CN103344652A - Crack detection sensor based on microstrip antenna and detection method thereof - Google Patents

Abstract

The invention provides a crack detection sensor based on a microstrip antenna and a detection method thereof. The invention is characterized in that the crack detection sensor comprises a dielectric substrate, one surface of the dielectric substrate is provided with a conductor patch through etching, deposition or corrosion, and the other surface of the dielectric substrate is adhered on a to-be-detected structure to form the complete sensor. According to the invention, a relationship between the length and the direction of a crack and resonant frequencies of radiation modes respectively parallel to the length direction and the width direction of the patch of the microstrip antenna can be established, and the length and the direction of the crack can be obtained based on the shifts of the resonant frequencies. The crack detection sensor based on the microstrip antenna provided by the invention has the advantages of a small size, light weight, low profile, capacity of being conformal to a carrier, simple manufacturing, low cost, etc.; moreover, the crack detection sensor employs microwave detection technology, which facilitates wireless detection and signal processing.

Description

A kind of crack detection sensor and its detection method based on microstrip antenna

Technical field

The present invention relates to the detection of structural crack prison and structural health monitoring technology field, and in particular to a kind of crack detection sensor and its detection method based on microstrip antenna, can detect crack length and its direction.

Background technology

The construction of many large complicated engineering structures, such as Large Scale Space Vehicle, super-span bridge, the super large span spatial structure for Large Physical Games, high-rise building, large hydraulic engineering, offshore platform structure and nuclear power station building, their validity period is up to decades, even upper a century, the coupling of the disaster factors such as environmental attack, the long-term effect of material aging and load, fatigue and mutation will inevitably lead to the damage accumulation and degradation resistance of structure and system, so as to trigger catastrophic burst accident in extreme circumstances.In order to ensure the safe and reliable of structure, many in-service civil infrastructures and infrastructure are badly in need of being monitored and being evaluated its safe condition using effective means；Newly-built large scale structure and infrastructure is additionally arranged Long Period Health Monitoring system on the basis of past experience is summarized, with the military service safe condition of monitoring of structures.Structure can not only be ensured by structural healthy monitoring system, the safe operation of equipment, the damage that can effectively reduce the expense of personal monitoring simultaneously and may be brought to structure, economic drain can also be effectively reduced by structural healthy monitoring system rational structural maintenance cycle etc..Monitoring structural health conditions turn into the important research direction in large scale structure equipment safety field.

A variety of relatively effective detection methods have been developed by the exploration of decades as the highly important one side in structural health field in crack detection.Crack detecting method more common at present has the detection methods such as magnetic particle method, osmosis, ultrasonic method, leakage method and eddy-current method.

But all there is obvious defect in these methods.Magnetic particle method, osmosis substantially, take time and effort, cost is larger as contaction measurement method, inherent defect, not enough facilitate convenient；Ultrasonic method application ultrasonic wave transmission information, but acoustic signals deal with loaded down with trivial details, and are easily disturbed by background noise；Leakage method equipment is complicated, detection difficult；Eddy-current method can only largely detect the presence or absence of crackle, it is impossible to obtain the quantitative and qualitative relation such as information such as crackle orientation of various crackles.

The content of the invention

In order to overcome the shortcomings of that above-mentioned prior art is present, it is an object of the invention to provide a kind of crack detection sensor based on microstrip antenna and its detection method, sensor has small volume, lightweight, low section can be conformal with carrier, it is simple to manufacture, the advantage of low cost；Detection method applied microwave detection technique, is easy to radio detection and signal transacting.

Microstrip antenna is on a thin-medium substrate, simultaneously to enclose thin metal layer as earth plate, the metal patch of definite shape is made of methods such as photoetching, corrosion for another side, the antenna constituted using microstrip line or coaxial probe to patch；Rectangular microstrip antenna has two kinds of basic resonance modes：TM of the direction of an electric field parallel to paster antenna length direction₀₁With TM of the direction of an electric field parallel to antenna patch width₁₀, the resonant frequency f of two kinds of radiation modes₀₁And f₁₀It is relevant with the effective current length in place direction, after structure is cracked, crackle electric field propagation path to change to change effective current length, and then resonant frequency drift is produced, along two resonant frequency drift amounts in length and width direction it is that can determine that length and the direction of crackle according to rectangular microstrip antenna.

