Variable-angle multi-magnetic-circuit steel bar non-uniform corrosion monitoring instrument and testing method thereof

Abstract

According to the variable-angle multi-magnetic-circuit steel bar non-uniform corrosion monitoring instrument and the testing method thereof, sensors are fixed to the periphery of a monitoring steel bar through variable-angle fixing supports, multiple sets of sensors are assembled through the variable-angle fixing supports, multiple magnetic fields are formed, and the included angles between the sensors can be adjusted; a plurality of Hall assemblies of the sensor monitor the change of the magnetic field intensity around the reinforcing steel bar in situ in the transverse and longitudinal directions of the reinforcing steel bar; the data collector converts a voltage signal output by the sensor into a numerical signal and transmits the numerical signal to the data processing system; the data processing system receives the voltage signal data and records and processes the voltage signal data in real time. The corrosion condition of the reinforcing steel bar in the reinforced concrete can be monitored in real time in a lossless and quantitative mode, and the method has the advantages of being easy to operate and high in precision.

Description

Technical Field

[0001] The present invention belongs to the technical field of material testing. Specifically, it relates to a variable-angle multi-magnetic-circuit non-uniform corrosion monitoring instrument for steel bars and its testing method, which is used for monitoring the corrosion rate of non-uniform corrosion of steel bars in the transverse and longitudinal directions in the engineering field, and can represent the corrosion conditions of non-uniform corrosion of steel bars in the transverse and longitudinal directions. Background Art

[0002] Reinforced concrete structures are widely used in the field of civil engineering due to their many advantages. However, after chloride erosion or concrete carbonation, the passivation film is damaged and the steel bars begin to corrode. Currently, the corrosion of steel bars in structures caused by chloride ion erosion is relatively common, especially in coastal areas or areas where deicing salts are frequently used in the north. However, there is no absolute method to prevent corrosion; or some protection measures are costly and cannot be applied to all projects. Therefore, regular inspections of building structures are necessary.

[0003] Currently, there are many methods for detecting the corrosion of steel bars, and all methods can be clearly divided into destructive testing and non-destructive testing. Since non-destructive testing methods cause no additional damage to concrete structures, they are widely used in the research on the corrosion of reinforced concrete. In actual engineering projects, there are mainly two types of sensors for monitoring the durability of reinforced concrete: one is a sensor based on the principle of macrocell, and the other is a sensor based on the principle of linear polarization. In addition, there are many other sensors in development, such as fiber optic sensors, piezoelectric sensors, ultrasonic detection sensors, and new ground penetrating radars. The above sensors can basically qualitatively judge whether the steel bars are corroded. However, due to the complexity of the on-site environment, it is impossible to accurately quantitatively analyze the deterioration of the durability of steel bars. Therefore, the corrosion conditions of the entire reinforced concrete structure cannot be obtained. There is still much room for development in the durability monitoring of actual projects.

[0004] Based on the theory of magnetic media and magnetic fields, a non-destructive dynamic monitoring instrument for steel bars based on magnetic fields (MCD or NMCD) has been developed. The MCD or NMCD instrument can non-destructively and quantitatively monitor the corrosion of steel bars in reinforced concrete in real time, and also has the characteristics of easy operation and high precision. Before concrete pouring, the steel bars are placed in the test area of the sensor, and the steel bars are in the magnetic circuit path of the MCD or NMCD, so they have a positive increasing effect on the magnetic field of the MCD or NMCD. When the reinforced concrete is in use and the steel bars are corroded under the action of substances such as water and chloride ions, due to the huge difference in the magnetic conductivity between the steel bars and the corrosion products, the magnetic field around the steel bars also changes. The change in this magnetic signal will be captured by the Hall component (14), and through the calibration curve of the instrument itself, the change in the magnetic signal is converted into the corrosion rate of the steel bars.

