An equally-spaced sampling device and a crack detection method

Abstract

The present invention relates to the field of non-destructive testing technology, and particularly to an equidistant sampling device and a crack detection method. The device includes a balanced electromagnetic detection probe, a detection signal processing module, an encoder, a three-axis sliding platform, and a acquisition control module. The acquisition control module is used to drive a specified slide rail to move so as to drive the balanced electromagnetic detection probe to move along the surface of the ferromagnetic test piece to be inspected. Whenever the specified slide rail moves a preset fixed distance, the encoder rotates a fixed angle and sends a pulse signal corresponding to the fixed angle to the acquisition control module. The detection signal processing module processes the signal output by the balanced electromagnetic detection probe. Whenever receiving the pulse signal, the acquisition control module acquires the electrical signal output by the detection signal processing module. It can conveniently and quickly perform equidistant sampling on ferromagnetic test pieces to be inspected such as pipelines, improve the sampling efficiency, and facilitate the rapid determination of cracks in the ferromagnetic test pieces to be inspected by using the balanced electromagnetic detection technology.

Description

Background Art

[0002] As an important lifeline for transporting energy, pipelines are extremely prone to failure during operation due to external environments, medium corrosion, etc. Among them, cracks play a decisive role in pipeline fractures. Once oil and gas leakage occurs due to cracking, catastrophic consequences such as explosions will occur. Due to the complexity of the crack morphology and the particularity of its geometric distribution in long-distance pipelines, the most commonly used magnetic flux leakage internal detection technology for long-distance pipelines has limited crack detection ability. Traditional ultrasonic crack detection is only applicable to liquid pipelines. Electromagnetic ultrasonic does not require coupling, but has high requirements for detection speed and is difficult to quantify crack sizes. The balanced electromagnetic detection technology is a non-destructive detection technology that combines alternating current magnetism and alternating current magnetic flux leakage. It uses an alternating current excitation method to determine the presence of defects through the change in the spatial magnetic field caused by the change in eddy current and magnetic flux on the surface of the component to be inspected. And it is not affected by the angle between the magnetic field and the defect, and can effectively detect cracks at any angle with respect to the detection direction. At the same time, compared with traditional eddy current detection, it overcomes the disadvantage of insufficient penetration force and can effectively detect surface cracks of ferromagnetic materials. However, there is currently a lack of a collection device, which is not convenient for collecting the electromagnetic signals of ferromagnetic specimens to be inspected such as pipelines required in the balanced electromagnetic detection technology. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide an equally spaced sampling device and a crack detection method in view of the deficiencies of the prior art.

[0004] The technical solution of an equally spaced sampling device of the present invention is as follows:

[0005] It includes a balanced electromagnetic detection probe, a detection signal processing module, an encoder, a three-axis sliding platform, and a collection control module. The output end of the encoder is connected to the input end of the collection control module, and the balanced electromagnetic detection probe is arranged on the specified slide rail of the three-axis sliding platform;

[0006] The collection control module is used for: driving the specified slide rail to move to drive the balanced electromagnetic detection probe to move along the surface of the ferromagnetic specimen to be inspected;

[0007] Whenever the specified slide rail moves a preset fixed distance, the encoder rotates a fixed angle and sends the pulse signal corresponding to the fixed angle to the collection control module;

[0008] The detection signal processing module is used for: processing the signal output by the balanced electromagnetic detection probe;

[0009] The collection control module is also used for: whenever receiving a pulse signal, collecting the electrical signal output by the detection signal processing module.

[0010] The beneficial effects of an equally spaced sampling device of the present invention are as follows:

[0011] It can conveniently and quickly perform equally spaced sampling on ferromagnetic specimens to be inspected, such as pipelines, improve the sampling efficiency, and facilitate the rapid determination of cracks in the ferromagnetic specimens to be inspected by using the balanced electromagnetic detection technology.

[0012] The technical solution of a crack detection method of the present invention is as follows:

[0013] Using an equally spaced sampling device described in any one of the above, the method includes:

[0014] S1. The acquisition control module drives the specified slide rail to move, so as to drive the balanced electromagnetic detection probe to move along the surface of the ferromagnetic specimen to be inspected;

[0015] S2. Whenever the specified slide rail moves a preset fixed distance, the encoder rotates a fixed angle and sends the pulse signal corresponding to the fixed angle to the acquisition control module;

[0016] S3. Whenever the acquisition control module receives the pulse signal, the acquisition control module acquires the electrical signal output by the detection signal processing module;

[0017] S4. Plot the electrical signal acquired by the acquisition control module to obtain a curve;

[0018] S5. Calculate the peak-valley distance between every two adjacent peaks and valleys in the curve;

[0019] S6. Based on the corresponding relationship between the peak-valley distance and the opening width of the crack of the ferromagnetic specimen to be inspected, calculate the opening width of each crack of the ferromagnetic specimen to be inspected according to each peak-valley distance.

[0020] The beneficial effects of a crack detection method of the present invention are as follows:

[0021] It can conveniently and quickly perform equally spaced sampling on ferromagnetic specimens to be inspected, such as pipelines, and can quickly determine the opening width of each crack of the ferromagnetic specimen to be inspected, with high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is one of the structural schematic diagrams of an equally spaced sampling device according to an embodiment of the present invention;

[0023] Figure 2 It is another structural schematic diagram of an equally spaced sampling device according to an embodiment of the present invention;

[0024] Figure 3 It is the structural schematic diagram of the balanced electromagnetic detection probe;

[0025] Figure 4 Schematic diagram of the circuit structure of the detection signal processing module;

[0026] Figure 5 Schematic diagram of the circuit structure of the analog-to-digital conversion chip;

[0027] Figure 6 Schematic diagram of the circuit structure of the single-chip microcomputer of model STM32F103;

[0028] Figure 7 Schematic diagram of the structure of the three-axis sliding platform;

[0029] Figure 8 Flow diagram of a crack detection method according to an embodiment of the present invention;

[0030] Figure 9 Schematic diagram of the structure of the test system.

