WO1993019362A1 - Procede et appareil de detection des discontinuites magnetiques d'un echantillon de materiau magnetique - Google Patents

Procede et appareil de detection des discontinuites magnetiques d'un echantillon de materiau magnetique Download PDF

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Publication number
WO1993019362A1
WO1993019362A1 PCT/DK1993/000102 DK9300102W WO9319362A1 WO 1993019362 A1 WO1993019362 A1 WO 1993019362A1 DK 9300102 W DK9300102 W DK 9300102W WO 9319362 A1 WO9319362 A1 WO 9319362A1
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WO
WIPO (PCT)
Prior art keywords
sensor
test sample
scanning
sensors
magnetic
Prior art date
Application number
PCT/DK1993/000102
Other languages
English (en)
Inventor
Allan Northeved
Hans Ole Olsen
Original Assignee
Force Institutterne
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Force Institutterne filed Critical Force Institutterne
Priority to EP93907823A priority Critical patent/EP0632891A1/fr
Publication of WO1993019362A1 publication Critical patent/WO1993019362A1/fr

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Classifications

    • 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

Definitions

  • the invention relates to a method of detecting magnetic discontinuities in a test sample, whereby a magnetic field is generated in said test sample and one or more magnetic sensors are placed adjacent said test sample for detection of a magnetic leakage flux, if any, and generation of an electric signal representing the leakage flux, if any, said sensors being moved across the surface of the test sample.
  • US-PS No. 4,814,705 discloses an apparatus for detection of magnetic discontinuities in an iron sheet.
  • the apparatus comprises a vehicle to be moved across the iron sheet.
  • the vehicle supports an elongated horse ⁇ shoe magnet the pole shoe of which faces the iron sheet. Without dis- continuities in the iron sheet, almost the entire magnetic field is transmitted through the sheet.
  • a number of magnetic field sensors are arranged between the pole shoes, said sensors being able to detect a leakage flux caused by discontinuities in the iron plate, said leakage flux being transmitted beside the iron sheet as a consequence of the discon- tinuity.
  • the signal of each sensor is subtracted from the mean value of a following and a succeeding sensor.
  • the detection perpendicular to the advancing direction of the apparatus can only be performed discon- tinuously.
  • the object of the invention is to provide a method of the above type, whereby the processing of the signal has been simplified and does not depend on the advancing speed of the sensors.
  • the method allows an improved scanning transverse to the advancing direction.
  • each sensor carries out a scanning movement substantially transverse to the advancing direction during said advancing movement.
  • the output signal of the sensor discloses sudden changes during a scanning.
  • the associated elec- tronic equipment can be considerably simplified.
  • the measur ⁇ ing does not depend on the advancing speed, as well as a continuous scanning transverse to the advancing direction is rendered possible, i.e. a highly improved scanning.
  • each sensor may carry out a difference measurement or a differential measurement, whereby the constant portion of the field has no influence on the measurement. As a result it is possible to achieve a very high sensitivity.
  • a sensor may be used for carrying out the difference measurement, said sensor comprising two juxtaposed mag- netic field detectors, the difference between the signals from the two detectors being used.
  • each sensor may be provided by mounting said sensor on a body placed on a rotatable shaft with a helical groove, a ratchet extending from the body and downwards into said groove.
  • the resulting scanning movement is carried out in a particularly simple manner.
  • each sensor may be provided by the rotatable shaft being provided with helical grooves in both directions in such a manner that a reciprocating movement can be carried out by the body on which the sensor is mounted.
  • the scanning movement may according to the invention alternatively be provided by the sensor being mounted on a chain with a substantially transverse run, said chain being driven by means of one or more sprockets.
  • the chain may comprise an upper run and a lower run, the scanning being performed at the lower run.
  • the invention relates furthermore to an apparatus for detecting magnetic discontinuities in a test sample of magnetic material, said apparatus being moved across said test sample and thereby generating a magnetic field in said test sample, where the apparatus comprises a number of sensors for the detection of magnetic leakage flux adjacent the surface of the test sample and for generating electric signals representing said leakage flux.
  • the apparatus is according to the invention characterised by each sensor being displaceable substantially transverse to the ad ⁇ vancing direction of the apparatus.
  • the resulting apparatus is more simple than previously known apparatuses, and in addition it is possible to carry out a continuous scanning transverse to the advancing direction of the apparatus.
  • each sensor may be mounted on a body placed on a rotatable shaft with a helical groove, means being provided for ensuring that said body does not rotate about the shaft, and a ratchet may extend from the body and downwards into the groove, whereby the scanning movement can be provided in a particu ⁇ larly simple manner.
  • Each sensor may according to the invention alternatively be mounted on a chain driven by means of one or more sprockets, said chain preferably comprising an upper run and a lower run, the scanning being performed at the lower run. In this manner a very fast scanning is allowed.
  • Fig. 1 illustrates an apparatus according to the invention with a scanning sensor for the detection of magnetic discontinuities in a test sample of magnetic material
  • Fig. 2 illustrates an apparatus with an alternative embodiment of a scanning sensor.
  • Fig. 3 is a side view of the apparatus of Fig. 2,
