0047] It should be noted that if Figure 1 As shown, five resonance units 31 are provided on the resonance unit group, two of the five resonance units 31 are located above the center axis of the dielectric substrate 10 , and three of the five resonance units 31 are located below the center axis of the dielectric substrate 10 .

[0048] In the embodiment of the present application, the resonant unit 31 adopts a microstrip open resonant ring as the resonant unit of the metal crack. In the equivalent circuit, the microstrip open resonant ring can be equivalent to an LC resonant circuit, so that the metal crack detection device based on the open resonator slow-wave structure uses a periodic interleaved distribution to enable the resonant unit 31 to excite the resonant unit 31 adjacent to it through magnetic field coupling while resonating, thereby generating a slow-wave structure and a relatively uniform magnetic field, thereby achieving the high detection sensitivity of the metal crack detection device based on the open resonator slow-wave structure. At the same time, since the resonant units 31 are periodically and equidistantly distributed on both sides of the central axis of the dielectric substrate 10, they can effectively detect metal cracks within the covered range, and the number of interleaved resonant units can be changed according to the coverage length requirements of the actual application scenario, with good adjustable characteristics and applicable range.

[0049] Figure 3 This is a schematic diagram of the magnetic field of the resonant unit of the metal crack detection device based on the open resonator slow-wave structure described in an embodiment of the present application.

[0050] In the embodiments of this application, Figure 2As shown, the working principle of the metal crack detection device based on the open resonator slow-wave structure is as follows: the energy that excites the metal crack detection device based on the open resonator slow-wave structure is transmitted from the first microstrip transmission line 21, and when it is transmitted to the end of the first microstrip transmission line 21, it excites the first resonant unit 31 adjacent to the first microstrip transmission line 21 through coupling. The resonant unit 31 is a resonant ring structure with a microstrip opening. The resonant unit 31 can be equivalent to a half-wavelength resonator. The resonant frequency of the resonant unit 31 decreases as the total length of the microstrip increases. When the resonant unit 31 resonates, the electric field is mainly concentrated near the opening, and the magnetic field of the resonant unit 31 is mainly concentrated on the opposite side of the opening, as shown in FIG. Figure 3 As shown, the interlaced resonant units 31 are adjacent to each other with the opposite sides of the openings being adjacent sides. The energy coupling between the resonant units 31 is a magnetic coupling model. When the first resonant unit 31 is excited, the resonant unit 31 can simultaneously resonate and excite the adjacent resonant unit 31 by means of magnetic field coupling, and thus excite the next resonant unit. The energy of the last resonant unit in the arrangement is transmitted to the second microstrip transmission line 22 at the other end of the dielectric substrate 10 by means of energy coupling, thereby completing the energy transfer process from the first microstrip transmission line 21 to the resonant unit group and then to the second microstrip transmission line 22.

[0051] It should be noted that when multiple resonant units 31 in a resonant unit group transfer energy through coupling, when two resonant units 31 of the same frequency couple with each other, frequency splitting occurs at that resonant frequency, depending on the coupling strength between the resonant units 31. The greater the coupling strength between the resonant units, the greater the separation between the two frequencies produced by the frequency splitting. Therefore, when multiple resonant units 31 are distributed between the first microstrip transmission line 21 and the second microstrip transmission line 22, multiple resonant frequencies are split, creating a passband on a macro scale. Only within the passband frequency range can electromagnetic waves be transmitted from the first microstrip transmission line 21 on one end of the dielectric substrate 10 to the second microstrip transmission line 22 on the other end of the dielectric substrate 10. When a metal crack perpendicular to the traveling wave propagation direction appears in the area covered by the resonant unit group (also known as the sensing area), according to perturbation theory, the slight perturbation caused by changing the shape or size of the resonant cavity causes the resonant unit to maintain its resonant characteristics without changing its fundamental characteristics, causing the resonant frequency of the resonant unit 31 to shift. Based on perturbation theory, when a metal crack exists in the sensing area, the frequency characteristics of the metal crack detection device will change, thereby determining the presence of a metal crack. The larger the size of the metal crack, the greater the perturbation caused, according to perturbation theory, and the greater the shift in the resonant frequency of the resonant unit 31 compared to a healthy resonant unit 31. Based on the linear relationship between the resonance point shift and the metal crack size, the resonance shift detected by the metal crack detection device based on the open resonator slow-wave structure can estimate the size of the metal crack.