[0005] However, after more test trials, it is found that the magnetic induction intensity measured by MCD or NMCD cannot well monitor the non-uniform corrosion of a certain section of steel bar, but represents the corrosion situation of a smaller area close to the steel bar measuring point. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art, such as the incomplete situation reflected by the measured steel bar corrosion rate. In order to more comprehensively obtain the corrosion situation of the steel bar cross-section, the present invention provides a variable-angle multi-magnetic-circuit steel bar non-uniform corrosion monitoring instrument and its testing method. The included angle between the detection instruments can be adjusted, with multiple magnetic circuits, and the magnetic circuits can be increased according to the project situation. At the same time, it is a monitoring instrument that considers the non-uniform corrosion in the transverse and longitudinal directions of the steel bar.

[0007] To solve the technical problem, the solution of the present invention is:

[0008] The variable-angle multi-magnetic-circuit steel bar non-uniform corrosion monitoring instrument includes a sensor, a variable-angle fixed bracket, a data collector, and a data processing system;

[0009] The said sensor is fixed on the periphery of the monitored steel bar through a variable-angle fixed bracket. Multiple groups of sensors are assembled through the variable-angle fixed bracket to form multiple magnetic fields, and the included angle between the sensors can be adjusted; multiple Hall components of the sensor in-situ monitor the change of the magnetic field intensity around the steel bar in the transverse and longitudinal directions of the steel bar;

[0010] The said data collector converts the voltage signal output by the sensor into a numerical signal and transmits it to the data processing system;

[0011] The said data processing system receives the voltage signal data and records and processes it in real time.

[0012] The said sensor includes:

[0013] A permanent magnet for generating a steady magnetic field;

[0014] A silicon steel frame for forming a magnetic field circuit;

[0015] Hall components are installed in the end mounting grooves of the magnetic field circuit of the silicon steel frame, and output the magnetic field change caused by the steel bar corrosion as a voltage change according to the Hall effect;

[0016] A sensor signal transmission circuit board for transmitting the sensing information of the Hall components;

[0017] A variable-angle fixed bracket for fixing multiple groups of sensors, and the angle can be adjusted;

[0018] A data acquisition board, which is an ADS1256IDB data acquisition board, for acquiring and transmitting the voltage signal of the Hall components;

[0019] The cable connects the sensor to the data collector. The cable is a multi-core cable.

[0020] The data collector specifically includes:

[0021] The ADS1256 signal acquisition main chip or a circuit board with similar performance converts the sensor output voltage signal into a numerical signal through four processes: sampling, holding, quantization and encoding;

[0022] RS232 USB or similar performance serial port chip to realize USB to serial port conversion, so as to connect the data collector to the USB interface of the data processing system.

[0023] The data processing system specifically includes:

[0024] The monitoring instrument module automatically stores, processes, and records the voltage signal output by the sensor in real time and displays it as a specific voltage value.

[0025] A method for monitoring non-uniform corrosion of variable-angle multi-magnetic-circuit steel bars, using the variable-angle multi-magnetic-circuit steel bar non-uniform corrosion monitoring instrument;

[0026] The method comprises the following steps:

[0027] Step 1: Measure the voltage value of a type of steel bar when it is not corroded;

[0028] Step 2: corrode the steel bar, measure the voltage value of the steel bar after corrosion, and measure the corrosion rate of the steel bar at the same time;

[0029] Step 3: Repeat step 2 to establish the relationship between the steel bar corrosion rate and the measured voltage;

[0030] Step 4: embed the sensor in the reinforced concrete component, measure the voltage value, and obtain the steel corrosion rate based on the relationship established in step 3.

[0031] In the present invention, the sensor is fixed at the monitored steel bar through a variable angle multi-magnetic circuit sensor variable angle fixing bracket. The sensor has a built-in Hall component and outputs different voltage signals according to different steel bar corrosion amounts. The data collector includes a circuit board with an ADS1256 signal acquisition main chip or similar performance, and an RS232 USB to serial port chip. The voltage signal is collected through a multi-core cable and the sensor, and the voltage signal is converted into a numerical signal through internal circuit board processing, and finally transmitted to the data processing system.

