A weak magnetic detection device for a component with a coating layer and a method for determining the excitation condition thereof

Abstract

The present invention discloses a weak magnetic detection device for a component with a coating layer and a method for determining the excitation conditions thereof, which belong to the field of non-destructive testing technology. The device comprises a probe and a host computer; the probe comprises an excitation module, a signal acquisition and processing module and a shell; the excitation module is composed of a U-shaped magnetic yoke and a coil, the signal acquisition and processing module is composed of a circuit board 1, a circuit board 2 and a wheel encoder, and the excitation module and the signal acquisition and processing module are integrated and arranged in the shell. The method for determining the excitation conditions comprises: (1) obtaining the variation law of the magnetization intensity of the component material with the intensity of the excitation magnetic field; (2) determining the excitation magnetic field intensity that is most sensitive to stress; (3) implementing a variable excitation calibration experiment of the component with a coating layer; (4) exploring the correlation between the excitation magnetic field intensity and the coating thickness and the excitation current; (5) determining the optimal excitation current. The purpose of the present invention is to accurately magnetize the component with a coating layer to achieve efficient, fast, convenient and accurate weak magnetic detection.

Description

Technical Field

[0001] The invention relates to the technical field of nondestructive testing, and in particular to a weak magnetic detection device for a component with a coating layer and a method for determining an excitation condition thereof. Background Art

[0002] In industrial production, pipes, tanks, pillars and other test pieces are often coated to prevent corrosion, keep warm or protect them. During long-term service, due to the combined effects of the external working environment and the internal medium, the test pieces under the coating will inevitably suffer damage such as corrosion and cracks. However, detecting damage to components with coatings has always been a difficult problem in industry. The commonly used method of stripping the coating for detection is time-consuming and has high detection costs. Therefore, rapid and effective non-destructive testing of components with coatings is of great significance to ensure safe production.

[0003] Chinese patent CN114965674A proposes a magnetic detection device and method for defects in the coating layer pipeline of an oil and gas station, which uses a permanent magnet arranged in a circular array to magnetize the pipeline and determines the defects of the pipeline by collecting leakage magnetic field information. This method successfully solves the magnetization problem of the pipeline with a coating layer, but the early damage signals such as microscopic defects and stress concentration of the pipeline will be covered up under the strong magnetic effect, and the magnetization intensity of the permanent magnet is fixed, and it cannot be flexibly adjusted in response to changes in the coating layer thickness. At the same time, the device cannot detect irregularly shaped components with a coating layer.

[0004] Chinese patent CN113092576A discloses a metal magnetic memory detection device under weak magnetic field excitation and its use method. The device strengthens the metal magnetic memory detection signal by setting an excitation yoke and makes the probe fully fit the workpiece surface by setting a spring, in order to improve the detection accuracy. However, the device is only suitable for fixed-point detection, not easy to move, and the detection range is limited; at the same time, the difference in lift-off effect of different coating thicknesses is not considered, and the optimal excitation conditions cannot be determined, which affects the detection results.

[0005] Therefore, there is currently a lack of a device and corresponding method that can efficiently and accurately magnetize components with coatings, determine the optimal excitation conditions based on component characteristics and coating thickness, and achieve efficient and rapid weak magnetic detection. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a device and a corresponding method that can efficiently and accurately magnetize components with coating layers, determine the optimal excitation conditions according to the component characteristics and the thickness of the coating layer, and realize efficient and rapid weak magnetic detection.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A weak magnetic detection device with a coating component comprises a probe and a host computer; the probe comprises an excitation module, a signal acquisition and processing module and a shell; the excitation module consists of a U-shaped yoke and a coil, and the coil is wound around the middle beam of the U-shaped yoke; the signal acquisition and processing module consists of a circuit board 1, a circuit board 2 and a wheel encoder, a magnetic sensor and a signal amplifier are arranged on the circuit board 1, and an A / D converter, a D / A converter, a single-chip microcomputer and a serial port chip are arranged on the circuit board 2; the excitation module and the signal acquisition and processing module are integrated and arranged in the shell.

[0009] Furthermore, the coil is electrically connected to the second circuit board; the wheel encoder is electrically connected to the second circuit board; the first circuit board and the second circuit board are electrically connected; and the second circuit board is electrically connected to the host computer.

[0010] Furthermore, a groove is provided at the bottom of the shell, the circuit board 1 is arranged in the bottom groove of the shell, the U-shaped yoke is arranged on the bottom surface of the shell, and the magnetic sensor on the circuit board 1 is kept at the bottom center of the U-shaped yoke, and the bottom surface of the leg of the U-shaped yoke is located on the same horizontal plane as the magnetic sensor; the circuit board 2 is arranged between the U-shaped yoke and the circuit board 1.

