Abstract:
To test transverse flanges terminating at a cylindrical wall of a workpiece, an installation includes a structure in a form of a U-shaped or C-shaped stirrup whose opposite branches carry respectively an ultrasound emitter transducer and receiver transducer, aligned with respect to one another, while leaving between them an internal space for relative passage of the flange to be tested, and whose base is mounted articulated at an extremity of a mobile control arm. The installation also includes an immersion canister including two parts assembled together by a closure mechanism, one of the parts exhibiting cutouts for engaging the transverse flange and for overlapping, with the other part, the flange up to the cylindrical wall of the workpiece.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an installation for the non destructive ultrasonic immersion testing of parts. 
     2. Description of the Related Art 
     In a preferential application of the invention, the installation is designed for testing tubular parts of turbomachines, such as fan casings of jet engines, it being understood that the invention could also be used for other types of part. 
     This type of part is known to be axisymmetric and to have manufacturing singularities such as regions having transverse end flanges for connecting to adjacent parts, connecting regions having variable inner and outer radii between the flange regions and the cylindrical wall of the tubular part, in which the air stream flows and which forms the principal region thereof, often having changes in thickness, holes, perforations or similar in the flange regions, etc. The casing is, moreover, made of a woven composite material consisting of a monolithic structure with three dimensional weaving of carbon fibers, of carbon fiber preforms and of an injected epoxy resin acting as a binder for the whole. 
     One example of such a tubular part to be tested is shown in  FIG. 1 , illustrating an outer casing  1  of a fan for a jet engine which has a longitudinal axis of symmetry X and is made of a high absorption composite material, which is why it is an ultrasonic transmission testing installation that is preferably chosen for a structural inspection of the material. 
     In particular, the casing  1  is defined by a cylindrical wall  2  (principal region) having variable thicknesses and delimiting the duct for air entering the fan, and by two transverse end flanges  3 ,  4  (flange regions) which terminate the wall  2  and which extend radially outward with respect to thereto. The transverse end flanges project from the cylindrical wall  2  via respective intermediate connecting regions  5  and  6 , each having a small inner radius on the flange side and a large outer radius opposed thereto. Holes  7  are moreover created in the flanges, through which fastening members (not shown) can pass, to permit connection to other parts. 
     In addition, in order to test these composite tubular parts having transverse flanges, the size of which is, moreover, significant (the diameter can reach two meters for a coaxial length of approximately one meter), an ultrasonic immersion testing installation is used, such an installation being particularly well suited to detecting therein, in terms of searched-for defects, delamination or loss of cohesion of the plies of the woven fabric at their interface, microcracking around perforations and machined features, inclusions, foreign bodies, dry areas without resin or areas with excess resin, etc. 
     A prior art testing installation  9 , using the ultrasonic immersion technique, is shown in part and schematically in  FIG. 2  and comprises transducers for emitting and receiving ultrasound. The transducer  10  which emits an ultrasound beam is mounted on a support  11  located at the end of a robotic arm  12  and, in this example, is oriented toward the outer periphery of the casing  1  which defines the tubular part. The transducer  13  which receives the beam, and is aligned coaxially with the emitter transducer  10 , is mounted on a support  14  located at the end of another robotic arm  15  and is then oriented toward the inner periphery of the casing  1 . Thus, between the aligned transducers  10 ,  13 , is the casing  1 , of which the constituting wall, made of composite material, is then tested by a relative movement of the two synchronized robotic transducers with respect to the part  1 . 
     Water jet nozzles  16 ,  17  are of course provided on the arms, coaxially with the transducers, and make it possible to facilitate the appropriate transmission or propagation of the beam of ultrasound waves by a continuous water jet in order to “couple” the transducers to the part, the latter being arranged in a container or a place specially conceived to that effect for recovering the liquid. 
     Although this installation gives good analysis results with respect to the ultrasound technique employed, it nonetheless presents drawbacks linked, in particular, to the geometry—having singularities—of the part. 
     Indeed, while such an installation tests the cylindrical wall effectively, with the transducers acting perfectly perpendicular thereto as in  FIG. 2 , it does not by contrast allow optimum accessibility to the regions having external transverse flanges  3 ,  4  and to the connecting regions  5 ,  6  of the fan casing  1 , in particular the small radius connecting region of each of the flanges, on the side of the outer periphery of the casing. 