[0031] Figure 10 Schematic diagram of a curve; Detailed implementation manners

[0032] As Figure 1 shown, an equal-spacing sampling device according to an embodiment of the present invention includes a balanced electromagnetic detection probe 1, a detection signal processing module 7, an encoder 3, a three-axis sliding platform 4, and an acquisition control module 2. The output end of the encoder 3 is connected to the input end of the acquisition control module 2, and the balanced electromagnetic detection probe 1 is arranged on a specified slide rail of the three-axis sliding platform 4;

[0033] The acquisition control module 2 is configured to: drive the specified slide rail to move so as to drive the balanced electromagnetic detection probe 1 to move along the surface of the ferromagnetic specimen 73 to be detected;

[0034] Whenever the specified slide rail moves a preset fixed distance, the encoder 3 rotates a fixed angle and sends a pulse signal corresponding to the fixed angle to the acquisition control module 2;

[0035] The detection signal processing module 7 is configured to: process the signal output by the balanced electromagnetic detection probe 1;

[0036] The acquisition control module 2 is further configured to: whenever receiving the pulse signal, acquire the electrical signal output by the detection signal processing module 7.

[0037] Wherein, the electrical signal output by the detection signal processing module 7 is: the signal obtained after the detection signal processing module 7 processes the signal output by the balanced electromagnetic detection probe 1.

[0038] Wherein, the output end of the three-axis sliding platform 4 is connected to the input end of the encoder 3. Specifically:

[0039] The principle of the encoder 3 is to convert displacement into an electrical signal. The output end of the three-axis sliding platform 4 is connected to the input end of the encoder 4, which means that the distance moved by the specified slide rail of the three-axis sliding platform 4 drives the inner code disk of the encoder 3 to rotate. The output end of the three-axis sliding platform 4 is the specified slide rail, such as the X-axis slide rail, etc., and the encoder 3 is connected to the specified slide rail.

[0040] Among them, as Figure 4 shown, the detection signal processing module 7 includes an instrumentation amplifier chip, an operational amplifier chip, a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1, a second capacitor C2, a fourth capacitor C4, and a fifth capacitor C5;

[0041] The first pin of the instrumentation amplifier chip is connected to the output end of the detection coil 13 of the balanced electromagnetic detection probe 1;

[0042] A first resistor R1 is connected between the second pin and the third pin of the instrumentation amplifier chip;

[0043] The fourth pin and the fifth pin of the instrumentation amplifier chip are both grounded;

[0044] The sixth pin of the instrumentation amplifier chip is respectively connected to the first pin and the fourth pin of the operational amplifier chip. The circuit between the sixth pin of the instrumentation amplifier chip and the first pin of the operational amplifier chip is grounded through a fifth capacitor C5;

[0045] The eighth pin of the instrumentation amplifier chip is connected to the output end of the first power supply;

[0046] The seventh pin of the instrumentation amplifier chip is the output end of the detection signal processing module 7;

[0047] The second pin of the operational amplifier chip is grounded;

[0048] The third pin of the operational amplifier chip is connected to the input end of the first power supply through a second resistor R2, and the third pin of the operational amplifier chip is grounded through a third resistor R3, and the second resistor R2 and the third resistor R3 are in parallel,

[0049] The fifth pin of the operational amplifier chip is connected to the output end of the first power supply. The circuit between the fifth pin of the operational amplifier chip and the output end of the first power supply is grounded through a fourth capacitor C4, and the two ends of the third resistor R3 are in parallel with a second capacitor C2.

[0050] Among them, the model of the instrumentation amplifier chip is AD8227, and the model of the operational amplifier chip is AD8613.

[0051] As Figure 2As shown, it further includes a stepper motor 5 and a drive unit 6; the drive unit 6 is configured to: under the control of the acquisition control module 2, drive a specified slide rail to move through the stepper motor 5, so as to drive the balance electromagnetic detection probe 1 to move along the surface of the ferromagnetic test piece 73 to be detected.

[0052] Among them, as Figure 7 shown, the three-axis sliding platform 4 is a mechanical transmission device with XYZ three-axis movement functions, including an aluminum profile frame 41, an X-axis slide rail 42, a Y-axis slide rail 43, a Z-axis slide rail 44, a lead screw 45, a first limiter 46, and a second limiter 47. It forms a control movement platform in combination with the stepper motor 5 and the drive unit 6. The stepper motor 5 is fixed at one end of the X-axis slide rail 42 of the three-axis sliding platform 4. The drive unit 6 is fixed on the frame of the XZ plane of the three-axis sliding platform 4. The encoder 3 is fixed at one end of the same slide rail as the stepper motor 5. Among them, the drive unit 6 can be selected as a driver of model

[0053] MA860C, or other models of drivers can also be selected according to the actual situation.

[0054] The model of the chip of the stepper motor 5 is 86HBM856-1000, and other models of stepper motors 5 can also be selected according to the actual situation.

[0055] The description of the specified slide rail is as follows: for example, if the balance electromagnetic detection probe 1 is fixedly connected to one end of the Z-axis moving end of the three-axis sliding platform 4 and fixedly connected to one end of the Z-axis slide rail 44 of the three-axis sliding platform 4, then the Z-axis slide rail 44 is the specified slide rail, and the specified slide rail can also be adjusted according to the actual situation.

[0056] Optionally, in the above technical solution, as Figure 3 shown, the balance electromagnetic detection probe 1 includes: an excitation coil 12, a detection coil 13, a U-shaped ferrite core 11, and a wear-resistant piece 14. The two feet of the U-shaped ferrite core 11 are arranged on the wear-resistant piece 14. The excitation coil 12 is wound around the middle of the U-shaped ferrite core 11. The detection coil 13 is arranged on the wear-resistant piece 14, and the detection coil 13 is located at the geometric center position between the two feet of the U-shaped ferrite core 11. The axis of the detection coil 13 is orthogonal to the axis of the excitation coil 12, and the axis of the detection coil 13 is perpendicular to the surface of the ferromagnetic test piece 73 to be detected. When the balance electromagnetic detection probe 1 moves along the surface of the ferromagnetic test piece 73 to be detected, a signal is output through the detection coil 13.

