EP2909620A1

EP2909620A1 - Ultrasound probe for contact measurement of an object and its manufacturing process

Info

Publication number: EP2909620A1
Application number: EP13780342.5A
Authority: EP
Inventors: Didier Simonet; Nicolas Colin
Original assignee: European Aeronautic Defence and Space Company EADS France
Current assignee: Airbus SAS
Priority date: 2012-10-19
Filing date: 2013-10-18
Publication date: 2015-08-26
Also published as: US20150268198A1; FR2997190A1; CN104755921A; FR2997190B1; US9766212B2; WO2014060574A1; CN104755921B

Abstract

The invention relates to an ultrasound probe for contact measurement of an object and its manufacturing process. According to the invention, this ultrasound probe comprises ultrasound sensors securely fastened to a first face (12) of a substrate (10), the opposite face (11) of said substrate (10) defining a measurement surface, said measurement surface having a shape that is the imprint of the surface of the object to be measured so as to closely follow the latter when the surface of the object is brought into contact with said measurement surface.

Description

Ultrasonic probe measuring by contact of an object

and its manufacturing process

BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates to an ultrasonic probe for measuring the contact of an object and its method of manufacture. This ultrasonic probe is particularly suitable for non-destructive testing of objects of complex geometry, such as certain mechanical parts for example.

The present invention applies in particular to the non-destructive testing of objects in the aeronautical, space, automobile, railway, ... Technological background

It is known to control structures including composite materials, in order to detect non-destructively possible surface defects and / or depth in these structures.

Ultrasonic measurement systems are thus known which have the advantage of allowing structural checks directly on manufacturing sites.

However, it is necessary to move the ultrasonic measurement system manually, typically by qualified personnel, or automatically. Guiding as well as locating means are then implemented to identify the part of the structure being measured.

In addition, in the case of structures having a complex geometry, it is necessary to perform several scans with possibly different ultrasonic measurement frequencies.

These operations are long, tedious for the operators and expensive. Moreover, some structures, particularly in the aeronautical field, must be able to be controlled in their entirety, which is not always possible by an ultrasonic transmission control method. Indeed, some areas of the structure may be inaccessible for this control technique.

The present invention aims at overcoming these various drawbacks by proposing an ultrasonic measurement system for the non-destructive inspection of objects such as mechanical or structural parts, simple in its design and in its operating mode, allowing the measurement of at least a part of an object of complex geometry in a single scan.

Another object of the present invention is a particularly simple and flexible manufacturing method of such an ultrasonic measurement system.

BRIEF DESCRIPTION OF THE INVENTION

To this end, the invention relates to an ultrasonic probe for measuring the contact of an object, said object having a non-regular surface.

According to the invention, this ultrasound probe comprises ultrasonic sensors integral with a first face of a substrate, the opposite face of this substrate determining a measuring surface, this measurement surface having a shape which is the imprint of the surface of the object to be measured so as to conform to it when the surface of the object is brought into contact with said measuring surface.

This ultrasonic probe thus operates in the field of ultrasonic reflection control where the same sensor acts as an ultrasonic wave emitter and receiver of ultrasonic waves reflected by the object to be analyzed, this sensor being coded in position.

The term "surface of the non-regular object" means that this surface of the object has at least one angle. This surface of the object can thus have an L, V or U shape. As a counterexample, this surface of the object to be measured is not a strictly flat surface or the outer surface of a cylinder, the latter being regular.

Advantageously, the measurement surface of this ultrasound probe covers at least half of the total surface of the object to be measured, which makes it possible to measure in a single sweep the part of the object whose outer surface is in contact with the measuring surface of the probe. Of course, the measuring surface has a shape which is the footprint of the surface of the object to be measured to within manufacturing tolerances, being understood that it has been defined with respect to theoretical ribs of the object to be measured. .

Advantageously, the substrate has a uniform thickness.

In different embodiments of this ultrasound probe, the present invention also relates to the following features which should be considered in isolation or in all their technically possible combinations:

said probe comprises a coupling element designed to provide acoustic impedance matching between said object and said probe, said coupling element comprising an envelope such as a membrane, defining an interior volume in which a liquid coupling medium is placed; .