     This is due to the fact that the support  11  for the nozzle and for the transducer in question (the emitter in this example) is too bulky, with the result that, after having followed, perpendicular thereto, the outer periphery of the cylindrical wall  2 , it cannot turn sufficiently in order to follow the region of curvature of the connector and the transverse flange in question. As shown by the chain line representation in  FIG. 2 , the support  11  for the nozzle  16  touches the cylindrical wall  2  as soon as the transducer  10 , driven by the arm  12 , starts to pivot in order to follow, perpendicular thereto, the regions in question  3  and  5 , such that the positioning of the two transducers is incorrect and, as a consequence, the profile is not correctly followed and the testing is imperfect. Thus, some of the aforementioned defects might not be identified. 
     This problem does not arise for the support  14  for the nozzle  17  and for the other transducer  13 , which is in no way encumbered by the transverse flange. 
     It should also be noted that synchronizing the two robotic arms, in order to keep the transducers in coaxial arrangement when following the flange regions and curved connectors, makes automating the installation more complex. 
     Furthermore, the testing itself of the tubular casing part, with its singularities, is relatively long since, after testing one transverse end flange, it is then necessary to test the opposite flange with, once again, the aforementioned problems. 
     Moreover, the installation makes it necessary to provide a container of considerable size in order to receive the fan casing and to recover the water sprayed by the nozzles. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention aims to provide a solution to these drawbacks and relates to an installation for ultrasonic immersion testing which, by its design, makes it possible to perfectly test singularities of tubular parts, such as regions having transverse end flanges and the connecting regions having inner and outer radii. 
     To that end, the installation for the ultrasonic immersion testing of a tubular part having a cylindrical wall terminated by transverse end flanges, of the type comprising controllable transducers for emitting and for receiving ultrasounds and which are designed to be arranged such that they are aligned respectively on either side of the flange to be tested, is noteworthy in that it comprises a structure in the form of a U shaped or C shaped stirrup, wherein the opposing branches bear respectively the emitter transducer and the receiver transducer aligned with respect to each other, creating between them a space through which the flange to be tested can pass, and wherein the base is mounted in an articulated manner at the end of a moveable control arm. 
     Thus, by virtue of the invention, accessibility to the flanges and to the connecting regions of the part is total, this being made possible by means of one and the same stirrup shaped (or clevis shaped) structure bearing the transducers in place of the two independent supports initially provided in the earlier installation. This structure makes it possible to reduce the size by virtue of the inherent U shape or C shape of the stirrup, to introduce the flange into the stirrup between the transducers attached to the branches thereof by following the profile in a suitable manner, and to access the radiused connecting regions by pivoting the structure while still keeping the transducers aligned perpendicular to the encountered profile of the curved connecting region of the casing. The testing of the material of the part and of its singularities is then optimal, without any contact between the part and the stirrup. 
     The entire periphery of the transverse flange, between which the branches of the stirrup engage in parallel, can be tested by virtue of a relative movement between the structure and the part, and the movement of the structure makes it possible to follow and test the radiused connecting regions as far as the principal transition region. 
     Moreover, a single robotic arm is then used in order to test the transverse flange in place of the two robotic arms of the earlier installation. 
     Finally, the simplicity of creating the structure in the form of a simple U shaped stirrup should be noted. Such a structure thus makes it possible to follow the profile of each transverse flange and of the associated radiused regions. 
     Advantageously, the emitter and receiver transducers are positioned at the ends of the opposing branches of the stirrup shaped structure, making it possible to optimize the depth and thus the internal space of the stirrup in order to receive the flange or other similar large singularity, and to move the stirrup without touching the flange. 
     Moreover, the emitter and receiver transducers are mounted such that they can be adjusted with respect to the respective opposing branches, making it possible to adapt their separation and focusing depending on the thickness of the flange to be tested. 
     According to another feature of the installation, the stirrup shaped structure bearing the transducers is arranged in an immersion container (or tub) which contains a liquid for coupling the transducers to one another and which is arranged over the flange to be tested. Thus, only partial immersion of the regions of the part that are to be tested, around the transducers, is required for the inspection and to ensure the coupling of the ultrasound waves between the transducers, without the need for an oversized tank big enough to hold the casing (the diameter of which can reach two meters) or a dedicated space therefor. 
