Microwave non-contact feed metal device strain detection sensor

Abstract

This invention discloses a microwave non-contact fed strain detection sensor for metal devices, comprising a vector network analyzer and a waveguide antenna connected thereto; a metamaterial array is arranged at a relative position to the waveguide antenna, and a feeding network is arranged on the side of the metamaterial array away from the waveguide antenna; the feeding network receives signals from the metamaterial array and outputs the signals to an interdigital strain sensing probe; the metal device under test is arranged on the side of the interdigital strain sensing probe away from the feeding network; the metamaterial array includes a dielectric substrate and radiating elements arranged in a periodic array on the surface of the dielectric substrate; the radiating elements are circular ring structures with a single opening, and the opening directions of the radiating elements are consistent; this invention has a simple structure, high electromagnetic signal capture efficiency, and an output shaft with an open structure, which can improve the output efficiency by 9.8% compared with traditional feeding networks; the interdigital capacitors provided have a more compact structure, lower profile, and stronger resonance characteristics.

Description

Technical Field

[0001] This invention relates to the field of strain detection sensor technology, and specifically to a microwave non-contact fed metal device strain detection sensor. Background Technology

[0002] Since their discovery by humankind, metals have evolved alongside human civilization in various forms. Several industrial revolutions ushered in an era of large-scale machinery and industrial equipment. Therefore, energy transportation, chemical production, and industrial product smelting all rely heavily on metal equipment. However, metal industrial products have permeated every sector of human industrial civilization. While serving as oil pipelines to facilitate the high-speed transport of hot gases, they also carry the risk of deformation and rupture, potentially leading to major disasters. Similarly, gas pipelines, while also enabling the high-speed transport of hot gases, also face the risk of deformation and rupture, potentially causing major accidents. Furthermore, as components for transporting raw materials in chemical reactions, facilitating reaction processes, they also pose the risk of deformation and rupture resulting in significant accidents. Therefore, monitoring the operational status of large-scale metal industrial equipment is crucial and of immense value.

[0003] Metal industrial equipment, especially various metal industrial pipeline systems, is often subjected to destructive tensile, tensile cracking, buckling, and bending failures due to external environmental forces and changes in the state of the transported coal. Both domestic and international regulations impose strict requirements on the tensile cracking, local buckling, and bending deformations that industrial metal pipeline systems may face. Therefore, various types of strain gauges have been proposed to monitor the strain state of various industrial equipment, including metal pipelines, enabling real-time assessment of their condition. However, while these strain gauges can effectively detect the working deformation of industrial equipment, they suffer from the drawback of requiring physical connections between the gauges and analytical equipment. Whether it's oil and gas pipelines, chemical reactors, or high-temperature, high-pressure gas pipelines in thermal power generation systems, the operating environments are extremely complex and demanding. Therefore, establishing complex connection networks between testing equipment in deeply buried or overhead pipelines is clearly impractical.

[0004] Microwaves, as electromagnetic waves with wavelengths between 0.1 mm and 1 m, have been used as information carriers in the communications industry, such as microwave satellite communications, analog microwave communications, and digital microwave communications. With the increasing application of microwave technology, microwaves are also beginning to be used in non-destructive testing (NDT). In microwave NDT, microwaves are used as the information transmission medium to perform non-destructive testing on the object under test to understand whether there are defects or other structural problems in its internal structure. For this purpose, microwave testing sensors with NDT capabilities have been proposed. These microwave NDT sensors are typically excited by coaxial lines, microstrip lines, or dual antennas. Therefore, it should also be noted that existing testing sensors based on microwave NDT technology still have shortcomings, such as the need for a physical connection between the sensor and the analysis equipment, or the overly complex system caused by bilinear excitation and reception. Summary of the Invention

[0005] This invention provides a microwave non-contact fed strain detection sensor for metal devices, addressing the problems existing in the prior art.

