Abstract:
A device and a method for ultrasonic testing by means of a local immersion technique of a stringer component section of a flat component are provided. The device includes a test head assembly mounted as moving floatingly by a holding device in the Y-direction longitudinally. The test head assembly includes: a test head that can be connected to an automatically actuated handling device and that can be moved by the handling device along the stringer; a test head holder; and a counter-holder coupled with the test head holder by an actuation element, wherein the actuation element is configured to steer the test head holder and the counter-holder from a closed position to an open position, the test head holder and the counter-holder being mounted floatingly along a guiding rail running in the X-direction transversely to the stringer, and fit, in a force-loaded manner, to each side surface of the stringer.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Embodiments of the present invention is are related to a device and a method for ultrasound testing by means of local immersion technique of a stringer component section of a flat component. 
         [0003]    2. Description of the Prior Art 
         [0004]    A device as well as a method of the type mentioned above is described in patent US-A-2007/0044563. The device comprises a sensor holder which is designed to record one or several linear ultrasound sensors. The device lies on rollers on the flat component to be tested and is guided by an operator along the component section in the form of a band that is to be tested. The ultrasound sensors can be oriented in parallel or essentially in parallel to the surfaces to be tested, whereby the distance to the tested surface can be adjusted by means of an adjusting screw. 
         [0005]    In the U.S. Pat. No. 7,464,596, a device for ultrasound testing of profiles, for example U-profiles, is described. The device comprises two sensor holders, of which at least one sensor holder is mounted in a mobile position along the guide rails, so that it can balance the oscillations of the profile to be tested. 
         [0006]    An ultrasound sensor for testing of laminated structures, such as T or double-T profiles, is known from the U.S. Pat. No. 4,848,159. The device is designed in particular to detect errors in the radius area and in the surrounding areas of the laminated structure. The sensor comprises many sliders which are mounted in such a way as to guarantee a coordinated movement relative to the part to be tested. The holder comprises a great number of ultrasound transducers. 
         [0007]    A method and a device for testing a component with a complex surface contour by means of ultrasound is described in patent DE-B-103 49 948. In this process a test head is moved by means of a multi-axial manipulator along a space curve at a distance in parallel to the surface of the tested component. Thereby the axle drives of a manipulator move synchronously along predetermined support points, whereby a trigger drive is moved in a synchronized manner, controlled with the axle drives and together with all axle drives in operation, according to a predetermined surface line reproducing the surface contour. The patent WO-A-03/065788 is related to a method and device for acoustic microscopy. The system comprises a controller and a “JIG,” which is mounted removably on the tested object. The “JIG” comprises an acoustic transducer connected to the controller, which controls the position of the acoustic transducer. The “JIG” is adjusted in a way that enables the controller to move the acoustic transducer over the object and to adjust its position during the scans in order to compensate the contours of the scanned section of the object. 
         [0008]    Requirements for the ultrasound testing of airplane structural components are particularly high. There is not only the requirement that large-area outer walls be tested, but also, preferably, the so-called longitudinal stiffening girders (stringers), which are mounted in the inside area of the component, should be subjected to ultrasound testing. In some cases, the longitudinal stiffening girders can be tested separately before their integration into another structural element. 
         [0009]    With the introduction of fiber composite materials in the aircraft construction, it is also possible to manufacture large-surface components directly with the help of integrated longitudinal stiffening girders (stringers), so that they have to be tested in their end state, i.e. as an integrated unit. 
         [0010]    A special challenge for ultrasound testing is the transition area between the longitudinal stiffening girder (stringer) and the stiffened surface of the structural element. This transition is described as a “foot,” and poses a particular challenge for ultrasound testing, because this transition area is difficult to access in many cases. 
         [0011]    In order to guarantee sufficient testing of this transition area as well as the stringer itself, a precise tracking control of the contour and gradient changes of the transition area and/or the profile of the stringer in the range of &lt;1 mm by means of longitudinal extension of the stringer in the range of &gt;5 m is necessary. 
         [0012]    On the basis of the above requirements, until now ultrasound testing of this type of components was performed by means of manual testing because automatic testing, due to the difficult geometric and spatial characteristics, required very precise test head holders and guides, which are very expensive and complex. 
         [0013]    Proceeding from this circumstance, embodiments of the present invention is based on a method and a device of the aforementioned type to be designed in such a way, so that this could be performed in a simple implementation form and with high speed. 
