Patent ID: 12222323

DETAILED DESCRIPTION

The device1schematically shown inFIG.1and allowing the invention to be illustrated is a device for analyzing the conformity of a faying-surface mastic3integrated into a structure2(FIG.2), and in particular into a structure of an aircraft.

In the context of the present invention, the structure2comprises at least two parts4A and4B, which are for example made of metal or of composite, and between which is arranged the faying-surface mastic3, as shown inFIG.2.

The envisioned structure2therefore comprises at least two parts4A and4B, for example planar or curved parts, such as panels or skins, that are at least partially superposed (i.e. that make contact with each other via at least one portion of their surfaces), and between which is arranged the faying-surface mastic3. This structure2may especially correspond to a portion of the fuselage of an aircraft, in particular of a cargo plane. By way of illustration, it may be a question of two fuselage segments that are assembled or of a panel that is fastened to one portion of the fuselage. In the example ofFIG.2, fastening elements5, in the present case rivets, which are intended to fasten the parts4A and4B to each other, have also been shown.

The structure2may also comprise more than two partially superposed parts, for example three or four parts as specified below, with, each time, faying-surface mastic3arranged between two superposed parts.

In the context of the present invention, the faying-surface mastic3is a polymer product (capable of being placed between two superposed parts) that has sealing properties and properties that result in adhesion to these parts. Such a faying-surface mastic may also have other characteristics or properties, depending on the envisioned application, such as for example properties that result in protection against corrosion. It may especially be a fast-curing mastic.

The faying-surface mastic3may thus, especially, serve to seal some or all of the region of overlap (or of superposition)6of the two superposed parts4A and4B (FIG.2).

The device1comprises, as shown inFIG.1, an ultrasonic measuring unit7. This ultrasonic measuring unit7is configured:to generate an ultrasonic signal S1. The ultrasonic signal S1may be an ultrasonic pulse;to transmit the ultrasonic signal S1(thus generated) into the structure2from at least one measurement point, as detailed below, in the direction illustrated by an arrow F inFIG.3, e.g., orthogonally to the external surface of the part2at the measurement point; andto measure the amplitude of the ultrasonic signal S2sent back by said structure2, in the direction opposite to the direction F (FIG.3). The ultrasonic signal S2corresponds to the portion of the ultrasonic signal S1that is sent back by the structure2.

To do this, in one particular embodiment, the ultrasonic measuring unit7comprises, as shown inFIG.3: an element8for controlling the ultrasonic measuring unit7; an element9for generating the ultrasonic signal S1; a transceiver element10provided for example with an antenna, for transmitting the generated ultrasonic signal S1and for receiving the ultrasonic signal S2sent back by the structure2; and an element11for measuring the received ultrasonic signal S2.

The measuring element11takes a measurement of the amplitude of the ultrasonic signal S2received as a function of the time-of-flight, i.e. of the time between the transmission of the ultrasonic signal S1by the transceiver element10and reception (after reflection from the structure) of the ultrasonic signal S2by the transceiver element10.

The propagation of the ultrasonic signal through the structure2is characterized by characteristic (reflection) peaks, which correspond to discontinuities in acoustic impedance in the structure, at the interfaces of different materials, and especially at the interface between the part4A and the faying-surface mastic3and at the interface between the faying-surface mastic3and the part4B.

InFIG.3, various signal portions S2A, S2B, S2C and S2D of the ultrasonic signal S2, which portions are sent back by different interfaces, have been illustrated. By way of illustration:the signal portion S2A corresponds to the peak P1in reflection (FIG.6) on entering the part4A;the signal portion S2B corresponds to the peak P2in reflection (FIG.6) on exiting the part4A.

In one embodiment, the ultrasonic signal (or pulse) S1has a frequency comprised between 10 MHz and 15 MHz. The use of an ultrasonic signal of such high frequency allows a maximum resolution to be achieved in relation to the analysis carried out. Specifically, identification of the peaks is facilitated by such high frequencies of the ultrasonic signal used.

Said device1also comprises, as shown inFIG.1, a processing module12. This processing module12comprises:a processing unit13configured to determine the thickness of the faying-surface mastic3at the one or more measurement points in question. The processing unit13determines the thickness of the faying-surface mastic on the basis of the measurements (carried out by the ultrasonic measuring unit7), which are received via a link14, and using a predetermined propagation model of said faying-surface mastic, which is for example incorporated into a database15(connected via a link16to the processing unit13). The processing unit13also takes into account auxiliary data (especially temperature and the time for which the faying-surface mastic has been applied in the structure), as specified below. The propagation model is characteristic of the type of faying-surface mastic used and delivers a thickness value of the faying-surface mastic depending on the time-of-flight of the ultrasonic signal through the faying-surface mastic, and on said auxiliary data as also specified below; anda processing unit17configured to deduce from the thickness of the mastic (which thickness is determined by the processing unit13and received via a link18) a conformity or non-conformity of the faying-surface mastic.