[0006] The technical solution adopted in this invention is:

[0007] A microwave non-contact fed strain detection sensor for metal devices includes a vector network analyzer and a waveguide antenna connected thereto; a metamaterial array is arranged at a relative position to the waveguide antenna, and a feeding network is arranged on the side of the metamaterial array away from the waveguide antenna; the feeding network receives the signal from the metamaterial array and outputs the signal to an interdigital strain sensing probe; the metal device under test is arranged on the side of the interdigital strain sensing probe away from the feeding network;

[0008] The metamaterial array includes a dielectric substrate and radiating elements arranged in a periodic array on the surface of the dielectric substrate; the radiating elements are circular ring structures with a single opening, and the openings of the radiating elements are aligned.

[0009] Furthermore, the power supply network includes a substrate, and the surface of the substrate near the metamaterial array is provided with through holes corresponding to the radiating units; the radiating units are connected to first metal shafts, which pass through the through holes; the first metal shafts are interconnected by wires and are all connected to a coaxial output connector with an open structure grounded on the substrate.

[0010] Furthermore, an interdigital capacitor is disposed on the surface of the interdigital strain sensing probe near the feed network; the interdigital capacitor includes a first resonant ring and a second resonant ring with a semi-circular structure arranged opposite each other; the first and second resonant rings have the same radius and coincident centers; two openings are formed between the first and second resonant rings; N metal strips extending toward one side of the second resonant ring are disposed inside the first resonant ring; M metal strips extending toward one side of the first resonant ring are disposed inside the second resonant ring; the metal strips are parallel to each other; a metal shaft is disposed at the center of the first and second resonant rings; the metal shaft passes through the interdigital strain sensing probe and extends to the other side.

[0011] Furthermore, the interdigital strain sensing probe comprises, in sequence, a first probe section, a second probe section, and a third probe section, all of which are cylindrical; the first probe section, the second probe section, and the third probe section are coaxially arranged, and their radii increase sequentially.

[0012] The outer surface of the second and first probe sections is made of metal, and the interior is made of polytetrafluoroethylene; the third probe section is made of glass fiber epoxy resin copper-clad laminate.

[0013] Furthermore, a metal grounding panel is provided around the interdigital strain sensing probe.

[0014] The beneficial effects of this invention are:

[0015] (1) The present invention has a simple structure and high electromagnetic signal capture efficiency. The metamaterial array structure is set up. The analysis results show that the microwave signal metamaterial receiving array has a capture efficiency of more than 90% for incident electromagnetic signals operating at the target frequency (10GHz).

[0016] (2) The present invention is provided with an output shaft with an open structure, which can improve the output efficiency by 9.8% compared with the traditional power supply network;

[0017] (3) The interdigital capacitor in this invention has a more compact structure, a lower profile, and stronger resonance characteristics; and this interdigital capacitor structure can achieve high-precision near-field resonance detection.

[0018] (4) The metal grounding panel in this invention can further improve the concentration of the resonant field and improve the detection accuracy of the detection probe; making the cavity characteristics of the detection probe more obvious and the field distribution of the detection probe significantly enhanced. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the device structure of the present invention.

[0020] Figure 2 This is a schematic diagram of the metamaterial array (a) and the power supply network (b) in this invention.

[0021] Figure 3 This is a schematic diagram of the output efficiency curves of a coaxial output connector and a conventional grounding post structure for a power supply network using the power supply network of this invention.

[0022] Figure 4 The diagram shows the structure of the interdigital strain sensing probe in this invention. a is a cross-sectional view, b is a schematic diagram of the interdigital capacitor structure, c is a front view, and d is a probe field distribution diagram.

[0023] Figure 5 This is a schematic diagram of the working characteristic curve of the cross-finger strain sensing probe in this invention.

[0024] Figure 6 This is a schematic diagram of the detection results when the cross-section of a metal device is in a planar state using the sensor of the present invention.

[0025] Figure 7 This is a schematic diagram showing the results of strain detection on different curved surfaces of a metal device using the sensor of this invention.

