Ultrasonic method for detecting air zone defects in a room

Abstract

One aspect of the invention relates to an ultrasonic method for detecting air zone defects in a part to be inspected, comprising: receiving an ultrasonic map of the part to be inspected; receiving a thickness map of at least a portion of the part to be inspected; determining, from the thickness map, a simulated ultrasonic map of a part without air zone defects having the same composition and thickness map as the part to be inspected; determining, from the ultrasonic map of the part to be inspected and the simulated ultrasonic map, a detection map of the part to be inspected; determining, from the detection map, the presence or absence of an air zone defect in the part to be inspected. Figure to be published with the abstract: Figure 3

Description

Title of the invention: Method for ultrasonic detection of air zone type defects in a part TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of non-destructive testing of a part by ultrasound, and in particular by analysis of the attenuation of ultrasonic waves in the part to be tested.

[0002] The invention thus relates to an ultrasonic method for detecting defects using thickness data from at least part of the part. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] In industry, some parts are manufactured from digital models. However, during the manufacturing of the part, there may be differences in structure or composition between the digital model of the part (which represents the “ideal” part that one wishes to manufacture) and the part actually manufactured. For example, for parts made of woven composite material, there may be a difference between the weave of the manufactured part and the theoretical weave supplied to the loom. These differences are not necessarily problematic and do not always need to be detected.

[0004] The manufactured part may also have defects such as cracks, fissures, delaminations or detachments (in the case of bonded materials), which result in the presence of "air zones" within the part. Such defects modify the mechanical properties of the part and weaken it, and must therefore be detected.

[0005] To detect defects of the "air zones" type, it is known to use ultrasonic testing methods. In ultrasonic testing methods, ultrasonic waves are emitted by a transducer placed on the surface of the part to be tested, and propagate inside it. When an ultrasonic wave encounters an interface separating two zones having different acoustic impedances in the part (in particular when the ultrasonic wave encounters a defect inside the part), a portion of the ultrasonic wave is reflected and the non-reflected portion is attenuated.

[0006] There are classically two categories in ultrasonic testing methods: reflection methods and transmission methods (also called attenuation methods). In reflection methods, the same transducer carries out both the emission of ultrasonic waves and the reception of reflected waves (i.e. "echoes", or "return signals" from the emitted waves). From the intensities and arrival time of the return signals, it is then possible to extract information relating to the presence and position of defects in the part. In transmission methods, a receiver separate from the transmitter and placed on another surface of the part (for example a surface opposite the surface on which the transducer that emits the ultrasonic waves is placed) receives the attenuated ultrasonic waves. Defect detection is carried out from the quantity of waves that have reached the second surface after having crossed the part (only once, compared to twice - outward and return - for reflection methods).

[0007] Since air zone type defects strongly attenuate ultrasonic waves, transmission methods are well suited to the detection of such defects.

[0008] For example, it is known to use such methods for parts obtained by bonding, such as aeronautical parts comprising a composite material part on which a metal reinforcement is bonded. An example of such parts is the composite material fan blade of the LEAP engine, on which a titanium reinforcement is bonded. On the bonded areas, there may be anomalies such as porosity or lack of glue, which are air zone type defects. An ultrasonic inspection is typically carried out on the manufactured part to verify that there are no such defects.

[0009] The 3D weaving of the composite material strongly scatters ultrasonic waves. In addition, the resin in the composite material strongly attenuates ultrasonic waves. For these reasons, a reflection method is very complicated to implement and it is preferable to use an attenuation method.

[0010] The result of the ultrasonic inspection can be represented using a C-type visualization, called "C-scan", which is a map linking the amplitude of the signal transmitted through the part to an inspection position for the surface of the inspected area. The C-scan therefore provides a plan and top view of the part.

[0011] Defects are not always easily visualized in the C-scan of the manufactured part, and generally a processing of the C-scan is implemented to highlight them. In particular, it is possible to use a reference part, which is a part of the same type as the part to be checked (for example, a composite blade with a bonded titanium leading edge having predefined dimensions), which is known not to have an air zone type defect. A C-scan map of this reference part is determined and used as a reference map of the part.

[0012] For each part to be checked, a C-scan map is determined and this map is subtracted from the reference map. The result of this subtraction is a “processed” map on which the defects appear, along with other patterns in the image. A thresholding of the image is then carried out to remove patterns other than the defects, so that only the defects remain apparent in the image thus thresholded. The threshold used for thresholding the image is a predefined threshold, which can be optionally readjusted as described below.

[0013] The detection of a defect according to the above method is shown in Figures 1a - 1c. In particular, Figures 1a - 1c represent a part 101 to be checked. In this example, the part 101 shown in [Fig. 1a] is a fan blade made of composite material having a leading edge 101b made of titanium bonded to a body 101a made of composite material. [Fig. 1b] represents a C-scan map 102 of the part 101. This map is conventionally obtained using an ultrasonic attenuation control method. The C-scan map 102 comprises several zones 102a, 102b, 102c, 102d which correspond to different ultrasonic attenuation values.

[0014] [Fig. 1c] represents a C-scan map 103 of a reference part. reference part corresponds to a part of the same type as the part to be checked 101 (for example manufactured from the same digital model, and therefore theoretically having the same dimensions, the same structure and the same components), but which is known not to have defects of the type that one seeks to detect in the part to be checked 101. In other words, the reference part is an "ideal" part without defects. In the example of Figures 1a - 1e, the reference part is an assembled blade consisting of a body made of a perfectly integral pre-machined composite material and a bonded titanium leading edge having the geometry as close as possible to the nominal geometry. The bonding has been previously controlled and checked to ensure that it does not have any defects.

[0015] Similar to the C-scan map 102 of the part to be checked, the C-scan map 103 of the reference part has several zones 103a, 103b, 103c, 103d which correspond to different ultrasonic attenuation values.

[0016] [Fig.1d] represents a processed map 104 obtained by subtracting the C-scan map 103 of the reference part from the C-scan map 102 of the part to be inspected. As shown in [Fig.1d], the map 104 generally has a more restricted amplitude of variations in the ultrasonic attenuation values ​​than the C-scan maps 102 and 103. The processed map 104, however, includes zones 104a, 104b, 104c called “ultrasonic indications”, which correspond to peak zones of the attenuation values, and which may correspond to air zone type defects. To determine such defects, thresholding can then be applied to the processed map 104, to obtain the thresholded map 105 of [Fig.1e]. In other words, a threshold is applied to the attenuation values ​​of the processed mapping 104. In particular, this threshold can be defined as a percentage of the maximum amplitude of the received signal (i.e.amplitudes below this percentage of the maximum amplitude are "cut off"). For example, the threshold can be a predefined value, which corresponds for example to an at . signal attenuation equal to -6 dB. In other words, the differences between the C-scan map 102 of the part to be checked and the C-scan map 103 of the reference part are considered as air zone type defects (in particular bonding defects) when they correspond to an attenuation beyond -6 dB. As described below, this threshold can be determined during a step detailed below. In the example of the thresholded map 105, a defect 105a appears.