       SUMMARY OF THE INVENTION 
       [0014]    One embodiment provides a method for ultrasonic testing by means of a local immersion technique of a stringer component section of a flat component with a device comprising a test head assembly mounted as moving floatingly by a holding device in the Y-direction longitudinally, the test head assembly comprising: a test head that can be connected to an automatically actuated handling device by the holding device; a test head holder; and a counter-holder, wherein the test head holder and the counter-holder are mounted floatingly along a guiding rail running in the X-direction transversely to the stringer component section. The method comprises: steering the test head holder and the counter-holder with an actuation element from a closed position to an open position such that the test head assembly is positioned by the handling device over the stringer component section to be tested; steering the test head holder and the counter-holder with the actuation element from the open position to the closed position, wherein the test head holder and the counter-holder are fitted by applied force to side surfaces of the stringer component section; and moving the test head assembly in a longitudinal direction to the stringer component section in a fully automated manner according to a preset dataset describing the course of the flat component and/or the stringer component section, wherein the contour changes of the stringer component section and/or the flat component are balanced by the test head holder and the counter-holder which move at least in the X and Y-directions. 
         [0015]    In an alternate embodiment, a device for ultrasonic testing by means of a local immersion technique of a stringer component section of a flat component is provided. The device comprises: a test head assembly mounted as moving floatingly by a holding device in the Y-direction longitudinally, the test head assembly comprising: a test head that can be connected to an automatically actuated handling device by the holding device and that can be moved by the automatically actuated handling device along the stringer component section; a test head holder configured to receive the test head; and a counter-holder coupled with the test head holder by an actuation element, wherein the actuation element is configured to steer the test head holder and the counter-holder from a closed position to an open position, wherein the test head holder and the counter-holder are mounted floatingly along a guiding rail running in the X-direction transversely to the stringer component section, and fit, in a force-loaded manner, to each side surface of the stringer component section. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Further details, advantages and characteristics of embodiments of the invention can be obtained from both the claims, the available characteristics, individually and/or in combination, and also from the following description of the figures of the available preferred implementations, in which: 
           [0017]      FIG. 1  shows a device for ultrasound testing of a component; 
           [0018]      FIG. 2  shows a perspective view from the left of a test head assembly; 
           [0019]      FIG. 3  shows a perspective view of the test head assembly according to  FIG. 2  from the right-hand side; 
           [0020]      FIG. 4  shows a front view of the test head assembly; 
           [0021]      FIG. 5  shows a side view of the test head assembly; 
           [0022]      FIG. 6  shows a rear view of the test head assembly; 
           [0023]      FIG. 7  shows a top view of the test head assembly; and 
           [0024]      FIG. 8  shows a cross-section representation of a test head. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]      FIG. 1  shows a device for ultrasound testing of a component section  12  such as a stringer, which, within a rectangular cartesian coordinate system as shown in  FIG. 1 , extends in the Y-direction from the surface lying in a X-Z plane (X-Z direction) of a flat component  14 . 
         [0026]    The data in  FIG. 1  regarding the X-, Y- and Z axes are taken into account in the application. 
         [0027]    The testing is performed by using a local immersion technique. The device  10  comprises a test head assembly  16 , which can be moved by means of a holding device  18  as a gravitation-balancing device with a handling machine such as a portal robot (not shown) along the stringer  12 . The test head assembly  16  is shown in details in  FIGS. 2 to 8 . The test head assembly  16  comprises a test head holder  20  as well as a counter-holder  22 , which are mounted in a sliding position and can each be moved by guiding elements  24 ,  26  along a guiding rail in the X-direction, i.e. transversally to the longitudinal extension of the stringer  12 . An actuation element, such as a pneumatic cylinder  30 , is fixed on the counter-holder  22 , which is coupled with the test head holder  20  by means of an actuation bar  32 . By means of the pneumatic cylinder  30 , the test head holder  20  as well as the counter-holder  22  can be steered from a first closed position to a second open position. The test head holder  20  as well as the counter holder  22  have, respectively, slide elements  38 ,  40  in the form of slide plates, which can move in parallel or essentially in parallel to each other and to the side surfaces  34 ,  36  of the stringer  12 . In the second, open position, the slide plates  38 ,  40  are arranged at a certain distance from the side surfaces  34 ,  36 . In this position, the test head assembly  16  can be positioned over the component section  12  that is to be tested. 
