WO2015140220A1 - Système de détection de champ magnétique - Google Patents

Système de détection de champ magnétique Download PDF

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Publication number
WO2015140220A1
WO2015140220A1 PCT/EP2015/055704 EP2015055704W WO2015140220A1 WO 2015140220 A1 WO2015140220 A1 WO 2015140220A1 EP 2015055704 W EP2015055704 W EP 2015055704W WO 2015140220 A1 WO2015140220 A1 WO 2015140220A1
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Prior art keywords
sensor
magnetic field
magnetic
sensor arrangement
measuring structure
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PCT/EP2015/055704
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German (de)
English (en)
Inventor
Matthias BÜRKLE
Hubert Grimm
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Sensitec Gmbh
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Publication of WO2015140220A1 publication Critical patent/WO2015140220A1/fr

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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

Definitions

  • the invention relates to a sensor arrangement for the magnetic flux leakage measurement in a ferromagnetic measuring structure according to the preamble of claim 1.
  • Sensor arrangements for the magnetic leakage flux test as a non-destructive test method have long been known from the prior art. They are used for manual or automated surface testing of components or semi-finished products made of magnetizable materials, such as iron, nickel, cobalt or related alloys. With the help of a leakage flux measurement cracks and pores that are open to the surface or even hidden within the material can be determined.
  • the measuring principle is based on the fact that the measuring structure to be examined is temporarily magnetized in order to be scanned contactless or touching with a test head.
  • the cracks or pores within or on the measurement structure cause a change in the magnetic flux profile and thus a scattering of the magnetic field lines, which can be detected by the sensor arrangement.
  • rotating sensor arrangements can be used, which revolve around the longitudinal axis of the measuring structure.
  • the measuring structure For the magnetization of the measuring structure, permanent magnets or current-carrying coils are used, with the measuring structure usually being magnetized near the surface.
  • the magnetic flux in the measurement structure propagates in the direction of the magnetic opposite pole in order to close the magnetic circuit.
  • a homogeneous magnetic flux is caused by a surface defect, a crack, an inhomogeneity or a structural defect in the material. disturbs, with the flow of a local disturbance evades and takes a different course.
  • the course of the field lines outside the measurement structure can be detected by a non-contact or touching probe comprising a corresponding magnetic field sensor.
  • an evaluation device is provided which analyzes the sensor signals and indicates a corresponding defect in the case of an error.
  • the measuring structure is generally moved relative to the sensor arrangement or the sensor arrangement relative to the measuring structure in order to be able to scan or scan all areas of the measuring structure.
  • MFL magnetic flux leakage
  • the location and arrangement of defects in the material can be detected.
  • Such sensor arrangements are used in particular for a so-called in-line inspection (ILI), in which an autonomously movable testing device inspects cracks and defects of the outer wall within a pipeline.
  • IPI in-line inspection
  • the magnetic field sensors are arranged between the poles of a magnetic field generating device, and are only designed to detect surface defects.
  • the magnetic flux density occurring here is on the order of up to 1 mT, and is thus far below the saturation of the magnetic material of the measuring structure, so that a magnetic field guidance is given only along the surface of the measuring structure. It is usually not possible to detect deeper defects with such leakage flux measuring methods, since the magnetic fields do not enter the measuring structure far enough.
  • DE 10 2008 020 194 A1 discloses a method and a device for detecting near-surface material defects by means of leakage flux measurement, wherein a magnetic alternating field is superimposed on a magnetic constant field to detect hidden defects in a measuring structure.
  • a sensor arrangement which is located between the poles of a magnetic field generating device, stray fields are measured, which are caused by both near-surface and hidden inside defects.
  • GB 2 012 966 A describes a sensor arrangement for the magnetic flux leakage measurement in a rope-shaped ferromagnetic measuring structure, for example in a steel wire rope.
  • the sensor arrangement comprises a magnetic field generating device with two substantially annular pole shoes, which are axially spaced, and through which a magnetic flux can be introduced into the measurement object.
  • a series of Hall sensors is arranged, which measure the radially introduced in the direction of the rope and / or outflowing magnetic flux.
  • An evaluation device shown evaluates the sensor signals, wherein a material error can be displayed when a limit value is exceeded.
  • the sensor arrangement for magnetic leakage flux measurement in a ferromagnetic measurement structure comprises a magnetic field generating device for generating a static magnetic field H, a sensor device by which the course of a magnetic flux ⁇ and a course of the leakage flux generated by material locations or inhomogeneities of the measurement structure in the direction of a surface the measuring structure can be detected by outputting at least one signal value, and an evaluation device which is designed to evaluate a signal value of the sensor device.
  • the magnetic field generating device comprises a permanent magnet with two magnetic poles, wherein the magnetic flux exit surface is defined at least at one magnetic pole or at a Flußaustrittsflä- surface of a magnetic field guide yoke.
  • the sensor device is arranged directly on a magnetic flux exit surface of the magnetic field generating device and is penetrated by magnetic field lines which emerge parallel to the surface of the measuring structure.
