阅读说明：本技术 基于电磁场原理的外置式钢筋锈蚀无损监测传感器及测试方法 (External reinforcement corrosion nondestructive monitoring sensor based on electromagnetic field principle and testing method ) 是由 付传清 黄家辉 金南国 李宗津 于 2019-10-18 设计创作，主要内容包括：一种基于电磁场原理的钢筋锈蚀监测传感器,包括磁感应强度监测单元和数据处理单元,磁感应强度监测单元包括磁芯、线圈、封装外壳、霍尔传感器和信号发生器；数据处理单元包括信号处理器和中央处理器。本发明还提供了一种于电磁场原理的钢筋锈蚀监测传感器的试验方法,包括待测试件预处理、测定磁感应强度、标定试验、根据标定拟合方程计算得到钢筋锈蚀率。本发明克服了传统测试方法对内置于混凝土中钢筋锈蚀监测的缺陷,通过霍尔传感器对称布置和控制电磁场强度来消除钢筋位置和卡口大小变化对钢筋锈蚀监测的影响,实现对钢筋混凝土锈蚀的精准监测；既适用于砂浆试件也适用于混凝土试件。(A steel bar corrosion monitoring sensor based on an electromagnetic field principle comprises a magnetic induction intensity monitoring unit and a data processing unit, wherein the magnetic induction intensity monitoring unit comprises a magnetic core, a coil, a packaging shell, a Hall sensor and a signal generator; the data processing unit comprises a signal processor and a central processing unit. The invention also provides a test method of the steel bar corrosion monitoring sensor based on the electromagnetic field principle, which comprises the steps of pretreatment of a piece to be tested, measurement of magnetic induction intensity, calibration test and calculation according to a calibration fitting equation to obtain the steel bar corrosion rate. The invention overcomes the defect of traditional testing method for monitoring the corrosion of the steel bar in the concrete, eliminates the influence of the change of the position of the steel bar and the size of the bayonet on the corrosion monitoring of the steel bar by symmetrically arranging the Hall sensors and controlling the strength of the electromagnetic field, and realizes the accurate monitoring of the corrosion of the steel bar; the test piece is suitable for both mortar test pieces and concrete test pieces.)

1. An external flowing type nondestructive testing and monitoring sensor for corrosion of a steel bar based on an electromagnetic field principle is characterized by comprising a magnetic induction intensity monitoring unit and a data processing unit;

the magnetic induction intensity detection unit comprises a signal generator, a coil, a magnetic core, a first Hall sensor and a second Hall sensor of a packaging shell, wherein the coil is uniformly wound on the magnetic core, and two ends of the coil are electrically connected with a signal input end of the signal generator; the middle position of the reinforced concrete test piece clamped by the fixing unit corresponds to the middle position of the bayonet of the magnetic core; the packaging shell comprises a first Hall sensor placing groove, a second Hall sensor placing groove and a sealing cover; the first Hall sensor and the second Hall sensor are symmetrically arranged by taking a bayonet center line as an axis and are respectively arranged in a first Hall sensor placing groove and a second Hall sensor placing groove of the packaging shell;

the data processing unit comprises a signal collector, a signal processor and a central controller, wherein the input end of the signal collector is electrically connected with the signal output ends of the first Hall sensor and the second Hall sensor, the signal output end of the signal generator and the output end of the signal collector are respectively electrically connected with the signal input end of the signal processor, and the signal output end of the signal processor is electrically connected with a port of the central controller.

2. The external flow type nondestructive testing and monitoring sensor for corrosion on steel bars based on electromagnetic field principle as claimed in claim 1, wherein in the magnetic induction intensity detection unit, the first hall sensor and the second hall sensor are symmetrically arranged, and the position of the steel bar is accurately detected by different magnetic induction intensities.

3. The external flowing type nondestructive testing and monitoring sensor for corrosion of steel bars based on the electromagnetic field principle as claimed in claim 1 or 2, wherein in the magnetic induction intensity detection unit, the magnetic core is made of silicon steel, and the packaging shell is made of plastic.

4. The external flowing type nondestructive testing and monitoring sensor for steel bar corrosion based on electromagnetic field principle as claimed in claim 1 or 2, wherein in the magnetic induction intensity detecting unit, the bayonet of the magnetic core is trapezoidal, and can be firmly clamped at the corner of the reinforced concrete square column to complete the monitoring of single steel bar corrosion detection, and the steel bar concrete columns with different sizes can be clamped according to the embedding depth or the distance of the bayonet of the magnetic core.