         [0028]    By controlling the pneumatic cylinder  30 , the test head assembly  16  can be steered from the second, open position to the first, closed position, in which the slide plates  38 ,  40  are lying spring-preloaded on the side surfaces  34 ,  36  of the stringer  12 . To this purpose, the test head holder  20  and the counter-holder  22  are coupled to each other by means of a spring element  42  as a tension spring. The guide rail  28 , along which the test head holder  20  and the counter-holder  22  are arranged in a shifting position, is connected by means of a swivel  44  with a connecting block  46  of the gravitation-balancing device  18 . The swivel  44  permits a swinging of rotational movement of the test head assembly  16  around an axis running in longitudinal direction (Z-direction) of the stringer  12 . By means of the gravitation-balancing device  18 , a floating suspension of the test head assembly in the Y-direction is implemented. By means of the characteristics described above, an advantage is achieved, which permits the test head assembly  16  to be moved with several levels of freedom, whereby by means of the spring-preloaded holders  20 ,  22  fitted at the side surfaces  34 ,  36  of the stringer  12  an adaptation to the contour changes of the stringer  12  takes place, and whereby by means of the floating suspension of the holders  20 ,  22  along the guiding rail  28 , the course changes of the stringer  12  in the X-direction, i.e. transversally to the longitudinal extension of the stringer  12  are balanced, and whereby the changes in the tilt of the stringer  12  can be balanced by means of the rotary bearing element  44 . The test head holder  20  comprises, preferably, a metal base body  48  for receiving the test head  50 , as a phased-array test head with sending and receiving elements, as well as the slide plate  38 . The base body  48  is built essentially in the form of a cuboid, with a hollow space  52 , which forms a water chamber. The chamber  52  is covered on one open side of the base body  48  by the slide plate  38 , which comprises a slit-like opening  54  as a water outlet opening running in the Z-direction. The slit-like opening is open to a surface running in the X-Z plane of the component  14  and has a slit-like opening  56  there. This allows a transition area between the stringer  12  and the flat component  14 , described as “foot,” to be tested by means of the phased-array test head  50 . 
         [0029]    In a wall  58 , which is positioned against the slide plate  38 , the base body  48  has a slit-like opening  60 , in which the test head  50  is fitted and which is extended within the water chamber  50  up to the slide plate  38 . In the side walls  62 ,  64 , which essentially run under a right angle to the front wall  58  and the slide plate  38 , water inlet connections  66 ,  68  are mounted, which lead to the water chamber  52 . 
         [0030]    In the lateral view according to  FIG. 5 , it can be seen that on the bottom side  70  of the test head holder  20  supporting and guiding elements  72  are mounted as roller elements, through which the test head assembly  16  can move over the surface of the component  14 . 
         [0031]    As is known, the device operates by means of local immersion technique. Through the water inlets  66 ,  68 , water is flushed in the water chamber  52 , which is then led through the slit-like opening  54  against the side surface  34  of the stringer  12 . The longitudinal extension of the slit-like opening  54  in the Y-direction is longer than the height of the stringer  12 , so that the water, which comes out of the slit-like opening  54 , fills both an intermediate space, formed between the slide plate  40  of the counter-holder  22  and the side surface  36 , and also an intermediate space formed between the slide plate  38  and the side surface  34 , in order to achieve an adequate coupling of the ultrasound waves. For better distribution of the water, furrows or grooves  74  for distribution of the water extended in the Y-direction are provided in the slide plate  40  of the counter-holder  22 . 
         [0032]    Another feature of the counter-holder  22  is characterized in that it runs pointedly to the fin base  58 , as shown in  FIG. 6 . In this way, the testing of stringers  12 , which run in a tilted position with respect to the component  14 , is also enabled. In order to balance the height differences of the component  12  in the Y-directions, the test head assembly  16  and the gravitation-balancing device  18  are guided along the stringer  12  that is to be tested. The gravitation-balancing device  18  comprises a base plate  102 , which can be connected firmly with a handling device, such as portal robot (not shown). The guiding cylinders  104 ,  106 , which are arranged in parallel to each other and at a certain distance between them, extend from one top side of the base plate  102 . The guiding bars  108 ,  110  are bearing-suspended in axially shifting position in the guiding cylinders  104 ,  106 . The first, bottom ends of the guiding bars  110 ,  108 , which extend under the base plate  102 , are connected to each other by means of the connecting block  112 . The swivel  44 , to which the test head assembly  16  is fixed, is mounted in the connecting block. The first, top ends  120 ,  122  of the guiding bars  110 ,  108 , which extend above the base plate  102 , are also connected to each other by means of the connecting block  124 . The connecting element  124  is connected with a closed belt  130 , which is led through a first guide pulley  126  and a second guide pulley  128  (not shown). Furthermore, the belt is coupled to a gravitation counterweight  132 , which slides along the guiding bars  134 ,  136  in opposition to the movement of the test head  10 . The ends of the guiding bars  134 ,  136  are connected to each other by means of an axle, on which the first guide pulley  126  is positioned revolvably between the guiding bars. The second guide pulley  128  is mounted in a revolvable manner in the base plate  102 . 