[0057] Among them, the material of the wear-resistant piece 14 is zirconia, and other materials of wear-resistant pieces 14 such as engineering plastics can also be selected according to the actual situation.

[0058] Among them, the detection principle of the balance electromagnetic detection probe 1 is:

[0059] The balanced electromagnetic detection combines the alternating current electromagnetic and alternating current magnetic flux leakage detection technologies. It uses an alternating current excitation method and discriminates the presence of defects by the changes in the spatial magnetic field caused by the surface eddy current and magnetic flux changes of the ferromagnetic specimen 73 to be inspected.

[0060] The wear-resistant piece 14 is placed above the ferromagnetic specimen 73 to be inspected. The detection module, such as a current source or a voltage source, generates an alternating current signal to produce a magnetic field around the excitation coil 12, and through the U-shaped high-permeability ferrite, it guides the magnetic field to the surface of the ferromagnetic specimen 73, such as a steel plate, to produce a magnetic field in the same direction as the excitation coil 12. The detection coil 13 is connected to the detection module and is used to sense the magnetic field changes on the surface of the steel plate. Due to the symmetric geometric structure of the detection coil 13 and the excitation coil 12, when there is no defect on the surface of the steel plate to be inspected, the magnetic field sensed by the detection coil 13 is in a balanced state, that is, there is no induced voltage. When there is a defect on the surface of the steel plate, this electromagnetic balance will be disrupted, causing the detection coil 13 to receive an induced voltage. Using this structure, it is possible to discriminate whether there are defects on the surface of the steel plate.

[0061] Among them, the crack signal generation mechanism is as follows:

[0062] When an alternating current passes through the excitation coil 12, a magnetic field that changes with the current direction will be formed on the surface of the steel plate. The changing magnetic field causes an eddy current field to be formed on the surface of the steel plate. At the same time, an induced current will be generated in the detection coil 13 under the action of the alternating magnetic field. The electromagnetic distribution on the surface of the steel plate is jointly affected by the changes in the magnetic field and the eddy current field. Specifically:

[0063] 1) Electromagnetic distribution without cracks:

[0064] When there is no defect on the surface of the steel plate, due to the skin effect, the magnetic flux always remains in the xy plane along with the different directions of the excitation current, that is, it flows perpendicular to the plane where the excitation coil 12 is located along the surface of the steel plate. The magnetic flux generated in the direction perpendicular to the excitation coil 12 will not pass through the detection coil 13. The eddy current generated under the excitation coil 12 and changing with the direction of the excitation current is axisymmetric about the excitation coil 12 on the surface of the steel plate. The electromotive forces generated on both sides of the detection coil 13 are equal in magnitude and opposite in direction with respect to the winding direction of the detection coil 13. At this time, it is in an electromagnetic balance state, and there is no signal in the detection coil 13.

[0065] 2) Electromagnetic distribution with transverse crack defects:

[0066] Due to the existence of transverse crack defects, it hinders the flow of the magnetic flux generated on the surface of the steel plate under the action of the excitation current, causing some of the blocked magnetic flux to flow into the air with a lower magnetic permeability, disrupting the original electromagnetic balance state, and there is a z-direction magnetic flux passing through the detection coil 13 above the steel plate.

[0067] 3) Electromagnetic distribution with longitudinal crack defects:

[0068] Due to the existence of longitudinal crack defects, the induced current on the surface of the steel plate flowing vertically directly below the excitation coil 12 is hindered, interfering with the spatial magnetic field and disrupting the electromagnetic balance on the surface of the steel plate without defects, resulting in the generation of electromotive force in the detection coil 13.

[0069] Optionally, as Figure 5 and Figure 6 shown, in the above technical solution, the acquisition control module 2 includes: a single-chip microcomputer, an analog-to-digital conversion chip, the twenty-sixth capacitor C26, the twenty-seventh capacitor C27, the twenty-eighth capacitor C28, the twenty-ninth capacitor C29, the thirty-fourth capacitor C34, the ninth resistor R9, the crystal oscillator Y2, and the program download interface D3;

[0070] The crystal oscillator Y2 is connected between the second pin and the third pin of the single-chip microcomputer;

[0071] The fourth pin of the single-chip microcomputer is grounded through the ninth resistor R9, and the fourth pin of the single-chip microcomputer is connected to the program download interface D3 through the thirty-fourth capacitor C34, and the ninth resistor R9 and the thirty-fourth capacitor C34 are in parallel;

[0072] The first pin, the sixth pin, the nineteenth pin, and the twenty-seventh pin of the single-chip microcomputer are all connected to the program download interface D3;

[0073] The fifth pin, the seventeenth pin, the eighteenth pin, the thirty-fifth pin, and the thirty-sixth pin of the single-chip microcomputer are all grounded;

[0074] The fifteenth pin of the single-chip microcomputer is connected to the twelfth pin of the analog-to-digital conversion chip;

[0075] The thirty-third pin of the single-chip microcomputer is connected to the eleventh pin of the analog-to-digital conversion chip;

[0076] The thirty-fourth pin of the single-chip microcomputer is connected to the fourteenth pin of the analog-to-digital conversion chip;

[0077] The seventh pin of the single-chip microcomputer is connected to the thirteenth pin of the analog-to-digital conversion chip;

[0078] The eighth pin of the single-chip microcomputer is connected to the twenty-fourth pin of the analog-to-digital conversion chip;

[0079] The ninth pin of the single-chip microcomputer is connected to the twenty-fifth pin of the analog-to-digital conversion chip;

[0080] The ninth pin and the tenth pin of the analog-to-digital conversion chip are connected, and the tenth pin of the single-chip microcomputer is connected in parallel between the ninth pin and the tenth pin of the analog-to-digital conversion chip; that is, after the ninth pin and the tenth pin of the analog-to-digital conversion chip are connected, they are then connected to the tenth pin of the single-chip microcomputer.