5. The external flowing type steel bar corrosion nondestructive testing and monitoring sensor based on the electromagnetic field principle as claimed in claim 1 or 2, wherein the signal generator can stably control the current of the coil; the signal collector and the signal generator are respectively provided with a first indicator light and a second indicator light of a circuit, and the first indicator light and the second indicator light respectively prompt whether the signal collector and the signal generator work normally or not.

6. The external flow type steel bar corrosion nondestructive detection and monitoring sensor based on the electromagnetic field principle as claimed in claim 1 or 2, wherein the hall sensors can be symmetrically arranged in one or more pairs according to the precision requirement and the actual engineering requirement.

7. The external flowing type steel bar corrosion nondestructive testing and monitoring sensor based on the electromagnetic field principle as claimed in claim 1 or 2 is characterized in that the uniform electromagnetic field generated by the magnetic core of the magnetic induction intensity detection unit and the uniformly wound coil depends on the coil current and the number of turns of the coil, and is not demagnetized due to time change, and the detection result is accurate.

8. The external flowing type steel bar corrosion nondestructive detection and monitoring sensor based on the electromagnetic field principle as claimed in claim 1 or 2 is characterized in that the electromagnet consisting of the magnetic core, the uniformly wound coil and the signal generator can change the electromagnetic field intensity by controlling the current of the coil and the number of turns of the coil, and the inventor tests prove that the influence of air field magnetic leakage caused by the change of the bayonet distance of the magnetic core can be effectively reduced by changing the magnetic field intensity, and the detection precision of the magnetic induction intensity of the sensor is improved.

9. The external flowing type steel bar corrosion nondestructive testing and monitoring sensor based on the electromagnetic field principle as claimed in claim 1 or 2 is characterized in that the data processing unit and the related control circuit thereof can be realized by the existing mature technology, and mainly comprises the steps of controlling the working current of the coil, and measuring the magnetic induction intensity values of the first hall sensor and the second hall sensor so as to calculate the corrosion rate. The magnetic induction intensity measuring system and the data processing system finish data storage, post-processing and real-time display through the signal processor and the central controller.

10. The method for testing the external steel bar corrosion nondestructive monitoring sensor based on the electromagnetic field principle as claimed in claim 1, wherein the method comprises the following steps:

firstly, preparing a reinforced concrete test piece before testing, wherein the process is as follows:

1.1 taking the smooth round steel bar with set length and diameter as a calibration steel bar and a steel bar to be measured, weighing the mass m of the steel bar to be measured_1I，m_2I，m_3I，m_4I，m_5I，m_6I，m_7IAnd calibrating the steel bar mass m₀And recording;

1.2 coating epoxy resin on the positions 5cm away from the two ends of the calibration steel bar and the steel bar to be detected, placing the epoxy resin in a mold, casting and molding, and soaking the cast and molded reinforced concrete test piece and the reinforced concrete test piece to be detected in a standard salt concentration solution until the samples are saturated with salt, wherein the concentration of the standard sodium chloride solution is 0.1-2 mol/L;

second, preparation before measurement, as follows:

2.1 uniformly winding an enameled copper wire in the same direction around a magnetic core to form a coil, mounting a first Hall sensor and a second Hall sensor in a first Hall sensor placing groove and a second Hall sensor placing groove of a packaging shell, then electrifying to form a uniform electromagnetic field, and covering a sealing cover for packaging;

2.2 controlling the acquisition frequency of the signal acquisition device and the current of the signal generator through the central controller, and electrifying the test magnetic field to ensure that the gauss values of the magnetic induction intensity of the first Hall sensor are the same as that of the second Hall sensor;

step three, a calibration test comprises the following processes:

3.1 recording mass m_1I，m_2I，m_3I，m_4I，m_5I，m_6I，m_7ICorresponding magnetic induction intensity data B of calibration reinforcing steel bar before corrosion of reinforced concrete test piece_1I，B_2I，B_3I，B_4I，B_5I，B_6I，B_7I；