Preferably, this liquid coupling medium is water or a coupling gel.

As a purely illustrative example, this ultrasonic coupling gel is an aqueous gel comprising polyols such as that marketed by the company METALSCAN, rue Désiré Gilot, 71 1 00 Saint-Rémy under the name Couplant UT 5.

Advantageously, this envelope has an acoustic impedance substantially equal to that of water, the latter being 1, 5x1 0 ⁶ Pa.s / m. By way of non-limiting example, this envelope has an acoustic impedance which is equal to 1 5% close to that of water.

Preferably, said coupling element has a thickness less than or equal to 3 mm.

In addition to the acoustic impedance matching between the object to be measured and the ultrasonic probe, said coupling element also ensures the adjustment, or compliance, of the surface of the object to be measured with the measurement surface of the probe. ultrasonic, which allows to take into account possible deviations related in particular to the manufacturing tolerances of the object.

said ultrasonic sensors form a network of piezoelectric ceramic sensors integral with this substrate.

Preferably, said substrate is a metal substrate, a polyimide substrate or a graphite / epoxy composite material. For purely illustrative purposes, the metal substrate is made of aluminum, steel, stainless steel, titanium, nickel, copper or the like.

this probe comprises an electronic means for processing the electrical signals supplied by the ultrasonic sensors when they receive ultrasound.

The invention also relates to a method for manufacturing an ultrasound probe for ultrasonic testing of an object by contact, in which at least the following steps are carried out:

a) providing a support having an inner surface defining a measuring surface of said probe and a smooth outer surface, said support having been shaped so that said inner surface is an imprint of the surface of the object to be measured so as to fit when the object is brought into contact with this internal surface,

b) mixing a ceramic powder with a sol / gel solution so as to form a uniform dispersion,

c) depositing a coating containing said uniform dispersion on the outer surface of said support by a thin-film deposition method,

d) baking said coating thus formed at a temperature T greater than or equal to 100 ° C for a time T to form a piezoelectric ceramic coating on said outer surface,

e) optionally repeating steps b), c) and d) to form a piezoelectric ceramic block comprising at least two ceramic coatings,

f) forming at least one electrode on the outer surface of said piezoelectric ceramic coating or block to define a sensor.

Advantageously, in step c), said coating containing said dispersion is deposited uniformly to obtain an equal ceramic coating thickness on said support.

In addition, the first coating containing said dispersion being deposited on the non-rough outer surface of the support, the firing temperature of at least 100 ° C implemented in step d) for firing each ceramic coating ensures a final thickness of coating or uniform ceramic block. Before step f), said coating or said piezoelectric ceramic block thus formed is polarized. This polarization can be obtained by a corona discharge process.

By way of example, in step f), the electrodes may be formed by a silver metallization paste.

In different embodiments of this manufacturing method, the present invention also relates to the following features which should be considered in isolation or in all their technically possible combinations:

placing on said measurement surface defined by the internal surface of the substrate, a coupling element intended to provide acoustic impedance matching between said object and said probe, said coupling element comprising an envelope defining an internal volume in which is placed a liquid coupling medium.

Preferably, this liquid coupling medium is water or a coupling gel.

in step f), several electrodes are produced on the surface of said coating or said piezoelectric ceramic block so as to form an array of piezoelectric sensors,

Preferably, these sensors are spaced equidistantly.

said ceramic powder is maintained in a range of 30% to 50% by weight of said solution.

This ceramic powder is advantageously selected from the group comprising BIT (Bismuth titanium composite), silica, alumina, silicon carbide, etc.

The ceramic powder PZT marketed under the name Pz23 by Ferroperm Piezoceramics, DK-3490 Kvistgard, is particularly suitable for the present invention.

said thin film deposition method is a spray deposition method,

after step f), each of said sensors is connected to an electronic means for processing the signals supplied by these sensors when they receive ultrasound, before step f), the thickness of said at least one ceramic coating is controlled so that the ceramic block thus obtained corresponds to the measurement frequencies of said probe,

said object having a non-regular surface, the inner surface of said support is conformed so that this internal surface is an imprint of the non-regular surface of the object to be measured.