[0017] The subtraction of a C-scan map 103 of a reference part from the C-scan map 102 of the part to be checked therefore makes it possible to overcome the complex geometry and the difference in thickness of the part, and thus better detectability of air zone type defects.

[0018] The threshold to be applied to the processed map 104 can be determined or adjusted during an additional step, from a so-called “defective” part. This part is a part of the same type as the part to be checked, but it includes “controlled” defects, in the sense that the location, dimensions and type of defect is known for each defect of the defective part. The defective part is typically obtained from a reference part (i.e. without defects) into which elements have been inserted which have the same behavior as air zone type defects. For example, Teflon elements can be inserted, knowing that a Teflon element has a behavior generally similar to that of an air bubble with respect to ultrasonic signals (the signals are attenuated approximately in the same way when they pass through a Teflon element and when they pass through an air bubble or an air blade).This defect room allows you to define the threshold to be applied, for example in Decibels (dB), according to tolerances relative to the actual size of the defects. In other words, as the positions of the defects in the defect room are known, it is possible to adjust the detection threshold to obtain the best compromise between "false positives" (detections on the thresholded map which do not correspond to a defect that we are trying to control) and "false negatives" (no element appears on the thresholded map while there is a defect).

[0019] A flowchart of the method for detecting defects in a part according to the prior art described above is shown in [Fig.2].

[0020] During a step 210, a C-scan map of a reference part without defects (C-scan map 103 of Figures 1a - 1c), also called a "gain correction vane", is obtained. During a step 220, a C-scan map of the part to be checked (C-scan map 102 of Figures 1a - 1c) is obtained. The C-scan map of the reference part (without defects) is subtracted (step 230) from the C-scan map of the part to be checked to obtain a so-called processed map (map 104 of Figures 1a - 1c).

[0021] During a step 240, a C-scan mapping of the part with defects (the defects being known, as detailed above) is obtained, and used to determine an optimal threshold (step 250) for detecting defects, as described above.

[0022] During a step 260, the threshold determined in step 250 can be applied to the processed map obtained in step 230. The defect(s) can then be identified in the thresholded map during a step 270. Indeed, the differences between the part to be checked and the reference part without defects, which are “ultrasonic indications”, should theoretically only be bonding anomalies, i.e. air zone type defects.

[0023] The C-scan mapping of the reference part, the C-scan mapping of the part to be inspected and the C-scan mapping of the part with defects are typically obtained by a transmission ultrasonic inspection method.

[0024] It is noted that steps 210, 220 and 240 can be implemented in parallel or in any order (even if in general, steps 210 and 240 on the reference part and the part with defects are implemented before carrying out the actual control of a part, therefore before step 220).

[0025] In the prior art method described above, the role of the defect-free reference part is to obtain a processed C-scan map that is as homogeneous as possible, which is free from the attenuation variabilities induced by the material(s) used and the thicknesses of the part (in particular of the composite material and / or the thicknesses of the different materials such as titanium in the previous example).

[0026] However, the defects that one seeks to detect are not the only ones to generate ultrasonic indications, i.e. areas of ultrasonic attenuation peaks. Other factors can generate ultrasonic indications, in particular the variability of structure or thickness of the part (in the case of the composite blade with a bonded titanium leading edge for example, the variability of the geometry of the leading edge and / or the variability of the woven armor generate such ultrasonic indications). These variabilities not anticipated at the implementation of the control can arise for example from the diversity of suppliers for the same product, from the evolution of the geometries, from the manufacturing process and / or from the broadening of the geometric acceptance criteria on the part (or the intermediate parts, i.e. the leading edge and the pre-machined body in the previous example).These variabilities give rise to false positives (false defects) detected on the mapping after thresholding.

[0027] One solution would be to adapt the threshold to the different parts of the part to be checked, but such a solution is difficult to implement because it requires determining upstream the zones in which attenuation variability is acceptable, and determining the associated acceptability threshold. This solution also presents the risk of increasing the number of false negatives, i.e. the number of undetected defects (in particular because they are located in a part of the part for which it has been considered that greater variability in attenuation is acceptable).

[0028] There is therefore a need to improve the detection of air zone type defects in parts and to avoid irrelevant ultrasonic indications (i.e. zones which appear on the thresholded map as defects when they are not). Summary of the invention

[0029] The invention provides a solution to the problems mentioned above, by using thickness data of the manufactured part that is to be controlled to construct a simulated ultrasonic map of a virtual part, and by using this simulated ultrasonic map as a reference map (instead of the ultrasonic map of a reference part without defects, as in the prior art method above). The use of such a simulated ultrasonic map makes it possible to reduce irrelevant ultrasonic indications due in particular to the variability of the geometry of the manufactured part compared to the digital model on the basis of which it is manufactured.

[0030] One aspect of the invention thus relates to a computer-implemented method for ultrasonic detection of air zone type defects in a part to be inspected. The method comprises:

[0031] - receive an ultrasonic map of the part to be checked;

[0032] - receive a thickness map of at least a portion of the part to be control;

[0033] - determine, from the thickness mapping of at least one portion of the part to be checked, a simulated ultrasonic mapping of at least one portion of a part without air zone type defects having the same composition and the same thickness mapping as the at least one portion of the part to be checked;

[0034] - determine, from the ultrasonic mapping of the part to be checked and the simulated ultrasonic mapping, a detection map of the part to be controlled;

[0035] - determine, by applying a predefined threshold to the detection mapping of the part to be checked, a presence or absence of an air zone type defect in the part to be checked.

[0036] By "air zone type defect" is meant a defect in the part whose behavior with respect to ultrasound (in particular the ultrasonic attenuation coefficient) is similar to that of an air zone present in the part. When they have such a defect, the ultrasonic waves are typically attenuated more than when they pass through the rest of the part. Such a defect may be for example an air bubble or a crack.