[0032] Working principle of the present invention:

[0033] The sensor based on the transverse and longitudinal non-uniform corrosion of steel bars by magnetic field includes four or more permanent magnets and a silicon steel frame. The permanent magnet itself can generate a fixed magnetic field. When combined with the silicon steel frame in the sensor, the magnetic flux will generate a magnetic circuit along the silicon steel frame and air. The sensor forms four or more magnetic circuits in total, including both magnetic circuits along the transverse direction of the steel bar and those along the longitudinal direction of the steel bar. When the steel bar is located at the test position in the middle of the sensor, that is, the air position on the magnetic circuit path, since the steel bar is a magnetic conductor while air is a non-magnetic conductor, the presence of the steel bar interferes with the magnetic circuit of the sensor. The change in the magnetic circuit is detected by the Hall component in the sensor and output as a voltage signal, which is processed by the data collector and presented as a certain magnetic induction intensity value at the terminal of the data processing system. As the steel bar corrodes, the interference with the magnetic circuit changes, resulting in a change in the finally output magnetic induction intensity value. In this way, the correlation between the steel bar corrosion rate and the magnetic induction intensity value is established, achieving the purpose of quantitatively judging the steel bar corrosion rate by monitoring the magnetic induction intensity value.

[0034] Based on the magnetic medium and magnetic field theory, the present invention can non-destructively and quantitatively monitor the corrosion of steel bars in reinforced concrete in real time, with the characteristics of easy operation and high precision. Therefore, it has great development potential in engineering applications.

[0035] Compared with the prior art, the beneficial effects of the present invention are mainly manifested in:

[0036] 1. The monitor is installed with a variable-angle fixed bracket. The included angle of the monitor can be adjusted, and the quantity can be increased or decreased, with simple operation.

[0037] 2. The sensor has multiple measuring points around the cross-section and longitudinally of the steel bar. The test results show that the magnetic induction intensity values of multiple measuring points around the steel bar can be measured respectively. The non-uniform corrosion of the steel bar in the transverse and longitudinal directions can be obtained from the magnetic induction intensity values of different measuring points to determine the corrosion situation of the steel bar cross-section and convert it into the steel bar corrosion rate.

[0038] 3. Before the sensor is embedded in the reinforced concrete, the relationship between the steel bar corrosion amount and the magnetic induction intensity value has been established. When applied in subsequent projects, the sensor can be embedded in the reinforced concrete to quantitatively determine the corrosion situation of the steel bar. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is the three-dimensional view of the variable-angle multi-magnetic circuit sensor;

[0040] Figure 2 is the front view of the variable-angle multi-magnetic circuit sensor;

[0041] Figure 3 is the side view of the variable-angle fixed bracket of the variable-angle multi-magnetic circuit sensor;

[0042] Figure 4It is a front view of a variable angle fixing bracket of a variable angle multi-magnetic circuit sensor;

[0043] Figure 5 This is the appearance diagram of a single sensor;

[0044] Figure 6 for Figure 1 The cross-sectional view is the internal structure of the sensor (without the circuit board);

[0045] Figure 7 for Figure 1 The cross-sectional view is the internal structure of the sensor (with circuit board);

[0046] Figure 8 Schematic diagram of the semi-immersion impressed current accelerated corrosion test. DETAILED DESCRIPTION

[0047] The specific technical solution of the present invention is described in conjunction with the accompanying drawings.

[0048] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 8 As shown, the variable angle multi-magnetic circuit steel bar non-uniform corrosion monitoring instrument includes a sensor 1, a variable angle fixing bracket 2, a data collector 3 and a data processing system 4;

[0049] The sensor 1 is fixed to the periphery of the monitoring steel bar 10 through the variable angle fixing bracket 2. Multiple groups of sensors 1 are assembled through the variable angle fixing bracket 2 to form a multi-path magnetic field. The angles between the sensors 1 can be adjusted; multiple Hall components 14 of the sensor 1 monitor the changes in the magnetic field intensity around the steel bar 10 in situ in the horizontal and vertical directions of the steel bar 10;

[0050] The data collector 3 converts the output voltage signal of the sensor 1 into a numerical signal and transmits it to the data processing system;

[0051] The data processing system 4 receives the voltage signal data and records and processes it in real time.

