A passive magnetic flux leakage field nondestructive testing portable device and a detection method thereof

Abstract

The application discloses a kind of passive magnetic flux leakage field nondestructive testing portable device, including probe, data line, portable host, the shell inside of probe is equipped with Hall element matrix, Hall element matrix includes circuit board, Hall element, Hall element is equipped with multiple, it is installed on circuit board with matrix type interval, one end of data line is rotatably connected with probe, the other end is connected portable host, so that Hall element matrix and portable host realize signal transmission.The detection method thereof is disclosed.The application directly measures metal structure affected by earth magnetic field magnetization using matrix type high-precision Hall element, without actively magnetizing the structure manually, greatly reducing the use cost;Rotatable probe can reduce the influence of permanent magnetism of metal structure, temperature compensation module can reduce the interference of temperature change, thereby improving detection accuracy.Portable host and display screen can realize real-time detection, improve detection efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of nondestructive testing devices, in particular to a kind of passive magnetic flux leakage field nondestructive testing portable device and its detection method. BACKGROUND

[0002] Ship and marine structure are in marine environment for a long time, and are affected by wind, wave and flow, etc., which are periodic external forces, and alternating load is generated in the structure, leading to fatigue damage. Relevant statistical data shows that fatigue cracks exist in the ship structure. In order to pursue economic benefits, the ship with fatigue cracks usually chooses to continue operation, because according to the specification, small-scale fatigue cracks do not need to be repaired immediately. However, the frequency of damage detection needs to be improved for the small-scale fatigue cracks found to prevent the cracks from growing to the critical length and causing structural failure.

[0003] Nondestructive testing refers to detecting the defects inside and on the surface of a structure by using the changes in the reaction of sound, light, heat, magnetism, etc. caused by the existence of internal defects of the material without damaging the object being detected. This technology has been widely used in the field of ship and marine engineering. However, traditional nondestructive testing techniques, such as ray detection, ultrasonic detection and magnetic powder detection, have high detection costs, heavy instruments, long time consumption, and need to actively emit rays, ultrasonic waves or magnetic fields to the structure, which is quite inconvenient to operate and is not suitable for high-frequency and low-cost detection of the growth of small-scale fatigue cracks found. SUMMARY

[0004] The purpose of the present application is to provide a passive magnetic flux leakage field nondestructive testing portable device to solve the problem of high cost of traditional nondestructive testing techniques and reduce the maintenance cost of ship and marine structure. The detection method thereof is also provided.

[0005] Technical solution: A passive magnetic flux leakage field nondestructive testing portable device includes a probe, a data line and a portable host. A Hall element matrix is arranged inside the shell of the probe. The Hall element matrix includes a circuit board and Hall elements. The Hall elements are arranged in a matrix on the circuit board. One end of the data line is rotatably connected to the probe, and the other end is connected to the portable host, so that the Hall element matrix and the portable host realize signal transmission.

[0006] Further, the number of Hall elements is 64-144, forming an 8x8-12x12 square matrix. The horizontal distance between two adjacent Hall elements is 3.5-4 mm, and the vertical distance between two adjacent Hall elements is 1.8-2 mm. The main body of the Hall element is a rectangular semiconductor single crystal wafer with a size of 4 mm x 2 mm x 0.1 mm.

[0007] The Hall elements are independently arranged on the circuit board and located at the bottom of the probe, each Hall element is close to the detected material and can independently detect the defects of the ferromagnetic material magnetized by the earth magnetic field.

[0008] Further, the portable host includes a host shell, a mainboard and a display, the mainboard is installed inside the host shell, the display is installed on one side of the host shell and is signal connected with the mainboard, and the mainboard is signal connected with the Hall element matrix through a data line.

[0009] Further, the mainboard includes an integrated temperature compensation module, a data conversion and acquisition module, a microprocessor and data storage module and a power module, the temperature compensation module, the data conversion and acquisition module, the microprocessor and data storage module are signal connected in sequence, the Hall element matrix is signal connected with the temperature compensation module, the display is signal connected with the microprocessor and data storage module, and the power module supplies power for the probe, the mainboard and the display.

[0010] The temperature compensation module, the data conversion and acquisition module, the microprocessor and data storage module and the power module are arranged in a 2*2 matrix.

[0011] Optimally, the temperature compensation module includes an adjustable resistor, the microprocessor and data storage module includes a Raspberry Pi microcomputer and an electronic thermometer and a memory card connected thereto respectively, and the adjustable resistor is connected with the Raspberry Pi microcomputer through the data conversion and acquisition module.

[0012] The adjustable load resistor is installed in the internal circuit of the temperature compensation module, and the influence of temperature on the Hall element can be offset by changing the size of the load resistor.

[0013] The conversion element is installed in the data conversion and acquisition module, which can convert the electromotive force signal output by the Hall element into a digital signal, and transmit the digital signal to the microprocessor and data storage module after data acquisition.