[0037] By "part to be checked" is meant the mechanical part in which one seeks to detect the possible presence of a defect. It is noted that the method can be applied to a complete part or to a part of a part (rather than to a complete part), both designated by "part" or "part to be checked" in the following, for the sake of simplification.

[0038] By "ultrasonic mapping" is meant a graphical representation of the ultrasonic behavior at different points of the part. For example, the ultrasonic mapping may be a 2D image of a projection of the part onto a predefined plane, representing the amplitudes of ultrasonic signals at the different points of the projection after having passed through the part. In particular, each point of the mapping may be associated with data relating to the ultrasonic behavior of the part in an axis passing through the point considered in a direction orthogonal to the projection plane. For example, the relative data may be an amplitude value of the signal at the output of the part, which reflects the attenuation undergone by the ultrasonic wave as it passes through the part. As air zone type defects attenuate the ultrasonic signals passing through them, these attenuations are visible in the ultrasonic mapping of the part.

[0039] The “ultrasonic mapping of the part to be checked” is therefore a mapping obtained on the complete part (or portion of part), after its manufacture.

[0040] By "thickness mapping" is meant a graphical representation of the thickness of the part in a given direction. Typically, the thickness mapping represents a projection of the part on the same plane as the ultrasonic mapping, in which each point of the projection is associated with data representative of the thickness of the part at this point, in the direction orthogonal to the plane considered. For example, the thickness mapping may be a 2D image comprising a plurality of pixels, each pixel having a value calculated as a function of the thickness of the part at a point corresponding to the pixel considered.

[0041] According to the method, the thickness map received is a thickness map of the entire part to be inspected or a thickness map of only a portion of the part to be inspected. For example, when the part to be inspected is an engine blade comprising a composite material body and a titanium leading edge bonded together, the thickness map received may be a map of the leading edge alone. Conversely, the ultrasonic map received is an ultrasonic map of the complete part.

[0042] By “simulated ultrasonic mapping” of the part or portion of part is meant a mapping which “simulates” an ultrasonic mapping of the part or portion of part, but which has not been established (at least in part) from an ultrasonic method applied to the part to be checked or to the portion of part to be checked. control. More precisely, the simulated ultrasonic mapping is here determined from the thickness mapping. In other words, the thickness mapping is "transformed" into an equivalent ultrasonic mapping, which would theoretically be obtained if an ultrasonic method were applied to the part or portion of the part to study its ultrasonic behavior and deduce an ultrasonic mapping, assuming that this part or portion of the part does not contain any defects.

[0043] The simulated ultrasonic mapping corresponds to the ultrasonic mapping of a “virtual” part which would be similar to the part considered, and which would not have an air zone type defect. The underlying idea is that in the absence of a defect, the attenuation of the ultrasonic waves depends on an average attenuation coefficient of the medium crossed and the length traveled by the ultrasonic signals (and therefore the thickness of the part). By using attenuation data for parts corresponding to the same medium (which may be heterogeneous, for example several media successively crossed) and the actual thickness data of the part (i.e. the true thickness of the manufactured part, integrating its possible variations compared to the digital model according to which it was manufactured), it is possible to deduce a simulated ultrasonic mapping of a part having the same thickness mapping, but which would not have a defect.The simulated ultrasonic mapping thus makes it possible to obtain a reference map of the ultrasonic behavior in the part in the absence of a defect.

[0044] By "composition" is meant a set of parameters defining the structure and the material(s) constituting the part (or portion of part). For example, for a part made of woven composite material, the composition covers in particular the type of weave, the type of weft and warp threads, the warp / weft ratio, etc. By "defect-free part having the same composition and the same thickness mapping" as the part to be checked, is therefore meant a virtual part "identical" in terms of composition and dimensions to the part to be checked, but which is assumed to be without air zone type defects.

[0045] By "detection mapping" is meant a representation of a projection of the part on which possible defects are determined. In the present method, this detection mapping is obtained from the (real) ultrasonic mapping of the manufactured part and the simulated ultrasonic mapping (which serves as a reference).

[0046] The above method advantageously uses the actual thickness data of the part to be inspected to construct a (simulated) ultrasonic map which serves as a reference to determine the presence or absence of an air zone type defect. The method is thus more precise than the traditional method of the prior art described above, in which the reference map comes from an “ideal” (physical) part, which may present differences in thickness compared to the part to be checked.

[0047] In one or more embodiments, the detection map of the part to be tested may comprise a plurality of pixels, each pixel among the plurality of pixels being associated with a respective value. Determining the presence or absence of an air zone defect in the part to be tested may comprise:

[0048] - determining whether there is a group of neighboring pixels in the detection map of the part to be checked for which the values ​​associated with the pixels of said group are lower or higher than the predefined threshold:

[0049] if there is a group of neighboring pixels in the detection map of the part to be checked for which the values ​​associated with the pixels of said group are lower or higher than the predefined threshold, detect an air zone type defect;

[0050] if there is no group of neighboring pixels in the detection map of the part to be checked for which the values ​​associated with the pixels of said group are lower or higher than the predefined threshold, detect an absence of an air zone type defect.

[0051] According to these embodiments, the detection map is an image comprising a plurality of pixels, each pixel being associated with a respective value. The value associated with a pixel may be, for example, a gray level or a light intensity value. It is understood that the invention is not limited to a single value per pixel, for example, each pixel may be associated with a triplet of values ​​representing the intensity values ​​on the three red, green and blue channels of the pixel.

[0052] By “neighboring pixels” is meant pixels connected to each other by a connectivity relationship, for example a 4-connectivity. By “group of neighboring pixels”, it is meant that each pixel of the group is neighbor of at least one other pixel of the group. The group of pixels may comprise a single pixel or more than two pixels. According to embodiments, a condition may be added on the number of pixels forming the group (thus, a set of neighboring pixels is considered a “group” in the above sense if it comprises a number of pixels greater than or equal to a predefined lower limit).

[0053] According to the embodiments, the groups of pixels may comprise pixels whose values ​​are greater than the predefined threshold or pixels whose values ​​are less than the predefined threshold. These embodiments are equivalent.

[0054] When the values ​​of the pixels in the detection map are higher (or lower) than the predefined threshold, this means that the signals were more strongly attenuated when passing through the part, which may indicate the presence of a defect.

[0055] In embodiments, the thickness map may be a thickness map of the entire part. The thickness map of the part to be inspected may comprise a plurality of pixels, each pixel of the plurality of pixels being associated with a respective value, and the simulated ultrasonic map may be determined by applying a transformation to the pixel values ​​of the thickness map of the part to be checked.

