Ultrasonic probe for contact measurement of an object and its manufacturing process

Abstract

An ultrasonic probe for contact measurement of an object and its manufacturing process. The ultrasonic probe has ultrasonic sensors securely fastened to a first face of a substrate. The opposite face of the substrate defines a measurement surface having a shape that is the imprint of the surface of the object to be measured to closely follow the latter when the surface of the object is brought into contact with the measurement surface.

Claims

1. A process for manufacturing an ultrasonic probe for ultrasonic testing of an object with contact, comprising the steps of: providing a carrier having an internal surface defining a measurement surface of said ultrasonic probe and a smooth external surface, said carrier being shaped so that the internal surface is an imprint of a surface of the object to be measured to closely follow the surface of the object in contact with the internal surface; mixing a ceramic powder in a sol-gel solution to form a uniform dispersion; depositing a coating containing said uniform dispersion on the external surface of said carrier using a thin-film deposition method; baking said coating at a temperature higher than or equal to 100° C. for a predetermined time to form a piezoelectric ceramic coating on said external surface; optionally repeating the steps of mixing, depositing and baking to form a piezoelectric ceramic block comprising at least two ceramic coatings; and forming at least one electrode on an external surface of said coating or said piezoelectric ceramic block to define a sensor.

2. The process as claimed in claim 1, further comprising the step of placing a coupling element configured to ensure matching of an acoustic impedance between said object and said ultrasonic probe on said measurement surface, said coupling element comprising an envelope defining an interior volume in which a liquid coupling medium is placed.

3. The process as claimed in claim 2, wherein said liquid coupling medium is water or a coupling gel.

4. The process as claimed in a claim 1, further comprising the step of producing a plurality of electrodes on the external surface of said coating or said piezoelectric ceramic block to form an array of piezoelectric sensors.

5. The process as claimed in claim 4, further comprising the step of connecting each of said piezoelectric sensors to an electronic device that processes signals received from the piezoelectric sensors in response to reception of ultrasound.

6. The process as claimed in claim 1, further comprising the step of maintaining said ceramic powder in a range of 30% to 50% by weight of said sol-gel solution.

7. The process as claimed in claim 1, wherein said thin-film deposition method is a sputtering deposition method.

8. The process as claimed in claim 1, further comprising step of controlling thickness of said at least one ceramic coating so that the piezoelectric ceramic block corresponds to measurement frequencies of said ultrasonic probe.

9. The process as claimed in claim 1, wherein said object has an irregular surface; and wherein the internal surface of said carrier is shaped so that the internal surface is an imprint of the irregular surface of the object to be measured.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other particular advantages, aims and features of the present invention will become apparent from the following completely non-limiting description given, by way of example, with regard to the appended figures, in which:

(2) FIG. 1 schematically shows an exploded view of a contact ultrasonic measuring probe according to one particular embodiment of the present invention; and

(3) FIG. 2 shows one method of implementing the present invention in nondestructive testing of a structural part of an aircraft.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

(4) Firstly, it will be noted that the figures are not to scale.

(5) FIG. 1 schematically shows an exploded view, for the sake of clarity, of the various constituent elements of a contact ultrasonic measuring probe according to one particular embodiment of the present invention.

(6) This measuring probe comprises a substrate 10, here made of a metal such as aluminum, this substrate 10 having been shaped so that its internal surface 11 is the imprint, to within manufacturing tolerances, of the outside surface of a portion of a mechanical part to be measured.

(7) Thus, when this portion of the mechanical part of complex geometry is placed making direct contact with the internal surface 11 of the substrate 10 thus shaped, its outside surface closely follows the internal surface 11 of the substrate 10 to within manufacturing tolerances. By way of illustration, the substrate 10 may be shaped by deep drawing.

(8) The piezoelectric ceramic block 13 comprising a plurality of piezoelectric ceramic layers is joined to the external surface 12 of this substrate 10, said layers having been formed in succession.

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

(10) Advantageously, the PZT sol-gel solution acts as an agent binding the ceramic powder to the corresponding surface on which the coating is deposited.

(11) The thickness of each ceramic coating of the block 13 is typically comprised between 1 μm and 20 μm, the total thickness of this piezoelectric ceramic block, which is equal or substantially equal over the entirety of this block, being defined so that the ultrasonic probe functions at a central frequency typically comprised between 1 and 30 MHz (high frequency) or typically comprised between 20 and 50 kHz (low frequency).

(12) On the external surface of this piezoelectric ceramic block 13 is placed a set of electrodes 14, these electrodes 14 optionally being regularly spaced. The thickness of the ceramic block 13, between an electrode 14 and the substrate 10, defines an ultrasonic sensor.

(13) Each sensor of this ultrasonic probe is connected by a cable 16 to a multichannel electronic means 17 that supplies power. A central processor (not shown) connected to the multichannel electronic means 17 processes the results measured by said ultrasonic sensors of the ultrasonic probe.

(14) FIG. 2 shows one method of implementing the present invention in nondestructive testing of a structural part 18 of an aircraft.

(15) This structural part 18 is curved so that it has a rounded portion 19 placed between two flat flanges. The contact ultrasonic measuring system 20 employed to test the quality of this structural part 18 has a measurement surface that is the imprint of the outside surface of this structural part 18 so as to closely follow the latter surface when this outside surface of the part is brought into contact with this measurement surface.

(16) A coupling element 21 consisting of an envelope such as a membrane, bounding an interior volume in which water is placed, is interposed between this outside surface and the measurement surface of the system 20. This coupling element 21 is intended to ensure matching of the acoustic impedance between the part and the measuring system 20.