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
• • 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
  • G01N27/83—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws by investigating stray magnetic fields
  • G01N27/87—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws by investigating stray magnetic fields using probes

Definitions

• the present invention relates to a device for the non-destructive inspection of a part by distribution analysis of the magnetic field leak emitted by the part when it is subjected to an excitation magnetic field, comprising means for generating a magnetic field of excitation within the room to be controlled, and means for measuring the distribution of the magnetic field emitted by the room in response to the excitation field.
• the set of means is integrated in a flexible support to form a device in the form of a flexible coating intended to be fixed on an area of the surface of the part to be controlled.
• the present invention finds applications for the non-destructive testing (NDT) of aircraft parts, but can be used in all industrial sectors where the control of the integrity of the parts is important, such as automobile, railway, shipbuilding or nuclear power.
• NDT non-destructive testing
• CND techniques are numerous and constantly evolving because the industrial sectors concerned are demanding an increase in performance of these NDT techniques.
• the air transport and civil engineering sectors are always looking for increasingly efficient NDT techniques to fulfill both safety requirements and a cost reduction policy.
• control techniques based on eddy currents are known. The principle of these techniques is based on the use of a magnetic excitation field which induces an eddy current flow in the part to be controlled.
• the circulation of these induced currents in the room is modified by the presence of defects, cracks or corrosions.
• This modification of the eddy current distributions acts on the distribution of the surface magnetic field of the part generated by the eddy currents. This distribution is generally measured by induction effect. Information on the defects is then extracted from the magnetic field distribution.
• the magneto-optical imaging device comprising a magnetic material makes it possible to measure a generated Faraday rotation which is proportional to the magnetization of the magnetic material in the presence of the distribution of the magnetic field emitted by the piece.
• the present invention proposes a device adapted to such a real-time control which makes it possible to monitor the structural health of a part throughout its period of use by local measurements of the configuration of the leakage magnetic field emitted by said part. in response to an excitation field.
• the problems to be solved for such a device are: to have a non-destructive control means adapted to be easily fixed on the surface of the structures to be controlled whether they are accessible or not while remaining negligible in weight and space and by requiring only a small electrical power for its operation, to have a control means adapted to be permanently installed on the structures to be controlled during their use to perform predictive maintenance by detecting the appearance of defects as soon as possible thus enabling less costly repairs and maximum safety of structures, a means of control that allows for automatic control management and a complete diagnosis of structural health to minimize Operator work to reduce the cost of maintenance.
• the invention relates to a device for non-destructive control of a part in real time.
• said device comprises means for generating an excitation magnetic field within the workpiece, said generating means being integrated in a support, said support being intended to cover a surface of said workpiece to be controlled. and means for measuring a distribution of the magnetic field emitted by said piece in response to the excitation field, said measuring means being superimposed on said excitation field generation means.
• the support is a flexible support intended to cover the surface of the part by matching the shape of the part.
• the measuring means have a sensitivity adapted to determine anomalies in the distribution of the magnetic field likely to reveal the presence of defects in the room.
• the means for generating said excitation magnetic field comprise a network of microbubines, each of said microbobines being traversed by an alternating current to generate said excitation magnetic field.
• the means for generating said excitation magnetic field comprise a network of micro-magnets.
• each optoelectronic microsensor comprises a photosensitive cell for transforming the received light radiation into electric charges, said cell being coupled to a charge transfer device for collecting the electric charges.
• said measuring means comprise an array of magnetoresistive microsensors for directly measuring said distribution of the magnetic field emitted by said piece.
• said networks are organized in columns column matrix.
• the device further comprises an interface electronics connecting said measuring means to a recording memory.
• the interface electronics and the memory are integrated in the flexible support so as to advantageously produce a monolithic control device.
• control device comprises a computer system such as a microprocessor for automatically determining information relating to defects such as the size, the location and the nature of the defects from the distribution of the magnetic field emitted by the part to be controlled. .