[0056] According to these embodiments, the thickness mapping is therefore carried out on the complete part (and not on a portion of the part). The thickness mapping is “transformed” into a simulated ultrasonic mapping, which is therefore the ultrasonic mapping that a part similar to the part to be checked would have in the absence of a defect.

[0057] In embodiments, the method may further comprise:

[0058] - recalibrate the thickness mapping of the part to be checked with the ul mapping trasonic of the part to be checked;

[0059] and the transformation can be applied to the thickness map of the recalibrated part.

[0060] By "registration", it is understood that pixels of the two maps corresponding to the same points of the projection of the part are matched. This makes it possible to combine the respective information of the maps.

[0061] According to these embodiments, the registration is applied before transforming the thickness map to obtain the simulated ultrasonic map.

[0062] Alternatively, the method may further comprise:

[0063] - re-align the simulated ultrasonic mapping of the part with the ul mapping trasonic of the room;

[0064] and the detection map can be determined from the ultrasonic map of the part and the simulated and registered ultrasonic map of the part.

[0065] According to these embodiments, the registration is applied after the transformation, on the simulated ultrasound mapping.

[0066] In alternative embodiments, the part to be tested comprises a first part and a second part assembled by gluing, the second part being manufactured according to a predefined digital model. The thickness mapping may be a thickness mapping of the first part of the part to be tested before assembly with the second part of the part to be tested, and the ultrasonic mapping of the part to be tested may be an ultrasonic mapping of the assembled part to be tested. The method may further comprise:

[0067] - receive a reference ultrasonic map of the second part of the part to be checked, the reference ultrasonic mapping of the second part of the part to be checked corresponding to an ultrasonic mapping of a second reference part manufactured from the predefined digital model and not including any air zone type defect;

[0068] and the simulated ultrasonic mapping can be determined from the thickness mapping of the first part of the part to be tested and the reference ultrasonic mapping of the second part of the part to be tested.

[0069] According to these embodiments, the part to be checked comprises at least two parts glued together. The bonding zone may typically comprise defects such as air zones, for example due to a lack of glue, or due to an air bubble in the glue. The ultrasonic mapping is always carried out on the complete (and assembled) part. On the other hand, the thickness mapping only concerns the first part of the part, before it is glued to the second part of the part. In these embodiments, a so-called “reference” ultrasonic mapping of the second part of the part is also received.This reference ultrasonic mapping of the second part of the part is typically an ultrasonic mapping carried out on a second part of the part “similar” to the second part of the part being checked but which is known to not include any defects (as was the case in the prior art method on the entire part; conversely, here this only concerns the second part of the part).

[0070] Such embodiments are particularly advantageous when the part comprises a portion whose thickness varies very little, and a portion whose thickness varies more.

[0071] In these embodiments, the thickness map of the first portion of the part to be inspected may comprise a plurality of pixels, each pixel of the plurality of pixels being associated with a respective value. The method may further comprise:

[0072] - applying a transformation to the plurality of pixels of the thickness map of the first part of the part to be checked;

[0073] wherein the simulated ultrasonic mapping can be determined from the reference ultrasonic mapping of the second portion of the part to be tested and the transformed thickness mapping of the first portion of the part to be tested.

[0074] The thickness mapping of the first part of the part is thus transformed into an equivalent ultrasonic mapping in the absence of a defect, and the simulated ultrasonic mapping is determined by “grouping” the reference ultrasonic mapping of the second part and the equivalent ultrasonic mapping obtained for the first part.

[0075] In embodiments, the method may further comprise:

[0076] - recalibrate the thickness mapping of the first part of the part and the car ultrasound tography of the second part of the part with ultrasound mapping of the part;

[0077] wherein the transformation can be applied to the thickness map of the recalibrated part; and

[0078] wherein the simulated ultrasonic mapping of the part can be obtained by summing the ultrasonic mapping of the second part of the recalibrated part and the mapping obtained by applying the transformation to the thickness mapping of the rejected part.

[0079] Alternatively, the method may further comprise:

[0080] - realign the mapping obtained by applying the transformation to the car thickness tography of the recalibrated part and ultrasonic mapping of the second part of the part with the ultrasonic mapping of the part;

[0081] wherein the simulated ultrasonic mapping of the part can be obtained by summing the ultrasonic mapping of the second part of the registered part and the mapping obtained by applying the transformation to the thickness mapping of the registered part.

[0082] In one or more embodiments, the transformation may be a multiplication by a predetermined coefficient.

[0083] In particular, the method may comprise a prior calculation of the predetermined coefficient. The prior calculation of the coefficient may comprise:

[0084] - for each part of a set of parts without air zone type defects having the same composition as the part to be checked:

[0085] receiving a thickness map of said part, the thickness map comprising a plurality of pixels, each pixel being associated with a respective value;

[0086] receiving an ultrasonic map of said part comprising a plurality of pixels, each pixel being associated with a respective value;

[0087] determining a ratio between pixel values ​​of the thickness map with corresponding pixel values ​​of the ultrasonic map;

[0088] - calculate the coefficient from the determined ratios.

[0089] In embodiments, the detection map is obtained by subtracting the ultrasonic map of the part to be tested and the simulated ultrasonic map.

[0090] For example, the part may be an aeronautical part. In particular, in the case where the part comprises two parts, the part may be an engine blade, in which the first part of the part is a metal leading edge, and in which the second part of the part is a body of woven composite material.

[0091] In embodiments, the air zone defect may be a presence of a crack, fissure, delamination or delamination.

[0092] In embodiments, the maps are C-type visualizations.

[0093] Another aspect of the invention relates to an ultrasonic detection device of air zone type defects in a room to be controlled. The device may include:

[0094] - an input interface configured to:

[0095] receive an ultrasonic map of the part to be checked;

[0096] receive a thickness map of at least a portion of the part to be checked;

[0097] - a circuit configured to:

[0098] determining, from the thickness map of the at least one portion of the part to be inspected, a simulated ultrasonic map of at least one portion of a part without air zone type defects having the same composition and the same thickness map as the at least one portion of the part to be inspected;

[0099] determining, from the ultrasonic mapping of the part to be checked and the simulated ultrasonic mapping, a detection mapping of the part to be checked;

[0100] determine, by applying a predefined threshold to the detection map of the part to be checked, a presence or absence of an air zone type defect in the part to be checked.