  • the magnetic flux exit surface is arranged perpendicular to the surface of the measuring structure, so that the central magnetic flux exits parallel to the measuring structure surface, however, the sensor device can also be arranged in the region of a leakage flux of the magnetic flux exit surface, in which the leakage flux is aligned parallel to the measuring structure surface.
  • the sensor arrangement is therefore not in the main flow of a closed magnetic circuit but only detects components, primarily leakage flux components, which are aligned in the direction of the measurement structure.
  • the magnetic field generating device is set up to generate the measurement magnetic field H in an order of magnitude sufficient to cause magnetic saturation of the magnetic flux at least in the region of the surface of the measurement structure, and that the evaluation device is set up to provide a quantitative progression of the signal value with at least one pre-stored signal value. run to detect a material defect or material inhomogeneity of the measurement structure.
  • a sensor arrangement comprises a magnetic field generating device with which a static measurement magnetic field H can be generated in a size sufficient to saturate near-surface regions of a measurement structure to be examined as magnetically as possible, so that the hysteresis characteristic flattens and a Slope of ⁇ ⁇ «1 approaches.
  • the magnetic field generating device is a permanent magnet and may additionally be a current-carrying coil. It is designed to generate a magnetic field that can cause saturation of the magnetic flux in the surface and in deeper regions of the measurement structure.
  • strong magnetic fields are to be generated in order to move in accordance with the hysteresis characteristic of the material of the measurement structure in a flattened area, in which the mass of Weiss'schen districts of the material is aligned, so that an additional change in the magnetic field strength, a change of the magnetic flow in the range of ⁇ 0 ⁇ , at ⁇ ⁇ ⁇ 1 can be generated.
  • the Weissian districts are approximately aligned in the vicinity of the measuring arrangement, so that a material disturbance in the magnetic field flux produces an extremely strong change in the flux lines in the air, so that they also escape in the case of deep cracks or pores from Cause magnetic fields in the air.
  • the permanent magnet comprises a north and a south pole, wherein the magnetic flux exit surface is defined at least at one magnetic pole or at a flux exit surface of a magnetic field guide yoke.
  • the sensor device is arranged on one of the pole exit surfaces of the north or south pole or on one of the iron yoke surfaces on which the measuring magnetic field H emerges, these magnetic fields being aligned parallel to the workpiece surface.
  • the sensor device comprising the magnetic field sensor is arranged directly or in close proximity to a pole of the magnetic field generating device.
  • the sensor device is exposed to the magnetic flux ⁇ , wherein a change in the magnetic field flux ⁇ due to a stray magnetic field has only a small effect on the total size of the magnetic field detected by the sensor device.
  • the sensor device is therefore to be designed in such a way that it is particularly sensitive in the region of high magnetic fields which have an order of magnitude which brings the material of the measuring structure largely into saturation.
  • An evaluation device evaluates a signal value, in particular a relative signal value change of the sensor device, and compares the quantitative profile of the signal value with prestored progressions of known defects or with a sensor value profile in an undisturbed material, a sensor value profile of a surface crack, a depth crack, a surface defect or a deep flaw. Since, of course, the imperfections cause only a small change in the absolute magnetic flux directly in the vicinity of a pole of the magnetic field generating means, a corresponding highly sensitive sensor device must be provided which has a high spatial resolution and high sensitivity, in particular a high sensor characteristic slope in the field of measuring magnetic field strength with respect to relatively small Changes a high static magnetic field can detect.
  • the sensor arrangement is simplified, since the sensor device must be arranged directly on a single pole, so that this example, in the form of a rod or pin over the surface of the measuring structure can be pulled, and not two poles must simultaneously be applied to the measuring structure. Due to the high field strength of the static measuring magnetic field H, saturation is achieved down to the depth of the material of the measuring structure, so that deeper defects and inhomogeneities can be detected which were not recognizable for previously known leakage flux measuring methods.
  • the sensor device can be sensitive to magnetic field lines perpendicular to the surface of the measurement structure.
  • sensor devices which are based, for example, on an AMR, GMR or XMR effect, detect magnetic field components in a single magnetic-field-sensitive preferred direction.
  • this preferred direction is aligned in normal use perpendicular to the surface of the measuring structure, so that magnetic fields that are aligned in the direction of the measuring structure, can be detected. Since the sensor device is penetrated by magnetic field lines oriented parallel to the measurement structure surface, magnetic fields which bend in the direction of the measurement structure can thus be detected with high sensitivity.
  • the sensor device can be arranged on an edge of the magnetic flux exit surface facing the surface of the measuring structure. If the magnetic flux exit surface is oriented perpendicular to the surface of the measurement structure, the main magnetic flux first emerges parallel to the surface of the measurement structure and passes through a sensor. Sor shark, which is arranged on the exit surface, wherein a high flux portion kinkickt in the direction of the measuring structure, if the measuring structure has an increased magnetic conductivity.