[0026] In the figure: 1-Vector network analyzer, 2-Waveguide antenna, 3-Metamaterial array, 301-Dielectric substrate, 302-Radiating element, 4-Feed network, 401-Substrate, 402-Through hole, 403-Wire, 404-Coaxial output connector, 5-Interdigital strain sensor probe, 501-First probe section, 502-Second probe, 503-Third probe section, 504-Metal shaft, 505-First resonant ring, 506-Second resonant ring, 507-Metal strip. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] like Figure 1 As shown, a microwave non-contact fed metal device strain detection sensor includes a vector network analyzer 1 and a waveguide antenna 2 connected thereto; a metamaterial array 3 is arranged at a relative position to the waveguide antenna 2, and a feeding network 4 is arranged on the side of the metamaterial array away from the waveguide antenna 2; the feeding network 4 receives the signal from the metamaterial array 3 and outputs the signal to the interdigital strain sensing probe 5; the metal device under test is arranged on the side of the interdigital strain sensing probe 5 away from the feeding network 4.

[0029] The microwave radio frequency signal generated by the vector network analyzer 1 and excited by the rectangular waveguide antenna 2 is first received by the metamaterial array 3. It is then output to the interdigital strain sensing probe 5 through the back-end feed network 4, realizing non-contact feeding of the detection probe.

[0030] The change in distance between the metal device under test and the interdigital strain sensing probe 5 due to the strain of the device causes a change in the parallel capacitance value of the detection probe, which in turn causes a shift in the resonant frequency of the interdigital probe, thereby changing the equivalent output impedance. This alters the electromagnetic radiation characteristics of the metamaterial array 3, which is ultimately received by the rectangular waveguide antenna 2 and reflected in the vector network analyzer 1.

[0031] like Figure 2 As shown, the metamaterial array 3 includes a dielectric substrate 301 and radiating elements 302 periodically arranged on the surface of the dielectric substrate 301. Each radiating element 302 is a ring structure with a single opening, and the openings of the radiating elements 302 are aligned. During the actual microwave signal capture process of the metamaterial, the symmetrical branches of the open ring provide the equivalent inductance required for resonance, and the gaps in the ring opening provide the equivalent capacitance required for resonance. Simultaneously, due to the asymmetrical opening structure of the ring, the activation sensitivity of the metamaterial is greatly increased (the received microwave signal is a γ-polarized electromagnetic wave). Therefore, the microwave capture signal from the metamaterial will only target the transmitting and receiving antennas of the system, avoiding the capture of other interfering signals.

[0032] like Figure 2 As shown in Figure b, the feed network 4 includes a substrate 401. The surface of the substrate 401 near the metamaterial array 3 has through-holes 402 corresponding to the radiating units 302. Each radiating unit 302 is connected to a first metal shaft passing through the through-holes 402. The first metal shafts are interconnected via wires 403, all connected to an open-structure coaxial output connector 404 grounded on the substrate 401. This structure connects to the radiating units 302 in the metamaterial array 3 through metallized grounding through-holes, where each small circular hole in the feed network corresponds to a surface radiating unit 302. This enables the output of electromagnetic signals captured by the metamaterial array 3. To achieve higher microwave signal output efficiency, the coaxial output connector 404 is designed with an open structure, indicating that this structure improves output efficiency by nearly 10% compared to a typical single grounding post structure. Test results are as follows... Figure 3 As shown, curve A represents the structure of this invention, and curve B represents the traditional single grounding post structure. It can be seen from the figure that, compared to a typical single grounding post structure, the coaxial output connector 404 with its open design improves output efficiency by nearly 10%.

[0033] like Figure 3As shown, an interdigital strain sensor 5 has an interdigital capacitor on its surface near the feed network 4. The interdigital capacitor includes a first resonant ring 505 and a second resonant ring 506 arranged opposite each other. The first resonant ring 505 and the second resonant ring 506 have the same radius and coincident centers. Two openings are formed between the first resonant ring 505 and the second resonant ring 506. N metal strips 506 extending toward the second resonant ring 506 are arranged inside the first resonant ring 505. M metal strips 506 extending toward the first resonant ring 505 are arranged inside the second resonant ring 506. The metal strips 506 are parallel to each other. A metal shaft 504 is arranged at the center of the first resonant ring 505 and the second resonant ring 506. The metal shaft 504 passes through the interdigital strain sensor 5 and extends to the other side.