[0011] Furthermore, the wheel encoder is arranged at the rear end of the shell, and two rollers are arranged at the front and rear ends of the shell respectively, wherein roller one is the moving wheel of the wheel encoder.

[0012] Furthermore, the shell is made of non-metallic material.

[0013] A method for determining an excitation condition of a weak magnetic detection device with a coating layer component specifically comprises the following steps:

[0014] Step 1: Obtain the variation law of the magnetization intensity of the component material with the intensity of the exciting magnetic field; substitute the magnetic parameters corresponding to the component material into the JA model, solve the JA model using the standard variable step-size Runge-Kutta method, and obtain the relationship curve between the magnetization intensity and the exciting magnetic field intensity under two different stress conditions; the formula of the JA model is as follows:

[0015] Formula (1)

[0016] Formula (2)

[0017] Formula (3)

[0018] in, H e is the effective magnetic field strength, A / m;

[0019] H is the excitation magnetic field strength, A / m;

[0020] α is the domain wall coupling coefficient;

[0021] M is the magnetization, A / m;

[0022] σ is the stress, Pa;

[0023] , , , is a constant related to the material;

[0024] μ 0 is the vacuum permeability, which is 4π×10 -7 H / m, where π is the ratio of the circumference of a circle to the circumference of a circle, which is 3.14;

[0025] M an is the hysteresis-free magnetization, A / m;

[0026] M s is the saturation magnetization, A / m;

[0027] a is the shape factor;

[0028] k is the hysteresis loss coefficient;

[0029] c is the reversibility coefficient;

[0030] δ is the directivity coefficient, when d H / d t >0, then δ =1; when d H / d t <0, then δ = -1, t It refers to time;

[0031] Step 2: Determine the excitation magnetic field intensity that is most sensitive to stress; based on the curve obtained in step 1, subtract different magnetization intensities corresponding to the same excitation magnetic field intensity, and obtain a curve of the change of the magnetization intensity difference with the excitation magnetic field intensity. Take the rising section of the curve, and the excitation magnetic field intensity corresponding to the 80% point of the peak value is the excitation magnetic field intensity that is most sensitive to stress;

[0032] Step 3: Implement a variable excitation calibration experiment for a component with a coating layer; make a plate-shaped test piece with the same material as the component with a coating layer, remove the circuit board 1 from the probe, and place it on the surface of the test piece, so that the tangential direction of the magnetic sensor on the circuit board 1 is consistent with the axial direction of the test piece; place the non-metallic pad and the probe layer by layer, so that the U-shaped magnetic yoke in the probe is placed along the axial direction of the test piece, and keep the circuit board 1 aligned with the groove at the bottom of the probe shell; apply direct current of different values ​​to the coil, place multiple layers of non-metallic pads of different thicknesses on the surface of the test piece, and use the magnetic sensor to collect different excitation currents and different coating thicknesses. The tangential magnetic field strength on the surface of the test piece is used to characterize the excitation magnetic field strength, and a relationship diagram between the excitation magnetic field strength and the excitation current and the coating thickness is obtained;

[0033] Step 4: Explore the correlation between the excitation magnetic field intensity, the coating thickness and the excitation current; use the multivariate nonlinear regression method to fit the relationship diagram between the excitation magnetic field intensity, the excitation current and the coating thickness measured in step 3, and obtain the function expression of the excitation magnetic field intensity, the coating thickness and the excitation current, as follows:

[0034] Formula (4)

[0035] in, h is the coating thickness, m;

[0036] I is the excitation current, A;

[0037] q , b , z , d , e , f To fit the data;

[0038] Step 5: Determine the optimal excitation current; substitute the excitation magnetic field intensity most sensitive to stress determined in step 2 and the coating layer thickness into formula (4) obtained in step 4 to calculate the excitation current most sensitive to stress.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The optimal excitation current determination method based on theoretical calculation and calibration experiment not only fully considers the influence of component material and coating thickness, but also has high stress sensitivity, which is conducive to the detection of micro defects and stress concentration, so as to achieve accurate magnetization of components with coating layers.

[0041] (2) Use an energized coil to apply a magnetic field for easy adjustment; use a U-shaped magnetic yoke to focus the magnetic field and direct it toward the component to achieve efficient magnetization of the component with a coating.