[0052] like Figure 5 , Figure 6 and Figure 7 As shown, the sensor 1 comprises:

[0053] A permanent magnet 11, used to generate a steady-state magnetic field;

[0054] Silicon steel frame 12, used to form a magnetic field loop;

[0055] The Hall component 14 is installed in the end installation groove 13 of the magnetic field loop of the silicon steel frame 12, and outputs the magnetic field change caused by the steel bar corrosion as a voltage change according to the Hall effect;

[0056] A sensor signal transmission circuit board for transmitting the sensing information of the Hall component 14;

[0057] A variable-angle fixing bracket 2 for fixing multiple groups of sensors with adjustable angles;

[0058] A data acquisition board, which is an ADS1256IDB data acquisition board for acquiring and transmitting the voltage signal of the Hall component 14;

[0059] A cable 15 connecting the sensor 1 to the data collector 3.

[0060] The data collector 3 includes:

[0061] An ADS1256 signal acquisition main chip, which converts the voltage signal output by the sensor 1 into a numerical signal through four processes of sampling, holding, quantization, and encoding;

[0062] An RS232 USB-to-serial chip to implement USB-to-serial conversion, thereby connecting the data collector 3 to the USB interface of the data processing system 4.

[0063] The data processing system 4 includes:

[0064] A monitoring instrument module that automatically stores, processes, and real-time records the voltage signal output by the sensor 1 and displays it as a specific voltage value.

[0065] The following takes a 20mm HRB400 ribbed steel bar as an example to specifically illustrate the implementation manner of the present invention.

[0066] 1. Prepare two steel bars with a length of 20 cm, measure the mass with an electronic scale, and calculate the mass at the middle 8 cm as m;

[0067] 2. Weld a wire on one side of the steel bar 10, then apply epoxy resin at both ends of 8 cm, and wrap waterproof tape after solidification to achieve the purpose of only rusting the middle 8 cm. (There is a large difference in the rusting rate between the energized rusted ends and the middle part of the steel bar, so only the middle part is measured);

[0068] 3. Measure the mass of the entire processed sample as M0;

[0069] 4. Mark two points at 1.5 cm on both sides of the center point of each steel bar 10, and measure the initial voltage value V0 with the sensor 1;

[0070] 5. As Figure 8 , place the steel bar 10 in a 5% NaCl solution 7 and put in an auxiliary electrode 6. The auxiliary electrode 6 and the steel bar 10 are respectively connected to a power supply 5, and the current density of the power supply 5 is 20 A / m 2, after every 24 hours, take out 10 corroded steel bars. Connect the sensor 1 to the data collector 3 and the data processing system 4 in sequence. Use the sensor 1 to measure the post-rust voltages V11, V21, …, V81 (voltages at eight measuring points), then use a steel bar rust remover to remove the external rust layer. After drying, measure the post-rust mass M1 with an electronic scale;

[0071] 6. Repeat step 5, record the post-rust voltages V12, … V82, V13, …, V83…; post-rust masses M2, M3…. When the corrosion rate of the steel bar is close to 20%, the measurement ends.

[0072] 7. Use the formula (V0—Vi j ) / V0 to calculate the voltage change rate ΔU at the i-th measuring point in the j-th cycle; calculate the corrosion rate Δm of the 8-cm steel bar in the middle with (M0—Mi) / m, and use this value as the corrosion rate of the two calibration points of each steel bar.

[0073] 8. Take the mass loss rate Δm as the abscissa and the voltage change rate ΔU as the ordinate. Substitute the voltage change rates and the corresponding mass loss rates of all points in all cycles, and obtain the correlation between the voltage change rate and the mass loss rate of this type of steel bar. The obtained relationship is a linear relationship: △U=k△m+b. Among them, ΔU is the voltage change rate, Δm is the mass loss rate, and k and b are coefficients.