  • the sensor device Since the sensor device is intended to detect, in particular, a variation of the magnetic flux triggered by material defects of the measurement structure, it makes sense to arrange the sensor device on the edge of the exit surface facing the surface of the measurement structure, since at this edge the variation of the magnetic flux triggered by material defects is highest and thus sensor values can be determined with high accuracy.
  • one of the two poles, on which no sensor device is arranged is arranged in a way that points the way in the intended use of the surface of the measuring structure.
  • a pin or bar shape of the sensor arrangement can be achieved in which only one of the two magnetic poles is guided in the immediate vicinity of the surface of the measuring structure, and the other pole is guided far away from the surface of the measuring structure.
  • a rod-shaped permanent magnet can be used as a magnetic field generating device.
  • a closed magnetic flux does not occur over the measuring structure, since the magnetic field lines cover a larger air gap at the end of the magnetic field over the far pole.
  • only a stray field penetrates into the measuring structure whose variation is detected by the sensor arrangement.
  • the sensor device may comprise a sensor carrier and a sensor chip arranged thereon, wherein the sensor carrier is arranged on the pole exit surface or on a side surface delimiting the pole exit surface.
  • the sensor chip is the carrier of the magnetic field sensor and is arranged in this exemplary embodiment on a sensor carrier, for example on a chip carrier or substrate.
  • the chip carrier may be directly on the Polaustritts Colour a permanent magnet or an iron yoke of an electromagnetic be arranged, in particular arranged perpendicular to the Polauslingers simulation, provided that the Polauslingers SQL is aligned parallel to the surface of the measuring structure.
  • the chip carrier can be arranged parallel to the Polaustritts Colour when the exit surface is aligned perpendicular to the surface of the measuring structure.
  • the sensor device is sensitive, in particular for magnetic field components, which are directed perpendicular to the surface of the measuring structure.
  • the sensor carrier may alternatively be arranged on a side surface delimiting the pole exit surface, which is exposed to a high magnetic field, in particular if the magnetic field strength is so high that the surface of the measuring structure is in magnetic saturation, and thus not all magnetic field lines directly into the magnetic field But a scattered magnetic field results, which shows a high change in particular in deeper disturbances in the interior of the measuring structure.
  • the sensor device comprises at least one sensor chip based on a GMR sensor chip (giant magneto-resistance chip), in particular a GMR multilayer sensor chip, the GMR sensor chip having an H50 parameter for a 50% total resistance change in one Range of the flux density of 100 mT to 400 mT, preferably 200 mT to 280 mT, in particular 250 mT to 280 mT of the magnetic flux through the sensor chip has.
  • the sensor device has at least one, preferably a plurality of sensor chips as GMR sensor chips, wherein these are preferably designed as multilayer sensor chips.
  • a GMR sensor chip also referred to as giant magneto-resistance, includes alternating magnetic and nonmagnetic thin layer structures of nanometer thickness, the GMR effect of which causes the electrical resistance of the structure to depend on the mutual orientation in the magnetization of the magnetic layers , and in a magnetization in the opposite direction is higher than in a magnetization in the same direction.
  • Multilayer GMR sensor chips have a very high resistance change and a symmetrical characteristic for positive and negative magnetic field directions and include as magnetic material in particular copper or ruthenium and as magnetic material Permalloy (Ni81 Fe19) or cobalt-iron (Co90Fe10).
  • the RKKY exchange interaction via non-magnetic intermediate layers leads to a parallel or antiparallel alignment of the magnetic layers to one another.
  • Multilayer GMR sensors have only about a 1 nm non-ferromagnetic interlayer that causes RKKY coupling between the ferromagnetic layers, thus coupling the magnetic layers together.
  • a parallel or antiparallel alignment of the magnetization of the coupled layers can be energetically preferred, wherein the electrical resistance is higher in an antiparallel orientation.
  • the H50 parameter for a 50% total resistance change in such GMR sensors is in the range of 100 mT to 400 mT, so that extremely high magnetic fields can be detected sensitively. In these field strength ranges there is thus a high slope of the characteristic.
  • GMR multilayer sensor chips are able to have a high sensitivity at such high field strengths, so that a change in the leakage flux causes a large change in resistance, and thus reliably deeper defects can be detected in a measurement structure.
  • GMR sensors have a magnetic preferential sensitivity level, wherein magnetic field components lying in the layer plane are detected with high sensitivity, and components perpendicular to the layer plane are not detectable at all or are only slightly detectable.
  • the plane of the sensor chip can be aligned perpendicular to the surface of the measurement structure, so that fields emerge from the magnetic flux output surface also perpendicular to the measurement structure surface, and initially run parallel to the surface of the measurement structure, and then into the Kick the measuring structure.
  • the magnetic flux can be detected in the region of the measuring structure surface that is bent over.
  • the plane of the sensor chip can also be aligned parallel to the surface of the measurement structure, wherein the magnetic field exit plane of the magnetic field generating device can likewise be aligned parallel to the surface of the measurement structure.