3.2 realize the simulation experiment of reinforcing bar corrosion with the mode of corrosion is accelerated to the electric current, and control current density is the same, and the quality is m_1I，m_2I，m_3I，m_4I，m_5I，m_6I，m_7ICorresponding reinforced concrete test piece is electrified at equal intervals t₁，t₂，t₃，t₄，t₅，t₆，t₇；

3.3 recording the magnetic induction intensity data B of the calibration steel bar after the reinforced concrete test piece is corroded_1II，B_2II，B_3II，B_4II，B_5II，B_6II，B_7IIAnd steel bar quality data m_1II，m_2II，m_3II，m_4II，m_5II，m_6II，m_7II；

3.4 respectively calculating and calibrating the change rate Delta m of the steel bar quality₁，△m₂，△m₃，△m₄，△m₅，△m₆，△m₇The calculation formulas are respectively formulas (1) to (7);

3.5 respectively calculating and calibrating the magnetic induction intensity change rate Delta B of the steel bars₁，△B₂，△B₃，△B₄，△B₅，△B₆，△B₇The calculation formulas are respectively the formulas (8) to (14)

3.6, carrying out linear fitting on the relationship between the change rate of the steel bar mass and the change rate of the magnetic induction intensity of the Hall sensor to obtain a linear relationship coefficient alpha;

step four, measuring and testing, comprising the following steps:

4.1 recording the magnetic induction intensity B before the piece to be tested is rusted_0I；

4.2 placing the reinforced concrete to be tested in an environment which is easy to cause the reinforcing steel bars to be corroded so as to promote the reinforcing steel bars to be corroded;

4.3 the corroded test piece to be tested is put back to the original position, and the magnetic induction intensity B after the steel bar is corroded is recorded_0II；

4.4 Corrosion Rate p of Steel bars_IIThe calculation formula is formula (15)

P_II＝α(B_0II-B_0I) (15)。

Technical Field

The invention relates to a reinforcing steel bar corrosion monitoring technology in constructional engineering, in particular to an external reinforcing steel bar corrosion nondestructive monitoring sensor based on an electromagnetic field principle and a testing method.

Background

The reinforced concrete structure combines the characteristics of tensile strength and compression strength of the reinforced steel bar, and has become the most widely applied structural form in the world due to the characteristics of low cost, wide material sources, convenience in construction and the like since the reinforced concrete structure is applied to the field of civil engineering in the middle of 19 th century. The damage caused by the failure of the durability of the concrete is huge for a long time and far exceeds the expectation of people, and the damage becomes a worldwide problem. The steel bar corrosion is the most serious in the cause of the durability damage of the concrete, and the method has attracted wide attention at home and abroad. A great deal of research is also made by the predecessors aiming at the research of the detection of the corrosion of the steel bar in the construction engineering.

At present, the monitoring method of the steel bar corrosion is divided into damage detection and nondestructive detection. The damage detection measurement result is more accurate, but need to carry out the broken type to reinforced concrete structure and take out the reinforcing bar, and the harm that causes the concrete structure is irreversible, and is not suitable for being adjusted the reinforced concrete structure in service period well. The nondestructive testing method is a hotspot of current research, and mainly comprises a half-cell potential method, an acoustic emission technology and a built-in monitoring technology. The half-cell potential method utilizes the potential change caused by the electrochemical reaction of the steel bar corrosion to determine the steel bar corrosion state, but the accuracy is lower, the probability of the steel bar corrosion can be only determined qualitatively, and no unified determination standard exists; the acoustic emission technology can only qualitatively judge the corrosion occurrence probability according to parameters such as accumulated impact number and the like, and can not quantitatively measure the corrosion rate of the steel bar; a steel bar corrosion monitoring method based on a magnetic field principle is disclosed, wherein the number of Chinese patent publication No. CN109374726A is that the publication date is 22 days in 2 months in 2019, the name of the publication date is 'a steel bar corrosion nondestructive dynamic monitoring sensor and system in concrete based on a magnetic field', the number of Chinese patent publication No. CN208420791U is that the publication date is 22 days in 1 month in 2019, the name of the publication date is 'a steel bar corrosion electromagnetic field variable response device', two patents provide a steel bar corrosion monitoring sensor built in concrete for monitoring the steel bar corrosion condition built in concrete, but the built-in monitoring sensor can seriously affect the mechanical property of the steel bar concrete and the natural corrosion rule of the steel bar, and the sensor built in the concrete can only be used once and has higher cost; the Chinese patent is entitled "monitoring equipment and method for steel bar corrosion behavior in concrete" with an authorization publication number CN108469514A, the publication date is 2018, 8 and 31, and the related sensor of the patent has the following defects: firstly, although the sensor can measure the corrosion condition of the steel bar, the sensor can only qualitatively judge the corrosion condition of the whole steel bar in the concrete and cannot judge the corrosion condition of a single steel bar, and the corrosion conditions of the steel bar in the concrete in actual engineering are different, so that the corrosion condition of the single steel bar needs to be measured; secondly, the test results of the inventor prove that the influence of different positions of the steel bars on the response condition of the Hall sensor is far larger than the influence of corrosion of the steel bars, so that the error is larger under the condition that the steel bars cannot ensure in-situ monitoring; thirdly, the Hall sensors are arranged in a single straight line direction, and the method cannot effectively monitor the change rule of the position of the steel bar; fourthly, actual concrete column size is great, and this patent test need effectively block whole reinforced concrete column, and required magnetic core bayonet socket is great, proves through the inventor's test result, the increase of bayonet socket can lead to hall sensor detectivity to reduce. In summary, the measurement result of the sensor related to the patent can not reflect the real corrosion condition of the steel bar, and accurate and reliable data can not be obtained to predict the corrosion degree of the steel bar under different conditions.

