CN113125551A - Built-in magnetic sensor with double magnetic circuits and four measuring points and testing method thereof - Google Patents
Built-in magnetic sensor with double magnetic circuits and four measuring points and testing method thereof Download PDFInfo
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
- G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
Abstract
A built-in magnetic sensor with double magnetic circuits and four measuring points comprises a magnetic induction intensity monitoring unit and a data processing unit; the magnetic induction intensity monitoring unit comprises a magnetic core, a permanent magnet, a packaging shell and a Hall sensor; the data processing unit comprises a signal collector, a signal processor and a central processing unit. The invention also provides a test method of the built-in steel bar corrosion magnetic sensor with double magnetic circuits and four measuring points, which comprises the steps of pretreating a piece to be tested, measuring the magnetic induction intensity, calibrating the test, and calculating the steel bar corrosion rate according to a calibration fitting equation; the invention not only meets the requirement of the traditional test method on monitoring the corrosion of the steel bar embedded in the concrete, but also realizes the monitoring on the uneven corrosion of the steel bar through the pairwise cooperation of the four Hall sensors, and also innovatively discloses a method for fixing the sensors on the steel bar; the invention is suitable for both mortar test pieces and concrete test pieces.
Description
Technical Field
The invention relates to a steel bar corrosion monitoring technology in constructional engineering, in particular to a built-in magnetic sensor with double magnetic circuits and four measuring points and a testing method thereof.
Background
The reinforced concrete structure combines the characteristics of reinforced tension resistance and concrete compression resistance, and has become one of the most widely applied structural forms in the world due to the characteristics of economic manufacturing cost, available local materials, low construction difficulty and the like since the reinforced concrete structure is applied to the field of civil engineering in the middle of 19 th century. Meanwhile, the loss caused by the failure of the durability of the concrete is huge for a long time and far exceeds the expectation of people, and how to improve the durability of the concrete in service period 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. Therefore, how to accurately detect and monitor the corrosion degree of the steel bars in the reinforced concrete structure has very important significance for predicting the service life of the existing reinforced concrete structure and reasonably establishing a maintenance scheme of the reinforced concrete structure. And a great deal of research is also made by the predecessors aiming at the research of monitoring the corrosion of the steel bars in the constructional engineering.
At present, the detection method of the corrosion of the steel bar is divided into damage detection and nondestructive detection. Breakage detects and takes out the reinforcing bar through destroying the concrete protection layer and measure, and the result is comparatively accurate, nevertheless can be to the irreversible harm that the concrete structure caused, and is not suitable for to being in the reinforced concrete structure of in active 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 magnetic field nondestructive testing method. The half-cell potential method is most commonly used, the potential change is caused by the electrochemical reaction of the steel bar corrosion, the steel bar corrosion state is measured, but the accuracy is low, the steel bar corrosion probability can only be judged qualitatively, no unified judgment standard exists, and the corrosion condition cannot be quantized; the acoustic emission technology sensitively captures the release of microcrack expansion stress waves in concrete by measuring the acoustic wave propagation characteristic caused by steel bar corrosion, and only can qualitatively judge the corrosion occurrence probability according to parameters such as accumulated impact number and the like, but cannot quantitatively measure the steel bar corrosion rate; the magnetic field nondestructive detection method can monitor the damage of the surface or the near surface of the steel bar under the condition that the concrete is in normal service, and although the internal defects of the steel bar cannot be detected, the method is obviously improved compared with other methods which cannot quantitatively detect the modification rate.
The external reinforcement corrosion nondestructive monitoring sensor is named as an external reinforcement corrosion nondestructive monitoring sensor based on an electromagnetic field principle and a testing method, the granted notice date of Chinese patent No. CN201910991189.8 is 1 month and 3 days in 2020, and the granted notice date of Chinese patent application No. CN201911157575.3 is named as a concrete reinforcement detection device and a method thereof, the published notice date of Chinese patent No. CN201911157575.3 is 2 months and 25 days in 2020, the two patents respectively utilize an electromagnetic principle and an electrostatic field principle, the former provides an external bayonet type magnetic sensor, the operation is simple and convenient, the condition of detecting a single reinforcement at the edge of a reinforced concrete square column can be effectively detected, but the detection object is single. The latter provides an external scanning type nondestructive detection device and a method, which can detect the corrosion condition of a steel bar at a distance. But both can only detect the corrosion condition of the steel bar facing to one side of the protective layer, and can not evaluate the uneven corrosion condition of the steel bar; the name is "a concrete reinforcement corrosion detector based on bipolar potential", Chinese patent authorizes publication No. CN211955297U, the date of the authorization announcement is 11 months and 17 days of 2020, the utility model patent is based on bipolar potential method to scan and judge whether the reinforcement has corrosion fast, and then the instrument converts the electric signal into the image, obtains the reinforcement corrosion quantitative value, although the patent combines the qualitative and quantitative determination, the step is tedious and the cost is great, is not suitable for being used in actual engineering in a large number; the patent is entitled 'a steel bar corrosion electromagnetic field variable response monitoring device', and has an authorization publication number CN208420791U, wherein the authorization publication date is 1 month and 22 days in 2019, the patent utilizes a Hall element to monitor the whole corrosion process of the steel bar from rusting to linear loss of quality in real time, but can not monitor the uneven corrosion condition of the steel bar quantitatively; the invention relates to a magnetic field-based nondestructive dynamic monitoring sensor and system for steel bar corrosion in concrete, which is named as 'magnetic field-based nondestructive dynamic monitoring sensor and system for steel bar corrosion in concrete', Chinese patent application publication No. CN201811213216.0, published as 2019, 2.22.2019, and the invention patent utilizes the magnetic field principle to detect the corrosion rate of steel bars, but the sensor related to the patent has the defects that: firstly, although three Hall sensors are installed on the sensor, only the Hall sensor beside the notch of the reinforcing steel bar clamp works in practice; secondly, the Hall sensors are arranged in a single linear direction, and the method cannot effectively monitor the change rule of the position of the steel bar; thirdly, the patent cannot effectively quantitatively detect the uneven corrosion degree of the steel bar; fourthly the magnetic core of this patent still has one section distance apart from the reinforcing bar notch, and the magnetic resistance in air space between monitoring reinforcing bar and the magnetic core can increase.