  • it also makes sense to use a Hall sensor chip as the sensor device, since it is sensitive in particular when it is flooded perpendicularly to the surface of the sensor chip. Hall sensors can be constructively designed so that they can detect high field strengths, especially in the range of 100 mT to 400 mT sensitive with a high slope.
  • the magnetic field generating device can supportively or alternatively comprise an electric current coil, wherein the magnetic flux exit surface is defined at least at one magnetic pole or at a flux exit surface of a magnetic field guide yoke.
  • the sensor device is arranged on one of the pole exit surfaces of the north or south pole or on one of the iron yoke surfaces of a current coil on which the measuring magnetic field H emerges, these magnetic fields being aligned parallel to the workpiece surface.
  • the magnetic flux exit surface may preferably be aligned perpendicular to the surface of the measurement structure, so that the measurement magnetic field is initially aligned parallel to the surface of the measurement structure, in order then to dip into the measurement structure in a bend.
  • the material of the measuring structure is in magnetic saturation, this can result in a large area Field of the measuring structure are flooded by magnetic fields, and accordingly created a large-scale scan area for the analysis of defects. Thus, a large area can be scanned and a large scanning depth can be examined inside the measuring structure.
  • the exit surface of the magnetic field generating device can be aligned perpendicular to the surface of the measuring structure, so that the magnetic flux of the measuring magnetic field H is aligned perpendicular to the measuring structure surface. As a result, a high magnetization of the near-surface regions of the measurement structure is achieved.
  • the sensor device can be arranged in the region of a stray field, preferably on an adjacent edge surface of the exit surface, in which the stray field magnetic field lines are aligned primarily parallel to the workpiece surface, whereby variations in the stray field can be measured.
  • the magnetic field generating device can be set up to generate the magnetic flux ⁇ between the magnetic flux exit surface and the surface of the measuring structure in a flux density of 50 mT to 2 T, in particular 150 mT to 700 mT, preferably 200 mT to 400 mT
  • a permanent magnet advantageously a neodymium-iron-boron magnet or a samarium-cobalt magnet can be used.
  • a permanent magnet By using a permanent magnet, a strong static measuring magnetic field H can be generated without expenditure of energy.
  • the above-mentioned magnet designs are extremely powerful and can permanently generate high magnetic fields of 50 mT to 2 T, so that a reliable saturation of a test structure to be tested can be achieved down to high depths without auxiliary energy.
  • the sensor device may comprise a bias magnetic field generating unit for generating a bias magnetic field for adapting the sensitivity of the sensor device.
  • a bias magnetic field generating unit may be located in the immediate vicinity of a sensor device. tion and serves to locally attenuate the surrounding magnetic field by generating a counter magnetic field in order to bring the magnetic field strength in an order of magnitude that can be detected sensitively accurately by the sensor array, ie in which there is a high slope of the sensor characteristic.
  • a bias magnetic field can serve to locally adapt the sensitivity of the sensor arrangement to the strong measuring magnetic field.
  • the sensor device may have a spatial resolution of the magnetic field change of 50 ⁇ or less, preferably 10 ⁇ or less, and in particular 3 ⁇ or less.
  • the sensor device may be advantageous for the sensor device to comprise an array or a plurality of sensor chips, or to comprise a sensor chip which has a high spatial resolution sensitivity in order to be able to determine not only the presence of a defect but also its extent and structure with high accuracy .
  • the finer the spatial resolution of the sensor device the more accurate the position, position, orientation and extent of defects on the surface and in the depth of a measurement structure can be determined. This can be achieved, for example, by an array of individual sensor devices, in particular a matrix arrangement or a linear arrangement of many sensor devices.
  • the use of at least two or more sensor devices may be included for forming a gradient sensor arrangement.
  • a gradient sensor arrangement is characterized in that by comparing the sensor values of two or more spatially adjacent sensor devices, a sensor gradient can be detected which more accurately detects defects as an absolute value leaves. As a result, the resolution accuracy and the sensitivity of the sensor arrangement can be increased. In particular, errors due to external interference fields can thereby be eliminated. As a result of this subtraction of the signals of the sensor devices, only a signal proportional to the field difference is detected. Since the magnetic field decreases 1 / x3 at a greater distance from the source, it follows that the gradient decreases by 1 / x4.
  • a magnetic field guide plate may be included, wherein the measurement structure between magnetic field generating device with sensor device and the magnetic field guide plate for measurement is movable.
  • the measuring structure can be moved between the sensor device with the magnetic field generating device and the magnetic field guide plate, wherein the magnetic field guide plate serves to guide through the measuring structure penetrating magnetic fields to curb propagation of the measuring magnetic field and to achieve an improved magnetic flux guide. It can thereby be achieved that, on the one hand, an improved guidance of the magnetic flux through the measuring structure is effected, and on the other hand an undesired spreading of the strong magnetic fields is prevented, so that adjacent objects are not detected by the measuring magnetic field of the sensor arrangement.
  • This can be advantageous in use in complex machines or systems in which the measuring magnetic field is to be spatially limited and a high depth sensitivity is to be achieved.