[0014] The electronic thermometer is contained in the microprocessor and data storage module, which can send instructions to automatically change the size of the load resistor in the temperature compensation module according to the ambient temperature.

[0015] The measurement circuit is installed in the microprocessor and data storage module, which can measure, store and output the measured digital signal to the display.

[0016] Further, the display includes a display screen, operation buttons, a power indicator and a switch, which are respectively installed on the same side of the host shell, and the display screen displays the structural defects in the form of black and white mosaic.

[0017] Further, the device further comprises a rotatable joint, the data line is rotatably connected with one side of the probe through the rotatable joint, a rotation scale is marked on the connecting surface of the probe, and the probe is freely rotatable by 360 degrees relative to the data line through the rotatable joint.

[0018] Optimally, the shell of the probe is cylindrical, the circuit board of the Hall element matrix is circular, and the diameter of the shell of the probe is 8-12 cm.

[0019] Optimally, the device further comprises a wire winder, and the wire winder is installed in the middle section of the data line.

[0020] A detection method of the passive magnetic field lossless detection portable device, comprising the following steps:

[0021] Step one: turn on the device, and the portable host automatically compensates the influence of temperature on the Hall effect according to the ambient temperature;

[0022] Step two: use the probe to closely scan and detect the surface of the metal material, and after the Hall element matrix finds the area where the magnetic induction line changes dramatically, the signal is transmitted to the portable host, and the angle of the probe is rotated to eliminate the influence of the permanent magnetism of the ferromagnetic material itself;

[0023] Step three: according to the display result of the portable host, the position and length of the crack are accurately positioned;

[0024] Step four: operate the portable host to save the measurement result.

[0025] Advantages: compared with the prior art, the advantages of the present application are that: the present application directly measures the ferromagnetic material affected by the earth magnetic field magnetization by using a matrix type high-precision Hall element, without the need for active artificial magnetization of the structure, but forming passive magnetization, which greatly reduces the use cost; the rotatable probe can reduce the influence of the permanent magnetism of the metal material itself, and the temperature compensation module can reduce the interference of temperature changes, thereby improving the detection precision. The small-size portable host can realize real-time detection, improving the detection efficiency, and the present application has the advantages of low production and use cost, high detection efficiency and precision, strong practicability, convenient carrying and the like. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic diagram of the overall structure of the present application;

[0027] Figure 2 is a schematic diagram of the exploded structure of the probe;

[0028] Figure 3 is a schematic diagram of the structure of the Hall element matrix;

[0029] Figure 4 is a schematic diagram of the structure of the portable host;

[0030] Figure 5 This is a schematic diagram of the motherboard structure;

[0031] Figure 6 This is the circuit diagram of the temperature compensation module;

[0032] Figure 7 This is the power supply logic flowchart for the power module;

[0033] Figure 8 This is a schematic diagram of the display's structure;

[0034] Figure 9 This is a schematic diagram showing the defect detection results of the present invention. Detailed Implementation

[0035] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0036] A portable device for passive magnetic field leakage non-destructive testing, such as Figures 1-9 As shown, the device includes a probe 1, a data cable 2, a portable host 3, a rotatable connector 11, and a cable reel 21. The middle section of the data cable 2 is wound around the cable reel 21, so that the extension length of the data cable 2 can be adjusted, making it more convenient to carry and use.

[0037] The probe 1 housing contains a Hall element matrix 12, which includes a circuit board and multiple Hall elements arranged in a matrix on the circuit board. One end of the data cable 2 is rotatably connected to the probe 1 via a rotatable connector 11, and the other end is connected to the portable host 3, enabling signal transmission between the Hall element matrix 12 and the portable host 3. The connection surface of the probe 1 is marked with rotation scales, allowing the probe 1 to rotate freely 360 degrees relative to the data cable 2 via the rotatable connector 11.

[0038] The number of Hall elements ranges from 64 to 144, forming an 8×8 to 12×12 square array. The horizontal spacing between two adjacent Hall elements is 3.5 to 4 mm, and the vertical spacing between two adjacent Hall elements is 1.8 to 2 mm. The main body of each Hall element is a rectangular semiconductor single-crystal thin film with dimensions of 4 mm × 2 mm × 0.1 mm. The outer shell of probe 1 is cylindrical, while the circuit board of the Hall element matrix 12 is circular. The diameter of the outer shell of probe 1 is 8 to 12 cm.

[0039] When a Hall element, after being powered on, is brought near a metal material magnetized by the Earth's magnetic field, a potential difference is generated across the Hall element. According to the Hall effect principle, the magnitude of this potential difference is proportional to the magnetic field strength, as shown in equation (1). Subsequently, the Hall potential difference will further generate a Hall current. The current of each Hall element is transmitted to the motherboard individually through the data line for further data processing.

