Patent Application
20090301152
The present invention relates to a cover element for a sonotrode and a peening chamber arrangement for the surface peening of components of the type described in the preambles of claims 1 and, respectively, 8.
Cover elements and peening chamber arrangements of this kind are used, for example, for the surface peening of components, such as blisks, rotor blades, blade roots or the like, with the aid of shot as peening material. In this context, the shot is accelerated by the cover element of the sonotrode within a peening chamber and hurled at a high velocity against the surface to be treated of the component in question. The fatigue strength under vibratory stresses and the corrosion resistance can be increased in this manner, without the component being subject to material shifting. A central problem of surface peening is that an irreversible weakening or even destruction of the component can be easily caused by faulty process monitoring and control, such as by overly long processing times, too small of a distance between the cover element and component, or too high of an acceleration of the peening material. Of particular interest, therefore, are sonotrodes, cover elements and peening chamber arrangements which make it possible to ensure a low-stress and targeted process monitoring and control, as well as the processing of a broad array of component types.
A cover element of this kind and a peening chamber arrangement of this kind are known from the German DE 600 17 681 T2, which describes a method for the ultrasonic shot peening of large sized, annular surfaces of thin-walled workpieces. In this context, a rotationally symmetric component, such as a drive cone of a turbine engine for aircraft, is surface peened using a peening chamber arrangement. To this end, the component is continuously moved in a rotary motion, at least five times past the top opening of the peening chamber arrangement and, in the process, is peened by shot accelerated by a sonotrode. The intention here is to ensure a low-stress and uniform surface treatment by a repeated execution of the pass-by motion. The peening chamber used is itself designed to be smaller than the component to be treated and is composed of a space that is open to the top and is bounded at the sides by a wall and is downwardly delimited by a bottom. The cover element of the sonotrode is configured at the bottom of the peening chamber and is set into vibration by a vibration generator. To avoid the loss of shot caused by the expelling of the same out of the peening chamber during the surface treatment, it is provided for a clearance to be set between the component and the wall of the peening chamber that is smaller than the diameter of the shot.
The inherent disadvantage of this known peening chamber arrangement is that the cover element must be fitted very precisely into the bottom of the peening chamber to prevent peening material from falling out of the peening chamber. Moreover, the peening material is accelerated by the cover element relatively nondirectionally, so that only a small portion is directed at the component to be peened.
A disadvantage of the described peening chamber arrangement is that it requires a complex adjustment of the clearance between the peening chamber and the corresponding component to be peened. This is often not possible, particularly when working with a component having an irregular surface geometry, so that the need arises to develop an individually adapted peening chamber for each component. Besides, the known peening chamber arrangement is only suited for relatively large, rotationally symmetric components and, in addition, cannot be used for complex geometries, such as the inner side of the components.
An object of the present invention is, therefore, to improve a cover element of a sonotrode of the type mentioned at the outset in a way that will make its use simpler and more readily variable and that will permit a more directed acceleration of the peening material. It is also an object of the present invention to devise a peening chamber arrangement of the type mentioned at the outset which will make possible a simpler and more readily controllable surface peening of components of different sizes, geometries and contours, and which will be able to be readily adapted to these components.
This objective is achieved in accordance with the present invention by a cover element for a sonotrode, as well as by a peening chamber arrangement having the features of claims 1, respectively 8. Advantageous embodiments characterized by useful and nontrivial refinements of the present invention are described in the remaining claims.
In accordance with the present invention, at least one wall is provided on the cover element of the sonotrode which is to be configured, in particular, for accelerating peening material within a peening chamber for the surface peening of components and is to be operated by an vibration exciter of the sonotrode. The wall is mounted in a predefined position on the cover element and is to be moved together with the same. Suited as a sonotrode are those types, in particular, which have vibration exciters designed as ultrasonic piezoactuators. The advantages of a cover element of this kind are clearly apparent. The guidance action of the wall allows the peening material, which is to be accelerated, to be directed in a more targeted manner at the surface of the component to be peened and thus ensures an improved and reproducible process monitoring and control. Moreover, the wall enhances the stability of the vibrating surface of the cover element, so that an improved and more efficient energy transfer from the sonotrode to the peening material is ensured.
