CN113777150B - Defect detection method based on ferromagnetic plate - Google Patents
Defect detection method based on ferromagnetic plate Download PDFInfo
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- CN113777150B CN113777150B CN202110908136.2A CN202110908136A CN113777150B CN 113777150 B CN113777150 B CN 113777150B CN 202110908136 A CN202110908136 A CN 202110908136A CN 113777150 B CN113777150 B CN 113777150B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
- G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
- G01N27/83—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws by investigating stray magnetic fields
Abstract
The invention belongs to the technical field of electromagnetic nondestructive testing, and discloses a defect detection method based on a ferromagnetic plate, which comprises the following steps: (1) Fixing a magnetic sensor on a ferromagnetic plate, wherein a through groove is formed in the ferromagnetic plate, the through groove penetrates through the ferromagnetic plate along the thickness direction of the ferromagnetic plate, and the through groove penetrates through the region, covered by the magnetic sensor, of the ferromagnetic plate; (2) In a magnetization field, the magnetic sensor and the ferromagnetic plate scan defects of the magnetized workpiece to be detected; the through grooves are magnetized and reinforced with the leakage magnetic field generated by the defects on the workpiece to be detected under the action of the magnetizing field. The invention avoids shaking, enhances the wear resistance of the magnetic sensor, enhances the magnetic leakage detection signal and improves the magnetic leakage detection sensitivity.
Description
Technical Field
The invention belongs to the technical field of electromagnetic nondestructive testing, and particularly relates to a defect detection method based on a ferromagnetic plate.
Background
The nondestructive detection technology is based on electromagnetic induction, and with the development of electronic technology and computer technology, the electromagnetic nondestructive detection technology has made breakthrough progress in development and application, wherein the magnetic leakage detection is widely applied to the nondestructive detection of ferromagnetic materials. In the embodiment, the electromagnet or the permanent magnet is used for magnetizing the workpiece, the defect on the workpiece generates disturbance on the magnetic field, so that a leakage magnetic field is generated in the air above the defect, the magnetic sensor is used for scanning the workpiece, the existence of the leakage magnetic field is sensed, and the defect is judged.
However, in the magnetic leakage detection, when the lift-off value of the magnetic sensor is large, the magnetic leakage signal is very weak, and when the lift-off value of the magnetic sensor is small, the abrasion of the magnetic sensor may be serious, and mechanical noise caused by vibration of the sensor is large under the condition of low lift-off value.
Disclosure of Invention
Aiming at the defects or improvement demands of the prior art, the invention provides a defect detection method based on a ferromagnetic plate, which is characterized in that a magnetic sensor is fixed on the ferromagnetic plate, and the leakage magnetic field of a through groove or a through hole on the ferromagnetic plate and the leakage magnetic field of the defect of a detected piece are mutually magnetized and mutually enhanced, so that the constant lift-off value of the magnetic sensor is realized, the shake is avoided, the wear resistance of the magnetic sensor is enhanced, the leakage magnetic detection signal is enhanced, and the leakage magnetic detection sensitivity is improved.
To achieve the above object, according to one aspect of the present invention, there is provided a ferromagnetic plate-based defect detection method comprising the steps of:
(1) Fixing a magnetic sensor on a ferromagnetic plate, wherein a through groove is formed in the ferromagnetic plate, the through groove penetrates through the ferromagnetic plate along the thickness direction of the ferromagnetic plate, and the through groove penetrates through the region, covered by the magnetic sensor, of the ferromagnetic plate;
(2) In a magnetization field, the magnetic sensor and the ferromagnetic plate scan defects of the magnetized workpiece to be detected; the through grooves are magnetized and reinforced with the leakage magnetic field generated by the defects on the workpiece to be detected under the action of the magnetizing field.
Further, the magnetic sensor and the ferromagnetic plate are attached to the surface of the workpiece to be detected to move so as to scan defects of the workpiece to be detected.
Further, the distance between the magnetic sensor and the surface of the workpiece to be measured is constant.
Further, the lift-off value of the magnetic sensor is the thickness value of the ferromagnetic plate.
Further, an energizing coil or a magnetizer is used to form a magnetizing field, and the workpiece to be measured is magnetized in the magnetizing field.
Further, the magnetizer comprises a U-shaped magnetic yoke and a magnetizing coil, wherein the magnetizing coil is arranged in the middle of the U-shaped magnetic yoke.