In actual conditions, the rust layer of the corroded steel bar is not uniformly distributed, one side of the corroded steel bar, which faces the protective layer, is more easily damaged by corrosion media such as water, oxygen and chloride ions, so that the corroded steel bar is corroded firstly, and finally, the corrosion condition is more serious than that of the other side. However, in the actual construction engineering, a built-in dynamic monitoring sensor and a test method for accurately measuring the uneven corrosion of the reinforcing steel bars still do not exist.
Therefore, the built-in nondestructive dynamic uneven corrosion monitoring sensor for the steel bars has the advantages of clear principle, simple and convenient method, high measuring speed, real-time monitoring, strong engineering applicability, good stability and the like, and has important significance for improving the evaluation and prediction of the corrosion degree of the steel bars.
Disclosure of Invention
In order to overcome the defects of the existing non-uniform corrosion nondestructive monitoring technology for the steel bar in the building engineering, the invention provides a built-in magnetic sensor with double magnetic circuits and four measuring points, which has high stability, simple and convenient operation and strong engineering applicability, applies the steel bar corrosion monitoring technology based on the magnetic field principle and is built in a reinforced concrete structure, and the invention provides a novel fixing mode of the sensor and the steel bar; the magnetic core is designed into an E-shaped special shape, so that the monitoring of four measuring points of the double magnetic circuit and the fixation of the permanent magnet can be effectively completed; the Hall sensors are symmetrically arranged pairwise so as to accurately detect the corrosion condition of the two sides of the facing and back protective layer of the steel bar; the method is used for measuring the corrosion rate and the uneven corrosion degree of the steel bar, evaluating the corrosion condition 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 uneven corrosion of the reinforced concrete material steel bar exists at present.
In order to solve the technical problems, the invention provides the following technical scheme:
a built-in magnetic sensor with double magnetic circuits and four measuring points comprises a magnetic induction intensity monitoring unit and a data processing unit;
the magnetic induction intensity detection unit comprises a built-in sensor left magnetic core, a built-in sensor right magnetic core, a built-in sensor permanent magnet, a first Hall sensor, a second Hall sensor, a third Hall sensor, a fourth Hall sensor and a built-in sensor packaging shell; the middle part of the upper end of the built-in sensor packaging shell is provided with a steel bar bayonet for clamping a steel bar to be measured, the built-in sensor packaging shell comprises a built-in sensor inner shell and a built-in sensor outer shell packaging cover, the built-in sensor inner shell is provided with a first Hall sensor placing groove, a second Hall sensor placing groove, a third Hall sensor placing groove, a fourth Hall sensor placing groove, a built-in sensor permanent magnet groove, a built-in sensor left magnetic core groove, a built-in sensor right magnetic core groove, a first cable bending space and a first wire hole, the first Hall sensor placing groove, the second Hall sensor placing groove, the third Hall sensor placing groove and the fourth Hall sensor placing groove are all arranged in the steel bar bayonet, and the built-in sensor permanent magnet groove is positioned between the built-in sensor left magnetic core groove and the built-in sensor right magnetic core groove, the first cable bending space is positioned below the built-in sensor permanent magnet groove, and the first wire hole is arranged at the bottom of the built-in sensor packaging shell and is communicated with the first cable bending space; the built-in sensor permanent magnet is connected with the built-in sensor left magnetic core and the built-in sensor right magnetic core at the same time and is arranged in a built-in sensor permanent magnet groove, and the first Hall sensor and the second Hall sensor, the third Hall sensor and the fourth Hall sensor are symmetrically arranged by taking the central line of a steel bar bayonet as an axis and are respectively arranged in corresponding Hall sensor placing grooves; the built-in sensor inner shell and the built-in sensor outer shell encapsulation cover are both provided with a first fixing hole and a second fixing hole;
the data processing unit comprises a signal collector, a signal processor and a central controller, wherein the signal input end of the signal collector is electrically connected with the signal output end of the Hall sensor, the output end of the signal collector is electrically connected with the signal input end of the signal processor, and the signal output end of the signal processor is electrically connected with the port of the central controller.