[0081] The twenty-second pin of the single-chip microcomputer is connected to the third pin of the analog-to-digital conversion chip;

[0082] The twenty-third pin of the single-chip microcomputer is connected to the fourth pin of the analog-to-digital conversion chip;

[0083] The twenty-fourth pin of the single-chip microcomputer is connected to the fifth pin of the analog-to-digital conversion chip;

[0084] The eleventh pin, twelfth pin, thirteenth pin, fourteenth pin, sixteenth pin, twentieth pin, twenty-first pin, twenty-ninth pin, thirtieth pin, thirty-first pin, and thirty-second pin of the single-chip microcomputer are left unconnected;

[0085] The third pin of the program download interface D3 is grounded; the first pin, thirty-seventh pin, thirty-eighth pin, and forty-eighth pin of the analog-to-digital conversion chip are connected to the output terminal of the second power supply;

[0086] A twenty-sixth capacitor C26 and a twenty-ninth capacitor C29 are sequentially connected between the thirty-sixth pin and the forty-second pin of the analog-to-digital conversion chip, and the thirty-ninth pin of the analog-to-digital conversion chip is connected to the connection between the twenty-sixth capacitor C26 and the twenty-ninth capacitor C29 through a twenty-seventh capacitor C27;

[0087] Both the forty-fourth pin and the forty-fifth pin of the analog-to-digital conversion chip are connected to the connection between the twenty-sixth capacitor C26 and the twenty-ninth capacitor C29 through a twenty-eighth capacitor C28;

[0088] The thirty-fourth pin, sixth pin, and seventh pin of the analog-to-digital conversion chip are all connected to the output terminal of the first power supply;

[0089] The second pin, the sixteenth pin, the seventeenth pin, the eighteenth pin, the nineteenth pin, the twentieth pin, the twenty - first pin, the twenty - second pin, the twenty - sixth pin, the twenty - seventh pin, the twenty - eighth pin, the twenty - ninth pin, the thirtieth pin, the thirty - first pin, the thirty - second pin, the thirty - third pin, the thirty - fifth pin, the fortieth pin, the forty - first pin, the forty - third pin, the forty - sixth pin, and the forty - seventh pin of the analog - to - digital conversion chip are all grounded. The forty - ninth pin and the fiftieth pin of the analog - to - digital conversion chip are respectively connected to both ends of the detection coil 13.

[0090] Among them, the first power supply is a 3V power supply, and the second power supply is a 5V power supply.

[0091] The following uses a complete embodiment to illustrate an equally - spaced sampling device of the present application:

[0092] It includes a balanced electromagnetic detection probe 1, a detection signal processing module 7, a three - axis sliding platform 4, a stepping motor 5, a driving unit 6, an encoder 3, and an acquisition control module 2. In this embodiment, an instrumentation amplifier chip of model AD8227, an operational amplifier chip of model AD8613, a single - chip microcomputer of model STM32F103, an analog - to - digital conversion chip of model AD7609, a stepping motor 5 of model 86HBM856 - 1000, a driver (i.e., the driving unit 6) of model MA860C, and an encoder 3 of model TA406 - 400P / R are used as core components. In the balanced electromagnetic detection probe 1, both the excitation coil 12 and the detection coil 13 are made of copper. The number of turns of the excitation coil 12 is 400 turns respectively, and the number of turns of the detection coil 13 is 500 turns respectively. The relative magnetic permeability of the U - shaped high - permeability ferrite is 2000, and the conductivity is 0.01 S / mm. The balanced electromagnetic detection probe 1 is mechanically connected to the three - axis sliding platform 4. The output end of the balanced electromagnetic detection probe 1 is connected to the input end of the detection signal processing module 7. The output end of the detection signal processing module 7 is connected to one end of the input end of the acquisition control module 2. The output end of the acquisition control module 2 is connected to the input end of the driving unit 6. The output end of the driving unit 6 is connected to the input end of the stepping motor 5. The output end of the stepping motor 5 is connected to the input end of the three - axis sliding platform 4. The output end of the three - axis sliding platform 4 is connected to the input end of the encoder 3.

[0093] Such as Figure 3As shown in the figure, the balanced electromagnetic detection probe 1 includes: an excitation coil 12, a detection coil 13, a U-shaped high-permeability ferrite, and a wear-resistant sheet 14 made of zirconia; the excitation coil 12 is wound around the surface of the U-shaped high-permeability ferrite, and both feet of the U-shaped high-permeability ferrite and the detection coil 13 are closely attached to the upper surface of the zirconia wear-resistant sheet 14. The detection coil 13 and the excitation coil 12 are orthogonal to each other, and the detection coil 13 is located at the geometric center position of the two feet of the U-shaped high-permeability ferrite. The plane where the excitation coil 12 is located is perpendicular to the upper surface of the zirconia wear-resistant sheet 14, and the plane where the detection coil 13 is located is parallel to the upper surface of the zirconia wear-resistant sheet 14.

