CN109613111A - A kind of gradient spiral vortex detection coil and its detection method - Google Patents

A kind of gradient spiral vortex detection coil and its detection method Download PDF

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CN109613111A
CN109613111A CN201811338949.7A CN201811338949A CN109613111A CN 109613111 A CN109613111 A CN 109613111A CN 201811338949 A CN201811338949 A CN 201811338949A CN 109613111 A CN109613111 A CN 109613111A
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coil
detection
sector
defect
inductance
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CN109613111B (en
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许�鹏
朱晨露
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Nanjing University of Aeronautics and Astronautics
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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
    • G01N27/90—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
    • G01N27/9006—Details, e.g. in the structure or functioning of sensors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

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  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)

Abstract

The invention discloses a kind of gradient spiral vortex detection coil and its detection methods, including high magnetic permeability shielded layer and a sector (-shaped) coil, the sector (-shaped) coil is gradually increased central angle by sector element or is gradually reduced central angle helically coiling and formed by a conducting wire, the center of circle angle difference of every two adjacent sector element is equal, it is 0-30 °, entire sector (-shaped) coil distribution gradient.The wire density of coil of the present invention is unevenly distributed, gradually sparse from inside to outside by coiling direction, and compared with traditional detection coil, the penetration depth distribution that coil of the present invention induces vortex in test specimen has directionality.After determining the Position Approximate of surface of test piece defect, coil of the present invention is placed in fault location rotation detection, can further obtain the width and depth information of defect.