[0052] In an embodiment of the present application, the resonant unit 31 can excite the adjacent resonant unit through magnetic field coupling while resonating, and excite the next resonant unit accordingly, thereby generating a slow-wave structure and a relatively uniform magnetic field. This makes the metal crack detection device based on the open resonator slow-wave structure position-insensitive during the metal crack detection process, that is, the position of the crack has little effect on the frequency characteristics of the generated passband, thereby improving the detection sensitivity of the metal crack detection device based on the open resonator slow-wave structure.

[0053] The present application provides a metal crack detection device based on an open resonator slow-wave structure, comprising a dielectric substrate, a microstrip transmission line, and a resonant unit group, wherein the resonant unit group is arranged between a first microstrip transmission line and a second microstrip transmission line, and the resonant unit group includes a plurality of resonant units periodically interwoven and distributed on both sides of the central axis of the dielectric substrate; the first microstrip transmission line is used to transmit energy of the resonant unit adjacent to the first microstrip transmission line to excite its own resonance through coupling, the second microstrip transmission line is used to receive and transmit energy output by the resonant unit adjacent to the second microstrip transmission line through coupling, and the resonant unit group is used to excite its own resonance through coupling of the plurality of resonant units and generate a uniform magnetic field of the slow-wave structure to generate a passband. The metal crack detection device based on the open resonator slow-wave structure realizes that the coverage area of the metal crack detection device can be adjusted according to demand by periodically interweaving several resonant units on both sides of the central axis of the dielectric substrate, and can realize metal crack detection over a larger range. During the electromagnetic wave transmission process, each resonant unit in the resonant unit group is excited by magnetic field coupling to generate a slow-wave structure and a relatively uniform magnetic field. As a result, the metal crack detection device is not sensitive to the location of the metal crack in the metal crack detection application and has high sensitivity. This solves the technical problems that existing metal crack detection devices usually need to deploy multiple sensors or multiple scanning tests when detecting over a large area, and the metal crack detection devices have low detection sensitivity.

[0054] like Figure 1 and Figure 2 As shown, in the embodiment of the present application, the resonant ring is a ring-shaped component consisting of a continuous thick edge and a thin edge in the form of a microstrip opening.

[0055] It should be noted that the resonant ring is a ring component composed of a continuous thick edge and a thin edge with a microstrip opening, which is mainly used to excite the adjacent resonant units 31 in the resonant unit group by coupling, thereby generating a slow-wave structure and a relatively uniform magnetic field.

[0056] like Figure 1 and Figure 2As shown, in one embodiment of the present application, the plurality of resonant units 31 on both sides of the central axis of the dielectric substrate 10 are periodically and equidistantly interwoven. The plurality of resonant units 31 on both sides of the central axis of the dielectric substrate 10 are periodically and unequally interwoven.

[0057] It should be noted that the plurality of resonant units 31 may be distributed equidistantly or unequally on both sides of the center axis of the dielectric substrate 10 . Both methods can realize the generation of a passband by the resonant unit group.

[0058] like Figure 1 and Figure 2 As shown, in one embodiment of the present application, the microstrip openings of the resonant units on both sides of the central axis of the dielectric substrate 10 are arranged opposite to each other.

[0059] It should be noted that the microstrip openings of the resonant units on both sides of the central axis of the dielectric substrate 10 are arranged opposite to each other mainly to facilitate energy coupling and transmission between the two resonant units.

[0060] Compared to traditional metal crack detection devices, which suffer from small coverage areas, narrow detection ranges, and low detection sensitivity, this metal crack detection device based on an open resonator slow-wave structure uses periodically distributed resonant rings in the form of microstrip openings as resonant units. When a crack appears within the coverage area of the metal crack detection device, the detected passband frequency characteristics shift, and the magnitude of the frequency characteristic shift indicates the size of the metal crack. Furthermore, the number of periodically distributed resonant units in this metal crack detection device based on an open resonator slow-wave structure can be adjusted according to actual needs, resulting in a larger coverage area and the ability to detect metal cracks within a wider range.

[0061] Example 2:

[0062] Figure 4 This is a flowchart of the steps of the metal crack detection method based on the open resonator slow-wave structure described in an embodiment of the present application. Figure 5 : is a passband diagram of the metal crack detection method based on the open resonator slow-wave structure described in an embodiment of the present application, Figure 6 This is a diagram showing the frequency variation and crack depth of the metal crack detection method based on the open resonator slow-wave structure described in an embodiment of the present application.

