CN105548347A - Method for detecting defects in conductor based on electromagnetic induction principle - Google Patents
Method for detecting defects in conductor based on electromagnetic induction principle Download PDFInfo
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- CN105548347A CN105548347A CN201510921357.8A CN201510921357A CN105548347A CN 105548347 A CN105548347 A CN 105548347A CN 201510921357 A CN201510921357 A CN 201510921357A CN 105548347 A CN105548347 A CN 105548347A
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- 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
- G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
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Abstract
The invention relates to a method for detecting defects in a conductor based on an electromagnetic induction principle; the method is characterized by including the steps: step 1, placing a small permanent magnet near a to-be-detected conductor, and making a magnetic field penetrate to the to-be-detected conductor; step 2, generating a relative motion between the small magnet and the to-be-detected conductor; step 3, measuring changes, caused by micro particles or defects, of an induction magnetic field around the to-be-detected conductor; and step 4, determining characteristics of the micro particles or defects through the changes of the induction magnetic field. The method for detecting the defects in the conductor based on the electromagnetic induction principle has clear electromagnetic principle; a measuring instrument is simple in structure; the measurement accuracy is high; the measurement efficiency is high; and the to-be-detected sample is not required for magnetic conduction, and thus the applicable scope is broader.
Description
Technical field
The present invention relates to a kind of based on defect detection method in the conductor of electromagnetic induction principle, particularly relate to monitoring and the detection of microparticle in a kind of conductive material or heterogeneous defect.
Background technology
In process of production, conductive material is due to preparation technology or the defect in the generation of usage process, and as particle or the defects such as crack defect, pore such as oxide, nitride, sulfide, their existence often has a strong impact on the use safety of conductive material.Such as, the impurity in cable had both seriously reduced the physical strength of conductor material, also can increase resistance by the change of conductive properties, produce extra Joule heat, thus weaken electric conductivity and serviceable life.Obviously, microparticle or defect are effectively detected and monitored there is important production meaning.
Traditional eddy current detection method is generally made up of drive coil and receiving coil.Alternating current is passed in drive coil, around it, induced field is produced according to Ampère law, it may penetrate in conductor to be measured, because the time humorous characteristic of input current produces vortex flow in the conductor, further, vortex flow produces induced field around conductor, when there is heterogeneous defect in conductor, above-mentioned vortex flow and induced field around thereof all can change, and can be found out the change of induced field around conductor by the impedance variation of receiving coil, and then obtain the characteristic information of defect.Coil in eddy current detection method is due to the design feature by wire spiral winding, and coil dimension is generally several millimeters, is difficult to reduce size further again, and thus measuring accuracy is restricted; Secondly, because the amount measured by receiving coil is impedance, and the induced field of spatial variations is vector, thus there is so-called Lift-off effect, and this is the deficiency that traditional eddy-current method exists.Instant invention overcomes above-mentioned deficiency.
Summary of the invention
The object of the invention is the defect for prior art, there is provided a kind of based on defect detection method in the conductor of electromagnetic induction principle, make to produce relative motion between little permanent magnet and conductor to be measured, vortex flow will be produced in the conductor by the Theory of Electromagnetic Field of Maxwell is known, due to the difference of conductivity between microparticle and conductor, according to Ampère law, also can there is corresponding change in the induced field that vortex flow produces in space, utilizes magnetoresistance directly to visit the change of this space magnetic field.
For achieving the above object, the invention provides a kind of based on defect detection method in the conductor of electromagnetic induction principle, described method comprises:
Step 1, is placed in little permanent magnet near conductor to be measured, makes magnetic field penetration in described conductor to be measured;
Step 2, makes to produce relative motion between described small magnet and conductor to be measured;
Step 3, measures the change of the induced field around by the conductor to be measured caused when microparticle or defect;
Step 4, determines the feature of described microparticle or defect by described induced field change.
Further, described in described step 1, little permanent magnet produces the static magnetic field of space distribution, and penetrates in conductor to be measured; The direction of magnetization of described little permanent magnet is perpendicular to conductive surface to be measured, or described little permanent magnet does not contact with between conductor to be measured.