Further, the magnetizing current in the magnetizing coil is 2A-20A.
Further, the width of the through groove is 0.025 mm-1 mm.
Further, the magnetic sensor is an induction coil or a hall element.
Further, the material of the workpiece to be detected is a ferromagnetic material.
In general, compared with the prior art, the defect detection method based on the ferromagnetic plate, which is provided by the invention, has the following advantages:
1. the magnetic sensor is fixed on the ferromagnetic plate, the ferromagnetic plate is provided with a through groove, the through groove penetrates through the ferromagnetic plate along the thickness direction of the ferromagnetic plate, and the through groove penetrates through the area, covered by the magnetic sensor, of the ferromagnetic plate, so that when a defect is scanned, a leakage magnetic field generated by the defect propagates upwards, the magnetization intensity of the through groove is enhanced, and the leakage magnetic field of the through groove is enhanced; meanwhile, the through groove can also generate a leakage magnetic field under the action of a magnetization field, the through groove which is vertically penetrated downwards can generate a leakage magnetic field, the upward leakage magnetic field can also generate a leakage magnetic field, and the downward leakage magnetic field acts on the defect of the workpiece to be detected to strengthen the magnetization of the defect, so that the leakage magnetic field of the defect is enhanced; the leakage magnetic field induced by the magnetic sensor is the superposition of the leakage magnetic field of the defect and the leakage magnetic field of the through groove, so that the leakage magnetic field induced by the magnetic sensor is enhanced, and the detection sensitivity is improved.
2. The magnetic sensor is fixed on the ferromagnetic plate, and the ferromagnetic plate is attached to the workpiece to be tested for scanning, so that mechanical noise caused by shaking of the magnetic sensor is avoided, and the wear resistance of the magnetic sensor is enhanced.
3. The ferromagnetic plate is stuck on the workpiece for scanning, so that the distance between the magnetic sensor and the surface of the workpiece to be detected is fixed, the lift-off value of the magnetic sensor is the thickness value of the ferromagnetic plate, the constant lift-off value is ensured, the shake of the magnetic sensor is avoided, the stability is good, and the detection sensitivity is improved.
4. The detection method is easy to implement and has higher sensitivity which is 2-4 times of the detection sensitivity of the air lift-off method.
Drawings
FIG. 1 is a schematic diagram of a ferromagnetic plate-based defect detection method according to the present invention;
FIG. 2 is a partial schematic view of a detection apparatus involved in the ferromagnetic plate-based defect detection method of FIG. 1;
FIG. 3 is a schematic diagram of the ferromagnetic plate-based defect detection method of FIG. 1;
FIG. 4 is a schematic diagram of a simulation model involved in the ferromagnetic plate-based defect detection method of FIG. 1;
FIG. 5 is a graph showing the correlation between magnetization and leakage magnetic field in the defect detection method based on a ferromagnetic plate of FIG. 1 and the conventional method;
fig. 6 is a graph showing correlation between the width of a through slot and a leakage magnetic field in the defect detection method based on a ferromagnetic plate in fig. 1 and the conventional method.
The same reference numbers are used throughout the drawings to reference like elements or structures, wherein: 1-probe, 2-workpiece to be measured, 3-U-shaped magnetic yoke, 4-magnetizing coil, 1-1-magnetic sensor, 1-2-ferromagnetic plate, 1-3-through slot and 2-1-defect.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
Referring to fig. 1, 2 and 3, the defect detection method based on a ferromagnetic plate provided by the present invention mainly includes the following steps:
firstly, magnetizing a workpiece to be tested by using a magnetizer, so that a leakage magnetic field is generated by defects on the workpiece to be tested.
Specifically, the magnetizer used when the workpiece 2 to be tested is magnetized comprises a U-shaped magnetic yoke 3 and a magnetizing coil 4, wherein the magnetizing coil 4 is arranged in the middle of the U-shaped magnetic yoke 3 and is connected to a magnetizing power supply, and the magnetizing power supply supplies power to the magnetizing coil 4. Wherein the material of the workpiece 2 to be measured is a ferromagnetic material. In addition, magnetization can also be realized by using an electrified coil or a permanent magnet magnetizer.