In the actual building engineering, an external dynamic monitoring sensor and a test method for accurately measuring the corrosion rate of the steel bars still do not exist.

Therefore, the external nondestructive dynamic steel bar corrosion monitoring sensor with the advantages of clear principle, simple method, high measuring speed, repeated use, strong engineering applicability, good stability and the like is found, and the sensor has important significance for continuously and deeply evaluating and predicting the steel bar corrosion degree.

Disclosure of Invention

In order to overcome the defects of the existing nondestructive monitoring technology for the corrosion of the steel bar in the constructional engineering, the invention provides a monitoring technology which has high stability and simple and convenient operation and can realize the corrosion of the external steel bar, in particular to the monitoring technology for the corrosion of the steel bar based on the electromagnetic field principle: externally arranged outside the reinforced concrete structure; the bayonet of the magnetic core is designed into a trapezoidal bayonet, so that the reinforced concrete square column can be effectively clamped, and the corrosion condition of a single detection reinforcing steel bar at the corner of the reinforced concrete square column can be effectively detected; the electromagnetic field intensity is changed by controlling the current of the coil and the number of turns of the coil, so that the air field magnetic leakage influence caused by the change of the bayonet distance of the magnetic core is reduced, and the detection precision of the magnetic induction intensity of the Hall sensor is improved so as to adapt to reinforced concrete square columns with different sizes; the position of the steel bar is accurately detected through the symmetrical arrangement of the Hall sensors; the method is used for measuring the corrosion rate of the steel bar, evaluating the corrosion degree of the steel bar and predicting the service life of the steel bar so as to solve the problem that no effective method for measuring the corrosion rate of the reinforced concrete material steel bar exists at present.

In order to solve the technical problems, the invention provides the following technical scheme:

an external steel bar corrosion nondestructive monitoring sensor based on an electromagnetic field principle comprises a magnetic induction intensity monitoring unit and a data processing unit;

the magnetic induction intensity detection unit comprises a signal generator, a coil, a magnetic core, a packaging shell, a first Hall sensor and a second Hall sensor, wherein the coil is uniformly wound on the magnetic core, and two ends of the coil are electrically connected with a signal input end of the signal generator; the middle position of the reinforced concrete test piece clamped by the fixing unit corresponds to the middle position of the bayonet of the magnetic core; the packaging shell comprises a first Hall sensor placing groove, a second Hall sensor placing groove and a sealing cover; the first Hall sensor and the second Hall sensor are symmetrically arranged by taking a bayonet center line as an axis and are respectively arranged in a first Hall sensor placing groove and a second Hall sensor placing groove of the packaging shell;

the data processing unit comprises a signal collector, a signal processor and a central controller, wherein the input end of the signal collector is electrically connected with the signal output ends of the first Hall sensor and the second Hall sensor, the signal output end of the signal generator and the output end of the signal collector are respectively electrically connected with the signal input end of the signal processor, and the signal output end of the signal processor is electrically connected with a port of the central controller.