[0074] 9. When casting a reinforced concrete member, embed the sensor 1 at the key points of the member (such as the mid-span of a flexural beam), measure the voltage V0 at the monitoring point before corrosion, and measure the voltage Vi at the monitoring point again after the member has corroded for a certain period of time j , calculate the voltage reduction rate, substitute it into the formula obtained in step 8, obtain the corrosion rates of multiple measuring points on the steel bar cross-section, respectively represent the corrosion conditions at different positions on the steel bar cross-section, and then the true corrosion rate of the steel bar can be obtained.

[0075] 10. Use the measured corrosion rate of the steel bar to evaluate the concrete structure. When the corrosion rate of the steel bar is less than 5%, appropriate measures can be taken to prevent further corrosion of the steel bar; when the corrosion rate of the steel bar is greater than 5% and less than 10%, it is necessary to evaluate the member and observe whether local maintenance of the member is required; when the corrosion rate of the steel bar is greater than 10%, maintenance or replacement of the member is required.

Claims

1. Variable-angle multi-magnetic-circuit steel bar non-uniform corrosion monitoring instrument, characterized in that: It includes a sensor (1), a variable-angle fixing bracket (2), a data collector (3), and a data processing system (4); The said sensor (1) is fixed around the monitored steel bar (10) through the variable-angle fixing bracket (2). Multiple groups of sensors (1) are assembled through the variable-angle fixing bracket (2) to form multiple magnetic fields, and the included angle between the sensors (1) can be adjusted; multiple Hall components (14) of the sensor (1) in-situ monitor the change of the magnetic field intensity around the steel bar (10) in the transverse and longitudinal directions of the steel bar (10); The said data collector (3) converts the voltage signal output by the sensor (1) into a numerical signal and transmits it to the data processing system; The said data processing system (4) receives the voltage signal data and records and processes it in real time.

2. The variable-angle multi-magnetic-circuit steel bar non-uniform corrosion monitoring instrument according to claim 1, characterized in that The said sensor (1) includes: A permanent magnet (11) for generating a steady magnetic field; A silicon steel frame (12) for forming a magnetic field loop; A Hall component (14) installed in the end mounting groove (13) of the magnetic field loop of the silicon steel frame (12), which outputs the magnetic field change caused by steel bar corrosion as a voltage change according to the Hall effect; A sensor signal transmission circuit board for transmitting the sensing information of the Hall component (14); A variable-angle fixing bracket (2) for fixing multiple groups of sensors, the angle of which can be adjusted; A data acquisition board, which is an ADS1256IDB data acquisition board, for acquiring and transmitting the voltage signal of the Hall component (14); A cable (15) connecting the sensor (1) and the data collector (3).

3. The variable-angle multi-magnetic-circuit steel bar non-uniform corrosion monitoring instrument according to claim 1, characterized in that The said data collector (3) includes: An ADS1256 signal acquisition main chip, which converts the voltage signal output by the sensor (1) into a numerical signal through four processes of sampling, holding, quantization, and encoding; An RS232 USB-to-serial port chip for realizing USB-to-serial port conversion, so as to connect the data collector (3) to the USB interface of the data processing system (4).

4. The variable-angle multi-magnetic-circuit steel bar non-uniform corrosion monitoring instrument according to claim 1, characterized in that, The said data processing system (4) includes: A monitoring instrument module for automatically storing, processing, and real-time recording the voltage signal output by the sensor (1) and displaying it as a specific voltage value.

5. Variable-angle multi-magnetic-circuit steel bar non-uniform corrosion monitoring method, characterized in that, Adopt the variable-angle multi-magnetic-circuit steel bar non-uniform corrosion monitoring instrument according to any one of claims 1 to 4; The said method includes the following steps: Step 1: Measure the voltage value of a certain type of steel bar when it is not corroded; Step 2: Corrode the steel bar, measure the voltage value of the corroded steel bar, and measure the steel bar corrosion rate at the same time; Step 3: Repeat Step 2 to establish the relationship between the steel bar corrosion rate and the measured voltage; Step 4: Embed the sensor (1) in the reinforced concrete member, measure the voltage value, and obtain the steel bar corrosion rate according to the relationship established in Step 3.

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