     For example, the immersion container straddles the flange with sealing as far as the cylindrical wall and can be moved relative to the part in order to permit a full test of the periphery of the flange. 
     The immersion container is preferably immobile with respect to the tubular part which can be rotated about its longitudinal axis of symmetry, said immersion container having rolling members designed to engage with the transverse outer face of the flange, making it easier to rotate the part with respect to the container. 
     The immersion container can, in particular, comprise two portions which are joined together using a closing means, one of the portions having cutouts for engaging the transverse flange and for straddling, with the other portion, said flange as far as the cylindrical wall of the part, seals being provided between the joined together portions and the part. 
     In order to rotate the part with respect to the immobile immersion container, a controllable rotating plate can rotate the tubular part. 
     Advantageously, two structures in the form of stirrups having emitter transducers and receiver transducers and respective controllable arms are provided so as to be able to test, simultaneously, the two transverse end flanges of the tubular part. The two robotic arms of the earlier installation can thus be used simultaneously for testing the two end flanges and the connecting regions of the casing, thus reducing testing times. The two arms are also used to test the cylindrical wall or principal region of the casing in the same way as in the preceding installation. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The realization of the invention will be readily understood with reference to the figures of the appended drawing. 
         FIG. 1  shows, in perspective, an exemplary embodiment of an axisymmetric part to be tested by the installation according to the invention. 
         FIG. 2  shows, schematically and in part, an ultrasonic testing installation according to the prior art. 
         FIG. 3  shows, schematically, an exemplary embodiment of the ultrasonic testing installation according to the invention, intended for testing the flange and connector singularities of said part. 
         FIG. 4  shows, as a partial perspective, the stirrup shaped structure and the associated transducers of the installation of  FIG. 3 , ready to test the flange in question of the part. 
         FIG. 5  shows, in perspective, an exemplary embodiment of the immersion container of the installation which provides for immersion of only that region of the part which is being considered by the transducers. 
         FIG. 6  shows the immersion container of the installation, mounted so as to be immobile on the part to be tested which is moveable. 
         FIGS. 7 and 8  show, schematically, phases of the operation of the stirrup shaped structure of the installation for inspecting the flange in question of said part. 
         FIG. 9  shows, schematically, two stirrup shaped structures of the installation for respectively inspecting, simultaneously, the two transverse end flanges of the axisymmetric part. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The axisymmetric part to be tested which is shown in  FIG. 1  is, as stated previously, an outer casing  1  of a fan for a jet engine which has a longitudinal axis of symmetry X and is made of a high absorption composite material. An ultrasonic transmission testing installation is, because of this high absorption, to be chosen for a structural inspection, although such an installation would also be suitable for a metal. This casing will not be described in any more detail and the same reference numbers are assigned thereto. 
     The casing  1 , having all of these flanges  3 ,  4 , connecting regions  5 ,  6 , changes in thickness of its cylindrical wall  2 , holes  7  and other singularities, is thus to be tested, in particular the composite material of which it consists. 
     The testing installation  20  according to the invention and as shown in  FIG. 3  is of the partial immersion ultrasonic type and is designed, more particularly, to inspect the transverse end flanges  3 ,  4  and the connecting regions  5 ,  6  which connect these with the principal region or cylindrical wall  2  of the casing  1 . To that end, the installation comprises, principally, two ultrasound transducers, respectively one emitter transducer  21  and one receiver transducer  22  and, advantageously, a common support structure  23  in the form of a stirrup  24  bearing the two transducers  21 ,  22  and articulated at the end of a moveable control arm  25 , for example a robotic arm such as those shown in the embodiment of  FIG. 2 . 