[0101] A computer program, implementing all or part of the method described above, installed on pre-existing equipment, is in itself advantageous.

[0102] Thus, the present invention also relates to a computer program comprising instructions for implementing certain steps of the method described above, when this program is executed by a processor.

[0103] This program may use any programming language (for example, an object-oriented language or other), and be in the form of interpretable source code, partially compiled code or fully compiled code.

[0104] The [Fig.3] described in detail below can form the flowchart of the general algorithm of such a computer program.

[0105] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0106] Other characteristics and advantages of the invention will appear on reading the description, which can be read in conjunction with the figures. These figures are presented for information purposes only and in no way limit the invention.

[0107] [Fig.la], [Fig.lb], [Fig.le], [Fig.ld], [Fig.le] Figures la to le illustrate certain steps of a method for detecting air zone type defects according to the prior art.

[0108] [Fig.2] [Fig.2] represents a flowchart of a method for detecting air zone type defects according to the prior art.

[0109] [Fig.3] [Fig.3] represents a flowchart of a method for detecting air zone type defects according to an embodiment of the invention.

[0110] [Fig.4] [Fig.4] represents a flowchart of a method for detecting air zone type defects according to another embodiment of the invention. [YES] [Fig.5a], [Fig.5b], [Fig.5c] Figures 5a, 5b and 5c illustrate a step of determining a simulated ultrasonic mapping of the part according to an embodiment of the invention.

[0112] [Fig.6] [Fig.6] represents a flowchart of a method for detecting air zone type defects incorporating a determination of the threshold to be applied according to embodiments of the invention.

[0113] [Fig.7] [Fig.7] represents an example of a device for detecting air zone type defects according to embodiments of the invention. DETAILED DESCRIPTION

[0114] [Fig.3] represents a flowchart of a method for detecting air zone type defects according to one embodiment of the invention.

[0115] According to this embodiment, the part is considered as a whole (whereas in the embodiment described with reference to [Fig.4], it is considered as an assembly of two parts glued together).

[0116] During a step 220 similar to that described with reference to [Fig. 2], an ultrasonic map, for example a C-scan map, of the part is received. The ultrasonic map of the part is typically an image comprising a plurality of pixels, in which each pixel is associated with a light intensity value which represents an amplitude of the received signal (or equivalently, an attenuation value of the ultrasonic signal during its propagation in the part, also called ultrasonic attenuation value) in the region of the part corresponding to said pixel. In other words, each pixel reflects the way in which the emitted ultrasonic signal is attenuated during its propagation in the part. Thus, pixels corresponding to areas of the part in which air zone type defects are located are generally associated with light intensity values ​​reflecting greater ultrasonic attenuation of the signal.

[0117] During a step 310, a thickness map of the part is obtained. The thickness map of the part is typically an image comprising a plurality of pixels, in which each pixel is associated with a light intensity value which represents a thickness of the part in a given direction. For example, if the part is in a (X, Y, Z) frame of reference, a map of the part along the Z axis represents the thickness of the part along the Z axis, represented in the (X, Y) plane.

[0118] The thickness mapping can be obtained, for example, using a dimensional control method of the state of the art. For example, the thickness mapping can be established from measurement data obtained using a three-dimensional measuring machine (CMM). Such a machine makes it possible, using probes and / or optical sensors moved by a measuring arm, to know the dimensions, shape, position of the measured object in a given reference frame, and therefore the thicknesses of this object in several directions. The measured data can then be, for example, processed by metrology software which allows the modeling of the object as well as the detection of dimensional deviations of the part compared to the digital model according to which it was manufactured.

[0119] The ultrasonic mapping of the part received in step 220 and the thickness mapping of the part received in step 310 are typically images of the same dimensions (i.e. having the same number of pixels along the two axes of the image). It is noted that steps 220 and 310 can be implemented in any order, or in parallel.

[0120] In one or more embodiments, it is possible to implement a registration 320 to register the ultrasonic mapping of the part and the thickness mapping of the part. Indeed, depending on how the two maps were obtained, the maps may not completely correspond. For example, a pixel corresponding to a point of the part may not have the same coordinates in the two images. Typically, there may be a rotation and / or a translation of one of the images relative to the other. To be able to match the two maps and thus be able to combine their respective information, a transformation can therefore be applied to one of the maps to “register” it with the other map.

[0121] Such techniques for registering images with each other are known to those skilled in the art. In particular, it is possible to use a registration technique based on reference points of the part, the positions of which are known. The pixels corresponding to these reference points can be identified on each of the maps, and the transformation to be applied to carry out the registration 320 can be determined from these pixels. For example, if a point M of the part is associated with the pixel p of coordinates (x, y) in the ultrasonic map and with the pixel p' of coordinates (x', y') of the thickness map, the transformation T to be applied is such that T(x', y') = x, y (or such that T(x, y) = (x', y')). As mentioned above, these techniques are known and are not detailed further here. An example of a registration is illustrated in Figures 5a, 5b and 5c, in a particular embodiment of the invention.

[0122] In one or more embodiments, a transformation may be applied to the thickness map of the part during a step 330 to modify the intensity values ​​of the pixels of the thickness map in order to obtain a so-called “simulated” ultrasonic map of a part similar to the part considered (i.e. having the same composition, the same structure, the same dimensions) which would not have any defects. At the end of step 330, a simulated ultrasonic map of the part is thus obtained. The word “simulated” here refers to the fact that the map obtained “simulates” an ultrasonic map while it is obtained (at least partially) from a thickness map. It is noted that the word “simulated” does not designate here a map which would be completely derived from a si- computer emulation.

[0123] For example, during step 330, it is possible to multiply the light intensity values ​​of each pixel of the thickness map by the same predefined coefficient, to obtain the simulated ultrasonic map. This coefficient can be determined upstream of the detection method according to the invention, for example from a part having several known thicknesses, for which an ultrasonic map is carried out. For example, it is possible to use a shim with steps of variable thicknesses (for example, 5 steps having thicknesses equal to 1 mm for the first step, 2 mm for the second step, ... and 5 mm for the fifth step, the number of steps and their respective thicknesses being provided by way of example only and in a non-limiting manner), the thickness of each step being known.Ultrasonic mapping allows ultrasonic attenuation values ​​to be displayed for each step (for example, -3 dB for the first step, -4 dB for the second step, ..., and -7 dB for the fifth step). A correlation between the thickness values ​​and the corresponding attenuation values ​​is then determined. For example, a relationship of the type: Att = (Ep xn) + z is established, where Att represents the ultrasonic attenuation, Ep represents the thickness and n and z are two parameters determined from the experimental ultrasonic attenuation and thickness values ​​obtained on the stepped wedge. Models of the relationship between ultrasonic attenuation and thickness other than a linear model as above are of course possible.