Thus, the device1is able, especially by virtue of the predetermined propagation model of the faying-surface mastic, and of the ultrasonic measurements carried out by the ultrasonic measuring unit7, to verify whether the faying-surface mastic3is in accordance (especially in terms of thickness) with expectations. Thus, a device1allowing a precise, rapid and reliable verification to be carried out, without disassembling the structure2, is obtained.

In one embodiment, the processing unit17is configured to also determine the presence or absence of swarf in the structure2. This embodiment allows, where appropriate, swarf to be identified and located, in particular in proximity to the fastening elements5(FIG.2).

All of these verifications are therefore performed without having to disassemble the structure2. The device1is thus particularly well suited to carrying out analyses during the type of aircraft assembly operations referred to as OWA operations, OWA being the acronym of “one-way assembly”.

Said device1also comprises a set19of means or devices (not shown individually) that are configured to deliver, to an operator or to a system, the result (received via a link20) of the processing operation implemented by the processing unit17. To do this, the set19may, especially, comprise:a conventional means for displaying the result (conformity or nonconformity of the faying-surface mastic; presence or absence of swarf and potentially the location thereof);a conventional means for printing the result;a conventional means for transmitting the result, for example via a wired link or a wireless link.

The device1such as described above, is able to implement a method P for analyzing the conformity of a faying-surface mastic integrated into a structure, for example a structure such as shown inFIG.2. Said method P, which is schematically shown inFIG.4, is described below, especially with reference toFIGS.5and6.

The method P comprises a measuring step E1(FIG.4), which is implemented by the ultrasonic measuring unit7(FIG.1). This measuring step E1consists in generating the ultrasonic signal S1, and in emitting the ultrasonic signal S1(thus generated) into the structure2from at least one measurement point, in the direction F illustrated inFIG.3.

In the context of the present invention, the method P may be used to carry out measurements at a particular measurement point of the structure2, for example in a place where it is considered that there might be a problem with conformity.

However, the measuring step E1may include carrying out measurements at a plurality of different measurement points of the structure2, for example allowing all of a given area of this structure2and in particular some or all of the region of overlap6of the two parts4A and4B (FIG.2) to be analyzed. By way of illustration, inFIG.5, a few measurement points M1, M2, M3on the part4A of a structure2(corresponding for example to the structure ofFIG.2, seen from above) have been shown. For each measurement point, the measurement carried out may be considered as being applicable to a given region (which is for example rectangular or circular) around the measurement point. Orifices21A to21F intended to receive fastening elements (not shown) have also been shown inFIG.5. These orifices are, for example, generated by drilling during a method for assembling the structure and especially during a one-way assembling method.

In the measuring step E1, the ultrasonic measuring unit7measures the amplitude of the ultrasonic signal S2sent back by the structure2. This measurement of the amplitude is carried out as a function of the time-of-flight, i.e. of the time between the transmission of the ultrasonic signal S1by the transceiver element10and reception (after reflection from the structure2) of the ultrasonic signal S2by the transceiver element10.

The propagation of the ultrasonic signal through the structure2is characterized by characteristic (reflection) peaks, which correspond to discontinuities in acoustic impedance in the structure, at the interfaces of different materials, and especially at the interface between the part4A and the faying-surface mastic3and at the interface between the faying-surface mastic3and the part4B.

By way of illustration, in the example ofFIG.6, the curve, which shows the variation in the amplitude of the ultrasonic signal S2as a function of the time-of-flight (expressed in μs—microseconds) comprises a plurality of characteristic peaks. More particularly, it especially comprises:the peak P1, which is the peak of entry into the part4A, via a coupling liquid (film of water). This peak P1is normalized, i.e. calibrated to an amplitude higher than or equal to 80%;the peak P2, which is the peak of exit from the part4A and the peak of entry into the faying-surface mastic3; andthe peak P3, which is the peak of exit from the faying-surface mastic3and the peak of entry into the part4B.

The difference Δt in time-of-flight between the peaks P2and P3therefore corresponds to the round-trip propagation time of the ultrasonic signal through the faying-surface mastic3. This difference Δt is used in the following processing step E2of the method P.

The method P therefore also comprises the processing step E2implemented by the processing unit13. This processing step E2consists in determining the thickness of the faying-surface mastic3at each of the measurement points M1, M2, M3. In the processing step E2, the processing unit13determines the thickness of the faying-surface mastic on the basis of the measurements carried out in the measuring step E1and especially of said difference Δt at the measurement point in question, and using the predetermined propagation model of faying-surface mastic.