To achieve the above object, the technical scheme is that：

Conductor patch 1 is provided with a kind of crack detection sensor based on microstrip antenna, including dielectric substrate 2, the one side of dielectric substrate 2, method to set up includes etching, deposition or corroded, and the another side of dielectric substrate 2 invests and complete sensor is constituted on geodesic structure 3.

Described conductor patch 1 uses good conductor, including silver, copper；Dielectric substrate 2 uses insulating materials, including polytetrafluoroethylene (PTFE), polyimides,

Conductor patch 1, dielectric substrate 2 use corresponding material and geomery all in accordance with different resonant frequencies, as shown by the following formula：

${\mathrm{\ϵ}}_e=\frac{\mathrm{\ϵ}+1}{2}+\frac{\mathrm{\ϵ}-1}{2\sqrt{1+10h/w_e}}$

$\mathrm{\Δ}{L}_c=0.412h\frac{({\mathrm{\ϵ}}_e+0.3)(w_e/h+0.264)}{({\mathrm{\ϵ}}_e-0.258)(w_e/h+0.813)}$

$f=\frac{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HDA00003333430500011.png,HDA00003333430500021.png"\; state="\{\{state\}\}">c</figure-callout>}}{2\sqrt{{\mathrm{\&epsiv;}}_e}}\frac{1}{L_e+2\mathrm{\&Delta;}{L}_c}$

Wherein：ε is the dielectric constant of dielectric substrate 2, ε_eFor the effective dielectric constant of dielectric substrate 2, h is the thickness of dielectric substrate 2, w_eFor the electric current width of conductor patch 1, c is the speed of light in a vacuum, L_eIt is effective current length, Δ L_cFor the linear compensation produced due to edge effect, f is antenna resonant frequency, when the sense of current is parallel to 1 length direction of conductor patch（That is radiation mode TM₀₁）Draw resonant frequency f=f₀₁, when the sense of current is parallel to 1 width of conductor patch（That is radiation mode TM₁₀）Draw resonant frequency f=f₁₀。

A kind of detection method of the crack detection sensor based on microstrip antenna, comprises the following steps：

It is attached to Step 1: dielectric substrate on sensor 2 is not provided with into the one side of conductor patch 1 on the tested surface of metal structure 3；

Step 2: the information of crackle by sensor passes to external equipment, obtain the resonant frequency f on sensor length and width₀₁And f₁₀Drift, be expressed as Δ f₀₁With Δ f₁₀；

Step 3: introducing individual parameter R：

Abscissa is obtained for crack length L, ordinate is the R-L curve maps of R values, every has a unique R-L curve to correspond to therewith along the crackle that different directions extend, so, each point on curve thinks corresponding with certain crack length and direction, so as to obtain crack length and directional information according to R-L curves.

Microstrip antenna sensor used of the invention has small volume, and lightweight, low section can be conformal with carrier, is simple to manufacture, low cost and other advantages；And applied microwave detection technique, it is easy to radio detection and signal transacting.

Brief description of the drawings

Fig. 1 is sensor of the invention structural representation.

Fig. 2 is the crackle schematic diagram of embodiment 1.

Fig. 3 is the crackle schematic diagram of embodiment 2.

Fig. 4 is the schematic diagram for studying the crackle of different directions under microstrip antenna paster.

Embodiment

The present invention will be described in more detail below in conjunction with the accompanying drawings.

As shown in Figure 1, conductor patch 1 is provided with a kind of crack detection sensor based on microstrip antenna, including dielectric substrate 2, the one side of dielectric substrate 2, method to set up includes etching, deposition or corroded, and the another side of dielectric substrate 2 invests and complete sensor is constituted on geodesic structure 3.Respective resonant frequency drift can be produced when crackle occurs in metal structure, direction of check and length are detected with this.