[0124] Alternatively, it is possible to define different coefficients for different regions of the part thickness map. For example, these regions may correspond to regions of the part having different materials (and therefore average attenuation coefficients), and the coefficients to be applied to the pixels of each region may be determined as before.

[0125] Other methods for determining the coefficient(s) may be implemented, for example machine learning methods. For example, a machine learning model may be trained on a training database comprising pairs of maps, each pair comprising a thickness map of a part and an ultrasonic map of the same part, to determine, from a thickness map, the coefficient(s) to be applied to obtain the “equivalent” ultrasonic map. Such a model may be, for example, a neural network, in particular a GAN (for “generative adversarial network” in English, or “generative adversarial network” in French), but the invention is not limited to this example.

[0126] At the end of step 330, the simulated ultrasonic mapping is “similar” to an ultrasonic mapping, in the sense that the light intensity value of a pixel of the simulated ultrasonic mapping is at least approximately equal to a light intensity value of a pixel corresponding to the same point of the part of the ultrasonic mapping. In other words, the applied transformation makes it possible to transform thickness values ​​into equivalent values ​​of ultrasonic attenuation.

[0127] The transformation applied in step 330 advantageously allows the light intensity values ​​of the ultrasonic mapping and the thickness mapping to be sufficiently comparable, to be able to combine the information from these two maps.

[0128] In the foregoing, step 330 has been described in the case where the transformation is applied to the thickness map of the part. It is noted that alternatively, the transformation may be applied to the ultrasonic map of the part to modify the pixel intensity values ​​of the ultrasonic map to coincide with the pixel intensity values ​​of the thickness map of the part, similarly to what has been described above.

[0129] In step 340, the simulated ultrasound mapping determined in step 330 is subtracted from the ultrasound mapping received in step 220. Alternatively, it is of course possible to subtract the ultrasound mapping from the simulated ultrasound mapping. By "subtraction" is meant a pixel-by-pixel subtraction, which means that each pixel of the subtracted image is associated with a value which corresponds to the difference between the value of the corresponding pixel (i.e. the pixel with the same coordinates) in one of the mappings and the corresponding pixel value in the other mapping.

[0130] The mapping obtained at the end of step 340, also called “detection mapping”, reveals air zone type defects. These zones are in fact associated with higher pixel values. This is due to the fact that in the absence of a defect, the ultrasonic attenuation values ​​are directly correlated to the thickness of the part. On the other hand, if the ultrasonic signal passes through an air zone type defect, it is more attenuated. For the pixels corresponding to this defect, there therefore appears a difference between the values ​​of the ultrasonic mapping (which integrate the defect) and the values ​​of the thickness mapping (which represent values ​​“equivalent” to the attenuation values ​​of the part, without defect).

[0131] The detection map obtained in step 340 has fewer false positives (i.e. false ultrasonic indications) than the processed map obtained in step 230 of the prior art method described with reference to [Fig. 2], because it is much less subject to factors related to the variability of the material. This detection map therefore allows for significantly more reliable detection than the prior art method described above.

[0132] Similar to the method of [Fig. 2], a threshold 260 may be applied to the detection map obtained in step 340. In particular, it is possible to retain only the pixel values ​​above a predetermined threshold. In one or more embodiments, the threshold may be determined as described with reference to [Fig. 2] (step 250). For example, the threshold may correspond to an attenuation percentage equal to -6 dB.

[0133] According to one embodiment, the pixels whose values ​​are above the threshold can be set to a first reference value, for example a gray level equal to 0 (black pixel), and the pixels whose values ​​are below the threshold can be set to a second reference value, for example a gray level equal to 255 (white pixel). The thresholded detection map is then a black and white image in which the defects appear in black and the background in white. Alternatively, the pixels whose values ​​are above the threshold can retain the same value and the pixels whose values ​​are below the threshold can be set to a reference value, for example a gray level equal to 255 (white pixel). The detection map is then an image whose background is white and the defects retain their intensity values ​​calculated in step 260. Other embodiments are possible.

[0134] In a similar manner to the method of [Fig.2], the presence or absence of air zone type defects can be determined in step 270, from the thresholded detection map obtained in step 260. According to one embodiment, zones corresponding to groups of neighboring pixels whose values ​​are all above the predefined threshold used for thresholding 260 are considered as defects. By "neighboring pixels", is meant a set of pixels in which each pixel is connected to at least one other pixel of the set by a connectivity link (for example a 4-connectivity). In certain embodiments, it is possible to define a minimum number Nmin of pixels for each group. According to these embodiments, to be detected as corresponding to a defect, the group of neighboring pixels must comprise at least Nmin neighboring pixels.If there are no groups of neighboring pixels whose values ​​exceed the predefined threshold, there is no defect in the part being tested.

[0135] [Fig.4] represents a flowchart of a method for detecting defects in type air zones according to another embodiment of the invention.

[0136] In this embodiment, the part to be inspected comprises two parts (a first part and a second part) intended to be assembled by gluing. For example, the part inspected may be an engine blade comprising a body and a leading edge, the body being made of a woven composite material and the leading edge being made of metal, for example titanium. The body and the leading edge are manufactured separately and are assembled by gluing to form the engine blade. In such parts comprising parts glued together, there is a risk that the bonding may have defects such as air zones (due for example to a lack or absence of glue or to porous zones), which weaken the part and must be detected. It is understood that this embodiment may extend to a part comprising more than two parts intended to be assembled by gluing (at least one part and another part).

[0137] During a step 220, an ultrasonic map, for example a C-scan map, of the complete and assembled part (i.e. the parts of the part are already glued) is received. This step is similar to step 220 described with reference to [Fig.2] or [Fig.3]. In the example of the engine blade above, during step 220, an ultrasonic map of the assembled blade is therefore received.

[0138] During a step 302, a reference ultrasonic map, for example a C-scan, of a first part of the part is received. By “reference ultrasonic map” it is understood that the ultrasonic map is not necessarily a map of the first part of the part to be checked, but may be an ultrasonic map of a first part of the part of the same type as the first part of the part to be checked.