Description

A kind of gradient spiral vortex detection coil and its detection method
Technical field
The invention belongs to technical field of nondestructive testing more particularly to a kind of gradient spiral vortexes based on eddy current detection principle Flow detection coil and its detection method.
Technical background
Non-destructive testing is a kind of under the premise of not injuring measurand using function, is detected in the structure of testee There is the detection technique of zero defect or the uneven situation of material.With the development of science and technology, non-destructive testing technology is widely used in producing The integrity assessment of the In-service testings and structure such as the quality control of product, the fatigue crack equipped.Wherein, eddy current detection is a kind of Lossless detection method based on electromagnetic induction principle, has the advantages that rapidity and low cost, in equipment key position microdefect Detection on play an important role.
Traditional test coil of eddy current is uniform coiling, induces equally distributed vortex in test specimen, and when detection adopts Use scanning mode.This traditional eddy current detection method can detecte presence and the specific location of defect, but some right The fields such as the more demanding industrial production of equipment safety performance, transport propose further requirement to EDDY CURRENT, i.e., to scarce The parameters such as sunken shape, size carry out accurate quantitative analysis, to avoid the generation of safety accident.
In recent years, numerous studies are expanded to the improvement of eddy current sensor both at home and abroad, it is intended to improve eddy current detection method Reliability.The research emphasis of Most scholars is mainly on several novel eddy current detection methods at present, as Pulsed eddy current testing, Precursor in far field and current vortex array detection etc..Penetration depth, detection range and working efficiency etc. of these methods in vortex Aspect is made that improvement, but the detection coil used is essentially traditional shim coil, analyzes experiment number with Impedance Analysis According to when the characteristic value extracted it is limited, which also limits the researchs of defect parameters quantitative estimation method in EDDY CURRENT.
Summary of the invention
Goal of the invention: in view of the deficiencies of the prior art, the present invention provides a kind of low cost, detection efficiency is high and has Directive test coil of eddy current and detection method.
Summary of the invention: a kind of gradient spiral vortex detection coil of the present invention, including high magnetic permeability shielded layer and one A sector (-shaped) coil, the sector (-shaped) coil are gradually increased central angle by sector element by a conducting wire or are gradually reduced central angle spiral Coiling forms, and the center of circle angle difference of every two adjacent sector element is equal, is 0-30 °, entire sector (-shaped) coil distribution gradient.
Wherein, each sector element is single turn coiling, and sector (-shaped) coil entirety outer profile is rounded.
A kind of detection method of gradient spiral vortex detection coil of the present invention, comprising the following steps:
(1) detection coil driving frequency f is selected according to test specimen parameter and surveyed indicated range, it is desirable that meet condition:And f >=1kHz；
Wherein, ReAnd LeThe respectively equivalent resistance and inductance of test specimen, μ are the magnetic conductivity of test specimen, and σ is tested The conductivity of test specimen, dmaxFor the greatest drawback depth of required differentiation；
(2) by rotation detection, fault location is measured into inductance valueSubtract inductance value L at zero defect0, obtain inductance variation Amount
(3) inductance variable quantity is extractedAverage value σ and standard deviation δ, by non-linear regression method be applied to surveyed lack Sample is fallen into, the Nonlinear regression equation of defect width is obtained
W=α0+α1σ+α2σ2+α3σ3+α4δ+α5δ2+α6δ3With the Nonlinear regression equation of depth
D=β0+β1σ+β2σ2+β3σ3+β4δ+β5δ2+β6δ3。
The step (2) the following steps are included:
(21) test coil of eddy current for being connected with exciting current is placed at test specimen zero defect, measures inductance value L0, whirlpool Flow lift-off value l≤1mm between detection coil and surface of test piece；
(22) test coil of eddy current for being connected with exciting current is placed in above defect, detection coil center and defect center pair Together, the inductance value that LCR table measures is read in 0 ° to 360 ° rotation detection of detection coil, 10 ° of every rotation
(23) fault location is measured into inductance valueSubtract inductance value L at zero defect0, obtain inductance variable quantity
The utility model has the advantages that compared with prior art, beneficial effects of the present invention: 1, detection coil entirety distribution gradient is led to After entering exciting current, the magnetic field strength in coil plane all directions is corresponding different around line density and has differences, Ke Yi The vortex of gradient distribution is induced in test specimen, test coil of eddy current has directionality when detecting；2, when using rotation detection side When method, changes in the vortex density distribution of fault location as coil and crack growth angular separation change, measure rotation with LCR table The inductance value to circle is easy to extract the realization of validity feature value to the quantitative evaluation of defect parameters in regularity variation.
Detailed description of the invention
Fig. 1 is the planar structure schematic diagram of detection coil of the present invention；
Fig. 2 is the detection method schematic diagram of detection coil of the present invention in specific implementation；
Fig. 3 is the schematic illustration of EDDY CURRENT；
Fig. 4 is the equivalent circuit diagram of EDDY CURRENT principle；
Fig. 5 is the inductance variation that detection coil of the present invention and its detection method are applied to individual defect detection；
Fig. 6 be on detection coil of the present invention detection aluminium sheet defect sample result do the width match value after nonlinear regression, Actual value；
Fig. 7 is that defect sample result does the relative error after nonlinear regression on detection coil of the present invention detection aluminium sheet；
Fig. 8 be on detection coil of the present invention detection aluminium sheet defect sample result do the depth match value after nonlinear regression, Actual value；
