System for automated ultrasonic inspection

Abstract

The invention relates to an ultrasonic inspection system (600) designed for the automated non-destructive testing of large composite structures, particularly in the aerospace industry. Traditional ultrasonic inspection requires precise probe positioning, which can be affected by discrepancies between the CAD model used for programming and the actual part. The proposed system includes a probe holder moved by an end effector (650), ensuring constant alignment of the ultrasonic probe (150) despite these discrepancies. The probe holder incorporates a dual compliance mechanism: an upper system allowing limited translational movement with elastic return to maintain alignment, and a lower system providing angular adjustments via two intersecting axes of rotation. Rolling elements ensure a constant distance and orientation between the ultrasonic probe and the surface to be inspected.Adapted to complex geometries, this system allows reliable automated ultrasonic control, compensating for positioning variations, thus improving the accuracy and repeatability of defect detection Figure 6.

Description

Title of the invention: System for automated ultrasonic inspection Technical field

[0001] The invention belongs to the field of non-destructive testing.

[0002] More particularly, but not exclusively, the invention belongs to the field of ultrasonic testing of complex composite parts of large dimensions, particularly in the aeronautical field, such as stiffened panels or spars. Prior art

[0003] Non-destructive testing of a composite material structure can be carried out by ultrasound. This technique makes it possible, in particular, to detect and quantify defects that are not visible from the surface of the part.

[0004] For example, the detectable and quantifiable defects in terms of extent are delaminations, the presence of porosities, resin shortages or drying or fiber breaks, including in thick parts.

[0005] The automation of this control, where an ultrasonic probe is moved by a robotic device, makes it possible, by knowing the precise position of the probe relative to the part, to obtain a map of the material health, after computer processing of the information received from the ultrasonic probe and thus, in particular, to precisely locate these defects.

[0006] The ultrasonic probe, remote from the inspected part, comprises at least one emitter, most often in the form of a piezoelectric element which, in an emitter configuration, is capable of generating a mechanical stress in a frequency range of the order of one megahertz (106 s'1) acting on an external surface of the part, thus generating a wave which propagates in the part.

[0007] Each defect encountered in the structure of the part generates reflections and diffusions of this wave. Thus, by capturing the signal modified by its propagation in the part, either by means of another piezoelectric element or the same piezoelectric element but configured as a sensor, it is possible, knowing the modes of propagation, reflection and diffusion of the ultrasonic waves in the material constituting the part subject to inspection, to draw up a map of the heterogeneities and more particularly of the defects present in the part in importance, extent and location.

[0008] Ultrasonic testing techniques are known to those skilled in the art and are particularly described in their principles with regard to composite materials. for example in the document “Ultrasonic C-Scan inspection of composite materials” A. Fahr et al. Engineering Journal of Qatar University, Vol. 5 1992, pp 201-222.

[0009] In order for the acoustic pressure source generated by the piezoelectric element acting as a transmitter to be transmitted into the inspected material and not simply reflected by the surface of the part, a coupling means between the transmitter and the surface of the part is necessary. The same applies to the element used as a sensor. This coupling achieves, as it were, an acoustic impedance matching between the face of the piezoelectric element and the surface of the part.

[0010] Thus, a coupling layer is interposed between a piezoelectric element, acting as an emitter or sensor, and a surface of the part being inspected. According to the prior art, this coupling layer is generally in the form of a liquid or gel.

[0011] According to examples of implementation, the acoustic coupling layer is produced by immersing the part, by a jet of water between the part and the sensor, by a gel either deposited directly on the part or included in a shoe attached to the piezoelectric element optionally comprising a film of water between the part and the piezoelectric element or its shoe, without these examples being limiting.

[0012] Whatever the coupling technology, the realization of reliable measurements requires that the distance between the piezoelectric element and the surface of the part, that is to say the thickness of the coupling layer, be kept within a relatively tight tolerance, of the order of ± 0.5 mm, as well as the orientation of the probe relative to the surface of the part, which in general must be contained within a range of ± 2°, to ensure the orthogonality of the ultrasonic beam relative to the surface to be inspected.

[0013] For automated control where the probe is moved by robotic means relative to the part, the programming of the trajectories imposed by the robot on the probe is carried out from a CAD file of the part.

[0014] However, the actual part, while dimensionally correct, may deviate significantly from the shapes defined in the CAD file.

[0015] Furthermore, the positioning of the actual part in the robot space does not correspond perfectly to the positioning considered when programming the trajectories.