Further, the first Hall sensor and the second Hall sensor are symmetrically arranged.

The magnetic core is a trapezoidal bayonet.

The magnetic core is made of silicon steel.

The packaging shell is made of plastic materials.

The signal generator can stably control the current of the coil.

The signal collector and the signal generator are respectively provided with a first indicator light and a second indicator light of a circuit, and the first indicator light and the second indicator light respectively prompt whether the signal collector and the signal generator work normally or not.

The Hall sensors can be symmetrically arranged in one or more pairs according to the precision requirement and the actual engineering requirement.

As an improvement, the magnetic core bayonet of the magnetic induction intensity detection unit is trapezoidal, can be firmly clamped at the corner of a reinforced concrete square column, completes the corrosion monitoring of a single detection reinforcing steel bar, and can clamp reinforced concrete columns of different sizes according to the embedding depth or the distance of the magnetic core bayonet.

As an improvement, a uniform electromagnetic field generated by the magnetic core of the magnetic induction intensity detection unit and the uniformly wound coil depends on the coil current and the number of turns of the coil, the coil cannot be demagnetized due to time change, and the detection result is accurate.

As an improvement, the electromagnet consisting of the magnetic core of the magnetic induction intensity detection unit, the coil wound uniformly and the signal generator can change the magnetic field intensity by controlling the current of the coil and the number of turns of the coil, and the inventor tests prove that the air field magnetic leakage influence caused by the change of the bayonet distance of the magnetic core can be effectively reduced by changing the magnetic field intensity, and the magnetic induction intensity detection precision of the sensor is improved.

As an improvement, the magnetic induction intensity detection unit is externally arranged on the reinforced concrete column, so that the reutilization and the dynamic monitoring are realized.

As an improvement, the first Hall sensor and the second Hall sensor of the magnetic induction intensity detection unit are symmetrically arranged by taking a bayonet center line as an axis, and the test result of an inventor proves that the position of the steel bar can be accurately detected.

As an improvement, the data processing unit and the related control circuit can be realized by the existing mature technology, and mainly comprises the steps of controlling the working current of the coil, measuring the magnetic induction intensity values of the first Hall sensor and the second Hall sensor, and calculating the corrosion rate. The magnetic induction intensity measuring system and the data processing system finish data storage, post-processing and real-time display through the signal processor and the central controller.

An external reinforcing steel corrosion nondestructive monitoring sensor test method based on an electromagnetic field principle comprises the following steps:

firstly, preparing a reinforced concrete test piece before testing, wherein the process is as follows:

1.1 taking the smooth round steel bar with set length and diameter as a calibration steel bar and a steel bar to be measured, weighing the mass m of the steel bar to be measured_1I，m_2I，m_3I，m_4I，m_5I，m_6I，m_7IAnd calibrating the steel bar mass m₀And recording;

1.2 coating epoxy resin on the positions 5cm away from the two ends of the calibration steel bar and the steel bar to be detected, placing the epoxy resin in a mold, casting and molding, and soaking the cast and molded reinforced concrete test piece and the reinforced concrete test piece to be detected in a standard salt concentration solution until the samples are saturated with salt, wherein the concentration of the standard sodium chloride solution is 0.1-2 mol/L;

second, preparation before measurement, as follows:

2.1 uniformly winding an enameled copper wire in the same direction around a magnetic core to form a coil, mounting a first Hall sensor and a second Hall sensor in a first Hall sensor placing groove and a second Hall sensor placing groove of a packaging shell, then electrifying to form a uniform electromagnetic field, and covering a sealing cover for packaging;

2.2 controlling the acquisition frequency of the signal acquisition device and the current of the signal generator through the central controller, and electrifying the test magnetic field to ensure that the gauss values of the magnetic induction intensity of the first Hall sensor are the same as that of the second Hall sensor;

thirdly, a calibration test is carried out, and the process is as follows:

3.1 recording qualityIs m_1I，m_2I，m_3I，m_4I，m_5I，m_6I，m_7ICorresponding magnetic induction intensity data B of calibration reinforcing steel bar before corrosion of reinforced concrete test piece_1I，B_2I，B_3I，B_4I，B_5I，B_6I，B_7I；