[0094] As Figure 4 shown in the figure, the detection signal processing module 7 includes: an instrumentation amplifier chip of model AD8227, a general-purpose operational amplifier chip of model AD8613, a 3V power supply, a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1, a second capacitor C2, a fourth capacitor C4, a fifth capacitor C5, and a ground connection point; the instrumentation amplifier chip includes 8 pins. The first pin of the instrumentation amplifier chip is connected to the output end of the detection coil 13, the second pin of the instrumentation amplifier chip is connected to one end of the first resistor R1, the third pin of the instrumentation amplifier chip is connected to the other end of the first resistor R1, the fourth pin and the fifth pin of the instrumentation amplifier chip are both connected to the ground connection point, the sixth pin of the instrumentation amplifier chip is connected to the first pin of the operational amplifier chip, the fourth pin of the general-purpose operational amplifier chip, and one end of the fifth capacitor C5. The eighth pin of the instrumentation amplifier chip is connected to the output end of the 3V power supply. The operational amplifier chip includes 5 pins. The first pin of the operational amplifier chip is connected to one end of the fifth capacitor C5, the second pin of the operational amplifier chip is connected to the ground connection point, the third pin of the operational amplifier chip is connected to one end of the second resistor R2 and one end of the third resistor R3, the fifth pin of the operational amplifier chip is connected to the output end of the 3V power supply. The other end of the second resistor R2 is connected to the output end of the 3V power supply, the other end of the third resistor R3 is connected to the ground connection point. The second resistor R2 and the third resistor R3 are in parallel, the second capacitor C2 and the third resistor R3 are in parallel, one end of the fourth capacitor C4 is connected to the output end of the 3V power supply, the other end of the fourth capacitor C4 is connected to the ground connection point, and the other end of the fifth capacitor C5 is connected to the ground connection point.

[0095] As Figure 5 and Figure 6As shown in the figure, the acquisition control module 2 includes: a single-chip microcomputer of model STM32F103, an analog-to-digital conversion chip of model AD7609, the twenty-sixth capacitor C26, the twenty-seventh capacitor C27, the twenty-eighth capacitor C28, the twenty-ninth capacitor C29, the thirty-fourth capacitor C34, the ninth resistor R9, a crystal oscillator Y2, a program download interface D3, a ground connection point, a 3V power supply, and a 5V power supply; the single-chip microcomputer includes 36 pins from the 1st to the 36th pin. The second pin of the single-chip microcomputer is connected to one end of the crystal oscillator Y2, the third pin of the single-chip microcomputer is connected to the other end of the crystal oscillator Y2, the fourth pin of the single-chip microcomputer is connected to one end of the ninth resistor R9 and one end of the thirty-fourth capacitor C34. The first pin, the sixth pin, the nineteenth pin, and the twenty-seventh pin of the single-chip microcomputer are connected to the fourth pin of the program download interface D3. The seventeenth pin, the eighteenth pin, the fifth pin, the twenty-sixth pin, the thirty-fifth pin, and the thirty-sixth pin of the single-chip microcomputer are connected to the ground connection point. The fifteenth pin, the thirty-third pin, the thirty-fourth pin, the seventh pin - the tenth pin, the twenty-second pin - the twenty-fourth pin of the single-chip microcomputer are respectively connected to the twelfth pin, the eleventh pin, the fourteenth pin, the thirteenth pin, the twenty-fourth pin, the twenty-fifth pin, the ninth pin and the tenth pin, the third pin - the fifth pin of the analog-to-digital conversion chip. The twenty-fifth pin and the twenty-eighth pin of the single-chip microcomputer are respectively connected to the second pin and the first pin of the program download interface D3, that is, the twenty-fifth pin of the single-chip microcomputer is connected to the 2nd pin of the program download interface D3, and the twenty-eighth pin of the single-chip microcomputer is connected to the first pin of the program download interface D3. The eleventh pin - the fourteenth pin, the sixteenth pin, the twentieth pin, the twenty-first pin, the twenty-ninth pin - the thirty-second pin of the single-chip microcomputer are not connected. The other end of the ninth resistor R9 is connected to the ground connection point. The tenth capacitor C10 is connected to the ground connection point. The third pin of the program download interface D3 is connected to the ground connection point. The analog-to-digital conversion chip includes 64 pins. The first pin, the thirty-seventh pin, the thirty-eighth pin, and the forty-eighth pin of the analog-to-digital conversion chip are connected to the 5V power supply. The thirty-sixth pin of the analog-to-digital conversion chip is connected to one end of the twenty-sixth capacitor C26. The thirty-ninth pin of the analog-to-digital conversion chip is connected to one end of the twenty-seventh capacitor C27. The forty-fourth pin and the forty-fifth pin of the analog-to-digital conversion chip are connected to one end of the twenty-eighth capacitor C28. The forty-second pin of the analog-to-digital conversion chip is connected to one end of the twenty-ninth capacitor C29. The thirty-fourth pin, the sixth pin, the twenty-third pin, and the seventh pin of the analog-to-digital conversion chip are connected to the 3V power supply. The second pin, the eighth pin, the sixteenth pin - the twenty-second pin, the twenty-sixth pin - the thirty-third pin, the thirty-fifth pin, the fortieth pin, the forty-first pin, the forty-seventh pin, the forty-third pin, the forty-sixth pin of the analog-to-digital conversion chip are connected to the ground connection point. The forty-ninth pin - the fiftieth pin are connected to both ends of the detection coil 13. The fifty-first pin - the sixty-fourth pin are reserved pins.

[0096] AsFigure 7 As shown in the figure, the three-axis sliding platform 4 is a mechanical transmission device with XYZ three-axis movement functions, including an aluminum profile frame, an X-axis slide rail 42, a Y-axis slide rail 43, a Z-axis slide rail 44, a lead screw 45, a first limiter 46, and a second limiter 47. It forms a control movement platform in combination with the stepper motor 5 and the drive unit 6. The stepper motor 5 is fixed at one end of the X-axis slide rail 42 of the three-axis sliding platform 4. The drive unit 6 is fixed on the frame of the XZ plane of the three-axis sliding platform 4. The encoder 3 is fixed at one end of the same slide rail where the stepper motor 5 is located.