• said control device comprises transmission means for sending electrical signals recorded in the recording memory to said system calculator using a wired, wireless, radio or infrared link.
• said computer system is integrated in said flexible support and is connected between said interface electronics and said recording memory.
• the computer system comprises a memory containing at least one map of a distribution of the reference magnetic field of the part or parts, calculation means converting the electrical signal received by said computer system into a signal representative of the distribution of the magnetic leakage field measured by the microsensors, and means for analyzing said distribution of the magnetic field with respect to the distribution of the reference magnetic field.
• the analysis means comprise means of comparative analysis between the distribution of the measured magnetic field leakage and the reference magnetic field distribution.
• said comparative analysis means comprise means for generating a state signal S and information relating to defects present in the part.
• said state signal S and said information are either transmitted by said computer system to alarm means or recorded in said recording memory connected to said computer system, then transmitted to alarm means using a wire link, wireless, radio or infrared.
• the alarm means preferably comprise, for example, display means and light or sound indicators.
• FIG. 1 a schematic representation of a sectional profile view of a control device according to an embodiment of the invention comprising a network of microbubines for generating an excitation magnetic field, a liquid crystal membrane and a network of Optoelectronic microsensors, the device covering the surface of a part to be inspected and being covered by a layer of paint;
• Figure 2 a schematic representation of a top view of a microbobine according to one embodiment;
• FIG. 3 is a diagrammatic representation of a sectional profile view of a control device according to another embodiment of the invention comprising a network of microbubines, a magnetoresistance-based magnetic microsensor network, said device covering the surface of a part to be inspected and covered by a layer of paint; in figure 4.A and 4.B: two schematic representations respectively illustrating the operating principle of a GMR (giant magnetoresistance) cell in zero field and in magnetic field; in FIG. 5: a schematic representation of a view from above of the control device illustrating an embodiment of the device; in FIG. 6: a schematic representation of the control device of FIG. 5 in the operational position of transmission of the electrical signal to a remote computer system; in Figure 7: a schematic view of a network of control devices disposed on the surface of the parts of a ground plane in the signal transmission position recorded during the flight of the aircraft.
• GMR giant magnetoresistance
• the excitation magnetic field induces the flow of eddy currents in the part.
• the eddy currents that appear in the room generate in turn a leakage magnetic field radiating around the room.
• the characteristics of these currents are closely related to the characteristics of the part such as its shape and conductivity.
• These currents can be modified by the existence of structural defects, cracks or corrosion.
• the modification of these eddy current distributions then acts on the distribution of the magnetic field emitted by the piece to be controlled.
• the excitation magnetic field directly redirects the magnetization of each domain and therefore modifies the magnetic domain configuration of the part.
• the new configuration in magnetic domains is then disturbed by the possible presence of defects, cracks or corrosion.
• Figures 1 and 3 are shown two embodiments of the non-destructive testing device of a part by analyzing the distribution of the magnetic field. It comprises means for generating an excitation magnetic field within the room and measurement means able to determine a distribution of the leakage magnetic field emitted by the room, the measuring means being superimposed on the generation means.
• the generation means are integrated in a support 2 which is fixed on an area of the surface of the part to be controlled.
• this support 2 is a flexible support which is for example made of a plastic material, making it possible to fix the control device 1 on the surface of the part to be checked by matching the shape of the part.
• This fixing is performed by means of an adhesive material.
• the chosen adhesive material makes it possible to remove the device from the part to be controlled, so that it can easily change the device when it is damaged.
• this device is made in a limited dimension adapted to be fixed on a critical area of the room where cracks are likely to appear.
• the device can be placed on critical areas considered for example at the level of the fasteners, at the assembly elements of the panels and areas of high stress concentration.
• control device is adapted to receive a surface layer 8 which may for example be a paint layer which is superimposed on the control device.
• the means for generating the magnetic field comprise a network of microbubines 6. adapted to generate an excitation magnetic field that can penetrate within a room 4 to control.
• the excitation magnetic field generating means comprise a network of micro-magnets whose magnetization is maintained by electronics located for example at the periphery 10 of the support.