Further, described step 2 is specially, and fixing described little permanent magnet, makes described conductor motion to be measured; Or fixing described conductor to be measured, make described little permanent magnet motion.
Further, the relative motion in described step 2 is specially linear movement that speed is constant or angular velocity is the circular motion of constant.
Further, the change of the sensor measurement space induced field based on magnetoresistance is adopted in described step 3.
Further, the pulse number of the changes of magnetic field in described step 4 is the number of microparticle or heterogeneous defect.
Further, the amount of the changes of magnetic field in described step 4 is larger, then the size of microparticle or heterogeneous defect is larger.
Further, the pulse signal that the changes of magnetic field in described step 4 produces is corresponding with microparticle or heterogeneous defect.
Further, in described step 2,3, change the speed of described relative motion, obtain microparticle or heterogeneous defect depth information in the conductor.
The present invention is based on defect detection method in the conductor of electromagnetic induction principle, electromagnetic principles is clear; Measuring instrument mechanism is simple; Accuracy of measurement is high; Measurement efficiency is high; And do not require sample to be tested magnetic conduction, thus the scope of application is more extensive.
Accompanying drawing explanation
Figure 1A is one of measuring principle schematic diagram of defect detection method in the conductor that the present invention is based on electromagnetic induction principle;
Figure 1B is the measuring principle schematic diagram two of defect detection method in the conductor that the present invention is based on electromagnetic induction principle;
Fig. 1 C is the measuring principle schematic diagram three of defect detection method in the conductor that the present invention is based on electromagnetic induction principle;
Fig. 1 D is the measuring principle schematic diagram four of defect detection method in the conductor that the present invention is based on electromagnetic induction principle;
Fig. 1 E is the measuring principle schematic diagram five of defect detection method in the conductor that the present invention is based on electromagnetic induction principle;
Fig. 1 F is the measuring principle schematic diagram six of defect detection method in the conductor that the present invention is based on electromagnetic induction principle;
Fig. 1 G is the measuring principle schematic diagram seven of defect detection method in the conductor that the present invention is based on electromagnetic induction principle;
Fig. 1 H is the measuring principle schematic diagram eight of defect detection method in the conductor that the present invention is based on electromagnetic induction principle;
Fig. 2 is the process flow diagram of defect detection method in the conductor that the present invention is based on electromagnetic induction principle;
Fig. 3 is the schematic diagram of defect detection method in the conductor that the present invention is based on electromagnetic induction principle.
Fig. 4 A uses one of measuring-signal schematic diagram that the present invention is based on defect detection method in the conductor of electromagnetic induction principle;
Fig. 4 B is the measuring-signal schematic diagram two using the defect detection method in the conductor of electromagnetic induction principle that the present invention is based on.
Embodiment
Below by drawings and Examples, technical scheme of the present invention is described in further detail.
Ultimate principle of the present invention is as follows: by small size, the permanent magnet of design shape can provide the static magnetic field of a local
make to produce relative motion between little permanent magnet and conductor sample to be measured,
As shown in Figure 1A, set up an electromagnetic susceptibility district in the conductor, scope is about three times of small magnet size, and all electromagnetic parameter changes mainly concentrate in this sensitizing range.According to Ohm law, a pair vortex flow ring that generation current direction is contrary in the conductor
as shown in Figure 1B; According to Ampère law, vortex flow produces induced field around it
as shown in Figure 1 C; Space magnetic field can be expressed as the form of vector:
as shown in figure ip.
Fig. 1 E shows the situation when microparticle enters electromagnetic susceptibility district with conductor motion; Due to microparticle or the difference of conductivity between heterogeneous defect and conductor to be measured, the vortex flow ring in conductor
size and distribution will change, as shown in fig. 1f; Correspondingly, the induced field that produces around it of vortex flow
also will change, as shown in Figure 1 G; The space magnetic field in region is changed to
as shown in fig. 1h.
