CN1334462A - Method for inspecting surface defects of ferromagnetic material by geomagnetic field - Google Patents
Method for inspecting surface defects of ferromagnetic material by geomagnetic field Download PDFInfo
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- CN1334462A CN1334462A CN 01123977 CN01123977A CN1334462A CN 1334462 A CN1334462 A CN 1334462A CN 01123977 CN01123977 CN 01123977 CN 01123977 A CN01123977 A CN 01123977A CN 1334462 A CN1334462 A CN 1334462A
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- 230000007547 defect Effects 0.000 title claims abstract description 20
- 238000000034 method Methods 0.000 title claims abstract description 17
- 239000003302 ferromagnetic material Substances 0.000 title claims abstract description 10
- 230000005358 geomagnetic field Effects 0.000 title abstract 3
- 230000005291 magnetic effect Effects 0.000 claims abstract description 40
- 239000000463 material Substances 0.000 claims abstract description 23
- 238000001914 filtration Methods 0.000 claims abstract description 5
- 230000002950 deficient Effects 0.000 claims description 12
- 238000012360 testing method Methods 0.000 claims description 11
- 230000003321 amplification Effects 0.000 claims description 4
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 4
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 239000012535 impurity Substances 0.000 abstract 1
- 238000001514 detection method Methods 0.000 description 10
- 229910000831 Steel Inorganic materials 0.000 description 6
- 239000010959 steel Substances 0.000 description 6
- 230000005415 magnetization Effects 0.000 description 3
- 239000011148 porous material Substances 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000009659 non-destructive testing Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
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Abstract
A method for inspecting the surface defects, e.g. crack, corroded pit, impurity and air bubble, of ferromagnetic material by geomagnetic field includes such steps as putting the ferromagnetic material to be inspected in geomagnetic field, measuring the intensities of magnetic field of different point in a horizontal plane near surface of said material, setting up the simulating defect thresholds of the known material same as the material to be inspected, amplifying and filtering obtained intensites of magnetic field, and comparing them with said defect thresholds to judge if there is defect.
Description
Technical field:
The present invention relates to a kind of method of utilizing the terrestrial magnetic field to detect surface defects of ferromagnetic material, belong to the technical field of nondestructive testing of ferrimagnet.
Background technology:
In the prior art, application number is 95212309 patented product steel pipe magnetic flux leakage testing device, adopt the dc magnetization mode, set upright clamp system, circumferential defect testing agency and axial flaw testing agency, and devices such as control desk, testing circuit and warning, demonstration, marking are formed by front and back two.Set upright before the steel pipe of advancing passes the rotating magnetic field of the fixed magnetic field of V-arrangement up and down wheel, circumferential defect testing agency of clamp system and probe, axial flaw testing agency and probe, after set upright the wheel of V-arrangement up and down of clamp system.Upwards distribute in detected week or axially go up promptly report to the police after the defective that distributes, demonstration, marking.
Summary of the invention:
The objective of the invention is to propose a kind of method of utilizing the terrestrial magnetic field to detect surface defects of ferromagnetic material, in the environment of terrestrial magnetic field, ferromagnetic material is magnetized, the changes of magnetic field that the test material surface produces, judge according to this variation whether material surface exists defective, comprise the nearly surface of surface crack, etch pit, material internal folder caye and pore, and stress is concentrated etc.
The method of surface defects of ferromagnetic material is detected in the terrestrial magnetic field that utilizes that the present invention proposes, and may further comprise the steps:
(1) ferrimagnet to be detected is placed horizontally in the environment of magnetic field of the earth, measures the magnetic field intensity of each point on the interior same surface level of the nearly surperficial 0.01mm～10mm of material, the distance between each measuring point is 0.01mm～0.2mm;
(2) under same testing conditions, the known materials identical with ferrimagnet to be detected is provided with the simulated defect threshold value;
(3) magnetic field intensity signal that the above-mentioned first step is obtained is carried out the amplification filtering processing, then itself and the above-mentioned prior defective threshold value that is provided with of second step is compared, and can judge has zero defect.
In the method for the present invention, also can carry out the A/D conversion to the signal after above-mentioned the 3rd step amplification filtering, obtain digital signal corresponding, then the digital defects detection threshold value of this digital signal with the known materials that is provided with in advance compared, to judge whether to exist defective.