     More particularly, as shown in  FIGS. 3 and 4 , the stirrup  24  shaped structure  23  is in the shape of a U (or a C or similar) having two opposing lateral branches  26  and  27  (these being parallel in the case of a U shape) and a base (or end)  28  from which the branches project and which is connected, at the other end from the branches, to the moveable arm  25  by means of an articulation (either cylindrical or spherical)  29 . The emitter transducer  21  is attached to one branch  26 , by means of a screwed-connection member (a bolt or other means)  30  and, conversely, the receiver transducer  22  is attached to the other branch  27 , also by means of a screwed-connection member  31 . The attachments are such that the transducers  21 ,  22 , once in place, are aligned with respect to one another along one and the same axis Y, which is perpendicular to the branches, for optimum measurement. The transducers  21 ,  22  are furthermore located close to the free ends  26 ′,  27 ′ of the branches  26 ,  27  such as to create a maximum inner space  32  in the stirrup  24 , between the transducers  21 ,  22  and the base  28  of the stirrup, so as to engage in its entirety the transverse flange to be tested. The separation between the two transducers is also defined beforehand depending, in particular, on the thickness of the flanges, in order to achieve high quality testing (focusing of the transducers). 
       FIG. 3  shows, in part, the moveable robotic arm  25  of the installation  20  which permits usual translations and rotations within a three dimensional frame of reference in order to present to the best possible effect the stirrup  24  with its transducers with respect to the singularities to be tested, such as the flange  3  and the connecting region  5  in this example. In this figure, a rectangle  33  represents the control panel for entering and programming the various movements of the arm  25  and of the structure  23 , in order to follow to the best possible extent the profile of the transverse flange and of the associated connecting region, as well as the operation and settings of the transducers  21 ,  22  connected by connections  35  to this panel  33 . Other installation controls can also be found on this panel, as will be explained later. 
     Moreover, by virtue of the fact that a single support structure  23  in the form of a stirrup  24  bears both the emitter transducer  21  and the receiver transducer  22 , it is necessary for the testing installation  20  to immerse the region to be tested (flange and connector) only around the stirrup  24  which bears the transducers, in order to facilitate the propagation of the ultrasound waves. 
     To that end, as is shown in  FIGS. 3, 5 and 6 , an immersion container (or tub)  36  (in chain line in  FIG. 3 ) is positioned on the flange in question  3  of the casing  1 , straddling this flange, so as to partially immerse, using an appropriate liquid L (water) contained therein, the stirrup  24  shaped structure  23  with its transducers. This container  36  is obtained from a sheet or plate which has been cut and folded as required and has, in the embodiment shown, a roughly parallelepipedal shape which is open on the top side but could have a completely different shape as long as the stirrup  24  shaped structure  23  is housed therein, at the level of the transducers. 
     In particular, the container  36  consists of two main portions  37  and  38 , of which one  37  is located on the inner side of the cylindrical wall  2  of the casing  1 , and the other  38  on the outer side. These two portions  37 ,  38  are joined together so as to prolong one another by a closing means  40  so as to fit together around the flange  3  and the connecting region  5  as far as the cylindrical wall  2 . In order to permit this, the outer portion  38  has cutouts  41  which are created in the edge  42  of its respective lateral flanks  43  and which are complementary in shape to the transverse flange  3 , such that the latter can engage and fit in the cutouts. 
     In order to ensure sealing between the container  36  and the casing  1 , and to ensure that no liquid leaks from the former, seals  44 , for example made of foam, are applied to the edge  42  of the outer portion  38  and to the corresponding edge  45  of the lateral flanks  46  of the inner portion  37  of the container  36 . Thus, once the flange  3  has been engaged in the cutouts  41  and the portions of the container have been brought together using the closing means  40 , which in this example is of the type having levers  47 , the seals  44  press on either side of the cylindrical wall  2  and provide the desired sealing. 
     Furthermore, the immersion container  36  also rests against the end face  3 ′ of the transverse flange  3  via rolling members  48  such as rollers or casters which are mounted respectively on the longitudinal flanks  43  of the outer portion  38 . Moreover, although not shown, rolling members are provided on the inner portion  37  of the container in order to engage with the inner face of the cylindrical wall  2  of the casing. 