Obvious, the variable quantity of space magnetic field
and there is corresponding relation between microparticle or heterogeneous defect.Because above-mentioned physical quantity is the change of field amount, the space magnetic field thus can surveyed changes spatial form, size and the quantative attribute that can reflect microparticle or heterogeneous defect.
Fig. 2 is the process flow diagram of defect detection method in the conductor that the present invention is based on electromagnetic induction principle, as shown in the figure, the present invention includes following steps:
Step 101, is placed in little permanent magnet near conductor to be measured, makes magnetic field penetration in conductor to be measured;
Concrete, in step 1, the medium and small permanent magnet of step 1 provides the static magnetic field of space distribution, and penetrates in conductor to be measured, and in order to obtain larger magnetic field penetration effect, the direction of magnetization of little permanent magnet is perpendicular to conductive surface to be measured.Or little permanent magnet provides the static magnetic field of space distribution, and penetrate in conductor to be measured, in order to obtain larger magnetic field penetration effect, the distance between little permanent magnet and conductor to be measured is little as far as possible under ensureing do not have the condition of Mechanical Contact.
Step 102, makes to produce relative motion between small magnet and conductor to be measured;
Concrete, this step is specially, and fixing described little permanent magnet, makes conductor motion to be measured; Or fixing conductor to be measured, little permanent magnet is moved.
In addition, relative motion is specially linear movement that speed is constant or angular velocity is the circular motion of constant.
As Fig. 3 the present invention is based on shown in the schematic diagram of defect detection method in the conductor of electromagnetic induction principle, rotating mechanism is adopted to realize a kind of mode of relative motion, comprise the conductor sample 2 to be measured be fixed on drive unit 1, be placed in the permanent magnet 3 on conductor 2 surface to be measured, and the magnetoresistive transducer 4 be arranged near described permanent magnet 3, magnetoresistive transducer has multiple arrangement mode near permanent magnet, do not draw one by one, and the data acquisition system (DAS) 5 to be connected with magnetoresistive transducer 4, distance measuring sensor 6, the microparticle 7 in conductor to be measured.
Step 103, measures the change of the induced field around by the conductor to be measured caused when microparticle or defect;
The change of the sensor measurement space induced field based on magnetoresistance is adopted in step.When magnetic field change time, then show to there is microparticle or heterogeneous defect in sample to be tested, obtaining measuring-signal schematic diagram, as shown in Figure 4 A, is signal during zero defect, as shown in Figure 4 B, signal when being defectiveness.
Step 104, determines the feature of microparticle or defect by induced field change.
The pulse number of the changes of magnetic field in this step is the number of microparticle or heterogeneous defect.The amount of changes of magnetic field is larger, then the size of microparticle or heterogeneous defect is larger.There is one-to-one relationship in the pulse signal caused by changes of magnetic field and microparticle or heterogeneous defect, instead can release microparticle or heterogeneous defect locus in the conductor and space distribution on space-time.
Optionally, by changing speed of related movement, microparticle or heterogeneous defect depth information in the conductor can be obtained.The yardstick of detectable microparticle or heterogeneous defect is micron order.
The present invention is based on defect detection method in the conductor of electromagnetic induction principle, there is following characteristics and advantage:
1, the inventive method provides magnetic field by little permanent magnet, and it is less that little magnet size can do, and electromagnetic susceptibility district can be less, detectable micron-sized microparticle or heterogeneous defect, and the measuring accuracy of more traditional vortex flow method has and significantly improves;
The change of the space magnetic field 2, detected by magnetoresistance in the present invention, overcomes the Lift-off effect in traditional eddy-current method; The change of vector field makes the information more horn of plenty of detection, can obtain the characteristic information of more microparticles or heterogeneous defect;
3, according to the inventive method design measuring instrument, structure is simple, and detection efficiency is high, easily is automated and miniaturization, can be applied in more field and environment.