[0097] As Figure 8 shown, a crack detection method according to an embodiment of the present invention includes:

[0098] S1. The acquisition control module 2 drives the specified slide rail to move to drive the balanced electromagnetic detection probe 1 to move along the surface of the ferromagnetic specimen 73 to be detected; specifically:

[0099] The acquisition control module 2 sends an instruction to the drive unit 6. The drive unit 6 makes the stepper motor 5 rotate at a constant speed, causing the Y-axis of the three-axis sliding platform 4 to move uniformly along the X-axis direction, driving the balanced electromagnetic detection probe 1 to move along the X-axis direction on the surface of the ferromagnetic specimen 73 to be detected. Every time the three-axis sliding platform 4 moves a fixed distance l1, it drives the encoder 3 to rotate a fixed angle. The angle of rotation of the encoder 3 generates a pulse signal correspondingly. After the acquisition control module 2 receives the pulse signal of the encoder 3, it acquires the output signal of the detection sensor.

[0100] S2. Whenever the specified slide rail moves a preset fixed distance, the encoder 3 rotates a fixed angle and sends the pulse signal corresponding to the fixed angle to the acquisition control module 2; specifically:

[0101] S3. Whenever the acquisition control module 2 receives the pulse signal, the acquisition control module 2 acquires the electrical signal output by the detection signal processing module 7;

[0102] For the encoder 3 with a circumference of C (unit: mm) and a count value of N, the relationship between the fixed distance l1 that the sensor moves corresponding to one pulse signal output by the above encoder 3 is:

[0103] When observing the output signal on the oscilloscope, if there are no obvious peaks and valleys near the signal, then there are no defects in this detection area; if the detection signal is first a peak and then a valley, then there are circumferential crack defects (along the Y-axis direction) in this detection area. If the detection signal is first a valley and then a peak, then there are axial crack defects (along the X-axis direction) in this detection area;

[0104] S4. Plot the electrical signal acquired by the acquisition control module 2 to obtain a curve;

[0105] S5. Calculate the peak-valley distance between every two adjacent peaks and valleys in the curve. Specifically:

[0106] Draw a curve based on the data collected by the acquisition control module 2 and stored in the PC. Each collected point corresponds to a fixed distance l1 of the sensor movement. Count the sampling points of the point numbers x1 where the peaks of the drawn curve appear and the points x2 where the valleys appear, and the peak-valley distance D can be obtained: D = (x2 - x1) * l1.

[0107] S6. Based on the correspondence between the peak-valley distance and the opening width of the crack in the ferromagnetic test piece 73 to be inspected, calculate the opening width of each crack in the ferromagnetic test piece 73 to be inspected according to each peak-valley distance. Specifically:

[0108] The peak-valley distance D is related to the opening width of the crack along the X-axis. For an axial crack, the opening width along the X-axis is the crack length; for a circumferential crack, the opening width along the X-axis is the crack width. Measure the actual opening width W0 of the crack along the X-axis, and the corresponding relationship between W0 and the peak-valley distance D can be obtained.

[0109] When using the pipeline crack detection device with equally spaced sampling to detect the remaining ferromagnetic test pieces containing cracks, the opening width W of the crack along the X-axis can be calculated for each of them through the peak-valley distance Di of the detection signal: W = δD. i ;

[0110] Before S1, it also includes:

[0111] S01. Connect the output end of the sensor to the input end of the signal processing module, connect the lock-in amplifier to the input end of the detection sensor and the output end of the signal processing module, tightly connect one end of the detection sensor to one end of the Z-axis mobile end of the three-axis sliding platform 4, connect the output end of the lock-in amplifier to the oscilloscope, and connect the 5V linear power supply to the input end of the detection sensor.

[0112] S02. Connect one end of the output end of the acquisition control module 2 to the input end of the PC, and the other end to the input end of the drive unit 6. Connect one end of the input end to the output end of the signal processing module, and the other end to the encoder 3. Connect the output end of the drive unit 6 to the input end of the stepping motor 5, and the aforementioned pipeline crack detection device with equally spaced sampling starts to work.

[0113] S03. Adjust the Z-axis of the three-axis sliding platform 4 to make the lower surface of the balanced electromagnetic detection probe 1 closely fit the surface of the ferromagnetic test piece 73 to be inspected with crack defects (taking the 52# steel plate as an example here). Adjust the Y-axis to make the sensor located at the geometric center of the crack on the surface of the ferromagnetic test piece 73 to be inspected. Adjust the positions of the limiters A and B to determine the moving distance of the sensor along the X-axis.

[0114] Through actual use tests, such as Figure 9 As shown, the lock-in amplifier 71 (selecting a frequency of 1 KHz and an alternating current output of 50 mA in magnitude) is connected to the detection signal processing module 7, the balanced electromagnetic detection probe 1, and the oscilloscope 72. The balanced electromagnetic detection probe 1 is connected to the three-axis sliding platform 4 and the 5V linear power supply 75 according to the above content. The acquisition control module 2 is connected to the PC 74, the drive unit 6, the detection signal processing module 7, and the encoder 3 (with a circumference of 20 mm and a count value of 2000). The drive unit 6 is connected to the stepping motor 5 according to the above content. The three-axis sliding platform 4 has been adjusted according to step 3 so that the lower surface of the sensor is in close contact with the surface of the ferromagnetic test piece 73 with crack defects and is located at the geometric center of the crack. The distance between the stopper A and the stopper B is adjusted to 40 mm. Starting from the stopper A as the moving starting point, the sampling control system is made to start working, and the balanced electromagnetic detection probe 1 is made to start moving. It will successively pass through two crack-containing regions (successively passing through D1 and D2) of the ferromagnetic test piece 73 to be detected. D1 and D2 are cracks along the X-axis direction and the Y-axis direction respectively, and there is a defect-free region between the two cracks. After passing through D1, the fixed distance corresponding to the movement of the sensor when the encoder 3 outputs a pulse signal can be calculated

[0115] The crack direction (axial or circumferential) can be discriminated according to S4 from the signal output by the oscilloscope; the data curve collected by the acquisition control module 2 is plotted on the PC, such as Figure 10 As shown, according to the signal corresponding to D1 passed through in the curve, the peak-valley distance D can be calculated according to S5 above as: D=(x2 - x1)*l1=(5200 - 1900)*0.01 = 33 mm;

[0116] Thus, the corresponding relationship between the peak-valley distance D and the known opening width W0 of 4 mm at D1 can be obtained

[0117] After calculating the peak-valley distance according to the signal of D2, the opening width W of D2 can be directly calculated according to step 7 above: W = δD i = 0.12 * 10 = 1.2 mm. This calculation result is basically consistent with the actual opening width of D2 being 1 mm. It shows the accuracy of a crack detection method of the present invention.