  • Fig. 4 illustrates an alternative embodiment of the apparatus whereby the sensors are permanently arranged and activated one by one
  • Fig. 5 illustrates an arrangement of several interconnected apparatuses.
  • the apparatus of Fig. 1 for the detection of magnetic discontinuities in a test sample therebelow of magnetic material comprises an elongated horseshoe electromagnet generating a magnetic field in the test sample.
  • the elongated pole shoes 1 of the electromagnet are maintained at a predetermined distance from the test sample by means of four wheels 104, cf. Fig. 3.
  • a plurality of permanent magnets 1 10 are arranged between the pole shoes 1.
  • One or more coils can alternatively be wound on the portion of the core connecting the poles shoes 1 , said coils being fed with an AC or a DC current.
  • One or more magnetic field sensors in form of Hall units are arranged between the elongated pole shoes 1 and are advanced in the direction of the arrow.
  • the Hall units carry out a scanning movement transverse to the advancing direction.
  • the scanning movement is provided by each sensor being mounted on a body 2 placed on a rotatable shaft 3, which is caused to rotate by means of an electromotor 4.
  • the rotatable shaft 3 is provided with a helical groove 5, a ratchet extending from the body 2 and downwards into said groove 5.
  • Some guide rails 6 are arranged parallel to the shaft 3 and abut the body 2. These guide rails 6 ensure that the body 2 does not follow the rotating movement of the shaft 3.
  • the body 2 is displaced from one end of the shaft 3 to the opposite end.
  • the body 2 can carry out a reciprocating movement during the rotation of the shaft 3.
  • the sensor mounted on the body 2 can detect changes, if any, in the scanned magnetic field during the above reciprocating movement. Such changes can for instance be caused by leakage flux deriving from dis ⁇ continuities in the test sample therebelow.
  • the scanning speed is in this embodiment limited to approximately 10 scannings/sec, which, how ⁇ ever, can be increased by arranging several similar scanning devices successively in the advancing direction of the apparatus. It is also poss- ible to arrange several juxtaposed scanning devices transverse to the advancing direction of the apparatus.
  • each sensor 7 is mounted on a chain 8 of a sprocket chain.
  • the sprocket chain is pro ⁇ vided by means of two sprockets 9, 10 and comprises an upper run and a lower run.
  • the sensor 7 is positioned in the lower run, it is in direct contact with the test sample to be examined.
  • the signal from the sensor 7 is transmitted to an oscilloscope indicating changes, if any, in the received signal during a scanning. In the latter case, the scanning can be performed very fast.
  • two sensors 7 are mounted on the same chain 8, cf. Fig.
  • Fig. 3 is a side view of the apparatus with the sprockets 104 and the perma ⁇ nent magnets 110 interconnecting the pole shoes 1. As illustrated in this Figure, it is possible to successively arrange several scanning devices in the direction of the arrow with the result that an even faster scanning speed is rendered .possible.
  • the sprockets at one end can be connected to a common driving shaft.
  • the sensors 7 may alternatively scan at varying speeds.
  • Fig. 3 is a side view of the apparatus with the sprockets 104 and the perma ⁇ nent magnets 110 interconnecting the pole shoes 1.
  • the signal from each sensor 7 is amplified and transmitted to an oscilloscope indicating changes, if any, in the received signal.
  • the associated electronic equip- ment is therefore relatively simple.
  • An additional advantage of this em ⁇ bodiment is that the total apparatus can even be static during a mea ⁇ surement.
  • the above chains can then be replaced by wire cables.
  • the scanning sensor has been replaced by a number of stationary sensors activated one by one, cf. Fig. 4.
  • Each sensor is formed by a U-shaped electromagnet 12, the pole shoes of which extend downwards towards the test sample to be examined.
  • the yoke of the U-shaped electromagnet 12 is provided with a notch 13.
  • the notch 13 implies that the sensor is not active.
  • the notch 13 can, how- ever, be filled with a body 14 of magnetically conductive material, said body 14 extending from one sensor to the next sensor by means of a wire cable 15 of non-magnetic material.
  • the wire cable 15 at the end of the run extends about a roller 16 and 17, respectively, the body 14 secured to the wire cable 15 being returned via a return run after having passed said roller 16.
  • Each apparatus 100 is preferably supported by four sprockets 104.
  • Several apparatuses can, however, be coupled in an arrangement as illustrated in Fig. 5.
  • This arrangement comprises a vehicle with some driving wheels 103 and a supporting wheel simultaneously driving an encoder providing information on the position.
  • a modular frame system 106 on both sides of the vehicle ensures that unimpeded by the rest of the arrangement each apparatus can maintain its distance to the surface of the test sample.
  • the distance to the surface of the test sample is determined by the position of the sprockets 104 on each apparatus. This arrangement renders it possible to scan a relatively wide path of the test sample, even when the surface of said test sample is not completely plane.
  • a boom 107 can be secured to the rearmost portion of the arrangement, a number of colour-spraying units 108 being arranged on said boom.
  • a computer ensures that dye is released proportional to and time-delayed relative to the found maximum or minimum exceedings of a material thickness of the test sample encoded in advance.
  • the apparatus according to the invention can, if desired, be lowered in a tank filled with liquid. Then the apparatus must be completely encap- sulated. The position of the apparatus is then indicated relative to the lowering location. The advancing direction is maintained by means of a built-in gyroscope, whereby it is not necessary to empty the tank before a measuring.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)