[0040]

[0041] where U H is the Hall potential difference; R is the Hall coefficient; I is the current intensity passing through; B is the magnetic induction intensity perpendicular to I; and d is the thickness of the conductor.

[0042] The portable host 3 comprises a host shell, a mainboard 4 installed inside the host shell, and a display 5 installed on one side of the host shell and signal-connected with the mainboard 4, and the mainboard 4 is signal-connected with the Hall element matrix 12 through the data line 2.

[0043] The mainboard 4 comprises an integrated temperature compensation module 41, a data conversion and collection module 42, a microprocessor and data storage module 43, and a power module 44, the temperature compensation module 41, the data conversion and collection module 42, and the microprocessor and data storage module 43 are signal-connected in sequence, the Hall element matrix 12 is signal-connected with the temperature compensation module 41, the display 5 is signal-connected with the microprocessor and data storage module 43, and the power module 44 supplies power for the probe 1, the mainboard 4, and the display 5.

[0044] The temperature compensation module 41 comprises an adjustable resistor, the microprocessor and data storage module 43 comprises a Raspberry Pi microcomputer and an electronic thermometer and a memory card connected therewith respectively, and the adjustable resistor is connected with the Raspberry Pi microcomputer through the data conversion and collection module 42.

[0045] As shown in Figure 6 , the adjustable resistor of the temperature compensation module can be a DS1669 type digital resistor manufactured by the Dallas Semiconductor Company, which automatically adjusts the size of the load resistor R according to the command of the microprocessor to compensate for the influence of temperature on the Hall effect.

[0046] The data conversion and collection module can be a TD-4017+ type analog quantity collection module produced by the Anhui Taihua Instrument Co., Ltd., which can convert the current generated by the Hall effect into a digital signal and collect it, and then convert the collected data into a digital signal and transmit it to the microprocessor and data storage module.

[0047] The memory card of the microprocessor and data storage module is a Micro SD memory card, the Raspberry Pi will automatically measure the ambient temperature using the electronic thermometer, and then send a command to adjust the size of the load resistor R in the temperature compensation module. At the same time, it will accept the data transmitted by the data conversion and collection module, convert the collected current intensity data into magnetic field size data according to formula (1), analyze the position of the magnetic leakage field, and then transmit the results to the display and the memory card.

[0048] AsFigure 7 As shown, the power module supplies power to the probe, main unit, and display separately. The power supply first independently powers the Hall element matrix in the probe, triggering the Hall effect and generating a Hall current at the other ends of the elements. The Hall effect creates a Hall potential difference, and the resulting current flows sequentially through the temperature compensation module and the data conversion and acquisition module; this process does not require direct power from the power module. Simultaneously, the power supply also independently powers each module on the motherboard and the display, ensuring their normal operation.

[0049] The display 5 includes a screen 51, operation buttons 52, a power indicator light and a switch, which are respectively installed on the same side of the main unit casing. The screen 51 displays structural defects in a black and white mosaic pattern.

[0050] like Figure 8 As shown, the monitor has a display screen on the left side and a power indicator light, power switch, and operation buttons on the right side.

[0051] like Figure 9 As shown, when the probe detects defects in a ferromagnetic material, it displays them on the screen as a black and white mosaic. The specific principle is as follows: based on the mechanism of magnetic field leakage, cracks in the metal material cause drastic changes in the distribution of magnetic field lines. Based on the magnetic field data transmitted from the microprocessor and data storage module, areas with drastic changes in magnetic field strength are represented by black mosaics, while other defect-free areas are represented by white mosaics. The left image shows a cracked metal sample, and the right image shows the display after the device detects the left image.

[0052] This invention employs a matrix-type high-precision Hall element to directly measure ferromagnetic materials affected by the Earth's magnetic field magnetization. The specific flaw detection principle is as follows: ferromagnetic materials placed in the Earth's magnetic field will be magnetized. When the probe sweeps across the surface of the ferromagnetic material, the matrix-type Hall element measures the change in magnetic field lines on the material surface. The measured magnetic field line intensity is transmitted to the temperature compensation module on the motherboard in the form of a current or potential difference signal via a data line. The probe can rotate freely to eliminate the influence of the ferromagnetic material's own permanent magnetism on the Earth's magnetic field magnetization effect. The temperature compensation module adjusts its load resistance according to the instructions of the microprocessor and data storage module to compensate for the effect of temperature changes on the Hall element. The processed current or potential difference signal is then transmitted to the data conversion and acquisition module. The data conversion module converts the signal into a digital signal that is easy to store and display. This digital signal is then acquired at a fixed frequency by the acquisition module and transmitted to the microprocessor and data storage module. The microprocessor and data storage module process the digital signal, store it, and output it to the display. The display then shows the measurement results in a black and white mosaic format.