[0016] More particularly, on a part of complex shape and large dimensions, these deviations, although small, are sufficient so that locally the position of the probe relative to the part and as programmed, deviates significantly from the positioning and orientation tolerances recommended to ensure control under good conditions. Summary of the invention

[0017] The invention aims to resolve the drawbacks of the prior art and to this end relates to an ultrasonic control system, comprising:

[0018] a swimming pool;

[0019] a part comprising at least one surface to be inspected;

[0020] an ultrasonic probe adapted to the at least one surface to be inspected;

[0021] a probe holder configured to carry the ultrasonic probe

[0022] an effector comprising movement means and a control bay configured to move the probe holder at least partially submerged in the pool, along programmed positions;

[0023] the probe holder comprising a lower portion and an upper portion, the lower portion being configured to carry the ultrasonic probe and the upper portion comprising a gripping interface configured for connection of the probe holder, in a complete connection, to the effector, wherein:

[0024] the upper part is connected to the gripping interface by an upper compliance device configured to allow limited movement with elastic return of the upper part relative to the connection interface along at least one translation axis;

[0025] the lower part is linked to the upper part by a lower compliance device configured to allow angular movements of the lower part relative to the upper part along at least two intersecting axes of rotation;

[0026] the lower part comprises at least two rolling elements of diameters di and d2, a positioning of the ultrasonic probe relative to the at least two rolling elements being fixed, the at least two rolling elements being configured to come into contact with the part to be inspected to define a distance and an orientation of the ultrasonic probe relative to the at least one surface to be inspected;

[0027] wherein at least one of the intersecting axes of rotation is distant from an axis of rotation of the at least two rolling elements by a distance less than or equal to a diameter of the at least two rolling elements.

[0028] Thus the probe holder makes it possible to keep the probe in a configuration of distance and orientation with respect to the surface of the part suitable for carrying out the inspection in good conditions even in the event of a difference between the programmed positions of the effector and the actual position of the surface.

[0029] More particularly, the distribution of the translational and rotational compliances between the upper part and the lower part, as well as the positioning as close as possible to the surface of the part to be controlled of at least one rotational compliance, makes it possible to ensure that a constant distance is maintained between the ultrasonic probe and the surface to be inspected independently of the deviations between the programmed points and trajectories and the actual position of the part to be inspected in the space of the effector.

[0030] The invention can be implemented according to the embodiments and variants set out below, which are to be considered individually or according to any technically effective combination.

[0031] The at least two rolling elements a pair of rollers guided in rotation along parallel axes

[0032] The at least two rolling elements may comprise a roller and a ball.

[0033] The at least two rolling elements may comprise two rollers guided in rotation along intersecting axes.

[0034] The at least one surface to be inspected may comprise a connection extending on a concave side between two intersecting surfaces, and the two rollers guided in rotation along intersecting axes are configured to bear on the intersecting surfaces on the concave side.

[0035] According to a variant, the at least one surface to be inspected may comprise a connection extending on a convex side between two intersecting surfaces of the part to be inspected, the two rollers are guided in rotation along intersecting axes configured to bear on the intersecting surfaces on the convex side.

[0036] The upper compliance device may comprise at least one compliance indicator configured to display a position in the limited travel along the at least one translation axis. Brief description of the drawings

[0037] Non-limiting embodiments are shown [Fig.l] to [Fig.6] in which: Fig.l

[0038] [Fig.l] shows in a perspective view a first example of embodiment of a probe holder Fig.2

[0039] [Fig.2] shows in perspective view a second example of embodiment of a probe holder; Fig.3

[0040] [Fig.3] shows in a perspective view an example of an embodiment of a third lower part of a probe holder; Fig.4

[0041] [Fig.4] shows in a profile view an example of the embodiment of a fourth lower part of a probe holder; Fig.5

[0042] [Fig.5] shows, in profile views, examples of checks carried out with a first lower part of the probe holder as shown [Fig.1], a third lower part of the probe holder as shown [Fig.3] and a fourth lower part of the probe holder as shown [Fig.4]; Fig.6

[0043] [Fig.6] shows in a schematic perspective view an example of an embodiment of an ultrasonic control system. Description of the embodiments

[0044] [Fig.6], according to an exemplary embodiment the ultrasonic control system (600) comprises a pool (610) in which a part to be controlled (190) is immersed.

[0045] An ultrasonic probe (150) is immersed and held in a probe holder (100) comprising compliances according to several degrees of freedom.