Fig. 9 is that defect sample result does the relative error after nonlinear regression on detection coil of the present invention detection aluminium sheet；
Marginal data: 1, test coil of eddy current；2, test specimen；3, the crackle on test specimen；11, sector (-shaped) coil；12, High magnetic permeability shielded layer.
Specific embodiment
The present invention is described in further details below with reference to Figure of description and specific embodiment.
Fig. 1 is the planar structure schematic diagram of detection coil 1 of the present invention, including high magnetic permeability shielded layer 12 and a fan-shaped line Circle 11, the sector (-shaped) coil 11 is gradually increased central angle by sector element by a conducting wire or is gradually reduced central angle helically coiling It forms, the center of circle angle difference of every two adjacent sector element is 15 °, entire sector (-shaped) coil distribution gradient.
Fig. 2 is the Practical Detection Method schematic diagram of coil 1, and after 3 specific location of crackle for determining test specimen 2, coil 1 is placed Above the crackle 3 of test specimen 2, it is passed through exciting current in coil 1, is rotated a circle the inductance value that measures of record around the center of circle.
As shown in figure 3, the working principle of eddy current detection is the friendship between the magnetic field of detection coil 1 and inductive loop magnetic field Interaction.When excitation coil 1 is passed through alternating current, alternating magnetic field will be generated around excitation coil 1, is now placed in excitation The surface of the test specimen 2 of 1 lower section of coil will induce current vortex, and this current vortex can generate a new magnetic field, with Former magnetic field is superimposed in detection coil 1 and forms Equivalent Magnetic Field.
It is the equivalent circuit diagram of above-mentioned eddy current detection principle in Fig. 4, wherein U is driving voltage；RoAnd LoRespectively examine The equivalent resistance and inductance of test coil itself；ReAnd LeThe respectively equivalent resistance and inductance of test specimen；IoFor in detection coil Exciting current, IeFor the inductive loop in test specimen；M is two mutual inductances between primary coil and secondary coil.Primary coil Complex impedance may be expressed as:
Zo=Ro+jωLo (1)
Similarly, the complex impedance of secondary coil may be expressed as:
Ze=Re+jωLe (2)
The inductance of M and two coil has relationship, and expression formula is as follows:
K is the coefficient of coup between two coils in formula.
When carrying out impedance analysis, it is contemplated that influencing each other between two coils is as caused by mutual inductance, so can lead to It crosses mutual inductance and the impedance in secondary coil circuit is folded to primary coil loops, to reflect this interactional relationship.When secondary When the impedance value of grade coil generates variation, this variation can be embodied by reduced impedance, to be reflected in entire electricity In the apparent impedance on road.
By the expression formula that can be calculated the equivalent resistance R and equivalent inductance L of equivalent rear coil:
When driving frequency f is sufficiently large, equivalent inductance L can be simplified to following formula.As can be seen that inductance is main Mutual inductance between primary and secondary coil is related, and mutually experiences the influence of the defects of test specimen.At this point, can be by detecting primary line The impedance variations value in circuit is enclosed to analyze the defects of test specimen.
To meet above-mentioned simplified condition, it is desirable that ω2Le 2>>Re 2, the gap of a quantitative levels is taken, then driving frequency f is answered Meet following formula:
In view of the increase of driving frequency f will lead to the penetration depth δ decaying of vortex, the differentiation for being unfavorable for depth of defect is known Not.Therefore, driving frequency cannot be excessive, otherwise will cause characteristic value when detecting the defect of super detectability and partly overlaps, difficult To distinguish.Using 2.6 times of standard osmotic depth as detection range, i.e. detectability in engineering.If the maximum of required differentiation Depth of defect is dmax, then 2.6 δ >=d should be met by being vortexed penetration depth δmax, can be calculated under driving frequency f should meet Formula:
In the present embodiment, by taking actually detected situation as an example, the specific steps are as follows:
(1) it is 6mm that greatest drawback depth on the aluminium sheet to be detected, which is arranged, according to calculation formulaSelection coil stimulating frequency is 1kHz；
(2) known defect sample on 9 groups of aluminium sheets to be detected is selected, width is respectively 0.5mm, 1mm, 2mm, depth difference For 1mm, 3mm, 6mm；
(3) test coil of eddy current for being connected with exciting current is placed on tested aluminium sheet at zero defect, measures inductance value L0= The test coil of eddy current for being connected with exciting current is placed at first above defect sample, is rotated by 0 ° to 360 °, every rotation by 14.3mH Turn 10 ° and reads the inductance value that LCR table measuresFault location is measured into inductance valueSubtract zero defect Locate inductance value L0, obtain first group of inductance variable quantityTo other defect sample Above step is repeated, nine groups of inductance variation delta L are successively obtainedj, j=1,2,3 ..., 9, Fig. 5 give detection width and are 2mm, depth are the inductance variable quantity under different rotary angle obtained by the defect of 6mm；
(4) the average value σ of every group of inductance variable quantity is extractedjWith standard deviation δj, nonlinear regression is done to nine groups of samples, is acquired The Nonlinear regression equation of defect width:
+ 91.1984 σ of w=0.95703-86.3695 σ2-25.8431σ3+327.0577δ-1272.6459δ2+ 1221.9112δ3With the Nonlinear regression equation of depth:
D=-0.17426+62.866 σ -67.8315 σ2+17.1246σ3-213.9333δ+882.6603δ2-555.8119 δ3, Fig. 6, Fig. 7 give match value, actual value and the error of defect width, Fig. 8, Fig. 9 give depth of defect match value, Actual value and error；
(5) two fit equations obtained with nonlinear regression in (4), to the unknown dimension defect detected do width and Depth is estimated.By width be 2mm, depth be 4mm defects detection result bring fit equation into, obtain estimating width be 2.0221mm, estimating depth is 4.2472mm, and the relative error estimated is no more than 7%.It is wide using existing detection coil pair defect Degree and depth do relative error that regression estimates obtain 20% or so, and coil of the present invention can effectively improve to defect parameters Evaluation accuracy.