[0139] In the example of the engine blade, the first part of the part is typically the composite material body. The body is conventionally manufactured from a reference digital model specific to a particular type of blade, which is the same for all the blades which are manufactured according to this particular type of blade. Thus, in step 302, a reference ultrasonic map of a blade body manufactured from the reference digital model associated with the blade which is to be controlled is received. Generally speaking, the first part of the part is a part whose thickness varies relatively little from one part to another (this is the case for parts made of woven composite material).

[0140] It is therefore understood that the same reference ultrasonic mapping of the first part of the part can be determined upstream of the control method of [Fig.4], and that it can be used to control several different parts originating from the same digital model specific to this type of first part of the part (i.e. that this reference mapping can be used for steps 302 of several control methods according to [Fig.4] applied to several parts to be controlled).

[0141] It is noted that the reference ultrasonic mapping of the first part part received in step 302 is an ultrasonic mapping of a first part part (e.g. a reference part) before it is bonded to the second part.

[0142] In step 304, a thickness map of the second part of the part to be checked is received, before it is bonded to the first part. In the example above, this is therefore the thickness map of the titanium leading edge of the part to be checked, before it is bonded to the composite material blade body. woven Indeed, in the engine blade comprising a bonded assembly of a woven composite material body and a titanium leading edge, it is the titanium leading edge which presents the greatest variability in thickness from one part to another. It is therefore from this part that we want to know the exact thickness for the part considered. Generally speaking, the second part of the part is chosen as the one having the greatest variability in thickness from one part to another (and therefore in relation to a reference model according to which the second parts of parts are manufactured).

[0143] It is therefore noted that step 302 concerns a reference ultrasonic mapping, while step 304 concerns a thickness mapping of the second part of the part considered (to be checked).

[0144] The thickness mapping of the second part of the part to be checked is typically obtained by a part thickness measurement technique as described above, with reference to step 310 of [Fig.3].

[0145] In step 325, a re-alignment of the different maps can be carried out. This re-alignment makes it possible to make the pixels corresponding to the same points of the part in the different maps “coincide” (i.e. to put them back to the same coordinates, so that all the maps correspond to the same image of the part).

[0146] An example of such a registration 325 is illustrated in Figures 5a, 5b and 5c. [Fig.5a] represents an ultrasonic map 510 of the assembled part to be checked. The crosses on the ultrasonic map 510 represent “reference” points, used to register the images with each other. In practice, these reference points are placed according to physical elements of the parts considered before assembly, visible on the different maps. On the ultrasonic map 510 of the assembled part to be checked appear the two parts 512 and 514 of the part, that is to say, in the example of the blade, the leading edge and the body, respectively.

[0147] [Fig.5a] also represents the reference ultrasonic mapping 520 of the second part 514 of the part (here, the body of the blade), as well as the reference points (also represented by crosses).

[0148] The reference points of the maps 510 and 520 are matched to determine the transformation making it possible to re-align the reference ultrasonic map 520 of the second part of the part to the portion 514 of the ultrasonic map 510 (the portion 512 is ignored for this step of the re-alignment). In the illustrated case, the transformation is composed of a translation, a rotation and a homothety. Once the transformation has been determined and applied to all the pixels of the reference ultrasonic map 520 of the second part of the part, a transformed reference ultrasonic map 530 of the second part of the part is obtained.

[0149] [Fig.5b] represents the same ultrasonic mapping 510 of the assembled part to be checked as [Fig.5a]. [Fig.5b] also represents the thickness mapping 540 of the first part of the part (here, the leading edge), as well as the reference points (also represented by crosses).

[0150] As previously, the reference points of the maps 510 and 540 are matched to re-align (step 325) the thickness map 540 of the first part of the part with the ultrasonic map 510 of the assembled part to be checked. In addition, a transformation can be applied to the thickness map 540 of the first part of the part (before or after the re-alignment) so that the light intensity levels of the pixels of the thickness map 540 of the first part of the part correspond globally to the light intensity levels of the corresponding pixels (i.e. representing the same point of the part after re-alignment), as detailed previously with reference to step 330 of [Fig. 3].At the end of the registration and the transformation (for example, multiplication of the values ​​of the pixels of the thickness map 540 of the first part of the part by one or more coefficients), a simulated ultrasonic map 550 of the first part of the part is obtained, registered with the ultrasonic map of the complete part 510 (more precisely, with the portion 512 of the map 510).

[0151] [Fig.5c] represents a simulated ultrasonic mapping 560 of the part obtained from the transformed reference ultrasonic mapping 530 of the second part of the part and simulated ultrasonic mapping 550 of the first part of the part. For example, this simulated ultrasonic mapping 560 of the complete part is obtained by summing, pixel by pixel, the maps 530 and 550. It is noted that here, the word “simulated” is used to designate the fact that the mapping 560 simulates an ultrasonic mapping while it is partially derived from thickness data (for the first part of the part, i.e. the titanium leading edge for the previous example).

[0152] At the output of step 330, a simulated ultrasonic map 560 of the part is therefore obtained as represented by element 560 of [Fig.5c].

[0153] Steps 340, 260 and 270 of [Fig. 4] are similar to steps 340, 260 and 270 of [Fig. 3]. Thus, in step 340, a detection map is obtained by subtracting the simulated ultrasonic map determined in step 330 and the ultrasonic map received in step 220 (in one direction or the other). Then, a threshold 260 can be applied to the detection map obtained in step 340, and the presence or absence of air zone type defects can be determined in step 270, from the thresholded detection map obtained in step 260.

[0154] [Fig.6] represents a flowchart of a method for detecting air zone type defects integrating a determination of the threshold to be applied according to modes of realization of the invention.

[0155] During a step 330 (which replaces step 210 of [Fig. 2]), a simulated ultrasonic mapping of the part is obtained. Step 330 can for example be implemented as described previously with reference to [Fig. 3] and 4. During a step 220, an ultrasonic mapping of the part to be inspected is obtained. The simulated ultrasonic mapping of the part can be subtracted (step 340) from the C-scan mapping of the part to be inspected to obtain a detection mapping.

[0156] As described with reference to [Fig.2], in a step 240, a C-scan map of the defective part (the defects being known, as detailed above) is obtained, and used to determine an optimal threshold (step 250) for detecting the defects, as described above. In a step 260, the threshold determined in step 250 may be applied to the processed map obtained in step 340. The defect(s) may then be identified in the thresholded map in a step 270.

[0157] Steps 330, 220 and 240 can be implemented in parallel or in any order (even if in general, steps 330 and 240 on the reference part and the part with defects are implemented before carrying out the actual control of a part, therefore before step 220).