Furthermore, a first circuit indicator lamp is arranged between the first Hall sensor and the signal collector, a second circuit indicator lamp is arranged between the fourth Hall sensor and the signal collector, and a third circuit indicator lamp is arranged between the fourth Hall sensor and the signal collector.
And furthermore, the left magnetic core and the right magnetic core of the built-in sensor are E-shaped special magnetic cores with two openings symmetrically arranged inwards, the connecting line of the upper ends of the openings of the first pair of magnetic cores is superposed with the top tangent of the steel bar to be detected, the openings of the second pair of magnetic cores are arranged into circular arcs, the connecting line of the bottom ends of the openings of the second pair of magnetic cores is superposed with the bottom tangent of the steel bar to be detected, and the openings of the third pair of magnetic cores are.
And furthermore, two fixed ends are arranged at the left end and the right end of the double-magnetic-circuit four-measuring-point built-in sensor, wire holes are respectively formed in the two fixed ends, and plastic binding wires penetrate through the wire holes and bind the fixed ends and the steel bars to be measured.
Furthermore, the permanent magnet of the built-in sensor is made of neodymium-nickel-boron, and the left magnetic core and the right magnetic core of the built-in sensor are both made of silicon steel; the built-in sensor packaging shell is made of plastic materials.
A built-in magnetic sensor testing method with double magnetic circuits and four measuring points comprises the following steps:
calculating the corrosion rate of the side, facing the protective layer, of the steel bar to be tested through the magnetic induction intensity values of the first Hall sensor and the second Hall sensor, calculating the corrosion rate of the side, facing away from the protective layer, of the steel bar to be tested through the magnetic induction intensity values of the third Hall sensor and the fourth Hall sensor, and comparing the corrosion rates of the two sides so as to analyze the non-uniform corrosion degree of the steel bar to be tested; the magnetic induction intensity monitoring unit and the signal collector finish data storage, post-processing and real-time display through the signal processor and the central controller.
The method comprises the following specific 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 measured1Ⅰ，m2Ⅰ，m3Ⅰ，m4Ⅰ，m5Ⅰ，m6Ⅰ，m7ⅠAnd calibrating the steel bar mass m0And recording;
1.2 coating epoxy resin on the 5cm positions of the two ends of the calibration steel bar and the steel bar to be detected;
second, preparation before measurement, as follows:
2.1 respectively installing a first Hall sensor, a second Hall sensor, a third Hall sensor and a fourth Hall sensor in a first Hall sensor placing groove, a second Hall sensor placing groove, a third Hall sensor placing groove and a fourth Hall sensor placing groove of a packaging shell, installing a permanent magnet in a permanent magnet groove, then covering a built-in sensor shell packaging cover for packaging, and coating epoxy resin at all gaps for sealing;
2.2, controlling the acquisition frequency of the signal acquisition device through the central controller, and testing a magnetic field to ensure that the gauss values of the magnetic induction intensities of the first Hall sensor, the second Hall sensor, the third Hall sensor and the fourth Hall sensor are the same;
2.3, the built-in sensor is arranged on the steel bar to be measured, and the front end and the rear end are fixed by plastic binding wires. Placing the steel bar to be tested and the calibration steel bar into a mold and pouring and molding, and soaking a pouring and molding calibration reinforced concrete test piece and the steel bar to be tested in a standard salt concentration solution until the standard salt concentration solution is saturated, wherein the concentration of the standard sodium chloride solution is 0.1-2 mol/L;
thirdly, a calibration test is carried out, and the process is as follows:
3.1 recording mass m1Ⅰ，m2Ⅰ，m3Ⅰ，m4Ⅰ，m5Ⅰ，m6Ⅰ，m7ⅠCorresponding magnetic induction intensity data B of one side of the calibration reinforcing steel bar facing the protective layer before the reinforced concrete test piece is corroded1Ⅰa，B2Ⅰa，B3Ⅰa，B4Ⅰa，B5Ⅰa，B6Ⅰa，B7Ⅰa(ii) a Magnetic induction intensity data B of one side of calibration reinforcing steel bar back to protective layer before corrosion1Ⅰb，B2Ⅰb，B3Ⅰb，B4Ⅰb，B5Ⅰb，B6Ⅰb，B7Ⅰb；
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 m1Ⅰ，m2Ⅰ，m3Ⅰ，m4Ⅰ，m5Ⅰ，m6Ⅰ，m7ⅠCorresponding 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 side of the calibration steel bar facing the protective layer after the reinforced concrete test piece is corroded1Ⅱa，B2Ⅱa，B3Ⅱa，B4Ⅱa，B5Ⅱa，B6Ⅱa，B7Ⅱa(ii) a Magnetic induction intensity data B of one side of calibration reinforcing steel bar back to protective layer after corrosion1Ⅱb，B2Ⅱb，B3Ⅱb，B4Ⅱb，B5Ⅱb，B6Ⅱb，B7Ⅱb. Taking out the steel bar after corrosion, cutting off the part coated with epoxy resin at two ends, removing iron rust on the surface of the steel bar by using a rust remover, weighing, and recording the mass data of the steel bar as m1Ⅱ，m2Ⅱ，m3Ⅱ，m4Ⅱ，m5Ⅱ，m6Ⅱ，m7Ⅱ；