Claims (5)

1. a kind of gradient spiral vortex detection coil, it is characterised in that: including high magnetic permeability shielded layer and a sector (-shaped) coil, institute It states sector (-shaped) coil and is gradually increased central angle by a conducting wire by sector element or is gradually reduced central angle helically coiling and form, every two The center of circle angle difference of a adjacent sector element is equal, is 0-30 °, entire sector (-shaped) coil distribution gradient.
2. test coil of eddy current according to claim 1, which is characterized in that each sector element is single turn coiling.
3. test coil of eddy current according to claim 1, which is characterized in that the sector (-shaped) coil entirety outer profile is in circle Shape.
4. a kind of detection method of gradient spiral vortex detection coil as described in claim 1, which is characterized in that including following Step:
(1) detection coil driving frequency f is selected according to test specimen parameter and surveyed indicated range, it is desirable that meet condition:And f >=1kHz；
Wherein, ReAnd LeThe respectively equivalent resistance and inductance of test specimen, μ are the magnetic conductivity of test specimen, and σ is test specimen Conductivity, dmaxFor the greatest drawback depth of required differentiation；
(2) by rotation detection, fault location is measured into inductance valueSubtract inductance value L at zero defect0, obtain inductance variable quantity
(3) inductance variation delta L is extractediAverage value σ and standard deviation δ, non-linear regression method is applied to the defect sample surveyed This, obtains the Nonlinear regression equation of defect width
W=α0+α1σ+α2σ2+α3σ3+α4δ+α5δ2+α6δ3With the Nonlinear regression equation of depth
D=β0+β1σ+β2σ2+β3σ3+β4δ+β5δ2+β6δ3。
5. a kind of detection method of gradient spiral vortex detection coil according to claim 5, which is characterized in that the step Suddenly (2) the following steps are included:
(21) test coil of eddy current for being connected with exciting current is placed at test specimen zero defect, measures inductance value L0, EDDY CURRENT Lift-off value l≤1mm between coil and surface of test piece；
(22) test coil of eddy current for being connected with exciting current being placed in above defect, detection coil center is aligned with defect center, The inductance value that LCR table measures is read in 0 ° to 360 ° rotation detection of detection coil, 10 ° of every rotationI=0,1,2 ..., 36；
(23) fault location is measured into inductance valueSubtract inductance value L at zero defect0, obtain inductance variable quantityi =0,1,2 ..., 36.
CN201811338949.7A 2018-11-12 2018-11-12 Gradient spiral eddy current detection coil and detection method thereof Active CN109613111B (en)

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Cited By (3)

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Publication number Priority date Publication date Assignee Title
CN111289609A (en) * 2019-10-11 2020-06-16 中国石油大学(华东) External-penetrating type rotating magnetic field wellhead sucker rod detection system
CN112782273A (en) * 2020-12-31 2021-05-11 天津因科新创科技有限公司 Pipeline crack detection method and device based on pulse eddy current
CN117907426A (en) * 2024-03-18 2024-04-19 电子科技大学 Metal vortex nondestructive testing method based on gradient method feature analysis

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111289609A (en) * 2019-10-11 2020-06-16 中国石油大学(华东) External-penetrating type rotating magnetic field wellhead sucker rod detection system
CN112782273A (en) * 2020-12-31 2021-05-11 天津因科新创科技有限公司 Pipeline crack detection method and device based on pulse eddy current
CN112782273B (en) * 2020-12-31 2024-02-20 天津因科新创科技有限公司 Pipeline crack detection method and device based on pulse vortex
CN117907426A (en) * 2024-03-18 2024-04-19 电子科技大学 Metal vortex nondestructive testing method based on gradient method feature analysis
CN117907426B (en) * 2024-03-18 2024-05-24 电子科技大学 Metal vortex nondestructive testing method based on gradient method feature analysis

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