[0046] The probe holder (100) is carried by a manipulator (650) controlled by a control bay (690) to move the ultrasonic probe (150) along the part (190) according to discrete programmed positions or according to a trajectory.

[0047] These programmed positions are defined from a digital model, such as a CAD file of the part to be checked. They can also be defined by learning during the inspection of a first part to be checked.

[0048] When inspecting a batch of parts to be inspected, the manufacturing tolerances of the batch as well as the variations in initial positioning mean that the programmed positions may be slightly offset from the surface to be inspected so that the ultrasonic inspection cannot be carried out under optimal conditions, or even cannot be carried out at all or lead to erroneous or at least unreliable results.

[0049] The ultrasonic control system (600) makes it possible to program theoretical positions in 1 space from the digital model and the physics of the probe can be adjusted with a slight offset thanks to the probe holder so as to absorb the positioning variations. The mounting of the ultrasonic probe (150) in a compliant device makes it possible to absorb these variations.

[0050] [Fig.l] according to an exemplary embodiment of the probe holder (100) adapted to the control of a stiffener, the latter comprises an upper part (101) and a lower part (102).

[0051] The upper part (101) comprises a gripping interface (110) adapted for gripping the probe holder by an effector, for example an anthropomorphic robot, a gantry or a parallel structure manipulator.

[0052] This gripping interface (110) is configured to provide a complete connection of the probe holder with the effector, for example by means of a clamp.

[0053] The lower part (102) carries an ultrasonic probe (150) adapted, in this example, to carry out an ultrasonic inspection on a face of a stiffener (191) extending substantially perpendicular to a skin (192), during a movement (195) of the probe holder relative to the part(s) to be inspected (191, 192).

[0054] This movement is carried out by a programmed trajectory imposed on the probe holder by the effector, while the part to be inspected as well as at least the lower part (102) of the probe holder are immersed in a pool (610), the water of which serves as a coupling agent between the inspected surface and the ultrasonic probe.

[0055] The ultrasonic probe is connected to the lower part (102) of the probe holder by a mechanism providing rotational compliances along at least two intersecting axes, which, according to this exemplary embodiment, comprise a first axis (121) substantially parallel to a face of the stiffener (191) and perpendicular to the skin (191), and a second axis (122) substantially parallel to the face of the stiffener (191) and parallel to the skin (191).

[0056] The skin (192) is here shown to be flat but may have one or two relatively high radii curvatures as in the case of a fuselage or wing panel of an aircraft.

[0057] The lower part also comprises a pair of rollers (125) of diameter di capable of rolling on the skin (192) during the control and thus ensuring the positioning relative to this skin of the ultrasound probe (150).

[0058] Only one roller of the pair of rollers (125) is visible [Fig. 1] on the front face of the lower part in the direction of movement (195), the second roller being located on the rear face symmetrical to the front face.

[0059] According to one embodiment (not shown), the lower part could comprise a pair of additional rollers bearing on the face of the stiffener (191) to be controlled, in this case the pair of rollers (125) can be replaced by two pairs of balls capable of rolling on the surface of the skin.

[0060] These rolling elements, rollers and / or balls, define a position of the ultrasonic probe (150) in the lower part of the probe holder, and being in contact with at least one surface of the part to be inspected, ensure precise positioning of the ultrasonic probe relative to a surface to be inspected both in distance and in relative orientations.

[0061] At least one of the axes of rotation (121, 122, here 122) of the lower compliance is located as close as possible to the guide surfaces of the ultrasonic probe, i.e. the surfaces with which the rolling elements are in contact. Thus, at least the second axis (122) is distant from the axis of a roller or the center of a ball by a distance d equal to or less than di where di is the diameter of the rolling element.

[0062] This arrangement avoids any interference between the probe or the probe holder when the compliance devices cause the probe to rotate relative to the surface to be inspected.

[0063] The upper part (101) of the probe holder comprises an elastic compliance device connecting the lower part (102) of the probe holder to the gripping interface (110). The compliance device comprises, according to this exemplary embodiment, a first pair of helical springs (116) acting in a first translation direction (111) and a second pair of helical springs (115) acting in a second translation direction (112) perpendicular to the first translation direction.

[0064] This upper compliance device allows limited movement in translation and along at least one axis (111, 112). In the case of [Fig.l], the compliance device acts along two directions (111, 112) of translation.