The present invention further relates to an installation for the non-destructive testing of ultrasonic parts.

According to the invention, this installation comprises two ultrasonic measuring probes as described above, said probes being intended to fit at least one opposite face of this part, at least one of these probes being mobile so that these probes can be moved away. each other for positioning or removal of the piece to be measured and brought together to fully cover the surface of that piece for non-destructive testing in a single sweep, or in a single pass.

By way of example, this installation comprises, consequently, a means for conveying the workpiece to be measured and / or gripping this workpiece for placing it on the measuring surface of one of said ultrasonic measuring probes as well as means for moving the other ultrasonic probe relative to this ultrasonic probe receiving the piece to be measured.

This non-destructive inspection facility can be part of a parts manufacturing line, ensuring simple and fast online control of these parts.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages, aims and particular features of the present invention will emerge from the description which follows, for an explanatory and non-limiting purpose, with reference to the appended drawings, in which:

FIG. 1 schematically represents an exploded view of an ultrasonic contact measurement probe according to a particular embodiment of the present invention,

FIG. 2 shows an embodiment of the present invention for non-destructive testing of a structural part of an aircraft, DETAILED DESCRIPTION OF THE EMBODIMENT OF THE INVENTION

First, we note that the figures are not scaled.

Figure 1 shows schematically an exploded view, for the sake of clarity, of the various constituent elements of an ultrasonic probe contact measurement according to a particular embodiment of the present invention.

This measurement probe comprises a substrate 10 made here of a metallic material such as aluminum, this substrate 10 having been shaped so that its inner surface 1 1 is the imprint, with manufacturing tolerances, of the outer surface of the substrate. part of a mechanical part to be measured.

Thus, when this part of the mechanical part of complex geometry is placed in direct contact with the inner surface 1 1 of the substrate 10 thus shaped, its outer surface matches the inner surface 1 1 of the substrate 10 to manufacturing tolerances. As an illustration, the conformation of the substrate 10 can be obtained by stamping.

On the outer surface 12 of this substrate 10 is bonded a piezoelectric ceramic block 13 comprising several layers of piezoelectric ceramic, which have been successively formed.

Each of these layers is obtained by a spraying method of a PZT sol / gel solution in which a piezoelectric ceramic powder (PZT) has been uniformly dispersed, the particles of which have a size typically between 1 and 80 μm, the coating thus uniformly deposited being fired at a temperature of at least 100 ° C by means of a source of hot air such as a heat gun.

Advantageously, the sol / gel solution PZT acts as a binding agent for the ceramic powder to the corresponding surface on which the coating is deposited.

The thickness of each ceramic coating of the block 13 is typically between 1 μιτι and 20 μιτι, the total thickness of this piezoelectric ceramic block, which is equal or substantially equal over the entirety of this block, being determined so that the Ultrasonic probe operates at a center frequency typically between 1 and 30 MHz (high frequency) or typically between 20 and 50 kHz (low frequency). On the outer surface of this piezoelectric ceramic block 13 is placed a set of electrodes 14, these electrodes 14 being spaced regularly or not. The thickness of the ceramic block 13 between an electrode 14 and the substrate 10 defines an ultrasonic sensor.

Each sensor of this ultrasonic probe is connected by a cable 16 to a multi-channel electronic means 17 which takes care of the supply. An analysis unit (not shown) connected to the multi-channel electronic means 17 analyzes the results measured by said ultrasonic sensors of the ultrasound probe.

Figure 2 shows an embodiment of the present invention for non-destructive testing of a structural part 18 of an aircraft.

This structural part 18 is curved so that it has a rounded portion 19 placed between two planar wings. The ultrasonic contact measurement system 20 implemented to control the quality of this structural part 18 has a measurement surface which is the imprint of the outer surface of this structural part 18 so as to conform to it when this surface outer part of the piece is brought into contact with this measuring surface.