• the means for generating the magnetic field are decoupled from the measuring means, in this case the magnetic field generating means comprises a single macrobobine adapted to generate a magnetic field that can penetrate within the part 4.
• the microbobine network is organized in a column-row matrix. Each microbobine is traversed by an alternating current.
• the microbubines are produced, for example, by a microlithography process comprising a photolithography step to obtain a resin mold of microbubines and a second step of electrolytic deposition of a metal, which is, for example, copper. The resin is then removed with a solvent.
• the substrate on which the microbubines are made is a flexible substrate made of a plastic material so as to match the shape of the surface of the workpiece on which the control device 1 is arranged in order to respond. if necessary, pieces of different shapes.
• FIG. 2 describes an example of a particular form of microbubine 6 consisting of a winding of three planar rectangular turns.
• the dimensions of each turn are of the order of tens of microns and the size of the microbobine is of the order of hundreds of microns.
• the dimensions of each turn are adapted to concentrate the current in the turn, while having a copper section surface that allows effective bonding to the substrate and heat dissipation.
• the local magnetic field obtained by these microbubines is able to penetrate within the room to be controlled.
• FIG. 1 shows an embodiment of the means for measuring a magnetic field distribution generated either by the eddy currents created within the part to be controlled or directly by the magnetic domains of the ferromagnetic part to be controlled, comprising a diaphragm of liquid crystals 7 superimposed on the network of microbubines 6.
• the liquid crystals are sensitive to the magnetic field and able to orient themselves according to the intensity and direction of the field.
• the liquid crystal membrane is for example trapped between two plastic supports.
• the structure of these liquid crystals is modified according to the direction and the intensity of the magnetic field of leakage generated by the eddy currents in the room, this results in a variation of the spectral composition of the waves reflected by the different liquid crystal planes, thus leading to a change of color on the surface of the liquid crystal membrane 7.
• the distribution of the emitted magnetic field of the part is thus restored by the liquid crystal membrane in the form of a light spectrum returned selectively by said planes of liquid crystals.
• this liquid crystal membrane 7 is superimposed on a network of optoelectronic microsensors 3.
• Each optoelectronic microsensor is capable of transforming the light radiation emitted by the liquid crystal membrane into electrical charges by means of a photosensitive cell that converts light energy into electrical charges.
• Each cell is coupled to a charge transfer device whose function is to evacuate the electrical charges.
• An electrical signal representative of the light energy is generated by the photosensitive cell.
• the light waves incident on the surface of the membrane come from a light source integrated in each optoelectronic microsensor 3.
• the means for measuring the distribution of the magnetic field comprise only a network of microsensors playing both the role of sensor thus ensuring the role of the liquid crystal membrane, transmitter and of receiver.
• the microsensors are able to store information representative of the distribution of the magnetic field and send it on command following a cyclic request or to send it automatically when the information indicating values above a threshold.
• FIG. 3 shows another embodiment of the measurement means comprising a magnetoresistor microsensor array 9 for directly measuring the distribution of the magnetic field generated either by the eddy currents or by the magnetic domains of the part to be controlled.
• the principle of operation of magnetoresistive microsensors is based on the variation of electrical resistance of a magnetic material depending on the direction of the applied magnetic field.
• the magnetoresistive microsensors are preferably GMR (giant magnetoresistance) microsensors exhibiting a significant variation in electrical resistance with respect to the zero field electric resistance. Generally this electrical variation is of the order of 16%.
• each GMR effect microsensor consists of a Wheatstone bridge of four magnetoresistors GMR.
• GMR magnetoresistors
• the bridge When the bridge is in equilibrium, the output voltage of the bridge is zero. Under the action of a non-uniform magnetic field, the bridge becomes unbalanced, causing the appearance of an output voltage proportional to the variation of the magnetic field.