[0063] like Figure 4 As shown, the present application also provides a metal crack detection method based on an open resonator slow-wave structure, which is applied to the above-mentioned metal crack detection device based on the open resonator slow-wave structure, also called a metal crack detection device, and the metal crack detection method includes the following steps:

[0064] S10. Place the metal crack detection device on the metal sample to be tested, and connect the metal crack detection device to a network analyzer, which is connected to the first microstrip transmission line and the second microstrip transmission line of the metal crack detection device through cables.

[0065] It should be noted that the details of the metal crack detection device based on the open resonator slow-wave structure have been described in Example 1 and will not be further described in this embodiment. In step S10, the metal crack detection device is primarily connected to a network analyzer for communication, so that the network analyzer can obtain passband data of the metal crack detection device detecting the metal sample under test.

[0066] Furthermore, before obtaining the passband data of the metal sample to be tested in a cracked state and the passband threshold of the metal sample to be tested in a healthy state under the same characteristic frequency band conditions through a network analyzer and a metal crack detection device, the metal crack detection method includes: the first microstrip transmission line of the metal crack detection device is connected to the energy output end of the network analyzer through a cable, and the second microstrip transmission line of the metal crack detection device is connected to the energy receiving end of the network analyzer through a cable.

[0067] S20. Obtain the passband data of the metal sample to be tested in a cracked state and the passband threshold of the metal sample to be tested in a healthy state under the same characteristic frequency band conditions through a network analyzer and a metal crack detection device.

[0068] It should be noted that in step S20, the passband of the metal crack detection device when detecting the metal sample to be tested can be obtained from the network analyzer, and a passband diagram (such as Figure 5 The passband diagram is shown in Figure 1 and displayed on a network analyzer. From the passband diagram, the passband data for a cracked metal sample and the passband threshold for a healthy metal sample can be directly obtained under the same characteristic frequency band conditions. A network analyzer is a comprehensive microwave measurement instrument capable of performing sweep measurements across a wide frequency band to determine network parameters. It is also called a microwave network analyzer.

[0069] Furthermore, the characteristic frequency band is a forward transmission coefficient of a -40dB passband.

[0070] It should be noted that this metal crack detection method based on an open resonator slow-wave structure uses a forward transmission coefficient of a 40dB passband as the characteristic bandwidth for obtaining the metal sample to be tested. Within this characteristic bandwidth, the passband threshold of the metal sample to be tested in a healthy state and the passband data of the metal sample to be tested in a cracked state are obtained. By using the high roll-off edge characteristic of the -40dB passband as the forward transmission coefficient, this metal crack detection method based on an open resonator slow-wave structure makes the data obtained by this metal crack detection method based on an open resonator slow-wave structure less affected by the test environment, thereby improving the accuracy of the detection data.

[0071] S30. Compare the passband data with the passband threshold to obtain the frequency change of the metal sample to be tested.

[0072] It should be noted that in step S30, the frequency change of the metal sample to be tested is mainly obtained by subtracting the passband threshold of the healthy state from the detected passband data under the same characteristic frequency band conditions, that is, the frequency change is the difference between the passband data and the passband threshold.

[0073] S40. Determine the crack size of the metal sample to be tested according to the frequency variation.

[0074] It should be noted that if Figure 6 As shown, according to the frequency change from Figure 6 Read the crack size of the metal sample to be tested.

[0075] In the embodiment of the present application, since the cracks on the metal sample to be tested cause changes in the frequency characteristics of the passband, the metal crack detection method based on the open resonator slow-wave structure selects the difference between the right edge and the left edge of the passband where the forward transfer coefficient of the passband is -40dB as the frequency change, and uses this frequency change as the change in the frequency characteristics of the entire passband. For example, Figure 5 The relationship between crack depth and passband bandwidth with error bars for different crack positions (0-10mm) with a step of 2mm and different crack depths (0.5-1mm) with a step of 0.50mm. Figure 5 It can be seen that as the crack depth increases, the passband width also increases. Figure 6 As shown in the figure, when the crack depth changes from the healthy state, that is, the crack depth is 0mm to the crack depth of 1mm, the frequency change changes from the original 840.5Mhz to 882.7Mhz, that is, when the crack depth changes by 1mm, the frequency change widens by 42.7Mhz, and the mean frequency change changes relatively linearly with the crack depth.