[0042] (3) The use of a wheel encoder for displacement signal acquisition avoids the problem of inaccurate defect location information caused by uneven probe movement speed during actual detection. At the same time, the setting of the wheeled moving mechanism not only enhances the adaptability of the probe, but also greatly improves the detection rate, thereby achieving efficient and rapid on-site detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a schematic diagram of the detection device;

[0044] Figure 2 It is a schematic diagram of the internal structure of the probe;

[0045] Figure 3 It is a graph showing the relationship between magnetization intensity and excitation magnetic field intensity under two different stress conditions;

[0046] Figure 4 It is a curve diagram of the change of magnetization intensity difference with the intensity of the exciting magnetic field;

[0047] Figure 5 It is a graph showing the relationship between the excitation magnetic field intensity, the excitation current and the coating thickness.

[0048] Among them, 1 is a probe, 2 is a host computer, 3 is a shell, 4 is a U-shaped yoke, 5 is a coil, 6 is a circuit board one, 7 is a circuit board two, 8 is a wheel encoder, 9 is a magnetic sensor, 10 is a signal amplifier, 11 is an A / D converter, 12 is a D / A converter, 13 is a single-chip microcomputer, 14 is a serial port chip, and 15 is a roller one. DETAILED DESCRIPTION

[0049] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0050] like Figure 1 and Figure 2 As shown, a weak magnetic detection device with a coating component includes a probe 1 and a host computer 2, wherein the probe 1 includes an excitation module, a signal acquisition and processing module and a housing 3. The excitation module is composed of a U-shaped magnetic yoke 4 and a coil 5, and the coil 5 is wound around the middle beam of the U-shaped magnetic yoke 4. The signal acquisition and processing module is composed of a circuit board 1 6, a circuit board 2 7 and a wheel encoder 8, a magnetic sensor 9 and a signal amplifier 10 are arranged on the circuit board 1 6, and an A / D converter 11, a D / A converter 12, a single-chip microcomputer 13 and a serial port chip 14 are arranged on the circuit board 2 7; the excitation module and the signal acquisition and processing module are integrated and arranged in the housing 3.

[0051] The coil 5 is electrically connected to the circuit board 2 7 , and the circuit board 2 7 is electrically connected to the host computer 2 . The host computer 2 supplies power to the D / A converter 12 on the circuit board 2 7 through the USB connection, and controls the current value transmitted to the coil 5 by the D / A converter 12 .

[0052] Circuit board 1 6 and circuit board 2 7 are electrically connected; the magnetic sensor 9 on circuit board 1 6 adopts a three-axis TMR magnetic sensor to simultaneously collect magnetic field signals in three directions; the serial port chip 14 on circuit board 2 7 is specifically a USB to serial port chip, which is used for data transmission and communication with the host computer 2.

[0053] A groove is provided at the bottom of the shell 3, and the circuit board 6 is arranged in the bottom groove of the shell 3 and is fixed by a detachable connection method such as screws or snaps; the U-shaped yoke 4 is arranged on the bottom surface inside the shell 3 and fixed by a limit plate; the magnetic sensor 9 on the circuit board 6 is kept at the bottom center of the U-shaped yoke 4, and the bottom surface of the leg of the U-shaped yoke 4 and the magnetic sensor 9 are located at the same horizontal plane to ensure the accuracy of the detection data; the circuit board 2 7 is arranged between the U-shaped yoke 4 and the circuit board 1 6; the circuit board 1 6 and the circuit board 2 7 are arranged separately and electrically connected, which not only facilitates the precise positioning of the magnetic sensor 9, but also can make full use of the space of the shell 3; the USB interface of the circuit board 2 7 is aligned with the side window of the shell 3 and passes through, which is convenient for wiring.

[0054] The wheel encoder 8 is arranged at the rear end of the housing 3, and two rollers are arranged at the front and rear ends of the housing 3, respectively. The roller 15 is the moving wheel of the wheel encoder 8, which rotates with the movement of the probe 1 to generate a certain number of pulse signals with a certain time interval. The wheel encoder 8 is electrically connected to the circuit board 2 7, and provides a pulse signal to the single chip 13 on the circuit board 2 7 to determine the displacement of the magnetic sensor 9.

[0055] The housing 3 is made of non-metallic material to avoid interference with the signal collected by the magnetic sensor 9 .

