The invention relates to a device for the non-destructive testing of an electrically conductive structure.
The field of the invention is that of non-destructive testing (NDT) making it possible to detect defects, such as nicks, cracks, corrosion, etc. in conductive parts or structures.
Among all of the methods used, the electromagnetic method is particularly adapted to inspecting thin not necessarily flat conductive structures, such as aeronautical light alloy structures or steam generator tubes in nuclear power plants, wherein a lack of material can provoke leaks. This method consists in emitting, using an induction portion, an electromagnetic field in the vicinity of the structure to be inspected and in measuring, using a receiving portion (magnetic field receivers or sensors) the interference of the magnetic flow generated by the presence of a possible defect in the structure. The unit comprising the magnetic field induction portion and the receiving portion is called “probe”.
The receivers can be either of the inductive type, or of the magnetic type for example AMR (Anisotropic magnetoresistance), GMR (Giant magnetoresistance), GMI (Giant magnetoimpedance), Hall effect, etc. The field of the invention relates more particularly to the second category, i.e. receivers of the magnetic type.
In order to increase the rapidity of the acquisitions, multi-element receiver units can be used, i.e. comprising multiple identical elementary receivers, in the same probe. With 1D (or one-dimensional) arrays, the displacement of the probe can be reduced to a single axis. With 2D (or two-dimensional) magnetic imagers a displacement of the probe is no longer required. In practice, there are substantial interfacing problems in order to make use of these elementary magnetic receivers, which generally have the form of quadrupoles. A highly substantial space in the probe must therefore be devoted to the interfacing, which leads to spacing the elementary receivers, and can result in the masking of the presence of a defect due to the existence of zones that are not covered by a receiver. In addition, substantial space is also taken by the electronics, which often comprise one amplifier per elementary receiver, and the means of multiplexing in the probe.
The document referenced as [1] at the end of the description describes the use of matrices or eddy current sensor arrays of the coil type, with a series connection of the emitting coils and receiving coils. The receivers of the magnetic type (GMR, etc.) are not concerned.
The field of the invention is more particularly that of inductors of the “layer” type, such as shown in
In the case of a multi-element receiver unit, as shown in
The interfacing of the devices of prior art is complex due to the use of at least one connection per element. As such, a magnetic detection of the GMR type conventionally requires two supply wires and two differential measurement wires. The latter are connected to differential amplifiers. Then analog multiplexer/demultiplexers are indispensable in order to reduce the number of connections between the probe and the instrumentation. The latter comprises, in a conventional manner, synchronous demodulators in order to make use of the signals as non-destructive testing via eddy currents, and in order to obtain the complex amplitude of the ray at the demodulation frequency.
The invention has for object to resolve these technical problems by proposing a device for testing comprising a multi-element receiver unit in the form of an array or matrix of elementary magnetic receivers, which makes it possible to minimise the interfacing and the electronics by supplying the elementary magnetic receivers in series or in parallel in order to increase their density and minimise the zones of the structure to be tested that are not covered by an elementary magnetic receiver.
The invention relates to a device for the non-destructive testing of an electrically conductive part comprising:
characterised in that the induction portion comprises an inductor dissociated into n elementary inductors of the layer type supplied at different frequencies f1, f2, . . . , fn,
and in that the receiving portion comprises n′ magnetic receivers distributed over m columns, each column comprising at most n receivers, the magnetic receivers being connected to one another over each column, the m columns of receivers being supplied by electrical signals v1′, v2′, . . . , vm′, of frequencies f1′, f2′, . . . , fm′ zero or non-zero, each magnetic receiver being arranged under an elementary inductor, m magnetic receivers being positioned under each elementary inductor, the indices n, n′ and m being positive integers such that n>=2, 1<n′<=n*m and m>=1
and in that the processing means make it possible to know the magnetic field in each of the magnetic receivers of a column, and in that each magnetic receiver is used as a demodulator.
Each elementary inductor can be a layer comprising a conductive wire, or several conductive strands in series, or several conductive strands in parallel.
Advantageously, the magnetic receivers are connected in series.