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 the magnetic induction intensity change rate delta B of the side, facing the protective layer, of the reinforcing steel bar1a、△B2a、△B3a、△B4a、△B5a、△B6a、△B7aAnd a magnetic induction intensity change rate Delta B of the side facing away from the protective layer1b、△B2b、△B3b、△B4b、△B5b、△B6b、△B7bThe calculation formulas are respectively formulas (8) to (14);
3.6 respectively carrying out linear fitting on the relationship between the change rate of the steel bar mass and the change rates of the magnetic induction intensity of the Hall sensors at two sides to obtain a linear relationship coefficient alphaa、αb；
Step four, measuring the test, the process is as follows:
4.1 recording the magnetic induction B of the two sides of the piece to be tested before rusting0Ⅰa、B0Ⅰb；
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 recorded0Ⅱa、B0Ⅱb；
4.4 corrosion rate P of the steel bar, and the calculation formula is an expression (15);
Pa＝αa(B0Ia-B0IIa),Pb＝αb(B0Ib-B0IIb) (15)
wherein, PaCorrosion rate, P, of the steel bar facing the protective layerbThe corrosion rate of the side back to the protective layer;
4.4, defining the non-uniform corrosion of the steel bar as R, wherein the larger R is, the more serious the non-uniform corrosion of the steel bar is, and the calculation formula is an expression (16);
the invention has the beneficial effects that: the invention is based on a nondestructive detection method, and utilizes a magnetic induction technology to realize nondestructive monitoring of the corrosion of the steel bar, thereby calculating the corrosion rate of the steel bar facing to and departing from two sides of the protective layer according to a theoretical formula, and analyzing the non-uniform corrosion degree of the steel bar through comparison; the test stability, accuracy and limitation of the traditional test method are broken through, and the non-uniform corrosion degree of the steel bars of the reinforced concrete test piece is tested; the measured steel bar corrosion rate and the non-uniform corrosion degree 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 reinforcing steel bars with different sizes, has the advantages of clear principle, simple and convenient method, high measuring speed, 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 is a schematic view of the assembly and the fixing method of the present invention.
FIG. 5 is a diagram showing the monitoring result of the sensor when the distance between the magnetic core and the magnetic core is 20 mm.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Referring to fig. 1 to 5, a dual-magnetic circuit four-point built-in magnetic sensor comprises a magnetic induction intensity monitoring unit and a data processing unit;
the magnetic induction intensity detection unit comprises a built-in sensor left magnetic core, a built-in sensor right magnetic core, a built-in sensor permanent magnet 4, a first Hall sensor 1-1, a second Hall sensor 1-2, a third Hall sensor 1-3, a fourth Hall sensor 1-4 and a built-in sensor packaging shell 9; the middle part of the upper end of the built-in sensor packaging shell 9 is provided with a steel bar bayonet used for clamping a steel bar to be detected, the built-in sensor packaging shell 9 comprises a built-in sensor inner shell and a built-in sensor outer shell packaging cover 9-6, the built-in sensor inner shell is provided with a first Hall sensor placing groove 9-1, a second Hall sensor placing groove 9-2, a third Hall sensor placing groove 9-3, a fourth Hall sensor placing groove 9-4, a built-in sensor permanent magnet groove 9-5, a built-in sensor left magnetic core groove, a built-in sensor right magnetic core groove, a first cable bending space and a first wire hole, the first Hall sensor placing groove 9-1, the second Hall sensor placing groove 9-2, the third Hall sensor placing groove 9-3, a first wire hole and a second wire hole, The fourth Hall sensor placing grooves 9-4 are all arranged in the reinforcing steel bar notch, the built-in sensor permanent magnet groove 9-5 is positioned between the built-in sensor left magnetic core groove and the built-in sensor right magnetic core groove, the first cable bending space is positioned below the built-in sensor permanent magnet groove 9-5, and the first wire hole is arranged at the bottom of the built-in sensor packaging shell 9 and is communicated with the first cable bending space; the built-in sensor permanent magnet 4 is connected with the built-in sensor left magnetic core and the built-in sensor right magnetic core at the same time and is arranged in a built-in sensor permanent magnet groove 9-5, and the space between the first Hall sensor 1-1 and the second Hall sensor 1-2 and the space between the third Hall sensor 1-3 and the fourth Hall sensor 1-4 are symmetrically arranged by taking the center line of a steel bar bayonet as an axis and are respectively arranged in corresponding Hall sensor placing grooves; the built-in sensor inner shell and the built-in sensor outer shell encapsulation cover 9-6 are both provided with a first fixing hole and a second fixing hole; two fixed ends 10 are arranged at the left end and the right end of the built-in sensor, wire holes are respectively formed in the two fixed ends 10-1 and 10-2, and plastic binding wires 10-3 can penetrate through the wire holes and bind the fixed ends with the steel bars 2 to be tested, so that the sensor is integrally fixed, and the phenomenon that the test effect is influenced due to dislocation is avoided.