Above-described embodiment; object of the present invention, technical scheme and beneficial effect are further described; be understood that; the foregoing is only the specific embodiment of the present invention; the protection domain be not intended to limit the present invention; within the spirit and principles in the present invention all, any amendment made, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (9)
1. based on a defect detection method in the conductor of electromagnetic induction principle, it is characterized in that, described method comprises:
Step 1, is placed in little permanent magnet near conductor to be measured, makes magnetic field penetration in described conductor to be measured;
Step 2, makes to produce relative motion between described small magnet and conductor to be measured;
Step 3, measures the change of the induced field around by the conductor to be measured caused when microparticle or defect;
Step 4, determines the feature of described microparticle or defect by described induced field change.
2. method according to claim 1, is characterized in that, described in described step 1, little permanent magnet produces the static magnetic field of space distribution, and penetrates in conductor to be measured; The direction of magnetization of described little permanent magnet is perpendicular to conductive surface to be measured, or described little permanent magnet does not contact with between conductor to be measured.
3. method according to claim 1, is characterized in that, described step 2 is specially, and fixing described little permanent magnet, makes described conductor motion to be measured; Or fixing described conductor to be measured, make described little permanent magnet motion.
4. method according to claim 1, is characterized in that, the relative motion in described step 2 is specially linear movement that speed is constant or angular velocity is the circular motion of constant.
5. method according to claim 1, is characterized in that, adopts the change of the sensor measurement space induced field based on magnetoresistance in described step 3.
6. method according to claim 1, is characterized in that, the pulse number of the changes of magnetic field in described step 4 is the number of microparticle or heterogeneous defect.
7. method according to claim 1, is characterized in that, the amount of the changes of magnetic field in described step 4 is larger, then the size of microparticle or heterogeneous defect is larger.
8. method according to claim 1, is characterized in that, the pulse signal that the changes of magnetic field in described step 4 produces is corresponding with microparticle or heterogeneous defect.
9. method according to claim 1, is characterized in that, in described step 2,3, changes the speed of described relative motion, obtains microparticle or heterogeneous defect depth information in the conductor.
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Cited By (6)
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| CN106290548A (en) * | 2016-08-29 | 2017-01-04 | 爱德森（厦门）电子有限公司 | A kind of device and method utilizing rotating excitation field detection metal impurities |
| CN106525668A (en) * | 2016-10-26 | 2017-03-22 | 中国科学院大学 | Electromagnetic microparticle detection method |
| CN108802170A (en) * | 2017-04-28 | 2018-11-13 | 中国科学院大学 | A kind of electromechanical detection method of whole audience formula defect using electronic speckle technology |
| CN108872364A (en) * | 2018-06-29 | 2018-11-23 | 中国科学院大学 | A kind of defect inspection method based on Lorentz force |
| CN109188320A (en) * | 2018-08-06 | 2019-01-11 | 哈尔滨工业大学 | A kind of flow field imaging system and imaging method based on magnetoresistance |
| CN109738514A (en) * | 2019-03-13 | 2019-05-10 | 中国科学院大学 | A kind of electromechanical detection method for defect detection in thin metal foil material |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106290548A (en) * | 2016-08-29 | 2017-01-04 | 爱德森（厦门）电子有限公司 | A kind of device and method utilizing rotating excitation field detection metal impurities |
| CN106525668A (en) * | 2016-10-26 | 2017-03-22 | 中国科学院大学 | Electromagnetic microparticle detection method |
| CN106525668B (en) * | 2016-10-26 | 2019-11-19 | 中国科学院大学 | Electromagnetism microparticle detection method |
| CN108802170A (en) * | 2017-04-28 | 2018-11-13 | 中国科学院大学 | A kind of electromechanical detection method of whole audience formula defect using electronic speckle technology |
| CN108872364A (en) * | 2018-06-29 | 2018-11-23 | 中国科学院大学 | A kind of defect inspection method based on Lorentz force |
| CN109188320A (en) * | 2018-08-06 | 2019-01-11 | 哈尔滨工业大学 | A kind of flow field imaging system and imaging method based on magnetoresistance |
| CN109738514A (en) * | 2019-03-13 | 2019-05-10 | 中国科学院大学 | A kind of electromechanical detection method for defect detection in thin metal foil material |
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Application publication date: 20160504 |