3.2 realize the simulation experiment of reinforcing bar corrosion with the mode of corrosion is accelerated to the electric current, and control current density is the same, and the quality is m_1I，m_2I，m_3I，m_4I，m_5I，m_6I，m_7ICorresponding reinforced concrete test piece is electrified at equal intervals t₁，t₂，t₃，t₄，t₅，t₆，t₇；

3.3 recording the magnetic induction intensity data B of the calibration steel bar after the reinforced concrete test piece is corroded_1II，B_2II，B_3II，B_4II，B_5II，B_6II，B_7IIAnd steel bar quality data m_1II，m_2II，m_3II，m_4II，m_5II，m_6II，m_7II；

3.4 respectively calculating and calibrating the change rate Delta m of the steel bar quality₁，△m₂，△m₃，△m₄，△m₅，△m₆，△m₇The calculation formulas are respectively formulas (1) to (7);

3.5 respectively calculating and calibrating the magnetic induction intensity change rate Delta B of the steel bars₁，△B₂，△B₃，△B₄，△B₅，△B₆，△B₇The calculation formulas are respectively the formulas (8) to (14)

3.6, carrying out linear fitting on the relationship between the change rate of the steel bar mass and the change rate of the magnetic induction intensity of the Hall sensor to obtain a linear relationship coefficient alpha;

step four, measuring the test, the process is as follows:

4.1 recording the magnetic induction intensity B before the piece to be tested is rusted_0I；

4.2 placing the reinforced concrete to be tested in an environment which is easy to cause the reinforcing steel bars to be corroded so as to promote the reinforcing steel bars to be corroded;

4.3 the corroded test piece to be tested is put back to the original position, and the magnetic induction intensity B after the steel bar is corroded is recorded_0II；

4.4 Corrosion Rate p of Steel bars_IIThe calculation formula is formula (15)

P_II＝α(B_0II-B_0I) (15)。

The working principle of the invention is as follows: the Hall sensor detects the magnetic induction intensity of the magnetic induction intensity detection unit and sends the magnetic induction intensity to the signal processor, and the current of the magnetic induction intensity detection unit is controlled by the signal generator; the signal processor collects data of the signal generator and the signal collector according to the set frequency, calculates and analyzes the data, stores the collected data and the calculation result in the central controller in real time, and displays the analysis and calculation result in real time through the display screen.

The invention has the beneficial effects that: the invention is based on a nondestructive testing method, and realizes the nondestructive monitoring of the corrosion of the steel bar by applying an electromagnetic induction technology, thereby calculating the corrosion rate of the steel bar according to a theoretical formula. The limit of the test stability, accuracy and use times of the traditional test method is broken through, and the test of the corrosion rate of the steel bar of the reinforced concrete test piece is realized; the measured corrosion rate of the steel bars can be applied to the evaluation of the current service performance and the prediction of the durability of the reinforced concrete structure. The test object can be suitable for reinforced concrete square columns with different sizes, has the advantages of clear principle, simple and convenient method, high measuring speed, repeated use, good stability and the like, and can make up the defects of the prior method and the prior device for measuring the corrosion rate of the reinforcing steel bars.

Drawings

FIG. 1 is a schematic structural diagram of the present invention.

Fig. 2 is a schematic structural diagram of the package housing of the present invention before the cover is closed.

Fig. 3 is a top view of the closure of the present invention.

Fig. 4 shows the detection result of the magnetic core bayonet enlarging sensor according to the present invention.

FIG. 5 shows the detection result of the sensor after the magnetic field amplification of the present invention.

FIG. 6 shows the position detection test results of the Hall sensor in the x and y directions.

FIG. 7 shows the z-direction position detection test results of the Hall sensor according to the present invention.

FIG. 8 shows the results of the Hall sensor steel bar corrosion detection test.

Reference numbers in the figures: 1-1, a first Hall sensor; 1-2, a second Hall sensor; 2. a coil; 3. a magnetic core; 4. a reinforced concrete square column; 5. detecting the reinforcing steel bars; 6. a signal collector; 7. a signal generator; 8. a signal processor; 9. a central processing unit; 10-1, a first indicator light; 10-2, a second indicator light; 11. a package housing; 11-1, a first Hall sensor placing groove; 11-2, placing a second Hall sensor groove; 11-3 and sealing the cover.