[0056] The present invention is based on a weak magnetic detection device with a coating layer component, and forms a method for determining an excitation condition of a weak magnetic detection device with a coating layer component, which specifically includes the following steps:

[0057] Step 1: Obtain the variation law of the magnetization intensity of the component material with the intensity of the excitation magnetic field; Substitute the magnetic parameters corresponding to the component material into the JA model, including α , , , , , M s , a , k and c There are 9 magnetic parameters in total. The JA model is solved using the standard variable step-size Runge-Kutta method to obtain the relationship between the magnetization intensity and the excitation magnetic field intensity under two different stress conditions, as shown in Figure 3As shown; the smaller stress value can be taken as the lowest stress value of the component in normal working state, and the larger stress value can be taken as 2~3 times of the highest stress value in normal working state to ensure the validity of the stress examination range; the formula of JA model is as follows:

[0058] Formula (1)

[0059] Formula (2)

[0060] Formula (3)

[0061] in, H e is the effective magnetic field strength, A / m;

[0062] H is the excitation magnetic field strength, A / m;

[0063] α is the domain wall coupling coefficient;

[0064] M is the magnetization, A / m;

[0065] σ is the stress, Pa;

[0066] , , , is a constant related to the material;

[0067] μ 0 is the vacuum permeability, which is 4π×10 -7 H / m, where π is the ratio of the circumference of a circle to the circumference of a circle, which is 3.14;

[0068] M an is the hysteresis-free magnetization, A / m;

[0069] M s is the saturation magnetization, A / m;

[0070] a is the shape factor;

[0071] k is the hysteresis loss coefficient;

[0072] c is the reversibility coefficient;

[0073] δ is the directivity coefficient, when d H / d t >0, then δ =1; when d H / d t <0, then δ = -1, t It refers to time;

[0074] Step 2: Determine the excitation magnetic field intensity that is most sensitive to stress; according to the curve obtained in step 1 ( Figure 3 ), subtract the different magnetization intensities corresponding to the same excitation magnetic field strength, and obtain the curve of the change of the magnetization intensity difference with the excitation magnetic field strength, such as Figure 4 As shown; take the rising section of the curve, the value is the excitation magnetic field intensity corresponding to the 80% point of the peak value, which is the excitation magnetic field intensity most sensitive to stress;

[0075] Step 3: Implement variable excitation calibration experiment of components with coating layers; make a plate-shaped test piece with the same material as the component with coating layer, remove circuit board 6 from probe 1, and place it on the surface of the test piece, so that the tangential direction of the magnetic sensor 9 on circuit board 6 is consistent with the axial direction of the test piece; place non-metallic pads and probe 1 layer by layer, so that the U-shaped magnetic yoke 4 in probe 1 is placed along the axial direction of the test piece, and keep circuit board 6 aligned with the groove at the bottom of shell 3; apply a certain value of direct current to coil 5 through host computer 2, simulate different coating thicknesses by placing multiple layers of non-metallic pads of different thicknesses, and use magnetic sensor 9 to detect the tangential magnetic field intensity on the surface of the test piece; change the current value, repeat the above operation, and the tangential magnetic field intensity of the test piece surface at different excitation currents and different coating thicknesses can be collected to characterize the excitation magnetic field intensity, and obtain the relationship diagram between the excitation magnetic field intensity and the excitation current and the coating thickness, as shown in Figure 5 shown.

[0076] Step 4: Explore the correlation between the excitation magnetic field intensity, the coating thickness and the excitation current; use the multivariate nonlinear regression method to fit the relationship diagram between the excitation magnetic field intensity, the excitation current and the coating thickness measured in step 3, and obtain the function expression of the excitation magnetic field intensity, the coating thickness and the excitation current, as follows:

[0077] Formula (4)

[0078] in, h is the coating thickness, m;

[0079] I is the excitation current, A;

[0080] q , b , z , d , e , f To fit the data;