[0065] [Fig.2] according to another exemplary embodiment suitable for controlling a flat panel or curved, the probe holder (200) comprises a gripping interface (110) in its upper part (201), an ultrasonic probe (250) for controlling a surface of the panel in its lower part (202), lower part which comprises two rolling elements in the form of rollers (225) capable of rolling on the surface to be inspected of the panel and whose diameter (dj is adapted to a curvature of the panel, the probe being positioned relative to the rollers so as to satisfy a relative distance between the ultrasonic probe and the surface to be inspected.

[0066] The upper portion (201) comprises an upper compliance device comprising a helical spring (216) acting in a translation direction (212).

[0067] The lower part (202) comprises a lower compliance device along two intersecting axes of rotation (221, 222), located as close as possible to the surface to be inspected. These axes of rotation (221, 222) are, according to this exemplary embodiment, oriented in perpendicular directions, themselves perpendicular to the translation direction (212) of the upper compliance device.

[0068] The lower compliance device comprises two pivot links along each of the two rotational compliance axes (221, 222) of the lower part (202) and four helical springs (215), configured to exert an elastic return on the ultrasound probe when the latter pivots along these two rotational axes (221, 222).

[0069] In the two embodiments [Fig.l] and [Fig.2] the angular movements around the rotational compliance axes (121, 122, 221, 222) are of the order of ± 10°.

[0070] When inspecting a part, the lower part (102, 202) of the probe holder is immersed and is therefore not visible.

[0071] Advantageously, the upper part comprises one or more compliance indicators (141, 142, 241, 242). These compliance indicators make it possible to visualize the position of the compliance devices according to the different compliance directions of the upper part and thus to visually check, during the execution of a trajectory corresponding to a movement program of an ultrasonic inspection, that these relative movements of the probe holder with respect to the gripping interface remain within the limits of the movements authorized by these compliances and, consequently, that the ultrasonic probe remains in good contact with the surfaces of the part being inspected.

[0072] These compliance indicators make it possible, in particular, in a development phase to develop the offset of the programmed positions so as to compensate for the differences between the parts to be checked in a batch.

[0073] [Fig.3] shows an example of embodiment of a third lower part (302) of a probe holder, adapted to an upper part (101) as shown [Fig.l].

[0074] [Fig.5], this example of third lower part (302) is, for example, intended to control a connection fillet (391) on the concave side of a part to be controlled (390) comprising two intersecting surfaces.

[0075] To this end, this example of a third lower part (302) of the probe holder comprises an ultrasonic probe (350) adapted to this type of surface to be inspected, a first pair of rollers (325) with a diameter diparallel to each other, and a second pair of rollers (326) with a diameter d2 also parallel to each other. The axes of rotation of the first pair of rollers and of the second pair of rollers are intersecting, forming an angle between them (here 90°) adapted to the guide surfaces, that is to say the intersecting surfaces on either side of the fillet (391) on the concave side.

[0076] The lower compliance device of this example of a third lower part (302) comprises compliances rotating along three axes (321, 322, 323) perpendicular to each other. These compliances are configured so that these three axes of compliance in rotation are as close as possible to the surfaces of the part to be controlled (390) on which the pairs of rollers (325, 326) roll.

[0077] Thus a second axis (322) is located at a distance equal to or less than di from the axes of rotation of the rollers of the first pair of rollers (325). The two other compliance axes (321, 323) are each located at a distance equal to or less than d2 from the axes of rotation of the rollers of the second pair of rollers (325), preferably, the second axis (322) passes through the center (392) of the connection fillet.

[0078] The position of the ultrasonic probe (350) relative to the rollers can be adjustable, the latter being, for example, maintained relative to the probe holder by a clamping device through an oblong hole (390) oriented towards an intersection between the axes of rotation of the rollers.

[0079] [Fig.4] shows an exemplary embodiment of a fourth lower part (402) of a probe holder adapted to an upper part (101) as shown [Fig. 1].

[0080] [Fig.5], this example of a fourth lower part (402) is, for example, intended to control a connection radius (491) on the convex side of a part to be controlled (490) comprising two intersecting surfaces.

[0081] To this end, this example of a fourth lower part (402) of the probe holder comprises a first pair of rollers (425) with a diameter diparallel to each other, and a second pair of rollers (426) with a diameter d2 also parallel to each other.

[0082] The axes of rotation of the first pair of rollers and of the second pair of rollers are intersecting, forming between them an angle (here 90°) adapted to the guide surfaces, that is to say the intersecting surfaces on either side of the connecting radius (491) on the convex side of the intersecting surfaces.