In a first embodiment, each column i of receivers is supplied in current, the voltage measured at the terminals of a column being the sum of at most 2n sinusoidal elementary voltages, at the frequencies f1±f′i, f2±f′i, . . . and fn±f′i and of the means demodulating à f1+f′i, f2+f′i, . . . , fn+f′i or f1−f′i, f2−f′i, . . . , fn−f′i.
In a second embodiment, each column of receivers is supplied in voltage, the current passing through a column i being the sum of at most 2n sinusoidal elementary currents, at frequencies f1±f′ii, f2±f′i, . . . and fn±f′i and of the means of demodulating à f1+f′i, f2+f′i, . . . , fn+f′i, or f1−f′i, f2−f′i, . . . , fn−f′i.
In a third embodiment, each column i of receivers constitutes a branch of a Wheatstone resistive bridge, supplied by an alternating voltage and of which the differential imbalance voltage is measured at frequencies f1±f′i, f2±f′i, . . . , fn±f′i and of the means of demodulating at f1+f′i, f2+f′i, . . . , fn+f′i or f1−f′i, f2−f′i, . . . , fn−f′i.
Advantageously, the magnetic receivers are directed according to the axis X of sensitivity, the main direction of the currents of these elementary receivers being directed according to the axis Y.
In an example embodiment, the device of the invention comprises a matrix of m×n magnetic receivers (i.e. n′=n: each column i contains as many receivers as there are elementary inductors), the frequencies f1, f2, . . . , fn are respectively equal to frequencies f+Δf, f+2Δf, . . . , f+nΔf and the frequencies f′1, f′2, . . . , f′n are all equal to the frequency f, the frequency f can be about 1 MHz and the frequency Δf about 10 KHz.
According to another example embodiment, the supplying of the receivers is carried out directly (f′1=f′2= . . . =f′n=0) and the frequencies f1, f2, . . . , fn are respectively equal to frequencies f+Δf, f+2Δf, . . . , f+nΔf. The frequency f can be about 1 MHz and the frequency Δf about 20 KHz.
Advantageously, the device of the invention comprises a support whereon are positioned the inductors and the magnetic receivers, which can be a flexible multi-layer printed circuit. These magnetic receivers can be direct wired receivers. The induction portion can include several layers distributed over at least one layer of a multi-layer substrate.
Advantageously, the magnetic receivers are receivers of the GMR type.
The device of the invention has many advantages, and in particular:
The device of the invention can be in particular used for multi-element applications for non-destructive testing via eddy currents, and more particularly for applications aimed at detecting small defects on the surface of a structure.
The device of the invention, as shown in
There is an inductor supply 30, a supplying 31 of the magnetic receivers 34 and of the receiving channels 32.
The electrical signals v1′, v2′, . . . , vm′ can be either direct currents or voltages, or alternating currents or voltages of respective frequencies f1′, f2′, . . . , fm′. In the remainder of this document, in order to simplify the cases, it shall be considered the most general case where the voltages v1′, v2′, . . . , vm′ are either sinusoidal of frequencies f1′, f2′, . . . , fm′, or are direct by considering in this case f1′=f2′= . . . =fm′=0.
Each elementary inductor 33 can be a layer comprising a conductive wire, or several conductive strands in series as shown in
Each magnetic receiver 34 is used as a demodulator. As such, for example, the voltage v1 measured at the terminals of the first column of magnetic receivers 34 placed in series is the sum of 2n sinusoidal elementary voltages, at f1±f′1, f2±f′1, . . . , and fn±f′1. Demodulations of v1 at f1−f′1, f2−f′1, . . . , and fn−f′1 or f1+f′1, f2+f′1, . . . , and fn+f′1 make it possible to derive the complex amplitude of the component of v1 at each of these frequencies and subsequently to derive the magnetic field present in each of the measuring points, or receivers, of the column. Multiplexers are not required.
The supplying 31 of the columns of magnetic receivers 34 in series can be a supplying in voltage, the current passing through these receivers then being the measured signal.
In a first embodiment, each column i comprising n′i receivers is supplied in current at the frequency f′i, the voltage measured at the terminals of this column i being the sum of 2n′i elementary voltages (n′i in the case where f′i=0), at most at the frequencies f1±f′i, f2±f′i, . . . and fn±f′i (with the amplitude at some of these frequencies being zero or very low in the absence of a receiver under an elementary inductor of the column).