[0158] The method of [Fig.6] is therefore similar to the method of [Fig.2], but instead of using an ultrasonic mapping of a reference part, the method uses a simulated ultrasonic mapping of the part, determined from thickness data of the manufactured part. The thickness variability linked to the manufacturing of the part (and which therefore does not necessarily reflect the presence of a defect) is thus advantageously taken into account, and integrated into the detection method. The detection method obtained is therefore more precise, and generates fewer false positives linked to the manufacturing variability of the part than the prior art method described with reference to [Fig.2],

[0159] [Fig.7] represents an example of a device for detecting air zone type defects according to embodiments of the invention.

[0160] In these embodiments, the device comprises a computer 700, comprising a memory 701 for storing instructions allowing the implementation of the method, the different maps from which the detection method is implemented, and temporary data for carrying out different steps of the detection method described previously.

[0161] The computer 700 further comprises a circuit 702. This circuit may be, for example, a processor capable of interpreting instructions in the form of a computer program, an electronic card whose steps of the method of the invention are described in the silicon, or even a programmable electronic chip such as an FPGA chip (for “Field-Programmable Gate Array” in English).

[0162] The computer 700 comprises an input interface 703 for receiving the ultrasonic maps and / or the thickness maps, and an output interface 704 for providing a detection map or one or more pieces of information relating to defect detections (for example, an indication concerning the absence or presence of defects, and / or, when a defect is detected, an indication relating to a position of the defect). Finally, the computer may comprise, to allow easy interaction with a user, a screen 705 and a keyboard 706. Of course, the keyboard is optional, in particular in the context of a computer having the form of a touch pad, for example.

[0163] Furthermore, the functional diagrams presented in Figures 3 and 4 are typical examples of programs, some of whose instructions can be carried out using the device described. In this respect, [Fig. 3] may correspond to the flowchart of the general algorithm of a computer program within the meaning of the invention.

[0164] Of course, the present invention is not limited to the embodiments described above as examples. It extends to other variants. For example, the method described above is advantageously applicable in cases of ultrasonic inspection of industrial parts having a complex geometry and thickness variations that can generate false indications. Such industrial parts may include glued or welded assemblies for which it is desired to guarantee the quality of the bonding or welding, and in particular to determine whether they have areas of lack of material, porosity, or in which foreign bodies are present. Such industrial parts may also include homogeneous parts subjected to a material health check, during which volume defects such as delaminations or inclusions are sought.

[0165] In order to obtain equivalent control results and reliable detection of possible defects over the entire inspected area, it is currently necessary to correct the attenuation variations linked to the different thicknesses crossed. This correction can be digital, by means of a multiple gain control or physical, by the use of a reference part.

[0166] In these cases, the invention makes it possible to reduce acquisition times by carrying out a single-gain acquisition but also to avoid misleading indications caused by differences between the production parts and the reference part.

Claims

Claims

1. A computer-implemented method for ultrasonic detection of air zone defects in a part to be inspected, the method comprising: - receiving an ultrasonic map of the part to be inspected; - receiving a thickness map of at least one portion of the part to be inspected; - determining, from the thickness map of the at least one portion of the part to be inspected, a simulated ultrasonic map of at least one portion of a part without air zone defects having the same composition and the same thickness map as the at least one portion of the part to be inspected; - determining, from the ultrasonic map of the part to be inspected and the simulated ultrasonic map, a detection map of the part to be inspected;- determine, by applying a predefined threshold to the detection map of the part to be checked, the presence or absence of an air zone type defect in the part to be checked.;

2. The method of claim 1, wherein the thickness map is a thickness map of the entire part, wherein the thickness map of the part to be tested comprises a plurality of pixels, each pixel of the plurality of pixels being associated with a respective value, wherein the simulated ultrasonic map is determined by applying a transformation to the values ​​of the pixels of the thickness map of the part to be tested.

3. A method according to claim 1, wherein the part to be inspected comprises a first part and a second part assembled by gluing, the second part being manufactured according to a predefined digital model, wherein the thickness mapping is a thickness mapping of the first part of the part to be inspected before assembly with the second part of the part to be inspected, wherein the ultrasonic mapping of the part to be inspected is an ultrasonic mapping of the assembled part to be inspected, the method comprising in furthermore: - receiving a reference ultrasonic map of the second part of the part to be inspected, the reference ultrasonic map of the second part of the part to be inspected corresponding to an ultrasonic map of a second reference part manufactured from the predefined digital model and not including an air zone type defect; wherein the simulated ultrasonic map is determined from the thickness map of the first part of the part to be inspected and the reference ultrasonic map of the second part of the part to be inspected.

4. The method of claim 3, wherein the thickness map of the first portion of the part to be inspected comprises a plurality of pixels, each pixel of the plurality of pixels being associated with a respective value, the method further comprising: - applying a transformation to the plurality of pixels of the thickness map of the first portion of the part to be inspected; wherein the simulated ultrasonic map is determined from the reference ultrasonic map of the second portion of the part to be inspected and the transformed thickness map of the first portion of the part to be inspected.

5. Method according to one of the preceding claims, in which the detection map is obtained by subtracting the ultrasonic map of the part to be checked and the simulated ultrasonic map.

6. Method according to one of the preceding claims, in which the part is an aeronautical part.

7. A method according to the preceding claim in combination with one of claims 3 and 4, wherein the part is an engine blade, wherein the first part of the part is a metal leading edge, and wherein the second part of the part is a body of woven composite material.

8. Method according to one of the preceding claims, in which the air zone type defect is a presence of crack, fissure, delamination or detachment.

9. Device for ultrasonic detection of air zone type defects in a part to be inspected, the device comprising: - an input interface configured to: • receive an ultrasonic map of the part to be inspected; • receive a thickness map of at least one portion of the part to be inspected; - a circuit configured to: • determine, from the thickness map of the at least one portion of the part to be inspected, a simulated ultrasonic map of at least one portion of a part without air zone type defects having the same composition and the same thickness map as the at least one portion of the part to be inspected; • determine, from the ultrasonic map of the part to be inspected and the simulated ultrasonic map, a detection map of the part to be inspected;• determine, by applying a predefined threshold to the detection map of the part to be checked, the presence or absence of an air zone type defect in the part to be checked.;

10. Computer program product comprising instructions for implementing the method according to one of claims 1 to 8 when this program is executed by a processor.

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