[0034] The interdigitated strain sensing probe 5 includes a first probe section 501, a second probe section 502, and a third probe section 503, all of which are cylindrical; the first probe section 501, the second probe section 502, and the third probe section 503 are coaxially arranged, and their radii increase sequentially.

[0035] The outer surface of the second probe section 502 and the first probe section 501 is made of metal, and the interior is made of polytetrafluoroethylene; the third probe section 503 is made of glass fiber epoxy resin copper-clad laminate. A metal grounding panel is provided around the interdigital strain sensing probe 5.

[0036] The interdigital capacitor of this invention has a circular structure. While maintaining the multi-resonance characteristics, it achieves a more compact structure by compressing different metal strips 507 in varying proportions, based on the equivalent inductance and capacitance required for resonance between the interdigital fingers. To further concentrate and enhance the distribution of the resonant field, a metal grounding panel is designed around the probe, forming a reflective cavity. This ensures that, in the resonant state, the field distribution is primarily concentrated in the detection area on the upper surface, thereby giving the detector higher detection sensitivity. Figure 4 As can be seen from d, the field distribution simulation of the resonant detector in the resonant state shows that the field of the resonant detector is concentrated on the upper surface of the detector, and the field distribution is concentrated and enhanced.

[0037] Figure 5 The working characteristic curve of the resonant detection probe shows that the resonator retains the multi-resonance characteristics of the traditional interdigital capacitor. Due to the structure of the interdigital capacitor, the detector has a stronger resonance characteristic at the target frequency of 10GHz (S11 is close to -40dB). In addition, other resonance peaks provide possibilities for further applications of the resonator.

[0038] Figure 6This figure shows the detection results of the metal device under test when its cross-section is planar. The metamaterial array 3 has radiating elements arranged in a 4×4 periodic pattern, and the distance between the waveguide antenna and the metamaterial array is 60 mm. As can be seen from the figure, when the surface of the metal device under test is close to the resonant detection probe, the resonance characteristic of the probe at 10 GHz decreases sharply, causing the intensity of the reflected electromagnetic wave from the metamaterial array 3 to reach its maximum. At this point, the antenna receives the strongest echo signal and has the largest reflection coefficient. At this time, S11 = -21 dB. As the surface of the metal device moves further away from the resonant detection probe, the resonance degree of the probe at 10 GHz increases accordingly, causing the intensity of the reflected electromagnetic wave from the metamaterial array to gradually decrease. Therefore, the echo signal received by the antenna weakens accordingly, and its reflection coefficient gradually decreases. It can be seen that the sensor has reliable strain detection capability within the equivalent strain range of metal devices from 0 mm to 2.0 mm, with a detection accuracy of 500 μm.

[0039] The radiation characteristics of the rectangular waveguide antenna are as follows: 1) -20dB (corresponding to a strain displacement of 2000μm in the metal device); 2) -22.52dB (corresponding to a strain displacement of 1500μm in the metal device); 3) -24.40dB (corresponding to a strain displacement of 1000μm in the metal device); 4) -26.41dB (corresponding to a strain displacement of 500μm in the metal device); 5) -29.42dB (corresponding to a strain displacement of 0μm in the metal device).

[0040] Considering that metal devices may have curved cross-sections, such as Figure 7 As shown in the above results, it can be demonstrated that due to the small cross-section of the sensor probe (12mm × 12mm), the sensor possesses excellent performance in detecting curved surface strain. The analysis and test results are as follows: Figure 7 As shown, the sensor's minimum equivalent surface radius is 30 mm. Based on strain detection, combined with the strain parameters of the metal device / system under test, information on strain abrupt changes in the device can be further obtained, thus providing guidance for the operational status and safety early warning of the metal device / system. The sensor's excellent surface strain detection performance can be observed.