In a second embodiment, each column i is supplied in voltage at the frequency f′i, the current passing through a column i being the sum of 2n′i elementary currents, at most at the frequencies f1±f′i, f2±f′i, . . . , and fn±f′i.
In a third embodiment, each column i comprising n′i receivers is inserted into a branch of a Wheatstone bridge. The three impedances of the bridge are for example resistances, each with a value close to the resistance of the total column of magnetic receivers. Each bridge i is supplied at the frequency f′i. The differential imbalance voltage, measured at the terminals of the intermediary branches of the bridge, is the sum of 2n′i elementary voltages, at most at the frequencies f1±f′i, f2±f′i, . . . and fn±f′i.
In any case, the demodulation is carried out either at the frequencies f1−f′i, f2−f′i, . . . and fn−f′i or at the frequencies f1+f′i, f2+f′i, . . . and fn+f′i, in order to determine the local magnetic field on each of the receivers. In the particular case wherein the supplying of the column of the receiver is direct, the demodulation must be carried out at the frequencies f1, f2, . . . and fn since f1′=f2′= . . . =fm′=0.
It is possible by correctly choosing the frequencies f1, . . . , fn, and f′1, . . . , f′m, to sum the reception voltages v1, v2, . . . , vm into a single signal by using means of amplification, and demodulate this single signal using means of demodulating at the n×m frequency differences fi−f′j. A single receiving cable is then required between the device of the invention (probe) and the means of demodulating. With the device of the invention, the number of connections is therefore limited.
The magnetic receivers 34 have an axis of sensitivity. They can be preferentially directed according to one of three axes X, Y or Z.
An example of a simplified embodiment in terms of the choice of frequencies is shown in
The support used for the magnetic receivers 64 and the elementary inductors 63, which can be positioned on either side of the latter, is a flexible printed circuit, for example a “flex” printed circuit made of epoxy of 400 μm in thickness. Such a circuit makes it possible for the device of the invention to mould complex forms. Each of the columns of magnetic receivers is supplied by an alternating voltage v′1, v′2, v′3 or v′4 and the resistances of a low value 74 inserted in series with the magnetic receivers 64 each make it possible to measure a image voltage of the current in the magnetic receivers 64. This voltage comprises in particular rays at the frequencies Δf, 2Δf, 3Δf and 4Δf, which, after demodulation at these frequencies, make it possible to detect the possible presence of a nick in the structure or in the part to be tested.
As shown in
The device of the invention shown as such in
A multi-element magnetic receiver unit can be carried out with magnetic receivers in the shape of a “C” (“yoke”) 103, as shown in
In the device of the invention, the elementary inductors 111 constituting the induction portion can be carried out either with a single solid conductor (wire), or with various conductive strands placed in series or in parallel. As shown on
In alternative embodiments of the device of the invention, the following can be used:
Number | Date | Country | Kind |
---|---|---|---|
09 52403 | Apr 2009 | FR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2010/054656 | 4/8/2010 | WO | 00 | 10/7/2011 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2010/115963 | 10/14/2010 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4706021 | Chamuel | Nov 1987 | A |
5047719 | Johnson et al. | Sep 1991 | A |
6914427 | Gifford et al. | Jul 2005 | B2 |
7385392 | Schlicker et al. | Jun 2008 | B2 |
7388462 | Ahn et al. | Jun 2008 | B2 |
7489129 | Meilland et al. | Feb 2009 | B2 |
20050007106 | Goldfine et al. | Jan 2005 | A1 |
20070029997 | Goldfine et al. | Feb 2007 | A1 |
20080258720 | Goldfine et al. | Oct 2008 | A1 |
20090206831 | Fermon et al. | Aug 2009 | A1 |
20100109658 | Decitre | May 2010 | A1 |
Number | Date | Country |
---|---|---|
2 904 693 | Feb 2008 | FR |
WO 2007095971 | Aug 2007 | WO |
Entry |
---|
International Search Report issued Jun. 28, 2010 in Application No. PCT/EP2010/054656. |
U.S. Appl. No. 13/386,041, filed Jan. 20, 2012, Decitre, et al. |
Number | Date | Country | |
---|---|---|---|
20120019239 A1 | Jan 2012 | US |