[0118] At present, the visible balance electromagnetic technology has good adaptability to crack detection. During the crack detection process, the quantification of size is particularly important for the subsequent evaluation of defects. The method of size quantification can be achieved by inverting signal characteristics, or by sampling settings or combined with multi-sensors for comprehensive calculation. Since there is currently no good means that meets the engineering environment for on-line internal detection of pipeline cracks, the emergence of the balance electromagnetic technology adds a method for on-line internal crack detection, and the crack quantification method for this technology also provides a basis for its better engineering application. Specifically:

[0119] A crack detection method of the present invention uses the modified detection device to achieve fixed-length and equidistant sampling, and the resulting crack detection signal quantifies the crack detection by the balance electromagnetic technology. Using the balance electromagnetic technology for crack detection itself has provided a good and effective means for internal detection of pipeline cracks. By using the content of the present invention, size quantification can be directly performed through the detection signal, and the detection results can be stored and displayed, providing a good basis for further evaluation of cracks, etc.

[0120] In the above embodiments, although the steps are numbered S1, S2, etc., these are only specific embodiments given in this application. Those skilled in the art can adjust the execution order of S1, S2, etc. according to the actual situation, and this is also within the protection scope of the present invention. It can be understood that in some embodiments, it may include some or all of the above embodiments.

[0121] Those skilled in the art know that the present invention can be implemented as a system, a method, or a computer program product.

[0122] Therefore, the present disclosure can be specifically implemented in the following forms: it can be completely hardware, or completely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software, which is generally referred to as "circuit", "module", or "system" in this article. In addition, in some embodiments, the present invention can also be implemented in the form of a computer program product in one or more computer-readable media, which contains computer-readable program code.

[0123] Any combination of one or more computer-readable media may be employed. The computer-readable media may be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium may be, for example - but not limited to - an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium include: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the present document, a computer-readable storage medium may be any tangible medium that contains or stores a program which can be used by or in connection with an instruction execution system, apparatus, or device.