The data processing unit comprises a signal collector 5, a signal processor 6 and a central controller 7, wherein the signal input end of the signal collector 5 is electrically connected with the signal output end of the Hall sensor, the output end of the signal collector 5 is electrically connected with the signal input end of the signal processor 6, and the signal output end of the signal processor 6 is electrically connected with the port of the central controller 7.
Furthermore, a first circuit indicator lamp is arranged between the first Hall sensor and the signal collector, a second circuit indicator lamp is arranged between the fourth Hall sensor and the signal collector, and a third circuit indicator lamp is arranged between the fourth Hall sensor and the signal collector. The first circuit indicator light 8-1 and the second circuit indicator light 8-2 respectively prompt whether two lines in the signal collector 5 work normally.
Furthermore, the left magnetic core and the right magnetic core of the built-in sensor are E-shaped special magnetic cores with two openings symmetrically arranged inwards, the connecting line of the upper ends of the openings of the first pair of magnetic cores is superposed with the top tangent of the steel bar to be detected, the openings of the second pair of magnetic cores are arranged into circular arcs, the connecting line of the bottom ends of the openings of the second pair of magnetic cores is superposed with the bottom tangent of the steel bar to be detected, and the openings of the third pair of magnetic cores are connected with. The magnetic induction line following the principle of 'shortest path' can be ensured to pass through the rusty area to the maximum extent, and the magnetic field area has great difference of medium relative permeability. The reinforcing steel bars 2 to be measured with different sizes can be clamped by changing the bayonet distance of the magnetic core.
The magnetic core 3 of the built-in sensor is made of silicon steel, and the permanent magnet 4 of the built-in sensor adopts a neodymium magnet (Nd)2Fe14B) The built-in sensor package shell 10 is made of plastic.
The magnetic induction intensity monitoring unit is arranged in the reinforced concrete structure, so that real-time dynamic monitoring is realized. The concrete can also protect the sensor from external disturbance, and the measurement accuracy is ensured.
The data processing unit and a related control circuit of the data processing unit can be realized by utilizing the existing mature technology, and mainly comprises the steps of measuring the magnetic induction intensity values of the first Hall sensor 1-1 and the second Hall sensor 1-2 so as to calculate the corrosion rate of one side, facing the protective layer, of the steel bar, measuring the magnetic induction intensity values of the third Hall sensor 1-3 and the fourth Hall sensor 1-4 so as to calculate the corrosion rate of one side, facing away from the protective layer, of the steel bar, and comparing the corrosion rates of the two sides so as to analyze the non-uniform corrosion degree of the steel bar. The magnetic induction intensity monitoring unit and the signal collector finish data storage, post-processing and real-time display through the signal processor 6 and the central controller 7.
The working principle of the invention is as follows: a stable magnetic field is manufactured by utilizing a permanent magnet, and the change of the magnetic induction intensity is detected by a Hall sensor and is sent to a signal processor; the signal processor is transmitted to the central processing unit according to the set frequency, and the display screen displays the analysis and calculation result in real time.
Embodiment 1, a method for testing a dual-magnetic-circuit four-point built-in magnetic sensor, taking an HPB300 smooth round bar with a diameter of 16mm as an example, 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 round steel bar with 16mm diameter as calibration steel bar and steel bar to be measured, weighing the mass m of the steel bar to be measured1Ⅰ，m2Ⅰ，m3Ⅰ，m4Ⅰ，m5Ⅰ，m6Ⅰ，m7ⅠAnd calibrating the steel bar mass m0And recording;
1.2 coating epoxy resin on the 5cm positions of the two ends of the calibration steel bar and the steel bar to be detected;
second, preparation before measurement, as follows:
2.1 respectively installing a first Hall sensor 1-1, a second Hall sensor 1-2, a third Hall sensor 1-3 and a fourth Hall sensor 1-4 in a first Hall sensor placing groove 9-1, a second Hall sensor placing groove 9-2, a third Hall sensor placing groove 9-3 and a fourth Hall sensor placing groove 9-4 of an encapsulation shell 9, installing a permanent magnet 4 in an internal sensor permanent magnet groove 9-5, and then covering a built-in sensor shell encapsulation cover 9-6 for encapsulation. Coating epoxy resin at all gaps for sealing;
2.2 the central controller 7 controls the collection frequency of the signal collector 5 to test the magnetic field, so as to ensure that the gauss values of the magnetic induction intensity of the first hall sensor 1-1, the second hall sensor 1-2, the third hall sensor 1-3 and the fourth hall sensor 1-4 are the same.
