Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/34—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor
  • G01N29/341—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with time characteristics
  • G01N29/345—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with time characteristics continuous waves
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/22—Details, e.g. general constructional or apparatus details
  • G01N29/24—Probes
  • G01N29/2412—Probes using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/36—Detecting the response signal, e.g. electronic circuits specially adapted therefor
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B11/00—Transmission systems employing ultrasonic, sonic or infrasonic waves

Definitions

• the present invention relates first of all to an installation with a piezoelectric element for the emission or reception of ultrasonic waves in a structure, for example a structure to be controlled, the electrodes of this element being connected as the case may be to a circuit of power supply producing electrical excitation signals suitable for causing it to emit ultrasonic signals in said structure, or to a circuit for receiving the electrical signals emitted by said element under the effect of an ultrasonic excitation received by it from said structure , said piezoelectric element being incorporated into the structure.
• the invention also relates to a piezoelectric element specially designed for use in such an installation.
• the particular structures' interested by the invention will, without this indication in no way limiting, the composite structures consisting of resistant fibers impregnated with, for example carbon-epoxy or fiberglass, used primarily in the construction of vehicles transport of all types (aeronautics, automotive, marine, railways), due to the fact that they have good mechanical characteristics and resistance to fatigue and corrosion, at a relatively low weight. To meet the safety requirements demanded in particular in this technical field, it is necessary to examine these structures regularly during systematic checks, and sometimes even permanently.
• the internal faults of the latter resulting in modifications of the characteristics of the transmission of the pressure field in this structure, for example between a piezoelectric element used as an ultrasound emitter and a another piezoelectric element serving as a sensor of the ultrasonic waves emitted by the transmitter; the same piezoelectric element can moreover serve in certain cases, at the same time or alternately, of transmitter and receiver.
• FIG. 1 shows by way of example an installation comprising a piezoelectric element 1 integrated into the piece PI and connected to an input and / or output connector 2 by cables 3, 4 and a connector d 'interface
• the object of the present invention is to remedy these drawbacks of the prior art by eliminating any connection between piezoelectric elements by electric cables inside the structure, or even outside of it, towards the supply and / or control and measuring devices.
• an installation according to the present invention is characterized in that the supply or reception circuits of the piezoelectric element are constituted each by a magnetic induction loop also incorporated into the structure and suitable for receiving " from an external circuit, or respectively for transmitting towards it, electromagnetic signals.
• the magnetic induction loop consists of a flat spiral of flexible printed circuit, a positioning mark located on the surface of said structure being provided opposite said spiral.
• the magnetic induction loop consists of a flat spiral of printed circuit directly engraved on the the piezoelectric element; it then fulfills the complementary function of the electrode of this element, so that the whole of the piezoelectric pad and the magnetic induction loop can remain extremely flat, is not likely to constitute an additional thickness on the surface of the structure, and does not significantly modify the geometrical and mechanical characteristics of the latter.
• a piezoelectric element and a magnetic induction loop having reversible functions it is understood that the invention may be presented under two families of different concepts, depending on whether the piezoelectric element is used as an ultrasonic transmitter or as an ultrasonic sensor .
• an installation in accordance with the invention can also be characterized either in that said external circuit is constituted in the form of a primary winding of transformer connected to an AC power source and coupled by induction to said loop.
• magnetic induction constituting the secondary of said transformer
• said piezoelectric element then constituting a source of emission of ultrasonic waves in said structure
• this external circuit is constituted on the contrary in the form of a secondary winding of transformer connected to a signal processing circuit and coupled by induction to said magnetic induction loop constituting the primary of said transformer, said piezoelectric element then constituting a receiver of ultrasonic waves emitted in said structure.
• listening to the acoustic emission of possible damage to the structure may be carried out in a manner known per se.
• the piezoelectric elements then behave like receivers, in frequency ranges which may be between 100 kHz and 1 MHz.
• the installation can also be characterized in that it comprises both the two types of piezoelectric elements arranged in pairs, one constituting a transmitter or receiver of ultrasonic waves, the other reciprocally a receiver or transmitter, since each, as indicated above, is reversible.
• An installation according to the invention can therefore be further characterized in that it comprises at least a first and one or more second piezoelectric elements incorporated in the structure, the first being associated with a magnetic induction loop constituting the secondary of a first transformer coupled by induction to the primary winding which constitutes an external circuit connected to an AC power source, said first piezoelectric element then constituting a source of emission of ultrasonic waves in said structure, and the one or more seconds being each associated with a magnetic induction loop constituting the primary of a second transformer coupled by induction to the secondary winding constituted by an external circuit connected to a signal processing circuit, the second piezoelectric element or elements then constituting one or more receivers of the ultrasonic waves emitted in said structure by the first piezoelectric element.