[0124] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. An equally-spaced sampling device, characterized in that, It includes a balanced electromagnetic detection probe, a detection signal processing module, an encoder, a three-axis sliding platform and an acquisition control module. The output end of the encoder is connected to the input end of the acquisition control module, and the balanced electromagnetic detection probe is arranged on a specified slide rail of the three-axis sliding platform; The acquisition control module is used for: driving the specified slide rail to move so as to drive the balanced electromagnetic detection probe to move along the surface of the ferromagnetic specimen to be detected; Whenever the specified slide rail moves a preset fixed distance, the encoder rotates a fixed angle and sends a pulse signal corresponding to the fixed angle to the acquisition control module; The detection signal processing module is used for: processing the signal output by the balanced electromagnetic detection probe; The acquisition control module is also used for: whenever receiving a pulse signal, acquiring the electrical signal output by the detection signal processing module; The balanced electromagnetic detection probe includes: an excitation coil, a detection coil, a U-shaped ferrite core and a wear-resistant sheet. The two legs of the U-shaped ferrite core are arranged on the wear-resistant sheet. The excitation coil is wound around the middle of the U-shaped ferrite core. The detection coil is arranged on the wear-resistant sheet and is located at the geometric center position between the two legs of the U-shaped ferrite core. The axis of the detection coil is orthogonal to the axis of the excitation coil, and the axis of the detection coil is perpendicular to the surface of the ferromagnetic specimen to be detected. When the balanced electromagnetic detection probe moves along the surface of the ferromagnetic specimen to be detected, a signal is output through the detection coil; It also includes a stepping motor and a driving unit; The driving unit is used for: under the control of the acquisition control module, driving the specified slide rail to move through the stepping motor so as to drive the balanced electromagnetic detection probe to move along the surface of the ferromagnetic specimen to be detected; The detection signal processing module includes an instrumentation amplifier chip, an operational amplifier chip, a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1, a second capacitor C2, a fourth capacitor C4, a fifth capacitor C5; The first pin of the instrumentation amplifier chip is connected to the output end of the detection coil of the balanced electromagnetic detection probe; The first resistor R1 is connected between the second pin and the third pin of the instrumentation amplifier chip; The fourth pin and the fifth pin of the instrumentation amplifier chip are both grounded; The sixth pin of the instrumentation amplifier chip is respectively connected to the first pin and the fourth pin of the operational amplifier chip, and the circuit between the sixth pin of the instrumentation amplifier chip and the first pin of the operational amplifier chip is grounded through the fifth capacitor C5; The eighth pin of the instrumentation amplifier chip is connected to the output end of the first power supply; The seventh pin of the instrumentation amplifier chip is the output end of the detection signal processing module; The second pin of the operational amplifier chip is grounded; The third pin of the operational amplifier chip is connected to the input terminal of the first power supply through the second resistor R2. The third pin of the operational amplifier chip is grounded through the third resistor R3, and the second resistor R2 and the third resistor R3 are in parallel. The fifth pin of the operational amplifier chip is connected to the output terminal of the first power supply. The circuit between the fifth pin of the operational amplifier chip and the output terminal of the first power supply is grounded through the fourth capacitor C4. The two ends of the third resistor R3 are in parallel with the second capacitor C2. The acquisition control module includes: a single-chip microcomputer, an analog-to-digital conversion chip, a twenty-sixth capacitor C26, a twenty-seventh capacitor C27, a twenty-eighth capacitor C28, a twenty-ninth capacitor C29, a thirty-fourth capacitor C34, a ninth resistor R9, a crystal oscillator Y2, and a program download interface D3. The crystal oscillator Y2 is connected between the second pin and the third pin of the single-chip microcomputer. The fourth pin of the single-chip microcomputer is grounded through the ninth resistor R9. The fourth pin of the single-chip microcomputer is connected to the program download interface D3 through the thirty-fourth capacitor C34, and the ninth resistor R9 and the thirty-fourth capacitor C34 are in parallel. The first pin, the sixth pin, the nineteenth pin, and the twenty-seventh pin of the single-chip microcomputer are all connected to the program download interface D3. The fifth pin, the seventeenth pin, the eighteenth pin, the thirty-fifth pin, and the thirty-sixth pin of the single-chip microcomputer are all grounded. The fifteenth pin of the single-chip microcomputer is connected to the twelfth pin of the analog-to-digital conversion chip. The thirty-third pin of the single-chip microcomputer is connected to the eleventh pin of the analog-to-digital conversion chip. The thirty-fourth pin of the single-chip microcomputer is connected to the fourteenth pin of the analog-to-digital conversion chip. The seventh pin of the single-chip microcomputer is connected to the thirteenth pin of the analog-to-digital conversion chip. The eighth pin of the single-chip microcomputer is connected to the twenty-fourth pin of the analog-to-digital conversion chip. The ninth pin of the single-chip microcomputer is connected to the twenty-fifth pin of the analog-to-digital conversion chip. The ninth pin and the tenth pin of the analog-to-digital conversion chip are connected, and the tenth pin of the single-chip microcomputer is in parallel between the ninth pin and the tenth pin of the analog-to-digital conversion chip. The twenty-second pin of the single-chip microcomputer is connected to the third pin of the analog-to-digital conversion chip. The twenty-third pin of the single-chip microcomputer is connected to the fourth pin of the analog-to-digital conversion chip. The twenty-fourth pin of the single-chip microcomputer is connected to the fifth pin of the analog-to-digital conversion chip. The eleventh pin, the twelfth pin, the thirteenth pin, the fourteenth pin, the sixteenth pin, the twentieth pin, the twenty-first pin, the twenty-ninth pin, the thirtieth pin, the thirty-first pin, and the thirty-second pin of the single-chip microcomputer are left unconnected. The third pin of the program download interface D3 is grounded; the first pin, the thirty-seventh pin, the thirty-eighth pin, and the forty-eighth pin of the analog-to-digital conversion chip are connected to the output terminal of the second power supply; A twenty-sixth capacitor C26 and a twenty-ninth capacitor C29 are sequentially connected between the thirty-sixth pin and the forty-second pin of the analog-to-digital conversion chip, and the thirty-ninth pin of the analog-to-digital conversion chip is connected to between the twenty-sixth capacitor C26 and the twenty-ninth capacitor C29 through a twenty-seventh capacitor C27; Both the forty-fourth pin and the forty-fifth pin of the analog-to-digital conversion chip are connected to between the twenty-sixth capacitor C26 and the twenty-ninth capacitor C29 through a twenty-eighth capacitor C28; The thirty-fourth pin, the sixth pin, and the seventh pin of the analog-to-digital conversion chip are all connected to the output terminal of the first power supply; The second pin, the sixteenth pin, the seventeenth pin, the eighteenth pin, the nineteenth pin, the twentieth pin, the twenty-first pin, the twenty-second pin, the twenty-sixth pin, the twenty-seventh pin, the twenty-eighth pin, the twenty-ninth pin, the thirtieth pin, the thirty-first pin, the thirty-second pin, the thirty-third pin, the thirty-fifth pin, the fortieth pin, the forty-first pin, the forty-third pin, the forty-sixth pin, and the forty-seventh pin of the analog-to-digital conversion chip are all grounded, and the forty-ninth pin and the fiftieth pin of the analog-to-digital conversion chip are respectively connected to both ends of the detection coil; The three-axis sliding platform is a mechanical transmission device with XYZ three-axis movement functions, including an aluminum profile frame, an X-axis slide rail, a Y-axis slide rail, a Z-axis slide rail, a lead screw, a first limiter, and a second limiter, and forms a control movement platform in combination with a stepping motor and a drive unit. The stepping motor is fixed at one end of the X-axis slide rail of the three-axis sliding platform, the drive unit is fixed on the frame of the XZ plane of the three-axis sliding platform, and the encoder is fixed at one end of the same slide rail as the stepping motor.

2. The equally-spaced sampling device according to claim 1, characterized in that, The model of the instrumentation amplifier chip is AD8227.

3. The equally spaced sampling device according to claim 1, characterized in that, The model of the operational amplifier chip is AD8613.

4. An equidistant sampling device according to claim 1, characterized in that, The model of the chip of the stepping motor is 86HBM856-1000, and the drive unit is: a driver of model MA860C.

5. The equal-spacing sampling device according to claim 1, wherein, The material of the wear-resistant sheet is zirconia.

6. A crack detection method, characterized in that, Using an equal-spacing sampling device according to any one of claims 1 to 5 above, the method includes: S1. The acquisition control module drives the specified slide rail to move, so as to drive the balanced electromagnetic detection probe to move along the surface of the ferromagnetic specimen to be detected; S2. Whenever the specified slide rail moves a preset fixed distance, the encoder rotates a fixed angle and sends the pulse signal corresponding to the fixed angle to the acquisition control module; S3. Whenever the acquisition control module receives the pulse signal, the acquisition control module acquires the electrical signal output by the detection signal processing module; S4. Plot the electrical signal acquired by the acquisition control module to obtain a curve; S5. Calculate the peak-valley distance between every two adjacent peaks and valleys in the curve; S6. Based on the corresponding relationship between the peak-valley distance and the opening width of the crack of the ferromagnetic specimen to be detected, calculate the opening width of each crack of the ferromagnetic specimen to be detected according to each peak-valley distance respectively.

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