2.3, the built-in sensor is arranged on the steel bar to be measured, and the front end and the rear end are fixed by plastic binding wires. Placing the steel bar to be tested and the calibration steel bar into a mould and pouring for forming, 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 test piece is 100mm multiplied by 100mm in a standard die, 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 test piece is subjected to standard maintenance for 28d in a maintenance room after casting molding, the cast molding calibration reinforced concrete test piece and the reinforced concrete test piece to be tested 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;
thirdly, a calibration test is carried out, and the process is as follows:
3.1 recording mass m1Ⅰ，m2Ⅰ，m3Ⅰ，m4Ⅰ，m5Ⅰ，m6Ⅰ，m7ⅠCorresponding magnetic induction intensity data B of one side of the calibration reinforcing steel bar facing the protective layer before the reinforced concrete test piece is corroded1Ⅰa，B2Ⅰa，B3Ⅰa，B4Ⅰa，B5Ⅰa，B6Ⅰa，B7Ⅰa(ii) a Magnetic induction intensity data B of one side of calibration reinforcing steel bar back to protective layer before corrosion1Ⅰb，B2Ⅰb，B3Ⅰb，B4Ⅰb，B5Ⅰb，B6Ⅰb，B7Ⅰb；
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 m1Ⅰ，m2Ⅰ，m3Ⅰ，m4Ⅰ，m5Ⅰ，m6Ⅰ，m7ⅠElectrifying the corresponding reinforced concrete test piece at equal intervals for 1 day, 2 days, 3 days, 4 days, 5 days, 6 days and 7 days;
3.3 recording the magnetic induction intensity data B of the side of the calibration steel bar facing the protective layer after the reinforced concrete test piece is corroded1Ⅱa，B2Ⅱa，B3Ⅱa，B4Ⅱa，B5Ⅱa，B6Ⅱa，B7Ⅱa(ii) a Magnetic induction intensity data B of one side of calibration reinforcing steel bar back to protective layer after corrosion1Ⅱb，B2Ⅱb，B3Ⅱb，B4Ⅱb，B5Ⅱb，B6Ⅱb，B7Ⅱb. Taking out the steel bar after corrosion, cutting off the part coated with epoxy resin at two ends, removing iron rust on the surface of the steel bar by using a rust remover, weighing, and recording the mass data of the steel bar as m1Ⅱ，m2Ⅱ，m3Ⅱ，m4Ⅱ，m5Ⅱ，m6Ⅱ，m7Ⅱ；
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 expressed as formulas (17) to (23);
3.5 respective calculation targetTriangle B of side of fixed steel bar facing protective layer1a、△B2a、△B3a、△B4a、△B5a、△B6a、△B7aAnd a magnetic induction intensity change rate Delta B of the side facing away from the protective layer1b、△B2b、△B3b、△B4b、△B5b、△B6b、△B7bThe calculation formulas are respectively formulas (24) to (30);
3.6 respectively carrying out linear fitting on the relationship between the change rate of the steel bar mass and the change rates of the magnetic induction intensity of the Hall sensors at two sides to obtain a linear relationship coefficient alphaa、αb. As shown in fig. 5, the horizontal axis represents the corrosion rate, and the vertical axis represents the magnetic flux density modulus.
Step four, measuring the test, the process is as follows:
4.1 recording the magnetic induction B of the two sides of the piece to be tested before rusting0Ⅰa、B0Ⅰb；
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 recorded0Ⅱa、B0Ⅱb；
4.4 corrosion rate P of the steel bar, and the calculation formula is an expression (15);
Pa＝αa(B0Ia-B0IIa),Pb＝αb(B0Ib-B0IIb) (15)
wherein, PaCorrosion rate, P, of the steel bar facing the protective layerbThe corrosion rate of the side back to the protective layer;
4.4, defining the non-uniform corrosion of the steel bar as R, wherein the larger R is, the more serious the non-uniform corrosion of the steel bar is, and the calculation formula is an expression (16);
example 2 identical test RC beams (800mm x 100mm x 150mm) were prepared with 2 Φ 16 HPB300 plain round steel bars as the bottom longitudinal bars, 2 Φ 10 steel bars as the erection bars, Φ 6@100 as the stirrups and a protective layer thickness of 20 mm. The cement adopts P.I 42.5 cement; the fine aggregate is river sand with fineness modulus of 2.5-2.6 mm, and the mud content is not more than 1.5%; the coarse aggregate is crushed limestone with the continuous gradation of 5-20 mm; the water is purified water. Table 1 shows the concrete mixing ratio.
Before pouring, 4 built-in magnetic sensors with bayonets of 16mm are respectively fixed at the midspan position of each longitudinal rib of each test RC beam by using plastic binding wires, and the sensors are guaranteed not to move.
TABLE 1 concrete mix proportion
And performing standard maintenance 28d in a maintenance room after pouring and forming. And after the maintenance is finished, recording the initial magnetic induction intensity values of the 4 magnetic sensors. A concentrated load of 30kN was applied to the midspan of each of the 2 test beams, and after the concentrated load was applied, the side faces thereof were coated with epoxy resin, and only the upper and lower surfaces of 100mm × 800mm were used as the surfaces into which chloride ions entered. All of the loaded components were then placed in a climatic multifunction test chamber simulating a tidal range chloride environment and the readings from each sensor were monitored in real time. According to the test data, the change rate of the magnetic field intensity of one side facing the protective layer is larger than that of the side opposite to the protective layer, and the steel bar is proved to be subjected to uneven corrosion.