Can also be with method of the present invention by following step, adopt digital signal processing method to improve detection sensitivity, promptly carry out difference processing, obtain a series of magnetic field intensity gradient signals on the nearly surperficial a certain plane of material with each value of vicinity of above-mentioned magnetic field intensity digital signal; Then each value of vicinity of this magnetic field gradient signal is carried out difference processing, obtain the magnetic field gradient rate of change of each check point; The ferrimagnet that be processed with Artificial discontinuity identical, draw the Artificial discontinuity as stated above and locate the magnetic field gradient rate of change, and this value is set at the threshold value that detects defective with the method with tested material; At last the magnetic field gradient rate of change of detected material and the threshold value of preset standard artificial defect are compared,, just think that there is defective in tested material surface when magnetic field gradient rate of change during greater than threshold value.
The detection method that the present invention proposes can be avoided requiring checking matter is carried out active magnetization in the traditional flux-leakage detection method, and the loaded down with trivial details operation of after detection is finished checking matter being demagnetized.And saved and be used to magnetize required electrical source consumption and magnetizable body, and then can reduce the volume of pick-up unit, be beneficial to the development portable detector.
The method utilizes the terrestrial magnetic field as the magnetization driving source, utilizes the method can detect the various defectives on ferrimagnet surface, comprise surface crack, etch pit, the nearly surface of material internal folder caye and pore, and stress is concentrated etc.
Description of drawings:
Fig. 1 is the detection schematic diagram of the inventive method, and 1 is detected material among the figure, the 2nd, and detection faces, the 3rd, artificial rectangular channel defective, h is a lift-off value.
The specific embodiment:
The 20# steel steel plate that 15mm to be detected is thick is placed horizontally in the environment of magnetic field of the earth, then, and fixedly to carry From value h (h equals 2mm) on the surperficial detection faces (number in the figure is 2) close to the measured material (number in the figure is 1) Spacing is that each measuring point magnetic field intensity of 0.01mm is measured, and obtains the magnetic field intensity of each point on the detection faces, and with it Carry out the A/D conversion, obtain the digital value f (i, j) with magnetic field intensity corresponding to each point position, i, j are each measuring points Coordinate, i span are the integers from 0 to n, and the j span is the integer from 0 to m, n, m depend on by Survey the size of material area.
Press following formula f (i, j) is carried out difference processing: g (i, j)=4f (i, j)-f (i-1, j)-f (i, j-1)-f (i, j+1)-f (i+1, j)
As 0＜i＜n, during and 0＜j＜m; G (0, j)=(1, j), g (n, j)=g (n-1, j) is as i=0 or n, during 0＜j＜m for g; G (i, 0)=g (i, 1), g (i, m)=g (i, m-1) be as j=0 or m, during 0＜i＜n; And g (0,0)=g (1,1), g (n, 0)=g (n-1,1),
g(0，m)＝g(1，m－1)，g(n，m)＝g(n－1，m－1)
The g (i, j) that calculates is the magnetic field intensity gradient signal of each measuring point, and is poorer by following formula to g (i, j) Divisional processing obtains the rate of change e (i, j) of each measuring point magnetic field gradient.
The thick 20# steel steel of 15mm that is processed with Artificial discontinuity (the groove width 0.1mm of defective, dark 0.5mm) Plate draws the gradient change rate k that the Artificial discontinuity locates magnetic field intensity as stated above, and this k value is set at usefulness The method detects the threshold value of this kind fault in material. The size of e (i, j) and k value relatively when e (i, j)＞k, is just recognized For tested material locates to exist blemish at point (i, j).
Recording the fault location maximum magnetic field strength is 0.82Gs, and magnetic field gradient is 0.02Gs herein, and magnetic field gradient becomes herein Rate is 0.015Gs, and corresponding crack detection threshold value k is 0.01Ga, and testing result shows can find that this type of lacks Fall into.
Claims (2)
1, a kind of method of utilizing the terrestrial magnetic field to detect surface defects of ferromagnetic material is characterized in that this method may further comprise the steps:
(1) ferrimagnet to be detected is placed horizontally in the environment of magnetic field of the earth, measures the magnetic field intensity of each point on the interior same surface level of the nearly surperficial 0.01mm～10mm of material, the distance between each measuring point is 0.01mm～0.2mm;
(2) under same testing conditions, the known materials identical with ferrimagnet to be detected is provided with the simulated defect threshold value;
(3) magnetic field intensity signal that the above-mentioned first step is obtained is carried out amplification filtering, then itself and the above-mentioned prior defective threshold value that is provided with of second step is compared, and can judge has zero defect.