Described conductor patch 1 uses good conductor, including silver, copper；Dielectric substrate 2 uses insulating materials, including polytetrafluoroethylene (PTFE), polyimides,

Conductor patch 1, dielectric substrate 2 use corresponding material and geomery all in accordance with different resonant frequencies, as shown by the following formula：

${\mathrm{\&epsiv;}}_e=\frac{\mathrm{\&epsiv;}+1}{2}+\frac{\mathrm{\&epsiv;}-1}{2\sqrt{1+10h/w_e}}$

$\mathrm{\&Delta;}{L}_c=0.412h\frac{({\mathrm{\&epsiv;}}_e+0.3)(w_e/h+0.264)}{({\mathrm{\&epsiv;}}_e-0.258)(w_e/h+0.813)}$

$f=\frac{\mathrm{<figure-callout\; id="2"\; label="c"\; filenames="HDA00003333430500011.png,HDA00003333430500021.png"\; state="\{\{state\}\}">c</figure-callout>}}{2\sqrt{{\mathrm{\&epsiv;}}_e}}\frac{1}{L_e+2\mathrm{\&Delta;}{L}_c}$

Wherein：ε is the dielectric constant of dielectric substrate 2, ε_eFor the effective dielectric constant of dielectric substrate 2, h is the thickness of dielectric substrate 2, w_eFor the electric current width of conductor patch 1, c is the speed of light in a vacuum, L_eIt is effective current length, Δ L_cFor the linear compensation produced due to edge effect, f is antenna resonant frequency, when the sense of current is parallel to 1 length direction of conductor patch（That is radiation mode TM₀₁）Draw resonant frequency f=f₀₁, when the sense of current is parallel to 1 width of conductor patch（That is radiation mode TM₁₀）Draw resonant frequency f=f₁₀。

A kind of detection method of the crack detection sensor based on microstrip antenna, comprises the following steps：

It is attached to Step 1: dielectric substrate on sensor 2 is not provided with into the one side of conductor patch 1 on the tested surface of metal structure 3；

Step 2: the information of crackle by sensor passes to external equipment, obtain the resonant frequency f on sensor length and width₀₁And f₁₀Drift, be expressed as Δ f₀₁With Δ f₁₀；

Step 3: introducing individual parameter R：

Abscissa is obtained for crack length L, ordinate is the R-L curve maps of R values, every has a unique R-L curve to correspond to therewith along the crackle that different directions extend, so, each point on curve thinks corresponding with certain crack length and direction, so as to obtain crack length and directional information according to R-L curves.

Embodiment one

The material of dielectric substrate 2 selects polytetrafluoroethylene (PTFE)（R4B-265）, size is 40mm*40mm*0.5mm thin slice, and the material of conductor patch 1 selects copper, and size is 16mm*20mm*0.035mm metallic film.The tested material of metal structure 3 selection copper, size is 40mm*40mm*3mm metallic plate, and the corresponding theoretical resonance frequency of sensor so designed is 4.59GHz and 5.68GHz.During working sensor, by the drift for measuring resonant frequency, you can obtain length and the direction of crackle.

Such as Fig. 2, to detect along exemplified by the centre burst length in patch length direction.As crack length increases, due to the resonant frequency f parallel to patch length direction₀₁It is basically unchanged, parallel to the resonant frequency f of width₁₀It is gradually reduced, resonant frequency f is depended on for this crack length₁₀Drift value be that can obtain.When overlapping crack length with microstrip antenna paster and expanding to 20mm by 0, corresponding resonant frequency f₁₀4.7GHz is reduced to from 5.5GHz, crack length is substantially linear with frequency drift, detection sensitivity is 0.04GHz/mm.

Embodiment two

Sensor is manufactured by laminate Rogers4350B, and the size of dielectric substrate 2 is 40mm*25mm*0.44mm thin slice, and the material of conductor patch 1 selects copper, and size is 15.25mm*12.75mm*0.035mm metallic film.The tested material of metal structure 3 selection LY12CZ aluminium alloy plates, size is 40mm*25mm*5mm, and the corresponding resonant frequency of the sensor so designed is 5.1GHz and 6.1GHz.During working sensor, by the drift for measuring resonant frequency, you can obtain length and the direction of crackle.