The propagation model is characteristic of the type of faying-surface mastic used and delivers a thickness value (for example expressed in millimeters) of the faying-surface mastic depending on the time-of-flight (for example expressed in μs) of the ultrasonic signal through the faying-surface mastic, and on said auxiliary data. The auxiliary data used may include the following data: temperature; and the time for which the faying-surface mastic has been applied to the structure.

Therefore, by virtue of said propagation model, the processing unit13associates, with the time-of-flight Δt through the material of the faying-surface mastic, a thickness value. More precisely, the processing unit13determines the thickness E (for example expressed in mm) of the faying-surface mastic3using the following relationship:
E=(vp·Δt)/2in which:vp is the speed of propagation (for example expressed in mm/μs), which is defined in the propagation model; andΔt is the round-trip propagation time (for example expressed in seconds) of the ultrasonic signal through the faying-surface mastic.

In one embodiment, the speed vp depends on the temperature of the environment in which the structure is located, and on the time for which the faying-surface mastic has been deposited in the structure. Specifically, the speed of an ultrasonic signal through the faying-surface mastic depends on the polymerization of the latter.

By way of illustration, the propagation model may make provision, for one particular type of propagation mastic, for a speed vp of 1.65 mm/μs, after a time of 20 hours (of deposition), for a temperature of 20° C. This speed vp may vary if the temperature conditions and time vary.

The method P also comprises a processing step E3implemented by the processing unit17. The processing step E3consists in deducing, from the thickness E of the faying-surface mastic determined in the processing step E2, a conformity or non-conformity of said faying-surface mastic.

To do this, in one particular embodiment, rectangular cells R1and R2, which rectangular cells are especially square, are taken into account to determine a conformity of the faying-surface mastic, as shown inFIG.5. Each of the rectangular cells R1and R2is defined by four fastening points provided to secure the parts of the structure2. InFIG.5, the fastening points are defined by orifices21A to21F (which are intended to receive fastening elements). The cell R1is a rectangle of which the corners are defined by the orifices21A,21B,21C and21D. Likewise, the cell R2is a rectangle of which the corners are defined by the orifices21B,21C,21E and21F.

It is known that correct (or compliant) flow of the faying-surface mastic3is characterized by a thickness that is minimum at the fastening elements and a thickness that is maximum at the center thereof, i.e. resulting from an effect referred to as “cushioning”.

Thus, the processing step E3consists in verifying, for each of a plurality of rectangular cells R1, R2of the structure23, that the following conditions have been met:at the center of the rectangular cell R1, R2, the thickness of the faying-surface mastic3is comprised in a first predetermined interval of values, and for example between 0.15 m and 0.2 mm; andat the corners (orifices21A to21F) of the rectangular cell R1, R2, the thickness of the faying-surface mastic3is smaller than a predetermined value, 0.05 mm for example.

Depending on these verifications:if the aforementioned conditions are met for all the cells between the two parts of the structure2, the processing step E3concludes that the faying-surface mastic3is in conformity; andif the aforementioned conditions are not met for all the cells between the two parts of the structure2, the processing step E3concludes that the faying-surface mastic3is not in conformity.

In the example ofFIG.5, the conditions are considered to have been met. To emphasize this conformity, inFIG.5the thickness of the faying-surface mastic3has been represented using hatching of variable density. More precisely, in this example:regions24A to24F (shown in white) around the orifices21A to21F (i.e. the corners of the cells R1and R2), respectively, are devoid of mastic or contain a small and acceptable thickness of mastic. In the example ofFIG.5, the measurement point3is located in the region24A;regions22and23(shown densely hatched) at the center of the cells have a large and compliant thickness of faying-surface mastic. In the example ofFIG.5, the measurement point M1is located in the region22;the rest of the region of overlap (shown less densely hatched) has a smaller and compliant thickness of faying-surface mastic. In the example ofFIG.5, the measurement point M2is located in this region.

By way of illustration, in contrast, in the example ofFIG.5, it could be concluded that the faying-surface mastic is not in conformity in the case of presence of faying-surface mastic of a thickness larger than 0.05 mm in the regions24A to24F around the orifices21A to21F and/or if the faying-surface mastic at the center of at least one rectangular cell (regions22and23) is larger than 0.2 mm.

In one embodiment, the processing step E3consists also in determining the presence or absence of swarf in the structure2. It is known that the presence of swarf around the fastening elements disrupts the natural flow of the faying-surface mastic under mechanical pressure, this disruption being such or being able to be such that the faying-surface mastic then does not meet the required conditions mentioned above. This embodiment allows, by virtue of measurement of the thickness of the faying-surface mastic, swarf, potentially present between the two parts, in particular in proximity to the fastening elements, to be identified and located.