A coupling element 21 consisting of an envelope such as a membrane, delimiting an interior volume in which water is placed, is interposed between this outer surface and the measuring surface of the system 20. This coupling element 21 is intended to provide acoustic impedance matching between the workpiece and the measuring system 20.

Claims

1. Ultrasonic probe measuring by contact of an object, said object having a non-regular surface, characterized in that said ultrasound probe comprises ultrasonic sensors integral with a first face of a substrate (1 0), the opposite face (1 1) of said substrate (1 0) determining a measuring surface, said measuring surface (1 1) having a shape which is the imprint of the surface of the object to be measured so as to marry it when the surface of the object is brought into contact with said measurement surface (1 1).

2. Probe according to claim 1, characterized in that it comprises a coupling element (21) for providing acoustic impedance matching between said object and said probe, said coupling element (21) comprising an envelope defining a internal volume in which is placed a liquid coupling medium.

3. System according to claim 1 or 2, characterized in that said ultrasonic sensors form an array of piezoelectric ceramic sensors integral with said substrate (1 0).

4. Probe according to any one of claims 1 to 3, characterized in that it comprises an electronic means (1 7) for processing the electrical signals provided by the ultrasonic sensors when they receive ultrasound.

5. A method of manufacturing an ultrasonic probe for ultrasonic testing of an object by contact, wherein at least the following steps are carried out:

a) providing a support (1 0) having an inner surface (1 1) defining a measurement surface of said probe and a smooth outer surface, said support (1 0) having been shaped so that said inner surface (1 1) an impression of the surface of the object to be measured so as to conform to it when the object is brought into contact with this internal surface, b) mixing a ceramic powder with a sol / gel solution so as to form a dispersion uniform,

c) depositing a coating containing said uniform dispersion on the outer surface (1 2) of said support (1 0) by a thin film deposition method, d) baking said coating thus formed at a temperature T greater than or equal to 100 ° C for a time T to form a piezoelectric ceramic coating on said outer surface (12),

e) optionally repeating steps b), c) and d) to form a piezoelectric ceramic block (13) comprising at least two ceramic coatings,

f) forming at least one electrode (14) on the outer surface of said piezoelectric ceramic coating or block (13) to define a sensor.

6. Method according to claim 5, characterized in that placed on said measurement surface defined by the inner surface (1 1) of the substrate, a coupling element (21) for ensuring acoustic impedance matching between said object and said probe, said coupling member (21) comprising an envelope defining an interior volume in which is placed a liquid coupling medium.

7. Method according to claim 6, characterized in that said liquid coupling medium is water or a coupling gel.

8. Method according to any one of claims 5 to 7, characterized in that in step f), a plurality of electrodes (14) is produced on the surface of said coating or said piezoelectric ceramic block (13) so as to form a network of piezoelectric sensors.

9. Method according to any one of claims 5 to 8, characterized in that said ceramic powder is maintained in a range of 30% to 50% by weight of said solution.

10. Method according to any one of claims 5 to 9, characterized in that said thin film deposition method is a spray deposition method.

1 1. Method according to any one of claims 5 to 10, characterized in that after step f), each of said sensors is connected to an electronic means (17) for processing the signals provided by these sensors when they receive ultrasound .

12. Method according to any one of claims 5 to 1 1, characterized in that before step f), the thickness of said at least one ceramic coating is controlled so that the ceramic block (13) thus obtained corresponds to at the measurement frequencies of said probe.

13. A method according to any one of claims 5 to 12, characterized in that said object having a non-regular surface, the inner surface (1 1) of said support is conformed so that said inner surface (1 1) is an imprint the non-regular surface of the object to be measured.

14. Installation for non-destructive testing of ultrasonic parts, characterized in that it comprises:

two ultrasonic measuring probes according to any one of claims 1 to 4 or obtained by the manufacturing method according to any one of claims 5 to 13, said probes being intended to fit an opposite face of this part,

at least one of these probes being mobile so that these probes can be moved away from one another for positioning or withdrawal of the part to be measured and brought together in order to cover the entire surface of this part to ensure its non-destructive testing in one measure.