And secondly, fixing the magnetic sensor on a ferromagnetic plate, wherein a through groove is formed in the ferromagnetic plate, the through groove penetrates through the ferromagnetic plate along the thickness direction of the ferromagnetic plate, and the through groove penetrates through the region, covered by the magnetic sensor, of the ferromagnetic plate.
Specifically, the probe 1 is used for sensing a leakage magnetic field, and further the sensed signal is transmitted to a signal processing device, and the signal processing device processes the received signal to judge the defect. The probe 1 comprises a magnetic sensor 1-1 and a ferromagnetic plate 1-2, wherein a through groove 1-3 is formed in the ferromagnetic plate 1-2, and the through groove 1-3 penetrates through the ferromagnetic plate 1-2. The magnetic sensor 1-1 is disposed on the ferromagnetic plate 1-2, and partially or entirely covers one side of the through groove.
In this embodiment, the ferromagnetic plate 1-2 is rectangular, and the through groove 1-3 penetrates the ferromagnetic plate 1-2 along the thickness direction of the ferromagnetic plate; the depth of the through groove 1-3 is the same as the thickness of the ferromagnetic plate 1-2, and the ferromagnetic plate 1-2 is stuck on the workpiece 2 to be detected for scanning, so that the distance between the magnetic sensor 1-1 and the surface of the workpiece 2 to be detected is fixed, and the lift-off value of the magnetic sensor 1-1 is the thickness value of the ferromagnetic plate 1-2. Of course, the through slots 1-3 may also be referred to as through holes.
In a magnetizing field, the magnetic sensor and the ferromagnetic plate are attached to the surface of the magnetized workpiece to be detected to move so as to scan defects of the workpiece to be detected; the through grooves are magnetized and reinforced with the leakage magnetic field generated by the defects on the workpiece to be detected under the action of the magnetizing field.
Specifically, when the probe 1 scans the defect 2-1, the leakage magnetic field generated by the defect 2-1 propagates upwards, so that the magnetization intensity of the through groove 1-3 is enhanced, and the leakage magnetic field of the through groove 1-3 is enhanced; meanwhile, the through groove 1-3 also generates a leakage magnetic field under the action of a magnetizing field, the through groove 1-3 which is vertically penetrated downwards generates a leakage magnetic field, the upward leakage magnetic field also generates a leakage magnetic field, and the downward leakage magnetic field acts on the defect 2-1 of the workpiece 2 to be detected to strengthen the magnetization of the defect 2-1, so that the leakage magnetic field of the defect 2-1 is enhanced.
The leakage magnetic field induced by the magnetic sensor 1-1 is the superposition of the leakage magnetic field of the defect 2-1 and the leakage magnetic field of the through groove 1-3, so that the leakage magnetic field induced by the magnetic sensor 1-1 is enhanced, and the detection sensitivity is improved.
Meanwhile, the magnetic sensor 1-1 is fixed on the ferromagnetic plate 1-2, and the ferromagnetic plate scans on the workpiece 2 to be detected, so that mechanical noise caused by shaking of the magnetic sensor 1-1 is avoided, and the wear resistance of the magnetic sensor is enhanced.
Referring to fig. 4, 5 and 6, for further explanation of the present invention, finite element model simulation is performed by simulation software, the model is composed of a magnetizing coil, a workpiece to be tested and a ferromagnetic filling layer with a slot, the magnetizing coil provides magnetization for the workpiece to be tested and the filling layer, the number of turns is 2000 turns, and the magnetizing current is I. The materials of the workpiece to be tested and the filling layer are 45#, the magnetization constitutive relation is set as a B-H curve, the defect depth is H, and the width is B c The filling thickness of the lift-off layer is t, and the width of the through groove is b s . The measuring point is a position which is 0.2mm away from the surface of the through groove and is just above the defect center. The magnetization current varies in the range of 2A to 20A, preferably 16A.
In the embodiment, air lift-off and slotting lift-off are simulated respectively, and a leakage magnetic field horizontal direction component B at a position which is 1mm away from the position just above the defect is obtained under each magnetizing current x Subtracting the background magnetic field to obtain a leakage magnetic field peak value; from simulation results, the signal amplitude of the detection method provided by the application is always larger than that of the air lift-off method under different magnetization intensities.