2, a kind of method of utilizing the terrestrial magnetic field to detect surface defects of ferromagnetic material is characterized in that this method may further comprise the steps:
(1) ferrimagnet to be detected is placed horizontally in the environment of magnetic field of the earth, measures the magnetic field intensity of each point on the interior same surface level of the nearly surperficial 0.01mm～10mm of material, the distance between each measuring point is 0.01mm～0.2mm;
(2) under same testing conditions, the known materials identical with ferrimagnet to be detected is provided with digital defective threshold value;
(3) magnetic field intensity signal that the above-mentioned first step is obtained is carried out amplification filtering, and the A/D conversion compares itself and the above-mentioned prior digital defective threshold value that is provided with of second step then, and can judge has zero defect.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 01123977 CN1131429C (en) | 2001-08-10 | 2001-08-10 | Method for inspecting surface defects of ferromagnetic material by geomagnetic field |
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| Application Number | Priority Date | Filing Date | Title |
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| CN 01123977 CN1131429C (en) | 2001-08-10 | 2001-08-10 | Method for inspecting surface defects of ferromagnetic material by geomagnetic field |
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| Publication Number | Publication Date |
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| CN1334462A true CN1334462A (en) | 2002-02-06 |
| CN1131429C CN1131429C (en) | 2003-12-17 |
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| CN 01123977 Expired - Fee Related CN1131429C (en) | 2001-08-10 | 2001-08-10 | Method for inspecting surface defects of ferromagnetic material by geomagnetic field |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102012397A (en) * | 2010-10-27 | 2011-04-13 | 南昌航空大学 | Nondestructive testing method for nonferromagnetic material |
| CN102590326A (en) * | 2011-10-31 | 2012-07-18 | 北京理工大学 | Magnetic memory/magnetic leakage integrated multi-probe detection device for tube and shaft type parts |
| CN103685839A (en) * | 2012-09-14 | 2014-03-26 | 株式会社理光 | Image inspection apparatus and image inspection method |
| CN105467000A (en) * | 2015-12-21 | 2016-04-06 | 中国石油大学(北京) | Non-excavation detection method and device of buried pipeline body defects |
| WO2017008621A1 (en) * | 2015-07-16 | 2017-01-19 | 宁波市鄞州磁泰电子科技有限公司 | Micro-magnetic detection method and device |
| CN108051763A (en) * | 2017-11-30 | 2018-05-18 | 宁波市鄞州磁泰电子科技有限公司 | A kind of weak magnetic detection method of composite material |
-
2001
- 2001-08-10 CN CN 01123977 patent/CN1131429C/en not_active Expired - Fee Related
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102012397A (en) * | 2010-10-27 | 2011-04-13 | 南昌航空大学 | Nondestructive testing method for nonferromagnetic material |
| CN102590326A (en) * | 2011-10-31 | 2012-07-18 | 北京理工大学 | Magnetic memory/magnetic leakage integrated multi-probe detection device for tube and shaft type parts |
| CN103685839A (en) * | 2012-09-14 | 2014-03-26 | 株式会社理光 | Image inspection apparatus and image inspection method |
| CN103685839B (en) * | 2012-09-14 | 2016-06-15 | 株式会社理光 | Image inspection equipment and image checking method |
| US9390493B2 (en) | 2012-09-14 | 2016-07-12 | Ricoh Company, Ltd. | Image inspection apparatus, image inspection method, and control program of image inspection apparatus |
| US9898814B2 (en) | 2012-09-14 | 2018-02-20 | Ricoh Company, Ltd. | Image inspection apparatus, image inspection method, and control program of image inspection apparatus |
| WO2017008621A1 (en) * | 2015-07-16 | 2017-01-19 | 宁波市鄞州磁泰电子科技有限公司 | Micro-magnetic detection method and device |
| CN105467000A (en) * | 2015-12-21 | 2016-04-06 | 中国石油大学(北京) | Non-excavation detection method and device of buried pipeline body defects |
| CN105467000B (en) * | 2015-12-21 | 2019-05-21 | 中国石油大学(北京) | Buried pipeline tube body defect Indirect testing method and device |
| CN108051763A (en) * | 2017-11-30 | 2018-05-18 | 宁波市鄞州磁泰电子科技有限公司 | A kind of weak magnetic detection method of composite material |
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| CN1131429C (en) | 2003-12-17 |
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