• Figures 4.A and 4.B respectively describe a magnetoresistance comprising a stack of ferromagnetic layers 16 and non-magnetic 17 of a few nanometers of thickness respectively in zero field, and in the presence of an applied magnetic field. In zero field, the magnetizations represented by arrows of the ferromagnetic layers 16 on either side of the non-ferromagnetic layer 17 are oriented in opposite directions.
• the magnetoresistances are made for example by a microlithography method in a stack of ferromagnetic and non-magnetic layers comprising a photolithography step and an etching step to obtain a magnetoresistive pillar network.
• FIG. 5 diagrammatically represents a view from above of the control device according to the embodiments presented above.
• the device has a substantially rectangular shape, here for example illustrative of a network of 56 optoelectronic micro-sensors 3 or magnetoresistive 9 organized in matrix rows columns.
• the control device further comprises an interface electronics 10 connecting the network of microsensors 3, 9 to a recording memory 11.
• the electronics 10 and the memory 11 are also integrated in the flexible support 2 so as to advantageously achieve a monolithic control device.
• Data in the form of an electrical signal characteristic of the local magnetic field measured by the microsensors 3, 9 are transmitted to the interface electronics 10 which consists, for example, of an amplifier for increasing the power of the signal in order to improve the signal-to-signal ratio. noise and also a digital-to-analog converter for converting the received analog electrical signal into a digital signal.
• the electrical signal at the output of the interface electronics may be an intensity, or a voltage.
• the amplified electrical signal is then routed to the recording memory 11.
• the interface electronics 10 is disposed at the end of the microsensor lines in FIG. 5. In another embodiment, the interface electronics 10 may be disposed at the end of the microsensor columns.
• the organization of the microsensors in columns column matrix makes it possible to obtain a mapping of the distribution of the magnetic field so that a defect in the part can be located on the surface of the part.
• the pitch between microsensors is preferably set at a value smaller than the minimum defect dimensions to be detected so that the discrimination of the position of the defects is possible and so that in case of localized damage of the In the network of microsensors, the microsensors located around the damaged area of the network can always make it possible to monitor the zones as close as possible to the fault likely to appear in the monitored area.
• the mode of transfer of the electrical signal from the microsensors 3, 9 to the interface electronics 10 is a mode of transfer to interline.
• a storage line 18 Above each line of microsensors is a storage line 18. The signal is temporarily stored in this storage line 18. The content of the storage lines is then transferred to the interface electronics 10 in a parallel mode. Then the electrical signals are evacuated in series to a recording memory 11.
• each microsensor is addressed directly to send the electrical signal to the interface electronics 10.
• control device further comprises a computer system 13 for converting the electrical signal into a signal representative of the leakage magnetic field emitted by the part and to determine a distribution of the magnetic field.
• the computer system is for example a microprocessor system.
• the device since the computer system is not integrated in the flexible support 2, the device includes transmission means 12 for sending the electrical signal recorded in the memory of the computer. recording 11 to the computer system 13 using a wireless link, radio or infrared.
• These transmission means comprise for example a transponder integrated in the flexible support which preferably operates at a fixed frequency, said frequency being chosen so that the emission of the electrical signal representative of the distribution of the magnetic field of leakage of the piece n does not interfere with the transmission of other data by devices other than the control device 1.
• the transmission means 12 for sending the electrical signal stored in the memory 11 to the computer system 13 may also be a wired connection.
• the electrical signal received by the computer system 13 is converted into a signal representative of the leakage magnetic field of the room by means of calculation in which is integrated a suitable theoretical model connecting the magnetic field to the electrical signal. These calculation means generate mappings that can be a mapping of the amplitude, and a mapping in spectral representation of the magnetic field. These representative data of the magnetic field distribution emitted by the piece are then sent to analysis means.
• the analysis means comprise comparative analysis means for performing a comparative study in amplitude between the distribution of the magnetic field measured by the microsensor network and the reference distribution.
• these comparative analysis means make it possible to establish a map of a distribution of variation of the magnetic field of leakage of the part.
• the calculating system comprises a memory in which a database of mappings of the distribution of the reference magnetic field of the part is recorded.