Detailed Description

The invention will be further explained with reference to the drawings

Referring to fig. 1 to 8, an external reinforcing steel corrosion nondestructive monitoring sensor testing method based on an electromagnetic field principle takes an HPB300 smooth round steel bar with a diameter of 16mm as an example, and includes the following steps:

firstly, preparing a reinforced concrete test piece before testing, wherein the process is as follows:

1.1 taking 20cm long plain steel bar with diameter of 16mm as calibration steel bar and steel bar to be measured, weighing the mass m of the steel bar to be measured_1I，m_2I，m_3I，m_4I，m_5I，m_6I，m_7IAnd calibrating the steel bar mass m₀And recording;

1.2 coating epoxy resin at 5cm positions at two ends of the calibration steel bar and the steel bar to be detected in a mold and pouring for molding, wherein the concrete comprises the following raw materials: the cement is P.I 525 grade Portland cement, river sand with fineness modulus of 2.6 is adopted as the sand, continuous graded broken stone (the maximum grain diameter is 25mm) is adopted as coarse aggregate, tap water is adopted as water, the effective section size of a cast test piece in a standard die is 100mm multiplied by 100mm, the length of a steel bar is 200mm, the protruding length of the steel bars on two sides is 50mm, the length of the test piece is 100mm, the standard maintenance is carried out in a maintenance room for 28d after the cast molding is carried out, the calibrated reinforced concrete test piece and the reinforced concrete test piece to be tested after the cast molding are soaked in a standard salt concentration solution until the salt is saturated, and the concentration of the standard sodium chloride solution is 0.1-2 mol/L;

second, preparation before measurement, as follows:

2.1 uniformly winding an enameled copper wire in the same direction around an upper magnetic core 3 to form a coil 2, mounting a first Hall sensor 1-1 and a second Hall sensor 1-2 in a first Hall sensor placing groove 11-1 and a second Hall sensor placing groove 11-2 of a packaging shell 11, then electrifying to form a uniform strong electromagnetic field, and covering a sealing cover 11-3 for packaging;

2.2 the central controller 9 controls the collection frequency of the signal collector 6 and the current of the signal generator 7, and the magnetic field is electrified and tested, so that the magnetic induction intensity gauss values of the first Hall sensor 1-1 and the second Hall sensor 1-2 are the same.

Thirdly, a calibration test is carried out, and the process is as follows:

3.1 recording mass m_1I，m_2I，m_3I，m_4I，m_5I，m_6I，m_7ICorresponding magnetic induction intensity data B of calibration reinforcing steel bar before corrosion of reinforced concrete test piece_1I，B_2I，B_3I，B_4I，B_5I，B_6I，B_7I；

3.2 realize the simulation experiment of reinforcing bar corrosion with the mode of corrosion is accelerated to the electric current, and control current density is the same, and the quality is m_1I，m_2I，m_3I，m_4I，m_5I，m_6I，m_7IElectrifying the corresponding reinforced concrete test pieces for 1 day, 2 days, 3 days, 4 days, 5 days, 6 days and 7 days respectively;

3.3 recording the magnetic induction intensity data B of the calibration steel bar after the reinforced concrete test piece is corroded_1II，B_2II，B_3II，B_4II，B_5II，B_6II，B_7IIAnd steel bar quality data m_1II，m_2II，m_3II，m_4II，m_5II，m_6II，m_7II；

3.4 respectively calculating and calibrating the change rate Delta m of the steel bar quality₁，△m₂，△m₃，△m₄，△m₅，△m₆，△m₇The calculation formulas are respectively formulas (1) to (7);

3.5 respectively calculating and calibrating the magnetic induction intensity change rate Delta B of the steel bars₁，△B₂，△B₃，△B₄，△B₅，△B₆，△B₇The calculation formulas are respectively the formulas (8) to (14)

3.6, carrying out linear fitting on the relationship between the change rate of the steel bar mass and the change rate of the magnetic induction intensity of the Hall sensor to obtain a linear relationship coefficient alpha;

step four, measuring the test, the process is as follows:

4.1 recording the magnetic induction intensity B before the piece to be tested is rusted_0I；

4.2 placing the reinforced concrete to be tested in an environment which is easy to cause the reinforcing steel bars to be corroded so as to promote the reinforcing steel bars to be corroded;