[0041] This invention, a metamaterial microwave signal receiving array, overcomes the challenge of contact-based feeding required by traditional microwave detection probes. A single microwave RF antenna further reduces the system complexity of non-contact feeding non-destructive testing using dual antennas. Non-contact feeding makes the sensor's application scenarios more flexible and significantly enhances its environmental adaptability. The sensor has a small overall size (maximum cross-sectional dimensions of 40mm × 40mm), excellent curved surface detection performance, and a minimum detectable radius of 30mm. It can be fabricated using high-temperature resistant materials, enabling applications such as strain condition monitoring of industrial metal equipment under extremely harsh conditions.

[0042] Furthermore, this invention features a simple structure and high capture efficiency; the microwave signal metamaterial receiving array achieves a capture efficiency exceeding 90% for incident electromagnetic signals operating at the target frequency (10GHz). By incorporating a coaxial output connector 404 with an open structure, the output efficiency can be improved by 9.8%. The interdigital capacitor structure enables high-precision near-field resonance detection, and is more compact, has a lower profile, and exhibits stronger resonance characteristics. To improve the concentration of the resonant field and enhance the detection accuracy of the probe, a metal ground plane is placed around the substrate, making the cavity characteristics of the probe more pronounced. By loading a reflection enhancement panel, the field distribution of the probe is significantly enhanced.

Claims

1. A microwave-powered non-contact strain detection sensor for metal devices, characterized in that, Includes a vector network analyzer (1) and a waveguide antenna (2) connected to it; a metamaterial array (3) is set at a relative position to the waveguide antenna (2), and a feed network (4) is set on the side of the metamaterial array away from the waveguide antenna (2); the feed network (4) receives the signal from the metamaterial array (3) and outputs the signal to the interdigital strain sensing probe (5); the interdigital strain sensing probe (5) is set on the side away from the feed network (4) with the metal device under test; The metamaterial array (3) includes a dielectric substrate (301) and radiating units (302) arranged in a periodic array on the surface of the dielectric substrate (301); the radiating unit (302) is a ring structure with a single opening, and the opening directions of the radiating units (302) are consistent. The interdigitated strain sensor (5) has an interdigitated capacitor on the surface of the side closest to the power supply network (4); The interdigital capacitor includes a first resonant ring (505) and a second resonant ring (506) arranged opposite to each other; the first resonant ring (505) and the second resonant ring (506) have the same radius and coincide their centers; two openings are formed between the first resonant ring (505) and the second resonant ring (506); N metal strips (507) extending toward one side of the second resonant ring (506) are arranged inside the first resonant ring (505); M metal strips (507) extending toward one side of the first resonant ring (505) are arranged inside the second resonant ring (506); the metal strips (507) are parallel to each other; a metal shaft (504) is arranged at the center of the first resonant ring (505) and the second resonant ring (506); the metal shaft (504) passes through the interdigital strain sensing probe (5) and extends to the other side. The interdigitated strain sensing probe (5) includes a first probe section (501), a second probe section (502), and a third probe section (503), all of which are cylindrical; the first probe section (501), the second probe section (502), and the third probe section (503) are coaxially arranged, and their radii increase sequentially. The outer surface of the second probe part (502) and the first probe part (501) is a metal layer, and the interior is made of polytetrafluoroethylene; the third probe part (503) is made of glass fiber epoxy resin copper clad laminate.

2. The microwave non-contact fed strain detection sensor for metal devices according to claim 1, characterized in that, The power supply network (4) includes a substrate (401). The surface of the substrate (401) near the metamaterial array (3) is provided with through holes (402) corresponding to the radiating units (302). The radiating units (302) are connected to a first metal shaft, which passes through the through holes (402). The first metal shafts are interconnected by wires (403) and are all connected to a coaxial output connector (404) with an open structure grounded on the substrate (401).

3. The microwave non-contact fed strain detection sensor for metal devices according to claim 1, characterized in that, The cross-finger strain sensing probe (5) is surrounded by a metal grounding panel.

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