     By virtue of its axisymmetric shape, the casing  1  of the installation  20  shown with reference to  FIG. 3  is mounted such that it can move whereas the immersion container  36  is immobile, wherein the rollers  48  roll on the face  3 ′ of the flange while the casing  1  rotates. To that end, the casing is placed on a horizontal rotating plate, represented schematically with the label  50  in  FIG. 3  and resting on a support or on the ground S, such that the longitudinal axis of symmetry X is vertical. The transverse flange  4  rests on the rotating plate  50  whereas the opposing transverse flange  3  receives the container  36 . The foam seals  44  do not damage the casing, and neither do the rollers—made of rubber or similar—which further hold the container  36  in place on the flanged end of the casing  1  as the casing rotates in order to bring a new sector of the flange to be inspected within the scope of the transducers. 
     Testing per se of the transverse flange and the associated connecting region by the ultrasonic and partial immersion technique, in order to identify the aforementioned defects therein, is carried out in a conventional manner and will not be discussed in more detail here. Only the operation is described with reference to  FIGS. 3, 7 and 8 . 
     Thus, once in particular the container  36  has been placed on the casing  1  and has been filled with water, and the separation of the transducers has been adjusted by the members  30 ,  31 , robotic arm  25  which is programmed for this purpose introduces the structure  23  into the container, such that the stirrup  24  faces the flange  3  as shown in  FIG. 3 . A preprogrammed horizontal movement (radial with respect to the axis X of the casing) of the arm  25  causes the two transducers  21 ,  22  to pass respectively either side of the flange  3  which is immersed in the liquid L, with the axis Y of these transducers perpendicular to the flange, which engages progressively, between them, into the internal space  32  of the stirrup. 
     The flange  3 , the profile of which is flat, is thus tested, and when the stirrup arrives at the connecting region  5 , the robotic arm  25 , which is articulated to the structure  23 , causes the stirrup to pivot progressively in order to follow the profile encountered, as shown in  FIG. 7 . The space  32  is such that it allows the flange to engage without touching the stirrup. The stirrup  24  continues to pivot in this way until the transducers  21  and  22  reach the cylindrical wall  2 , the axis Y still being perpendicular to the wall encountered for optimum testing, as shown in  FIG. 8 . The U shape of the stirrup thus makes it possible to follow the profile of the flange  3  and the connecting region  5  as far as the wall  2 , the internal space  32  of the stirrup serving to receive the flange and the connector without touching them. 
     Once this sector of the flange has been tested in order to identify any aforementioned defects therein, the stirrup  24  shaped structure  23  is withdrawn from the flange  3  by a reverse movement of the arm  25  and, via the rotating plate  50  connected by the connection  51  to the control panel  33  and driving the casing  1  in rotation, a subsequent sector of the flange  3  is brought into the immobile immersion container for analysis. 
     In this case testing of the flange proceeds stepwise, but it is also conceivable to conduct continuous testing of the flange, without stopping the rotating plate. 
     As shown highly schematically in  FIG. 9 , testing of both transverse end flanges—respectively the upper flange  3  and the lower flange  4 —of the casing  1  can be conducted concomitantly using two robotic arms  25  and  25 ′ such as those  12 ,  15  of the preceding installation  9 . The latter is used before or after testing of the flanges for testing the cylindrical wall  2  using the supports  11 ,  14  of the transducers  10 ,  13 . The two stirrup  24 ,  24 ′ support structures  23 ,  23 ′ having the transducers are mounted at the end of the respective arms and each of these is housed in the immersion container provided on each flange (and not represented in this figure). Of course, the lower flange does not rest on the rotating plate and the casing is driven in rotation by another means. Thus, using one and the same installation, the entire profile of the casing  1  and thus the composite material is tested perfectly, simply by changing the transducer support structures at the ends of the robotic arms. 
     The advantages of the solution having a support structure in the form of a stirrup bearing both transducers and the associated immersion container are in particular: being able to approach and access the flange regions and connecting regions of the casing without difficulty by virtue of the stirrup shape; ensuring effective and lower cost coupling (a simple folded and cutout container); using one or both of the robotic arms of the initial installation in order to test the flanges either successively or simultaneously; avoiding testing with the flanged casing being entirely immersed; easily following the profile of the flanges by the tolerance left by the stirrup; mounting the stirrup shaped structure onto the arms and removing it therefrom simply and quickly, and doing the same for the container on the casing without damaging the latter; and testing the flanges and connecting regions quickly and reliably, thus improving the quality of the ultrasonic testing.