         [0033]    Furthermore, the base plate  110  has a pneumatic cylinder  138 , preferably between the guiding bars  110 ,  108 , whereby a piston rod  140  of the pneumatic cylinder  138  is connected with the connecting block  112 , in order to adjust the test head  10  in work position. 
         [0034]    In order to guarantee that the test head is always lying on a side surface of the component section to be tested, it is ensured that the test head assembly has one test head holder receiving the test head, as well as a counter-holder, that the test head holder as well as the counter-holder are suspended along a guide rail running in the X-direction transversely to the component section in a moving or floating state and are lying in a spring-preloaded position on one side surface of the component section. The guide rail may be mounted with a capability for a rotational movement around an axis running in the Z-direction. 
         [0035]    Furthermore, the test head assembly may be suspended moving high in the Y-direction over the holding device built as a gravitation-balancing device, preferably in a floating position. 
         [0036]    An actuation element such as a pneumatic cylinder may be provided to control the counter-holder and the test head holder. 
         [0037]    In order for the test head holder to lie in a spring-preloaded manner on the side surface of the component to be tested, the test head holder and the counter holder may be coupled with each other by means of a spring element such as a tension spring. 
         [0038]    The end positions of the test head holder and the counter-holder may be recorded by an end switch such as a proximity switch. 
         [0039]    The test head holder and the counter-holder may each have a slide plate clinging to the side surface of the component section, whereby the slide plate of the test head holder has a slit-like opening with a hole on the top side, which is extended in the Y-direction, whereby the height dimension (Y-direction) of the slit-like opening is larger than the height of the component section and that the slide plate of the counter-holder has grooves running in the Y-direction. 
         [0040]    The slide plates or the slide elements may be made of plastic. 
         [0041]    In order to simplify the movement of the test head assembly along the component to be tested, the test head holder may have, on its bottom side, a supporting and guiding element, such as a roller, for supporting and guiding the component to be tested. 
         [0042]    The test head holder may have a base body with a cuboid form, comprising a metal base body, with a milling groove that forms a water chamber, which is covered by the slide plate, whereby in one of the walls opposite to the slide plate a recess for receiving the test head is built and whereby in the side walls of the base body intakes are mounted which lead to the water chamber. 
         [0043]    A method for testing of, in particular, the stringer  12  of the flat component  14  is characterized in that the test head holder  20  and the counter-holder  22  are arranged first in an open position over the component section  12 . After a safety check by querying the limit switches, which check the end positions of the test head holders  20  as well as of the counter-holders  22 , the water inlet is opened and the test head assembly  16  is replaced by the handling machine over the component section  12 . 
         [0044]    By controlling the pneumatic cylinder, the test head holder  20  and the counter-holder  22  are steered into the closed position, so that the holders  20 ,  22  are fitted spring-preloaded on the side surfaces  34 ,  36 . 
         [0045]    Next, the test head assembly is moved in the direction (Z-direction) along stringer  12  and measurement values are taken, whereby the ultrasound testing is performed, preferably by using the amplitude-runtime local curve method (ALOK method) and/or alternatively combined with the standard clearance evaluation. 
         [0046]    The methods according to embodiments of the invention achieve a situation where the test head holder and/or the test head, which are moved by the handling machine, are suspended in a movable position with several levels of freedom in relation to the component and/or the component section. In this way, the test head can follow minimal course alterations or contour changes of the component or the component section, without a need for the handling machine to perform corresponding corrective movements. 
         [0047]    A time-consuming setup of the device is eliminated, and compared to manual testing, very fast, reproducible and automated testing is achieved. Since the control is alleviated, the testing as a whole can be performed faster. 
         [0048]    By the implementation of the test head assembly as a test head holder and a counter-holder, a bracket-like configuration is obtained, with which the test head is always in contact with the side surface of the component to be tested. 
         [0049]    According to an alternate embodiment, an intermediate space formed between the test head holder and the counter-holder and oriented towards the component section is completely overflown by water flowing from the test head holder. 
         [0050]    In this way, a local immersion technique is implemented. To compensate for the changes in the height of the component to be tested, the test head assembly is guided by a gravitation-balancing device. The measurement values obtained by the test head are preferably recorded and evaluated by means of an amplitude-runtime local curve method (ALOK method) and/or standard clearance evaluation. As a result of embodiments of the present invention, on the one hand, of the test head assembly and, on the other hand of the suspension by means of a gravitation balancing device, testing speeds are possible in the range of 100 mm/s to 500 mm/s, preferably 200 mm/s, in longitudinal direction.