[0053] The above-mentioned portable device for passive magnetic field leakage non-destructive testing includes the following steps:

[0054] Step one: open the device, the microprocessor will automatically adjust the size of the load resistance according to the ambient temperature, compensate for the influence of temperature on the Hall effect;

[0055] Step two: use the probe to scan the surface of the metal material, and after finding the area with dramatic change of magnetic induction lines, rotate the probe angle to eliminate the influence of the permanent magnetism of the ferromagnetic material itself;

[0056] Step three: according to the display result of the display, accurately position the crack existing position and length;

[0057] Step four: operate the display panel to save the measurement result.

[0058] The application is mainly used for detecting small-scale fatigue cracks found in the design of ship and marine engineering structures, so as to avoid the growth of cracks to the critical length. Through the high-precision Hall element matrix, the ferromagnetic material magnetized by the earth's magnetic field is directly measured, without manual magnetization, so that the detection procedure is simplified and the detection cost is reduced.

Claims

1. A passive magnetic flux leakage field non-destructive testing portable device, characterized in that: The device comprises a probe (1), a data line (2) and a portable host (3), the inside of the shell of the probe (1) is provided with a Hall element matrix (12), the Hall element matrix (12) comprises a circuit board and Hall elements, the Hall elements are provided in a plurality of and are installed on the circuit board in a matrix type, one end of the data line (2) is rotatably connected with the probe (1), the other end is connected with the portable host (3), so that the Hall element matrix (12) and the portable host (3) realize signal transmission; The portable host (3) comprises a host shell, a mainboard (4) and a display (5), the mainboard (4) is installed in the inside of the host shell, the display (5) is installed on one side surface of the host shell and is signal connected with the mainboard (4), the mainboard (4) is signal connected with the Hall element matrix (12) through the data line (2); The mainboard (4) comprises an integrated temperature compensation module (41), a data conversion and collection module (42), a microprocessor and data storage module (43) and a power module (44), the temperature compensation module (41), the data conversion and collection module (42) and the microprocessor and data storage module (43) are signal connected in sequence, the Hall element matrix (12) is signal connected with the temperature compensation module (41), the display (5) is signal connected with the microprocessor and data storage module (43), and the power module (44) supplies power for the probe (1), the mainboard (4) and the display (5).

2. The portable passive magnetic flux leakage field non-destructive testing device according to claim 1, wherein: The number of the Hall elements is 64-144, forming an 8x8-12x12 square matrix, the interval between two horizontally adjacent Hall elements is 3.5-4 mm, the interval between two vertically adjacent Hall elements is 1.8-2 mm, the main body of the Hall element is a rectangular semiconductor single crystal sheet with a size of 4 mm x 2 mm x 0.1 mm.

3. The portable passive magnetic flux leakage field non-destructive testing device of claim 1, wherein: The temperature compensation module (41) comprises an adjustable resistor, the microprocessor and data storage module (43) comprises a Raspberry Pi microcomputer and an electronic thermometer and a memory card connected therewith, and the adjustable resistor is connected with the Raspberry Pi microcomputer through the data conversion and collection module (42).

4. The portable passive magnetic flux leakage field non-destructive testing device of claim 1, wherein: The display (5) comprises a display screen (51), operation buttons (52), a power indicator and a switch, which are installed on the same side surface of the host shell, and the display screen (51) displays the structural defects in the form of black and white mosaic.

5. The portable passive magnetic flux leakage field non-destructive testing device of claim 1, wherein: The device further comprises a rotatable joint (11), the data line (2) is rotatably connected with one side surface of the probe (1) through the rotatable joint (11), a rotation scale is marked on the connecting surface of the probe (1), and the probe (1) is freely rotatable by 360 degrees relative to the data line (2) through the rotatable joint (11).

6. The portable passive magnetic flux leakage field non-destructive testing device of claim 1, wherein: The shell of the probe (1) is cylindrical, the circuit board of the Hall element matrix (12) is circular, and the diameter of the shell of the probe (1) is 8-12 cm.

7. The portable passive magnetic flux leakage field non-destructive testing device of claim 1, wherein: The device further comprises a wire winder (21), which is installed in the middle section of the data line (2).

8. A method of detecting a passive magnetic flux leakage field non-destructive testing portable device according to any one of claims 1 to 7, characterized in that The device comprises the following steps: Step one: turn on the device, and the portable host automatically compensates the influence of the ambient temperature on the Hall effect; Step two: scan the surface of the metal material with the probe, and when the Hall element matrix finds the area where the magnetic induction line changes dramatically, it transmits the signal to the portable host, and rotates the probe angle to eliminate the influence of the permanent magnetism of the ferromagnetic material itself; Step three: according to the display result of the portable host, accurately locate the position and length of the crack; Step four: operate the portable host to save the measurement result.

Images