[0083] The compliances of the fourth lower part (402) are configured so that the three rotational compliance axes are as close as possible to the surfaces of the part to be controlled (490) on which the pairs of rollers (425, 426) roll.

[0084] Thus a third axis of rotational compliance (423) is located at a distance equal to or less than di from the axes of rotation of the rollers of the first pair of rollers (425), and a second axis of rotational compliance (422) is located at a distance equal to or less than d2 from the axes of rotation of the rollers of the first pair of rollers (426).

[0085] The position of the ultrasonic probe relative to the rollers can be adjustable, it being, for example, held relative to the probe holder by a clamping device through an oblong hole (390) oriented towards an intersection between the axes of rotation of the rollers.

[0086] The exemplary embodiments show that the ultrasonic control system makes it possible to compensate for dimensional and positioning differences between a batch of parts and a CAD model used for programming positions along surfaces to be inspected.

[0087] The probe holder of the control system ensures constant alignment of the ultrasonic probe by a double compliance mechanism: an upper system allowing limited translational movement with an elastic return to maintain alignment, and a lower system offering angular adjustments thanks to two intersecting rotation axes. Rolling elements ensure a constant distance and orientation between the ultrasonic probe, in particular the orthogonality of the ultrasonic beam relative to the surface to be inspected.

[0088] Suitable for complex geometries, this system guarantees automated and reliable ultrasonic control by compensating for positioning variations, thus improving the accuracy and repeatability of defect detection.

Claims

1. Claims An ultrasonic monitoring system (600), comprising: a pool (610); a part to be checked (190, 390, 490) comprising at least one surface to be inspected; an ultrasonic probe (150, 250, 350) adapted to the at least one surface to be inspected; a probe holder (100, 200) configured to carry the ultrasonic probe, an effector (650), and a control bay (690) configured to move the probe holder (100, 200) at least partially submerged in the pool, along programmed positions; the probe holder (100, 200) comprising a lower portion (102, 202, 302, 402) and an upper portion (101, 201), the lower portion being configured to carry the ultrasound probe (150, 250, 350, 450) and the upper portion comprising a gripping interface (110) configured to connect the probe holder, in a complete connection, to the effector (650), wherein: the upper part (101, 201) is linked to the gripping interface (110) by an upper compliance device configured to allow limited movement with elastic return of the upper part relative to the gripping interface along at least one translation axis (111, 112, 212); the lower part (102, 202, 302, 402) is linked to the upper part (101, 201) by a lower compliance device configured to allow angular movements of the lower part relative to the upper part along at least two intersecting axes of rotation (121, 122, 221, 222, 321, 322, 323); the lower part comprises at least two rolling elements (125, 225, 325, 326, 425, 426), a positioning of the ultrasonic probe being fixed relative to the at least two rolling elements, the at least two rolling elements being configured to come into contact with the part to be inspected to define a distance and an orientation of the ultrasonic probe relative to the at least one surface to be inspected; characterized in that at least one of the intersecting axes of rotation is distant from an axis of rotation of the at least two rolling elements by a distance (d) less than or equal to a diameter (dl, d2) of the at least two rolling elements.

2. An ultrasonic testing system according to claim 1, wherein the at least two rolling elements comprise a pair of rollers (125, 225) guided in rotation about two parallel axes.

3. An ultrasonic testing system according to claim 1, wherein the at least two rolling elements comprise a roller and a ball.

4. An ultrasonic testing system according to claim 1, wherein the at least two rolling elements comprise two rollers (325, 326, 425, 426) guided in rotation about intersecting axes.

5. Ultrasonic testing system according to claim 4, wherein the at least one surface to be inspected comprises a connection (391) extending on a concave side between two intersecting surfaces of the part to be tested, and wherein the two rollers guided in rotation along intersecting axes are configured to bear on the intersecting surfaces on the concave side.

6. Ultrasonic testing system according to claim 4, wherein the at least one surface to be inspected comprises a connection (491) extending on a convex side between two intersecting surfaces of the part to be tested, and wherein the two rollers guided in rotation along intersecting axes are configured to bear on the intersecting surfaces on the convex side.

7. An ultrasonic testing system according to claim 1, wherein the upper compliance device comprises at least one compliance indicator (141, 142, 241, 242) configured to display a position in the limited travel along the at least one translation axis.