[0076] In an embodiment of the present application, the metal crack detection method based on the open resonator slow-wave structure is measured by a metal crack detection device based on the open resonator slow-wave structure using a transmission pole, which has the characteristics of a high roll-off edge, is less affected by the environment, and is easier to measure during the detection process.

[0077] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0078] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0079] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0080] In addition, the functional units in the various embodiments of the present application may be integrated into a single processing unit, or each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0081] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0082] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A metal crack detection device based on an open resonator slow-wave structure, characterized in that: The invention comprises a dielectric substrate, a microstrip transmission line and a resonant unit group arranged on the dielectric substrate, wherein the input end of the resonant unit group is arranged between a first microstrip transmission line and a second microstrip transmission line, and the resonant unit group includes a plurality of resonant units periodically interwoven and distributed on both sides of the central axis of the dielectric substrate; the first microstrip transmission line is used to transmit energy excited by the resonant unit adjacent to the first microstrip transmission line through coupling, and the second microstrip transmission line is used to receive and transmit energy output by the resonant unit adjacent to the second microstrip transmission line through coupling; the resonant unit group is used to excite self-resonance through coupling of the plurality of resonant units and generate a uniform magnetic field of a slow-wave structure to generate a passband; The resonant unit includes a resonant ring in the form of a microstrip opening; the resonant ring is an annular component consisting of a continuous thick edge and a thin edge in the form of a microstrip opening; The excitation energy is transmitted from the first microstrip transmission line. When it is transmitted to the end of the first microstrip transmission line, the first resonant unit adjacent to the first microstrip transmission line is excited by coupling. The first resonant unit can excite the resonant unit adjacent to it by magnetic field coupling while resonating, and thus excite the next resonant unit. The last resonant unit in the arrangement is transmitted to the second microstrip transmission line at the other end of the dielectric substrate by energy coupling, thereby completing the energy transfer process from the first microstrip transmission line to the resonant unit group and then to the second microstrip transmission line.

2. The metal crack detection device based on the open resonator slow-wave structure according to claim 1 is characterized in that: The plurality of resonant units on both sides of the central axis of the dielectric substrate are periodically and equidistantly interwoven and distributed.

3. The metal crack detection device based on the open resonator slow-wave structure according to claim 1 is characterized in that: The plurality of resonant units on both sides of the central axis of the dielectric substrate are distributed in a periodic and non-equidistant interlaced manner.

4. The metal crack detection device based on the open resonator slow-wave structure according to claim 1, characterized in that: The microstrip openings of the resonance units on both sides of the central axis of the dielectric substrate are arranged opposite to each other.

5. A metal crack detection method based on an open resonator slow-wave structure, applied to a metal crack detection device based on an open resonator slow-wave structure as described in any one of claims 1 to 4, also referred to as a metal crack detection device, characterized in that: The metal crack detection method comprises the following steps: Placing a metal crack detection device on a metal sample to be tested, and connecting the metal crack detection device to a network analyzer, wherein the network analyzer is respectively connected to a first microstrip transmission line and a second microstrip transmission line of the metal crack detection device through cables; Obtaining, by means of the network analyzer and the metal crack detection device, the passband data of the metal sample to be tested in a cracked state and the passband threshold of the metal sample to be tested in a healthy state under the same characteristic frequency band conditions; Comparing the passband data with the passband threshold to obtain a frequency change of the metal sample to be tested; The crack size of the metal sample to be tested is determined according to the frequency variation.

6. The metal crack detection method based on the open resonator slow-wave structure according to claim 5, characterized in that: Before obtaining the passband data of the metal sample to be tested in a cracked state and the passband threshold of the metal sample to be tested in a healthy state under the same characteristic frequency band conditions through the network analyzer and the metal crack detection device, the metal crack detection method includes: the first microstrip transmission line of the metal crack detection device is connected to the energy output end of the network analyzer through a cable, and the second microstrip transmission line of the metal crack detection device is connected to the energy receiving end of the network analyzer through a cable.

7. The metal crack detection method based on the open resonator slow-wave structure according to claim 6, characterized in that: The characteristic frequency band is a forward transmission coefficient of a -40dB passband.

8. The metal crack detection method based on the open resonator slow-wave structure according to claim 6, characterized in that: Comparing the passband data with the passband threshold to obtain the frequency change of the metal sample to be tested includes: the frequency change is the difference between the passband data and the passband threshold.

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