  • an additional magnetic field generating device can be included which generates an additional magnetic field which amplifies the measuring magnetic field H, wherein the measuring structure can be moved between magnetic field generating device with sensor device and the additional magnetic field generating device.
  • an auxiliary magnetic field generating device may be included, wherein the measuring structure between the magnetic field generating device and the sensor arrangement and the additional magnetic field generating device is movable.
  • the additional magnetic field generating device can serve to guide the measuring magnetic field through the measuring structure and selectively effect guidance of the measuring magnetic field and a restriction of the magnetic field scattering range, so that shielding of the measuring magnetic field and improved guidance of the magnetic field lines, in particular in the vicinity of magnetic field sensitive structures can be achieved.
  • an intermediate layer with a magnetic susceptibility ⁇ ⁇ ⁇ 100 can be provided between the sensor device and the measuring structure to form a defined distance between the pole exit surface and the surface of the measuring structure.
  • the sensor arrangement can sweep over the surface of the measuring structure in a touching or non-contact manner.
  • an intermediate layer for example a plastic film or a plastic cover with a relatively low magnetic susceptibility
  • a predefinable distance between sensor arrangement and measuring structure surface can be achieved, so that the measuring distance is fixed, and thus reproducible sensor values can be achieved with homogeneous material distribution. This increases the accuracy in the detection of defects in the measurement structure and protects the sensor device from mechanical damage.
  • the evaluation device can comprise a memory unit and a comparison unit, wherein the memory unit can store at least one set of predefinable signal value profiles for the detection of a material error type and / or a material inhomogeneity type.
  • the comparison unit can be set up on the basis of the prestored signal value profile and a measured signal value profile to indicate a size or type of a material error and / or a material inhomogeneity. zu sentence.
  • the evaluation device can store patterns of signal value profiles in the memory units by a "teach-in" with a measurement structure without material defects, with a measurement structure with known surface material defects or with depth material errors, so that certain types of errors in the material of the measurement structure are very easily detected by comparison with predefinable signal value profiles can be.
  • quantitative signal value profiles can be compared with predefinable signal value profiles of pattern error structures, so that a detection of the type and size of errors can be simplified and, for example, a scan speed and accuracy can be increased.
  • the comparison unit is used to compare quantitative signal value curves with previously stored error value curves, and to evaluate and display the size and type of material error or inhomogeneity. Tolerance limits can be defined, whereby characteristic value curves within the tolerance limits can be assigned according to the prestored pattern progressions.
  • a sensor apparatus for magnetic flux leakage measurement which comprises at least one sensor arrangement according to one of the above embodiments, and comprises a movable structural support for receiving and transporting a measurement structure with which the measurement structure transports relative to the sensor arrangement during the measurement can be.
  • the sensor device is used for the automated examination of measurement structures, which requires that the structure carrier guides the measurement structure past the sensor arrangement with magnetic field generation device or the sensor arrangement is guided past the measurement structure.
  • the measurement structure can be accommodated in a structural support, for example clamped, in order to be guided past the sensor arrangement in a rotational or translatory manner.
  • the structural support can be rotated relative to the sensor arrangement and / or rotated in at least two directions. be moved in different directions to increase a scan size, scan speed, spatial resolution or a measurement accuracy.
  • a plurality of sensor arrangements can be arranged in an array arrangement relative to the measurement structure.
  • a large surface area of the measurement structure can be examined, and the spatial resolution and thus the accuracy of a test scan can be improved.
  • a two-dimensional test image can be created in which an error localization can be made in both the X and the Y axis.
  • a common magnetic field generating device to at least a multiplicity of sensor devices of the sensor arrangements, the static measuring magnetic field H being supplied to the sensor devices by means of magnetically conducting elements, for example a yoke comb.
  • all sensor devices can be flooded by the same measuring magnetic field, and a central magnetic field generating device can be used for a plurality of sensor devices.
  • a plurality of sensor arrangements in a geometric shape complementary to the surface of the measurement structure in particular concave or convexly curved or arranged in a complementary curve to a curved surface of the measurement structure.
  • a peripheral region of a tube or the complete circumference of the tube can be scanned simultaneously along the inner or outer surface by a sensor device in which several sensor arrangements are arranged equidistantly on a shape-complementarily curved edge of a sensor carrier. It is conceivable to replicate any complex surfaces of a measurement structure to be examined in complementary shape by an edge of a measurement carrier arrangement carrying a plurality of sensor devices.
  • a test head which is geometrically adapted to a measuring structure surface shape in this way, it is possible to obtain plex formed measuring structures with high accuracy and high scan width and therefore high speed.
  • a use of a sensor arrangement according to one of the precedingskysbeispie- le proposed to investigate material defects, cracks or material inhomogeneities or to determine a crystal structure in a measuring structure, or a ferromagnetic characteristic caused by a bias of Weiss'scher districts is inserted within a measurement structure, read out.