[0081] Step 5: Determine the optimal excitation current; substitute the excitation magnetic field intensity most sensitive to stress determined in step 2 and the coating layer thickness into formula (4) obtained in step 4 to calculate the excitation current most sensitive to stress.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining excitation conditions of a weak magnetic detection device with a coating layer component, characterized in that: The weak magnetic field detection device comprises a probe (1) and a host computer (2); the probe (1) comprises an excitation module, a signal acquisition processing module and a housing (3); the excitation module comprises a U-shaped magnetic yoke (4) and a coil (5), the coil (5) being wound around the middle beam of the U-shaped magnetic yoke (4); the signal acquisition processing module comprises a circuit board (6), a circuit board (7) and a wheel encoder (8), the circuit board (6) being provided with a magnetic sensor (9) and a signal amplifier (10), the circuit board (7) being provided with an A / D converter (11), a D / A converter (12), a single chip microcomputer (13) and a serial port chip (14); the excitation module and the signal acquisition processing module are integrated and arranged in the housing (3); the excitation condition determination method comprises the following steps: Step 1: Obtain the variation law of the magnetization intensity of the component material with the intensity of the exciting magnetic field; substitute the magnetic parameters corresponding to the component material into the JA model, solve the JA model using the standard variable step-size Runge-Kutta method, and obtain the relationship curve between the magnetization intensity and the exciting magnetic field intensity under two different stress conditions; the formula of the JA model is as follows: Among them, H e is the effective magnetic field strength, A / m; H is the excitation magnetic field strength, A / m; α is the domain wall coupling coefficient; M is the magnetization, A / m; σ is stress, Pa; γ1, γ2, γ1′, γ2′ are constants related to the material; μ0 is the vacuum permeability, which is 4π×10 -7 H / m, where π is the ratio of the circumference of a circle to the circumference of a circle, which is 3.14; M an is the hysteresis-free magnetization, A / m; M s is the saturation magnetization, A / m; a is the shape factor; k is the hysteresis loss coefficient; c is the reversibility coefficient; δ is the directional coefficient. When dH / dt>0, δ=1; when dH / dt<0, δ=-1, and t refers to time. Step 2: Determine the excitation magnetic field intensity that is most sensitive to stress; based on the curve obtained in step 1, subtract different magnetization intensities corresponding to the same excitation magnetic field intensity, and obtain a curve of the change of the magnetization intensity difference with the excitation magnetic field intensity. Take the rising section of the curve, and the excitation magnetic field intensity corresponding to the 80% point of the peak value is the excitation magnetic field intensity that is most sensitive to stress; Step 3: Implement a variable excitation calibration experiment for a component with a coating layer; prepare a plate-shaped test piece made of the same material as the component with a coating layer, remove a circuit board (6) from the probe (1), and place it on the surface of the test piece so that the tangential direction of the magnetic sensor (9) on the circuit board (6) is consistent with the axial direction of the test piece; place non-metallic pads and probes (1) layer by layer so that the U-shaped magnetic yoke (4) in the probe (1) is placed along the axial direction of the test piece, and the circuit board (6) is kept aligned with the groove at the bottom of the shell (3); apply direct current of different values ​​to the coil (5), place multiple layers of non-metallic pads of different thicknesses on the surface of the test piece, and use the magnetic sensor (9) to collect different excitation currents and different coating layer thicknesses. The tangential magnetic field strength on the surface of the test piece is used to characterize the excitation magnetic field strength, and a relationship diagram between the excitation magnetic field strength and the excitation current and the coating layer thickness is obtained; Step 4: Explore the correlation between the excitation magnetic field intensity, the coating thickness and the excitation current; use the multivariate nonlinear regression method to fit the relationship diagram between the excitation magnetic field intensity, the excitation current and the coating thickness measured in step 3, and obtain the function expression of the excitation magnetic field intensity, the coating thickness and the excitation current, as follows: H = qh + bI + zh 2 + dI 2 + ehI + f Formula (4) Where, h is the coating thickness, m; I is the excitation current, A; q, b, z, d, e, and f are fitting data; Step 5: Determine the optimal excitation current; substitute the excitation magnetic field intensity most sensitive to stress determined in step 2 and the coating layer thickness into formula (4) obtained in step 4 to calculate the excitation current most sensitive to stress.

2. The method for determining the excitation condition of a weak magnetic detection device for a component with a coating layer according to claim 1, characterized in that: The coil (5) is electrically connected to the second circuit board (7); the wheel encoder (8) is electrically connected to the second circuit board (7); the first circuit board (6) is electrically connected to the second circuit board (7); the second circuit board (7) is electrically connected to the host computer (2).

3. The method for determining the excitation condition of a weak magnetic detection device for a component with a coating layer according to claim 1, characterized in that: The shell (3) is provided with a groove at the bottom, the circuit board (6) is arranged at the groove at the bottom of the shell (3), the U-shaped magnetic yoke (4) is arranged on the bottom surface of the shell (3), and the magnetic sensor (9) on the circuit board (6) is kept at the bottom center of the U-shaped magnetic yoke (4), and the bottom surface of the leg of the U-shaped magnetic yoke (4) and the magnetic sensor (9) are located at the same horizontal plane; the circuit board (7) is arranged between the U-shaped magnetic yoke (4) and the circuit board (6).

4. The method for determining the excitation condition of a weak magnetic detection device for a component with a coating layer according to claim 1, characterized in that: The wheel encoder (8) is arranged at the rear end of the housing (3), and two rollers are arranged at the front and rear ends of the housing (3), respectively, wherein roller one (15) is the moving wheel of the wheel encoder (8).

5. The method for determining the excitation condition of a weak magnetic detection device of a component with a coating layer according to claim 1, characterized in that: The shell (3) is made of non-metallic material.

Images