Abstract

Procédé de détection des discontinuités magnétiques d'un échantillon de matériau magnétique, selon lequel on génère un champ magnétique dans ledit échantillon, on place un ou plusieurs capteurs magnétiques près de l'échantillon pour détecter le flux de fuite magnétique, s'il en existe un, près de la surfae de l'échantillon, et on génère des signaux électriques représentant le flux de fuite, s'il en existe un, lesdits capteurs étant déplacés au-dessus de la surface de l'échantillon. Chaque capteur (7) effectue un mouvement de balayage qui est sensiblement transversal au sens de la progression pendant le mouvement vers l'avant. De cette manière on peut observer si le signal de sortie du capteur présente des variations brusques pendant un balayage. Ce système permet par conséquent de simplifier l'électronique qui lui est associée.
PCT/DK1993/000102 1992-03-23 1993-03-22 Procede et appareil de detection des discontinuites magnetiques d'un echantillon de materiau magnetique WO1993019362A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP93907823A EP0632891A1 (fr) 1992-03-23 1993-03-22 Procede et appareil de detection des discontinuites magnetiques d'un echantillon de materiau magnetique

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DK37692A DK169956B1 (da) 1992-03-23 1992-03-23 Fremgangsmåde og apparat til detektion af magnetiske diskontinuiteter i et prøveemne af magnetisk materiale
DK0376/92 1992-03-23

Publications (1)

Publication Number Publication Date
WO1993019362A1 true WO1993019362A1 (fr) 1993-09-30

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Application Number Title Priority Date Filing Date
PCT/DK1993/000102 WO1993019362A1 (fr) 1992-03-23 1993-03-22 Procede et appareil de detection des discontinuites magnetiques d'un echantillon de materiau magnetique

Country Status (4)

Country Link
EP (1) EP0632891A1 (fr)
AU (1) AU3889193A (fr)
DK (1) DK169956B1 (fr)
WO (1) WO1993019362A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1980002594A1 (fr) * 1979-05-11 1980-11-27 Bergstrand Kvalitetskontroll Procede et appareil de detection de solution de continuite dans un materiau
GB2071331A (en) * 1979-07-31 1981-09-16 Dalcy Hall T J Non-destructive Testing of Ferromagnetic Articles
EP0076684A1 (fr) * 1981-10-05 1983-04-13 Exxon Production Research Company Détection de défauts dans les embouts à vis d'un objet allongé tel que tuyau
GB2111217A (en) * 1981-11-02 1983-06-29 Magnetic Analysis Corp Apparatus and process for flux leakage testing using diagonal transverse magnetization
US4814705A (en) * 1986-03-17 1989-03-21 The Secretary Of State For United Kingdom Atomic Energy Authority In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Method and apparatus for magnetic discontinuity detection in a specimen of magnetizable material
EP0420147A1 (fr) * 1989-09-25 1991-04-03 Nkk Corporation Appareil de détection magnétique des défauts pour bandes d'acier

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1980002594A1 (fr) * 1979-05-11 1980-11-27 Bergstrand Kvalitetskontroll Procede et appareil de detection de solution de continuite dans un materiau
GB2071331A (en) * 1979-07-31 1981-09-16 Dalcy Hall T J Non-destructive Testing of Ferromagnetic Articles
EP0076684A1 (fr) * 1981-10-05 1983-04-13 Exxon Production Research Company Détection de défauts dans les embouts à vis d'un objet allongé tel que tuyau
GB2111217A (en) * 1981-11-02 1983-06-29 Magnetic Analysis Corp Apparatus and process for flux leakage testing using diagonal transverse magnetization
US4814705A (en) * 1986-03-17 1989-03-21 The Secretary Of State For United Kingdom Atomic Energy Authority In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Method and apparatus for magnetic discontinuity detection in a specimen of magnetizable material
EP0420147A1 (fr) * 1989-09-25 1991-04-03 Nkk Corporation Appareil de détection magnétique des défauts pour bandes d'acier

Also Published As

Publication number Publication date
DK37692D0 (da) 1992-03-23
EP0632891A1 (fr) 1995-01-11
AU3889193A (en) 1993-10-21
DK37692A (da) 1993-09-24
DK169956B1 (da) 1995-04-10

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