In another simulation example, the magnetizing current is set to 16A, the defect width is set to 0.3mm, the variation range of the through groove width is 0.025 mm-1 mm, preferably 0.25mm, and the simulation model is the same as the simulation model; as can be seen from simulation results, with the increase of the width of the through slot, the intensity of the leakage magnetic field is increased and then reduced, and the signal amplitude of the detection method provided by the application is always larger than that of the air lift-off method, so that the detection method can achieve higher detection sensitivity.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (10)
1. A ferromagnetic plate-based defect detection method, characterized in that the detection method comprises the following steps:
(1) Fixing a magnetic sensor on a ferromagnetic plate, wherein a through groove is formed in the ferromagnetic plate, the through groove penetrates through the ferromagnetic plate along the thickness direction of the ferromagnetic plate, and the through groove penetrates through the region, covered by the magnetic sensor, of the ferromagnetic plate;
(2) In a magnetization field, the magnetic sensor and the ferromagnetic plate scan defects of the magnetized workpiece to be detected; the through grooves are magnetized and reinforced with the leakage magnetic field generated by the defects on the workpiece to be detected under the action of the magnetizing field.
2. A ferromagnetic plate-based defect detection method according to claim 1, wherein: the magnetic sensor and the ferromagnetic plate are attached to the surface of the workpiece to be detected to move so as to scan defects of the workpiece to be detected.
3. A ferromagnetic plate-based defect detection method according to claim 2, wherein: the distance between the magnetic sensor and the surface of the workpiece to be measured is constant.
4. A ferromagnetic plate-based defect detection method according to claim 2, wherein: the lift-off value of the magnetic sensor is the thickness value of the ferromagnetic plate.
5. A ferromagnetic plate based defect detection method according to any of claims 1-4, wherein: a magnetizer is used to form a magnetizing field, and the workpiece to be measured is magnetized in the magnetizing field.
6. A ferromagnetic plate-based defect detection method according to claim 5, wherein: the magnetizer comprises a U-shaped magnetic yoke and a magnetizing coil, and the magnetizing coil is arranged in the middle of the U-shaped magnetic yoke.
7. A ferromagnetic plate-based defect detection method according to claim 6, wherein: the magnetizing current in the magnetizing coil is 2A-20A.
8. A ferromagnetic plate-based defect detection method according to claim 5, wherein: the width of the through groove is 0.025 mm-1 mm.
9. A ferromagnetic plate based defect detection method according to any of claims 1-4, wherein: the magnetic sensor is an induction coil or a Hall element.
10. A ferromagnetic plate based defect detection method according to any of claims 1-4, wherein: the workpiece to be measured is made of ferromagnetic materials.
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| JPH0812178B2 (en) * | 1990-03-28 | 1996-02-07 | 日本鋼管株式会社 | Magnetic flaw detector |
| CN1289907C (en) * | 2002-11-01 | 2006-12-13 | 华中科技大学 | Magnectic-conductive member end-part defect detection device |
| CN104034793B (en) * | 2014-05-08 | 2016-11-23 | 中国人民解放军装甲兵工程学院 | The Magnetic Memory probe detector of a kind of jib remanufacturing old parts and method |
| CN104198576A (en) * | 2014-09-11 | 2014-12-10 | 北京理工大学 | Device for rapidly detecting inner crack of metal bent component |
| RU2587695C1 (en) * | 2015-04-29 | 2016-06-20 | Открытое акционерное общество "Акционерная компания по транспорту нефти "Транснефть" (ОАО "АК "Транснефть") | Magnetic flaw detector for detecting defects in welds |
| US9746446B2 (en) * | 2015-07-31 | 2017-08-29 | Olympus Scientific Solutions America Inc. | Probe holder providing constant lift-off for in-line bar-pipe testing |
| CN107632063B (en) * | 2017-08-22 | 2020-11-24 | 华中科技大学 | Magnetic flux leakage detection device for outer wall of variable-diameter pipe |
| CN108562640B (en) * | 2018-03-29 | 2021-05-11 | 南京航空航天大学 | Magnetic leakage signal enhancement structure |
| CN110220969B (en) * | 2019-06-28 | 2024-04-12 | 苏州大学 | Magnetic flux leakage detection probe with high sensitivity |
| CN111521689B (en) * | 2020-03-30 | 2022-12-16 | 北京工业大学 | Magnetostrictive guided wave and magnetic flux leakage dual-function scanner |
| CN113109420B (en) * | 2021-04-19 | 2024-02-02 | 北京工业大学 | Micromagnetic nondestructive testing system for revolving body part |
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