In the specific implementation, the invention does not limit the specific device type, as long as the device can complete the above functions.
Finally, it should be noted that the above list is only for the specific examples of the determination of the newly configured concrete in the laboratory and does not limit the present invention. For the reinforced concrete structure sampled from the existing engineering, the process and method are completely consistent, and the details are not repeated here.
The embodiments of the invention described herein are merely illustrative of implementations of the inventive concept and the scope of the invention should not be considered limited to the specific forms set forth in the embodiments but rather by the equivalents thereof as may occur to those skilled in the art upon consideration of the present inventive concept.
Claims (7)
1. The built-in magnetic sensor with double magnetic circuits and four measuring points is characterized in that: the sensor comprises a magnetic induction intensity monitoring unit and a data processing unit;
the magnetic induction intensity detection unit comprises a built-in sensor left magnetic core, a built-in sensor right magnetic core, a built-in sensor permanent magnet, a first Hall sensor, a second Hall sensor, a third Hall sensor, a fourth Hall sensor and a built-in sensor packaging shell; the middle part of the upper end of the built-in sensor packaging shell is provided with a steel bar bayonet for clamping a steel bar to be measured, the built-in sensor packaging shell comprises a built-in sensor inner shell and a built-in sensor outer shell packaging cover, the built-in sensor inner shell is provided with a first Hall sensor placing groove, a second Hall sensor placing groove, a third Hall sensor placing groove, a fourth Hall sensor placing groove, a built-in sensor permanent magnet groove, a built-in sensor left magnetic core groove, a built-in sensor right magnetic core groove, a first cable bending space and a first wire hole, the first Hall sensor placing groove, the second Hall sensor placing groove, the third Hall sensor placing groove and the fourth Hall sensor placing groove are all arranged in the steel bar bayonet, and the built-in sensor permanent magnet groove is positioned between the built-in sensor left magnetic core groove and the built-in sensor right magnetic core groove, the first cable bending space is positioned below the built-in sensor permanent magnet groove, and the first wire hole is arranged at the bottom of the built-in sensor packaging shell and is communicated with the first cable bending space; the built-in sensor permanent magnet is connected with the built-in sensor left magnetic core and the built-in sensor right magnetic core at the same time and is arranged in a built-in sensor permanent magnet groove, and the first Hall sensor and the second Hall sensor, the third Hall sensor and the fourth Hall sensor are symmetrically arranged by taking the central line of a steel bar bayonet as an axis and are respectively arranged in corresponding Hall sensor placing grooves; the built-in sensor inner shell and the built-in sensor outer shell encapsulation cover are both provided with a first fixing hole and a second fixing hole;
the data processing unit comprises a signal collector, a signal processor and a central controller, wherein the signal input end of the signal collector is electrically connected with the signal output end of the Hall sensor, the output end of the signal collector is electrically connected with the signal input end of the signal processor, and the signal output end of the signal processor is electrically connected with the port of the central controller.
2. The dual magnetic circuit four-point built-in magnetic sensor as claimed in claim 1, wherein: first circuit indicating lamps are arranged between the first Hall sensor and the signal collector, second circuit indicating lamps are arranged between the third Hall sensor and the signal collector, and second circuit indicating lamps are arranged between the fourth Hall sensor and the signal collector.
3. A dual magnetic circuit four-point built-in magnetic sensor as claimed in claim 1 or 2, wherein: the left magnetic core and the right magnetic core of the built-in sensor are E-shaped special magnetic cores with two openings symmetrically arranged inwards, the upper end connecting line of the openings of the first pair of magnetic cores is superposed with the top tangent of the steel bar to be measured, the openings of the second pair of magnetic cores are arranged into circular arcs, the bottom connecting line is superposed with the bottom tangent of the steel bar to be measured, and the openings of the third pair of magnetic cores are connected with the permanent magnet of the built-in sensor.
4. A dual magnetic circuit four-point built-in magnetic sensor as claimed in claim 1 or 2, wherein: two fixed ends are arranged at the left end and the right end of the double-magnetic-circuit four-measuring-point built-in sensor, wire holes are formed in the two fixed ends respectively, and plastic binding wires penetrate through the wire holes and bind the fixed ends and the steel bars to be measured.
5. A dual magnetic circuit four-point built-in magnetic sensor as claimed in claim 1 or 2, wherein: the permanent magnet of the built-in sensor is made of neodymium-nickel-boron, and the left magnetic core and the right magnetic core of the built-in sensor are both made of silicon steel; the built-in sensor packaging shell is made of plastic materials.
6. The built-in magnetic sensor testing method based on the double-magnetic-circuit four-test-point as claimed in claim 1 is characterized in that: the method comprises the following steps: calculating the corrosion rate of the side, facing the protective layer, of the steel bar to be tested through the magnetic induction intensity values of the first Hall sensor and the second Hall sensor, calculating the corrosion rate of the side, facing away from the protective layer, of the steel bar to be tested through the magnetic induction intensity values of the third Hall sensor and the fourth Hall sensor, and comparing the corrosion rates of the two sides so as to analyze the non-uniform corrosion degree of the steel bar to be tested; the magnetic induction intensity monitoring unit and the signal collector finish data storage, post-processing and real-time display through the signal processor and the central controller.