The method P in addition comprises a step E4of presenting and/or transmitting results (conformity or non-conformity of the faying-surface mastic, presence or absence of swarf and potentially the location thereof) obtained in the processing step E3to an operator or to a system. These results may be presented by various conventional means in the form of a display or a printout. In one particular embodiment, a map of the analyzed structure may be produced with the faying-surface mastic represented thereon by a set of colors (or color code), the colors depending on the thickness of the faying-surface mastic. This particular embodiment allows an operator to rapidly identify, visually, any problem with conformity from the colors of the map.

Moreover, the method P comprises a preliminary step E0implemented before the sequence of steps E1, E2, E3and E4. The preliminary step E0consists in determining the propagation model of the type of faying-surface mastic used. The type of faying-surface mastic may vary depending on its components, on its properties, etc.

To do this, the faying-surface mastic used is analyzed in order to define the propagation speed of the ultrasonic signal through said faying-surface mastic depending on the time (for example in days or in hours) said faying-surface mastic has spent curing and on the temperature of the environment in which said faying-surface mastic is located. To this end, ultrasonic measurements are carried out on faying-surface mastic (having these properties) integrated into a structure and the thickness of which is known exactly. The time-of-flight of the ultrasonic signal through this thickness of faying-surface mastic is measured, and thus a relationship between the (known) thickness of the faying-surface mastic and the (measured) time-of-flight is obtained, which allows the aforementioned propagation speed vp (for example expressed in mm/μs) to be determined. The ultrasonic measurements may be taken using a measuring unit similar to the ultrasonic measuring unit7.

A behavioral characterization of the faying-surface mastic used, as a function of the time (in days or in hours) spent curing and of the temperature of the environment (for example between 18° C. and 30° C.) is obtained.

In one particular embodiment, in the preliminary step E0, a propagation model is determined for a plurality of different types of faying-surface mastic. The various obtained models may thus, for example, be incorporated into the database15(FIG.1).

In this particular embodiment, the analyzing method P is able to analyze the conformity of any one of these various types of faying-surface mastic. To do this, it is sufficient for the propagation model corresponding to the type of faying-surface mastic for which the measurements were taken in the measuring step E1to be used in the processing step E2.

In the context of the present invention, the structure2that is analyzed may also comprise more than two partially superposed parts, for example three parts4A,4B and4C as shown inFIG.7, with, each time, one layer of faying-surface mastic3arranged between two directly successive superposed parts, namely between the parts4A and4B and between the parts4B and4C in the example ofFIG.7. In this case, on the basis of the analysis of the ultrasonic signal S2sent back and especially of the characteristic peaks of this ultrasonic signal S2, it is possible to determine the time-of-flight through each of the layers of faying-surface mastic3, and thus to deduce therefrom conformity or non-conformity.

Moreover, the method P may be implemented on various types of structure, formed for example: from superposed metal parts; or from superposed composite parts; or from a superposition not only of at least one metal part and but also of at least one composite part.

The device1and method P, such as described above, thus have many advantages. In in particular, they allow: with an associated quantification in case of doubt, correct flow of the faying-surface mastic to be guaranteed, without disassembly; and the absence of swarf at the interfaces of the structure to be guaranteed, without disassembly.

The device1may be used in various applications.

In a first possible application, the device1is used to carry out verifications of conformity during assembly operations, for example of an aircraft, and especially during “one-way assembly” operations. The device1allows, in this application, a precise, rapid and reliable verification of the conformity of the faying-surface mastic integrated into the structure and an absence of swarf to be achieved, without disassembling the structure.

In such an application, the device1may be used to take measurements at one or more particular measurement points of the structure2, for example in one or more places where it is considered that there might be a problem with conformity. These measurements may be taken during an assembly operation, or during a subsequent verification.

The device1may also be used to take measurements at a plurality of different measurement points of the structure, so as to analyze all of a given area, for example all the area to which the faying-surface mastic has been applied.

In one particular embodiment, at least one ultrasonic measuring unit7of the device1is mounted on a working head of an, in particular automated, drilling and riveting system. The device1thus follows the movements of the working head and is able to carry out analyses in all the places covered by this working head and therefore especially at the fastening points. In this particular embodiment, the processing module12of the device1may be integrated into a control unit of the drilling and riveting system.

Furthermore, in a second possible application, the device1is used to validate new steps or new actions of aircraft assembly operations, and especially of “one-way assembly” operations. By way of example, the device1may be used to validate new fastening elements or a new faying-surface mastic.

While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.