  • a sensor arrangement according to one of the precedingskysbeispie- le proposed to investigate material defects, cracks or material inhomogeneities or to determine a crystal structure in a measuring structure, or a ferromagnetic characteristic caused by a bias of Weiss'scher districts is inserted within a measurement structure, read out.
  • deeper cracks or material defect sites can be measured with high resolution, since due to the magnetic field saturation within the material of the measurement structure, deeper inhomogeneities also produce a leakage flux at the surface in the region of the sensor device.
  • Crystalline materials of the measuring structure can be investigated and their homogeneity or defects detected.
  • a magnetic characteristic i. Invisible magnetic watermark
  • FIG. 1 in perspective a first embodiment of a sensor arrangement
  • FIG. 2 shows in perspective another embodiment of a sensor arrangement
  • FIG. 4 shows embodiments of gradient sensor arrangements according to FIG.
  • FIG. 6 schematically shows further embodiments of sensor arrangements with iron yoke structure
  • FIG. 8 shows typical sensor value profiles in the detection of a material defect
  • FIG. 10 shows a magnetic leakage flux in the detection of a crack of a further embodiment
  • FIG. 11 block diagram representation of an embodiment of a sensor arrangement according to the invention.
  • FIG. 1 shows a perspective view of a first embodiment 10 of a sensor arrangement for determining a leakage flux measurement.
  • the sensor arrangement 10 comprises a permanent magnet 34 as the magnetic field generating device 40.
  • the permanent magnet 34 has a north and a south pole 24a, 24b, wherein both poles 24a, 24b comprise a magnetic flux exit surface 22.
  • the measuring magnetic field H is perpendicular to the magnetic flux outlet surface 22 of the pole 24 and forms the magnetic flux ⁇ 18, and initially parallel to the surface 20 of a test structure to be examined 14. After exiting the magnetic flux exit surface 22 of the magnetic flux ⁇ 18 in the direction of surface 20 of the measuring structure 14 deflected.
  • a sensor device 16 is arranged at the magnetic flux exit surface 22 of the south pole 24a of the permanent magnet 34.
  • the sensor device 16 on the magnetic flux exit surface 22 comprises a sensor carrier 32 as a chip carrier which has a sensor chip 30 as a GMR multilayer sensor.
  • the GMR multilayer sensor is arranged on an edge of the magnetic flux outlet surface 22, so that the exiting magnetic flux ⁇ 18 bend through the sensor carrier 32 and the sensor chip 30 and enter the surface 20 of the measuring structure 14.
  • a crack 26 located on the surface 20 can be detected by relatively moving the sensor arrangement 10 relative to the measuring structure surface 20 by a relative change in the sensor value of the sensor chip 30.
  • the sensor arrangement 10 is moved on the surface 20 of the measurement structure 14 in the direction of the indicated scan arrow 28.
  • the pattern profile of a sensor value change can be recorded, for example, on pattern measurement structures 14, so that in a real measurement structure 14 a sensor value variation similar to tolerance ranges can be compared with the sensor value changes caused by the test measurement structures to determine the type and size of the crack 26 or To close material inhomogeneity.
  • FIG. 2 a further embodiment of a sensor arrangement is shown corresponding to FIG. 1.
  • the structure of the sensor arrangement 10 corresponds doing the example shown in FIG. 1.
  • a 3-dimensional structure is shown, for example a print head for printing magnetisable particles whose individual ferromagnetic microstructures 42 are to be examined for surface cracks 26 and material inhomogeneities.
  • the sensor arrangement 10 can be moved relative to the surfaces 20 of the microstructures 42 in order to determine the quality of the material distribution of the microstructures 42.
  • Such microstructures 42 are produced, for example, by lithographic processes.
  • Fig. 3a and 3b further embodiments are shown, which are based on the embodiments shown in Fig. 2.
  • the sensor arrangement 50 comprises a permanent magnet 40 whose north and south poles 24a, 24b are aligned such that the magnetic flux exit surface 22 is parallel to the surface 20 of the measurement structure 14.
  • the magnetic flux ⁇ 18 and thus the measuring magnetic field H of the permanent magnet 40 are aligned perpendicular to the surface 20 of the microstructures 42.
  • a sensor arrangement 16 Arranged on the magnetic flux outlet surface 22 is a sensor arrangement 16, wherein the sensor carrier 32 is arranged at right angles to the magnetic flux exit surface 22, and the sensor chip 30 is thus likewise arranged at right angles to the orientation of the magnetic flux exit surface 22.
  • Such an arrangement is particularly suitable for the inspection of deeper cracks and inhomogeneities within the material of the microstructures 42.
  • an additional magnetic field guide plate 44 is shown, which is arranged below the measuring structure 14.
  • the magnetic field guide plate 44 is made of a highly permeable material, such as iron or nickel iron, which can bundle and divert penetrating magnetic fields. Stray fields in the vicinity of the sensor arrangement 10 can be minimized. Furthermore, the magnetic flux ⁇ 18 is focused to penetrate through the measurement structure 14, so that the deep interior of the microstructure 42 can be examined.