• These reference maps constitute a predefined comparison model with respect to the behavior of the area covered by the control device.
• These reference maps can be predetermined on a reference part.
• reference piece is meant a part judged to have no defect, for example a part at the end of its production line and having passed all the qualification steps. They can also be predetermined by modeling.
• the computer system is preferably a portable system.
• the analysis means make a comparison in amplitude between the distribution of the reference magnetic field and the distribution of the magnetic field measured by the microsensors, if the differential value determined between the reference field and the measured field exceeds a threshold value, a state signal S is generated by the analysis means.
• the analysis means comprise spectral analysis means which determine a spectral representation of the magnetic leakage field measured by the microsensors in order to determine information relating to the defects present in the part.
• the spectral analysis makes it possible to determine the nature of the defect and its dimension.
• the control device is for example programmed to be activated when the aircraft is no longer on the ground and then performs measurements at regular time intervals, for example every 5 minutes during a specified period so as to make measurements as a function of time.
• the control device makes it possible to obtain a map of the monitored area as a function of time in order to establish the evolution of the distribution of the magnetic field.
• the status signal as well as all the information relating to faults such as the nature of the faults, the size of the faults and the location of the faults are transmitted by the computer system to alarm means 14 which comprise, for example, a display screen.
• alarm means 14 comprise, for example, a display screen.
• display 22 to display the information and lights and / or audible indicators 20 to warn the maintenance operator.
• the transmission of electrical signals stored in the memory 12 to the computer system can be programmed so that it is performed automatically at the end of a flight of the aircraft for example. This transmission can also be activated manually by the maintenance operator by interrogating the control device during the inspection of the aircraft.
• the computer system 13 is integrated directly into the flexible support 2 and connected between the interface electronics 10 and the recording memory 11. In this embodiment, the computer system 13 directly receives the electrical signal from the interface electronics 10 and sends to the recording memory 12 only the status signal and the information relating to the defects.
• the operator discharges the status signal and the information stored in the memory of the control device to alarm means 14 using a wired link, wireless, radio or infrared .
• FIG. 7 presents a schematic view of a network of control devices 1 disposed on the surface of the structures of a plane 15.
• the aircraft is at ground and the network of control devices 1 is in the signal transmission position recorded during the flight of the aircraft to a computer system 13 which is connected to alarm means 14 which here include for example a computer with a screen display 22 and sound indicators 20.
• All electronic components integrated in the flexible support are made from a microfabrication technology on a hard substrate transposed here on a flexible substrate such as a plastic substrate. However the temperature used during the microfabrication process is likely to destroy the plastic substrate.
• One of the solutions currently proposed consists first of all in making the components on a hard substrate deposited itself on glass.
• the hard substrate is for example silicon, Al2O3 alumina.
• Another layer of protective glass is attached to the components by means of a soluble adhesive, the hard substrate is then removed from the stack by ablation by means of a laser. The components are applied to a plastic substrate and attached thereto by means of a permanent adhesive and the protective glass is removed.
• control device is in the form of a thin film having a thickness of the order of 50 ⁇ m, and a surface of 10 ⁇ 10 cm side which integrates microsensors of the order of a hundred micron, with a step of about ten micron for example.
• the invention has been presented in the context of the control of aircraft parts, but can be used in all industrial sectors where the integrity of the parts worked is important such as the automobile, the railway, the shipbuilding industry or nuclear.

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• 2006
  • 2006-05-24 FR FR0651901A patent/FR2901611B1/fr not_active Expired - Fee Related
• 2007
  • 2007-05-16 CN CN2007800185646A patent/CN101449158B/zh not_active Expired - Fee Related
  • 2007-05-16 CA CA002650829A patent/CA2650829A1/fr not_active Abandoned
  • 2007-05-16 EP EP07729199A patent/EP2030010A1/de not_active Ceased
  • 2007-05-16 WO PCT/EP2007/054751 patent/WO2007135051A1/fr active Application Filing
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