4.3 the corroded test piece to be tested is put back to the original position, and the magnetic induction intensity B after the steel bar is corroded is recorded_0II；

4.4 Corrosion Rate p of Steel bars_IIThe calculation formula is formula (15)

P_II＝α(B_0II-B_0I) (15)。

An external steel bar corrosion nondestructive monitoring sensor based on an electromagnetic field principle comprises a magnetic induction intensity monitoring unit and a data processing unit;

the magnetic induction intensity detection unit comprises a signal generator 7, a coil 2, a magnetic core 3, a packaging shell 11, a first Hall sensor 1-1 and a second Hall sensor 1-2, wherein the coil 2 is uniformly wound on the magnetic core 3, and two ends of the coil 2 are electrically connected with a signal input end of the signal generator 7; the middle position of the reinforced concrete test piece clamped by the fixing unit corresponds to the middle position of the bayonet of the magnetic core 3; the packaging shell 11 comprises a first Hall sensor placing groove 11-1, a second Hall sensor placing groove 11-2 and a sealing cover 11-3; the first Hall sensor 1-1 and the second Hall sensor 1-2 are symmetrically arranged by taking a bayonet center line as an axis and are respectively arranged in a first Hall sensor placing groove 11-1 and a second Hall sensor placing groove 11-2 of the packaging shell 11;

the data processing unit comprises a signal collector 6, a signal processor 8 and a central controller 9, wherein the input end of the signal collector 6 is electrically connected with the signal output ends of the first Hall sensor 1-1 and the second Hall sensor 1-2, the signal output end of the signal generator 7 and the output end of the signal collector 6 are respectively electrically connected with the signal input end of the signal processor 8, and the signal output end of the signal processor 8 is electrically connected with a port of the central controller 9.

Further, the first Hall sensor 1-1 and the second Hall sensor 1-2 are symmetrically arranged.

The magnetic core 3 is a trapezoidal bayonet.

The magnetic core 3 is made of silicon steel.

The packaging shell is made of plastic materials.

The signal generator 7 can stably control the current of the coil.

The signal collector 6 and the signal generator 7 are respectively provided with a first indicator light 10-1 and a second indicator light 10-2 of a circuit, and the indicator lights respectively prompt whether the signal collector 6 and the signal generator 7 work normally or not.

The Hall sensors 7 can be symmetrically arranged in one or more pairs according to the precision requirement and the actual engineering requirement.

As an improvement, the bayonet 3 of the magnetic core of the magnetic induction intensity detection unit is trapezoidal, can be firmly clamped at the corner of a reinforced concrete square column to complete the corrosion monitoring of a single detection reinforcing steel bar 5, and can clamp reinforced concrete columns with different sizes according to the embedding depth or the distance of the bayonet of the magnetic core.

As an improvement, the uniform electromagnetic field generated by the magnetic core 3 and the uniformly wound coil 2 of the magnetic induction intensity detection unit depends on the current of the coil 2 and the number of turns of the coil 2, and is not demagnetized due to time change, so that the detection result is accurate.

As an improvement, the electromagnet consisting of the magnetic core 3, the uniformly wound coil 2 and the signal generator 7 of the magnetic induction intensity detection unit can change the magnetic field intensity by controlling the coil current and the number of turns of the coil, and the inventor tests prove that the air domain magnetic leakage influence caused by the change of the bayonet distance of the magnetic core can be effectively reduced by changing the magnetic field intensity, and the magnetic induction intensity detection precision of the sensor is improved.

As an improvement, the magnetic induction intensity detection unit is externally arranged on the reinforced concrete column 4, so that the reutilization and dynamic monitoring are realized.

As an improvement, the first Hall sensor 1-1 and the second Hall sensor 1-2 of the magnetic induction intensity detection unit are symmetrically arranged by taking a bayonet center line as an axis, and the inventor test results prove that the position of the steel bar can be accurately detected.

As an improvement, the data processing unit and related control circuits of the data processing unit can be realized by using the existing mature technology, and mainly comprises the steps of controlling the working current of the coil 2, measuring the magnetic induction intensity values of the first Hall sensor 1-1 and the second Hall sensor 1-2, and calculating the corrosion rate. The magnetic induction intensity measuring system and the data processing system complete data storage, post-processing and real-time display through the signal processor 8 and the central controller 9.