  • FIG. 3b in contrast to FIG. 3a, no magnetic field guide plate 44, but an additional magnetic field generating device 46 is arranged below the measuring structure 14.
  • the additional magnetic field generating device 46 in turn comprises a permanent magnet 34 whose magnetization direction is aligned in the same direction as the magnetic flux direction 18 of the magnetic field generating device 40.
  • the additional magnetic field generating device 46 and the magnetic field guide plate 44 can be combined if necessary, preferably by positioning a magnetic field guiding plate 44 under an additional magnetic field generating device 46.
  • FIGS. 4a to 4c show sensor wheel embodiments which each have a permanent magnet 34 as magnetic field generating device 40, in which a sensor carrier 32 is arranged on a magnetic flux exit surface 22 of the permanent magnet 34 aligned at right angles to the surface 20 of a measuring structure.
  • the sensor device 16 comprises a sensor carrier 32, on which two sensor elements 30 a, 30 b are arranged at different heights in relation to the surface 20 of a measuring structure 14.
  • two sensor elements 30a, 30b are likewise arranged on the sensor carrier 32, which are not arranged at different heights but at different distances from one another along an edge of the magnetic flux exit surface 22 of the magnetic field generating device 40.
  • 4c corresponds to a combination of the sensor devices 16 illustrated in FIGS. 4a and 4b, so that four individual sensor chips 30a to 30d can scan a surface 20 of a measuring structure 14 at different heights and at different distances from one another.
  • a plurality of such sensor elements 30a, 30b can be used to produce a high spatial resolution depth and a Allow gradient measurement, so that accurate dimensions and sizes of imperfections or inhomogeneities can be measured and interference fields can be suppressed.
  • FIGS. 5a and 5b show further embodiments of gradient sensor arrays 80.
  • two sensor arrangements 16a, 16b are arranged on different pole faces 22a, 22b of a single magnetic field generation device 40, as shown in FIG. 5a.
  • the sensor arrangement 80 comprises two magnetic field generating devices 40a, 40b, wherein two sensor devices 16a, 16b are each arranged on an oppositely polarized pole exit surface 22 of the respective magnetic field generating device 40a, 40b.
  • FIG. 6 shows various embodiments of a gradient sensor arrangement 90.
  • the gradient sensor arrangement 90 comprises a magnetic flux guide yoke 38 with which the magnetic flux ⁇ 18 of a magnetic field generating device 40, which, as shown in Fig. 6a, a current coil 36, or, as shown in Fig. 6b, a permanent magnet 34 with poles 24a, 24b can be guided.
  • the magnetic flux ⁇ 18 is generated by a current-locked coil 36.
  • the magnetic field guide yoke guides the magnetic flux through the north and south pole exit surfaces 22a, 22b, wherein either directly on the magnetic flux exit surface 22 a sensor arrangement 16a and 16b can be arranged, as shown in FIG. 6c.
  • the sensor devices 16 a and 16 b are respectively arranged on side surfaces 48 a and 48 b which are adjacent to the magnetic flux exit surfaces 22.
  • the magnetic flux ⁇ 18 also flows over the surrounding side surfaces of the magnetic flux exit surfaces 22 in the direction of measurement structure, with a high and defects in inhomogeneities Change this cause the magnetic flux ⁇ 18, and on the side surfaces 48 stray flux changes can be well detected. Because the magnetic flux exit surfaces 22 directly adjoin the surface 20 of the measuring structure 14, high penetration depths and a correspondingly good saturation of the measuring structure 14 can be achieved.
  • FIG. 7 shows an embodiment of a sensor arrangement 60 which has a magnetic field generation device 40 as a permanent magnet 34.
  • the magnetic flux exit surface 22 of the south pole 24a of the permanent magnet 34 is aligned in the direction of a surface 20 of a measuring structure 14.
  • the magnetic flux ⁇ 18 penetrates a sensor device 16, which comprises a chip carrier 32 and a chip 30 located thereon, the plane of which is aligned parallel to the surface 20 of a measuring structure 14.
  • the sensor chip 30 is preferably a Hall sensor that is magnetic-field-sensitive orthogonal to its chip surface.
  • FIGS. 8a and 8b show typical signal profiles of a sensor arrangement 10 or a gradient sensor arrangement 70 (FIG. 8b) which occur when a crack or material inhomogeneity of a measurement structure is crossed.
  • FIG. 8a shows a sensor value change of a sensor arrangement 10 with a sensor device 16 shown.
  • FIG. 8b shows a profile of a gradient sensor arrangement 70.
  • FIG. 9 shows a measuring field generating device with a generated magnetic flux ⁇ 18 and a magnetic flux distribution 54 during the investigation of a measuring structure. 14, which is scattered by a surface crack 26.
  • the measuring arrangement 10 comprises a permanent magnet 34 as a magnetic field generating device 40, on whose magnetic flux exit surface 22 aligned perpendicular to the surface 20 of the measuring structure 14 a sensor arrangement 16 is arranged.
  • the sensor arrangement 16 is moved from left to right relative to the measuring structure 14.