As shown in figure 3, it is centre burst parallel to microstrip antenna length direction to appoint, and when overlapping crack length with microstrip antenna paster and expanding to 15mm by 0, corresponding resonant frequency f₁₀2.5GHz is reduced to from 6.1GHz, crack length is substantially linear with frequency drift, detection sensitivity is 0.24GHz/mm.

As shown in figure 4, studying the crackle of different directions under microstrip antenna paster.By two frequency f₁₀And f₀₁Drift value can determine the direction of crackle, we use frequency f₀₁And f₁₀The ratio between drift R weighs crack length and direction, can obtain comparing curve with each unique corresponding frequency of inclination angle crackle institute.Thus crack length and direction be can detect that.For example：Five kinds of situations when for direction of check being respectively 0 °, 15 °, 20 °, 30 °, 45 ° and 60 °, when crack length is 8mm, R is respectively 1.45,1.35,1.25,1.2 and 1.15；When crack length is 10mm, R is respectively 1.7,1.5,1.25,1.0,0.9 and 0.8.

Claims (3)

1. a kind of crack detection sensor based on microstrip antenna, it is characterised in that including dielectric substrate（2）, dielectric substrate（2）One side on be provided with conductor patch（1）, method to set up is including etching, deposition or corrodes, dielectric substrate（2）Another side is invested by geodesic structure（3）It is upper to constitute complete sensor；Conductor patch（1）, dielectric substrate（2）Corresponding material and geomery are used all in accordance with different resonant frequencies, as shown by the following formula：

${\mathrm{\&epsiv;}}_e=\frac{\mathrm{\&epsiv;}+1}{2}+\frac{\mathrm{\&epsiv;}-1}{2\sqrt{1+10h/w_e}}$

$\mathrm{\&Delta;}{L}_c=0.412h\frac{({\mathrm{\&epsiv;}}_e+0.3)(w_e/h+0.264)}{({\mathrm{\&epsiv;}}_e-0.258)(w_e/h+0.813)}$

$f=\frac{c}{2\sqrt{{\mathrm{\&epsiv;}}_e}}\frac{1}{L_e+2\mathrm{\&Delta;}{L}_c}$

Wherein：ε is dielectric substrate（2）Dielectric constant, ε_eFor dielectric substrate（2）Effective dielectric constant, h is dielectric substrate（2）Thickness, w_eFor conductor patch（1）Electric current width, c be the speed of light in a vacuum, L_eIt is effective current length, Δ L_eFor the linear compensation produced due to edge effect, f is antenna resonant frequency, when the sense of current is parallel to conductor patch（1）It is radiation mode TM during length direction₀₁Draw resonant frequency f=f₀₁, when the sense of current is parallel to conductor patch（1）It is radiation mode TM during width₁₀Draw resonant frequency f=f₁₀。

2. a kind of crack detection sensor based on microstrip antenna according to claim 1, it is characterised in that described conductor patch（1）Use good conductor, including silver, copper；Dielectric substrate（2）Use insulating materials, including polytetrafluoroethylene (PTFE), polyimides.

3. a kind of detection method of the crack detection sensor based on microstrip antenna, it is characterised in that comprise the following steps：

Step 1: by dielectric substrate on sensor（2）It is not provided with conductor patch（1）One side be attached to tested metal structure（3）On surface；

Step 2: the information of crackle by sensor passes to external equipment, obtain the resonant frequency f on sensor length and width₀₁And f₁₀Drift, be expressed as Δ f₀₁With Δ f₁₀；

Step 3: introducing individual parameter R：

Abscissa is obtained for crack length L, ordinate is the R-L curve maps of R values, every has a unique R-L curve to correspond to therewith along the crackle that different directions extend, so, each point on curve thinks corresponding with certain crack length and direction, so as to obtain crack length and directional information according to R-L curves.

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