• a single piezoelectric element as an emitter of ultrasonic waves and as a receiver, this for example measuring the travel time of impulse waves emitted by this element in the structure, after their reflection on a surface (or an internal defect), and return to the element.
• the erosion rate of a surface for example the surface of a heat shield during ablation, can be continuously measured.
• a film of magnetic material is interposed between each external winding of the transformer and the corresponding magnetic induction loop, incorporated in said structure, this to further increase this magnetic coupling.
• the transmission of signals to the magnetic induction loop of a piezoelectric element integrated into a structure can be carried out remotely, without a transformer, especially when it comes to signals that the nature of the control makes it necessary to transmit at high frequency, for example in the band from 50 kHz to 1 MHz in order to carry out the non-destructive control of a structure by shearography.
• an installation according to the invention is characterized in that the structure, equipped with at least one piezoelectric element which is incorporated therein with its magnetic induction loop, is associated to a source of emission of electromagnetic signals in the range of frequencies required by the non-destructive test envisaged, and in the event of control by shearography, to an optical system for viewing the ultrasonic waves emitted in the structure, said source and said system located at a distance from said structure.
• the invention also relates to the piezoelectric elements themselves, as well as the shape characteristics of the magnetic induction loops associated therewith.
• FIG. 2 represents the block diagram of 'a link by magnetic coupling between an external winding and a piezoelectric element incorporated in a structure of composite material
• FIG. 3 represents the basic configuration for the generation of ultrasound in a structure
• - Figure 4 shows the basic configuration for the detection of ultrasound emitted in a structure
• FIG. 5 represents the basic configuration of a structure equipped with both piezoelectric elements emitting ultrasound and piezoelectric elements receiving
• FIG. 6 represents the implementation of the invention for measuring the ablation speed of the surface of a structure
• FIG. 7 is a diagram of an installation for the emission of electromagnetic waves in a structure equipped in accordance with the invention, this installation allowing a remote and non-destructive control of this structure by shearography.
• the composite structure is referenced 6 and incorporates manufacturing, according to one of the methods indicated above, a thin piezoelectric element 7 whose electrodes 8 are connected to the ends of a magnetic induction loop 9 also incorporated in the structure and advantageously shaped in a flat spiral.
• This loop is coupled by magnetic induction to the flat winding 10 of a transformer connected to an electronic circuit 11, this winding being attached temporarily or permanently to the structure 6 opposite the loop 9.
• the circuit 11 can consist of an AC power source, in which case the winding 10 is to be considered as the primary of a transformer whose secondary is constituted by said loop 9, the piezoelectric element 7 then being a device emitting d ultrasound in the structure 6. It can also be an amplifier circuit of the received signals, in which case the winding 10 is to be considered as the secondary of a transformer whose primary is constituted by the loop 9, the being piezoelectric element then an ultrasound receiving device emitted in said structure 6.
• the magnetic induction loop can be made in a thin layer of the flexible printed circuit type, with a thickness of 50 to 100 ⁇ m
• the piezoelectric element which can be placed in the center of the loop spiral. 9, can be in the form of a pellet with a thickness of the order of 100 ⁇ m.
• a prototype was built in two plates of a carbon-epoxy composite material 4 mm thick.
• the piezoelectric element 7 had a diameter of 5 mm and a thickness of 100 ⁇ m.
• the spiral loop 9 comprised two superimposed spirals of 18 turns each, of 25 mm outside diameter and 10 mm inside diameter, carried by two Kapton films.
• the spiral loop 9 comprised two superimposed spirals of 18 turns each, of 25 mm outside diameter and 10 mm inside diameter, carried by two Kapton films.
• windings 10 or the like in the form of double flat wound coils so that their fluxes add up and at a very small distance from each other (from about 0.1 mm); each spiral can comprise for example 17 turns and have a thickness of 18 ⁇ m.
• the magnetic coupling in the transformers thus formed is a function of the distance between the loops and the windings for a given geometry, and it can be assumed that the losses of captured flux are negligible for a distance less than 2 mm; beyond, we take into account the attenuation.
• the magnetic transparency of the materials it should be noted that it is a function of their electrical conductivity and their thickness. All dielectrics have good magnetic transparency in a frequency range of up to 10 MHz.