  • the magnetic flux distribution 54 in the measuring structure 14 is shown in the upper left part of FIG. 9b. As it approaches a crack 26, it becomes clear that the magnetic flux 54 is deflected, and this change in the magnetic flux 54 can be detected by the sensor arrangement 16 on the magnetic flux exit surface 22.
  • FIG. 10 shows a representation similar to that shown in FIG. 9 for detecting a crack 26 in a measuring structure 14.
  • the measuring arrangement 50 used also comprises a permanent magnet 34 as magnetic field generating device 40 whose magnetic flux exit surface 22 is aligned parallel to the surface 20 of the measuring structure 14. Perpendicular to the magnetic flux exit surface 22, a sensor assembly 16 is mounted, which is located directly in the magnetic flux ⁇ 18.
  • the magnetic flux distribution 54 is scattered, as shown in FIG. 10 b in three different positions of the sensor arrangement 50 relative to the crack 26, which can be detected by the sensor device 16 in the course of a movement in the scanning direction 28.
  • FIG. 11 shows a block diagram of an exemplary embodiment 10 of a sensor arrangement.
  • the sensor arrangement 10 comprises a magnetic field generation device 40, through which a magnetic flux ⁇ 18 is guided in the direction shown by an arrow through a sensor arrangement 16.
  • the sensor arrangement 16 is arranged on a magnetic flux exit surface 22 of the magnetic field generating device 40.
  • the sensor device 16 comprises a sensor chip 30, which is arranged on a sensor carrier 32.
  • the sensor chip 32 is electrically connected to an evaluation device 56, wherein the evaluation device 56 generates a sensor value that is generated by the sensor chip 32 will be able to evaluate.
  • the evaluation device 56 is set up to evaluate a multiplicity of sensor values which are recorded at different spatial locations during a relative displacement of the sensor chip 32 relative to a measuring structure 14 in the scanning direction 28 by a magnetic flux change.
  • the evaluation device 56 comprises a comparison unit 64 to which a plurality of storage units 58a, 58b and 58c are connected.
  • the quantitative profile of a sensor value of the sensor chip 32 can be compared with prestored sensor value curves in the memory units 58a, 58b and 58c.
  • the memory unit 58a may store a sensor history that indicates a low-lying defect, texture offset, or a deep crack.
  • the sensor history stored in memory unit 58b may correspond to a surface crack history.
  • the sensor value profile in the memory unit 58c can be compared for defects in the examination of a crystal structure or a structure of the material of a measurement structure 14.
  • the evaluation unit 56 is furthermore connected to an I / O unit 72, by means of the input means 66 of which measurement parameters, such as a field strength / / or a desired sensitivity range can be set, and by its output means 68 a measurement result, for example a display , a printer or a storage medium such as the number and type of detected errors can be output and logged.

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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

L'invention concerne un système de détection (10, 50, 60, 70, 80) servant à mesurer le flux de fuite magnétique dans une structure de mesure ferromagnétique (14). Le système (10, 50, 60, 70, 80) comprend un dispositif de génération de champ magnétique (40), un dispositif de détection de champ magnétique (16) et un dispositif d'évaluation (56). Selon l'invention, le dispositif de génération de champ magnétique (40) comprend un aimant permanent (34) pourvu de deux pôles magnétiques (24a, 24b), la zone de sortie de flux magnétique (22) étant définie au moins au niveau d'un pôle magnétique (24a, 24b) ou d'une surface de sortie de flux d'une culasse de guidage de champ magnétique (38) et le dispositif de détection (16) étant disposé directement au niveau de la surface de sortie de flux magnétique (22) du dispositif de génération de champ magnétique (40) et étant traversé par des lignes de champ magnétique qui sortent parallèlement à la surface (20) de la structure de mesure (14), le dispositif de génération de champ magnétique (40) étant adapté pour générer le champ magnétique de mesure H avec une amplitude suffisante pour provoquer une saturation magnétique du flux magnétique au moins dans la zone de la surface (20) de la structure de mesure (14) et le dispositif d'évaluation (56) étant adapté pour évaluer une variation quantitative de la valeur de signal avec au moins une variation de valeur de signal mémorisable à l'avance afin de détecter un défaut de matière ou un manque d'homogénéité de matière de la structure de mesure (14).
PCT/EP2015/055704 2014-03-18 2015-03-18 Système de détection de champ magnétique WO2015140220A1 (fr)

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Cited By (1)

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GB2012966A (en) * 1977-10-06 1979-08-01 Health & Safety Executive Apparatus for non-destructive testing of elongate objects
JPS5730943A (en) * 1980-08-04 1982-02-19 Showa Koji Kk Detecting method for defect in ferromagnetic material
JPS626154A (ja) * 1985-07-02 1987-01-13 Kubota Ltd 浸炭計測用プル−ブ
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CN110108782A (zh) * 2019-04-18 2019-08-09 东南大学 应用于斜拉索的基于磁阻效应的漏磁检测装置

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