7. The test method of claim 6, wherein: the method further comprises the steps of:
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 measured1Ⅰ，m2Ⅰ，m3Ⅰ，m4Ⅰ，m5Ⅰ，m6Ⅰ，m7ⅠAnd 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 respectively installing a first Hall sensor, a second Hall sensor, a third Hall sensor and a fourth Hall sensor in a first Hall sensor placing groove, a second Hall sensor placing groove, a third Hall sensor placing groove and a fourth Hall sensor placing groove of a packaging shell, installing a permanent magnet in a permanent magnet groove to form a uniform-strength static magnetic field, covering a built-in sensor shell packaging cover for packaging, and coating epoxy resin in all gaps for sealing;
2.2, controlling the acquisition frequency of the signal acquisition device through the central controller, and testing a magnetic field to ensure that the gauss values of the magnetic induction intensities of the first Hall sensor, the second Hall sensor, the third Hall sensor and the fourth Hall sensor are the same;
2.3, mounting the built-in sensor on the steel bar to be measured, and fixing the front end and the rear end by using plastic binding wires;
thirdly, a calibration test is carried out, and the process is as follows:
3.1 recording mass m1Ⅰ，m2Ⅰ，m3Ⅰ，m4Ⅰ，m5Ⅰ，m6Ⅰ，m7ⅠCorresponding magnetic induction intensity data B of one side of the calibration reinforcing steel bar facing the protective layer before the reinforced concrete test piece is corroded1Ⅰa，B2Ⅰa，B3Ⅰa，B4Ⅰa，B5Ⅰa，B6Ⅰa，B7Ⅰa(ii) a Magnetic induction intensity data B of one side of calibration reinforcing steel bar back to protective layer before corrosion1Ⅰb，B2Ⅰb，B3Ⅰb，B4Ⅰb，B5Ⅰb，B6Ⅰb，B7Ⅰb；
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 m1Ⅰ，m2Ⅰ，m3Ⅰ，m4Ⅰ，m5Ⅰ，m6Ⅰ，m7ⅠCorresponding 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 side of the calibration steel bar facing the protective layer after the reinforced concrete test piece is corroded1Ⅱa，B2Ⅱa，B3Ⅱa，B4Ⅱa，B5Ⅱa，B6Ⅱa，B7Ⅱa(ii) a Magnetic induction intensity data B of one side of calibration reinforcing steel bar back to protective layer after corrosion1Ⅱb，B2Ⅱb，B3Ⅱb，B4Ⅱb，B5Ⅱb，B6Ⅱb，B7Ⅱb. Taking out the steel bar after corrosion, cutting off the part coated with epoxy resin at two ends, removing iron rust on the surface of the steel bar by using a rust remover, weighing, and recording the mass data of the steel bar as m1Ⅱ，m2Ⅱ，m3Ⅱ，m4Ⅱ，m5Ⅱ，m6Ⅱ，m7Ⅱ；
3.4 respectively calculating and calibrating the change rate Delta m of the steel bar quality1，△m2，△m3，△m4，△m5，△m6，△m7Meter for measuringThe calculation formulas are respectively expressed as formulas (1) to (7);
3.5 calculating the delta B of the side of the calibrated steel bar facing the protective layer1a、△B2a、△B3a、△B4a、△B5a、△B6a、△B7aAnd a magnetic induction intensity change rate Delta B of the side facing away from the protective layer1b、△B2b、△B3b、△B4b、△B5b、△B6b、△B7bThe calculation formulas are respectively formulas (8) to (14);
3.6 respectively carrying out linear fitting on the relationship between the change rate of the steel bar mass and the change rates of the magnetic induction intensity of the Hall sensors at two sides to obtain a linear relationship coefficient alphaa、αb；
Step four, measuring the test, the process is as follows:
4.1 recording the magnetic induction B of the two sides of the piece to be tested before rusting0Ⅰa、B0Ⅰb；
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 recorded0Ⅱa、B0Ⅱb；
4.4 corrosion rate P of the steel bar, and the calculation formula is an expression (15);
Pa＝αa(B0Ia-B0IIa),Pb＝αb(B0Ib-B0IIb) (15)
wherein, PaCorrosion rate, P, of the steel bar facing the protective layerbThe corrosion rate of the side back to the protective layer;
4.4 defining the uneven corrosion of the steel bar as R, wherein the larger R is, the more serious the uneven corrosion of the steel bar is, and the calculation formula is an expression (16);
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| CN112034034A (en) * | 2020-08-21 | 2020-12-04 | 浙江工业大学 | Veneering type steel bar non-uniform corrosion monitoring sensor based on magnetic field principle and testing method |
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| CN209784255U (en) * | 2019-04-25 | 2019-12-13 | 青岛理工大学 | Novel sensor device for monitoring corrosion of steel bar in large-volume concrete |
| CN110646505A (en) * | 2019-10-18 | 2020-01-03 | 浙江工业大学 | External reinforcement corrosion nondestructive monitoring sensor based on electromagnetic field principle and testing method |
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