• FIG. 3 there is shown another installation according to the invention, comprising a composite structure 6a integrating a piezoelectric element 7a intended to generate ultrasound in the structure and whose magnetic induction loop 9a is therefore established as a secondary a transformer whose primary winding 10a, attached to the loop, is connected to a variable frequency current supply source lia.
• FIG. 4 shows yet another installation in accordance with the invention, comprising a composite structure 6b integrating a piezoelectric element 7b intended to constitute an ultrasound receiver emitted in the structure and whose loop magnetic induction 9b, connected to the element's electrodes, is therefore established as the primary of a transformer whose secondary winding 10b, attached to the loop, is connected to a signal processing circuit 11b by the through an amplifier and filter assembly 12.
• FIG. 5 shows an installation comprising a structure made of composite material 6c in which two piezoelectric elements 7c and 7d are integrated, both of which can operate as emitters or receivers of ultrasound (the drawing being simplified, we did not represent the magnetic induction loops associated with these elements).
• the corresponding windings transformers have been shown here, also schematically, in 10c and 10d. These transformers can be used for transmitting electrical signals or for receiving, depending on whether the associated piezoelectric element 7c or 7d is intended to transmit or receive ultrasound.
• FIG. 6 there is shown an installation implemented on a structure 6d may see its thickness vary for example to decrease by ablation or wear or increase, for example by accretion of frost.
• This structure is equipped with a piezoelectric element which is both an emitter and a receiver of ultrasound 7e coupled by magnetic induction to an external circuit winding 10e connected to a measurement and supply system of impulse current, at a frequency of a few hundred kHz.
• the ultrasonic pulses emitted by the element 7e towards the wall P undergoing the thickness variation are reflected on this wall and received by the element 7e with a delay time which will thus provide, advantageously permanently, the measurement of the variation d 'thickness of the structure.
• FIG. 7 shows another installation in accordance with the invention, in which the structure 6e, equipped with at least one piezoelectric element 7f which is incorporated therein with its magnetic induction loop 9f, is associated with a source lOf, llf of emission of electromagnetic signals in the range of frequencies required by the non-destructive control envisaged, and in the case of control by shearography, to an optical system 12 for viewing the ultrasonic waves emitted in the structure by the element 7f, said source 10f, 11f and said system 12 being located at a distance from said structure 6e.
• This principle of control can apply to all cases in which it is necessary to have a mechanical stress at high frequency, as in the case of shearography.
• the power of the emission source 10f, 11f must be sufficient to excite the piezoelectric element 7f thanks to the magnetic flux developed remotely in its loop 9f, so that it emits ultrasound in the structure; the remote viewing, by the system 12, of the ultrasonic waves in the structure 6e, will give information on its possible damage.
• the structure is a structure to be checked, but the invention is not always limited to this application. It could be any structure, for example a structure serving only as a transition medium for the transmission of data between two other structures or devices.
• any combination of piezoelectric elements in the structure can be envisaged, for example several piezoelectric receivers for receiving signals from a single transmitting element or vice versa, as has already been mentioned above.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• General Health & Medical Sciences (AREA)
• Immunology (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• Pathology (AREA)
• Signal Processing (AREA)
• Electromagnetism (AREA)
• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
• Transducers For Ultrasonic Waves (AREA)
• Apparatuses For Generation Of Mechanical Vibrations (AREA)
• Piezo-Electric Transducers For Audible Bands (AREA)
• Electrically Driven Valve-Operating Means (AREA)
• General Electrical Machinery Utilizing Piezoelectricity, Electrostriction Or Magnetostriction (AREA)
• Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)

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• 2000
  • 2000-03-23 FR FR0003721A patent/FR2806823B1/fr not_active Expired - Fee Related
• 2001
  • 2001-03-22 JP JP2001570004A patent/JP4593054B2/ja not_active Expired - Lifetime
  • 2001-03-22 WO PCT/FR2001/000867 patent/WO2001071953A1/fr not_active Ceased
  • 2001-03-22 AU AU2001246621A patent/AU2001246621A1/en not_active Abandoned
  • 2001-03-22 ES ES01919542T patent/ES2208579T3/es not_active Expired - Lifetime
  • 2001-03-22 AT AT01919542T patent/ATE253273T1/de not_active IP Right Cessation
  • 2001-03-22 US US10/221,938 patent/US6960867B2/en not_active Expired - Lifetime
  • 2001-03-22 DE DE60101095T patent/DE60101095T2/de not_active Expired - Lifetime
  • 2001-03-22 EP EP01919542A patent/EP1266467B1/fr not_active Expired - Lifetime

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