In addition, a sonotrode provided with a cover element of this kind renders possible an especially compact embodiment of a peening chamber, so that even sterically complex surface geometries, such as the inner sides of components, for example, may be worked. A further advantage is achieved in that, for example, in contrast to the related art in accordance with the German DE 600 17 681 T2, there is no longer a need for the lateral clearance between the cover element of the sonotrode and the wall of the peening chamber to be adjusted in a complex process.
Another advantageous embodiment of the present invention provides for the wall to be configured at a lateral peripheral region of the cover element. A wall of this kind makes it especially simple to devise a lateral bounding, effectively preventing a loss of peening material at the bottom side of the peening chamber.
In addition, the wall is ideally designed to extend peripherally around the cover element, so that the peening chamber is completely bounded by the cover element, both downwardly as well as laterally. Special advantages are attainable, in particular, in that the wall, which is moved together with the cover element, itself constitutes the wall of the peening chamber.
Since the wall is exchangeable and/or is designed to be removable from the cover element, an especially simple option is devised for adapting the cover element to a broad array of surface geometries of various components quickly and, accordingly, cost-effectively, while entailing very little installation expenditure. Since the wall, which is moved together with the cover element, itself forms the peening chamber, one single sonotrode may be used for peening a great variety of surfaces, as the wall is exchangeable. A further improvement in the adaptability to different spatial conditions may be achieved in an especially simple manner in that the wall is adjustable in its position on the cover element and is fixable in the adjusted position. This kind of adjustability and capability to be fixed in position may be achieved using suitable releasable connecting elements, such as screw or clamp connections, for example. Also conceivable, however, are all other suitable types of connection known to one skilled in the art.
Another advantageous embodiment of the present invention provides that, in proportion to the width, in particular to the diameter, of the cover element, the height of the wall is substantially smaller and is preferably in a ratio of between 1:6 and 1:14 and, in particular, 1:10 thereto. Since a wall that is substantially smaller than the cover element also has a correspondingly smaller inert mass that must be accelerated by the cover element, an especially rapid response and largely delay-free co-movement of the wall may be ensured in this manner. It has been shown that a ratio of approximately 1:10 is especially suited as a compromise between the requirements for co-movement capability, thus for a smallest possible mass, and for the guide-element properties for peening material, thus for a greatest possible height. Finally, a form of the cover element that is structurally very simple and especially suited for deflecting the peening material toward the surface of the component may be achieved by positioning the wall at least at approximately right angles to the cover element.
In accordance with the present invention, a peening chamber arrangement for the surface peening of components, in particular for ultrasonic shot peening, includes a peening chamber bounded by at least one wall and at least one sonotrode having a cover element which is used to accelerate peening material within the peening chamber, it being provided for the cover element to include at least one wall portion of the wall that is to be moved together with the same. In other words, in the case of a peening chamber arrangement according to the present invention, it is provided that the cover element of the sonotrode include at least one wall portion of the wall of the peening chamber, and that this wall portion be movable together with the cover element. The cover element transmits the oscillation produced by the sonotrode to the peening material, which is to be introduced into the peening chamber, thereby accelerating the same toward a surface of a component to be placed at an opening of the peening chamber. The opening is preferably located on the side of the peening chamber opposing the cover element of the sonotrode, spatial configurations deviating therefrom also being conceivable, however. Therefore, in contrast to the related art, there is no longer a need for the cover element of the sonotrode to be fit into place in the bottom of the peening chamber arrangement in order to close off the same in a precisely fitting manner to thereby avoid a loss of peening material. The need is also eliminated for adapting the clearance between the wall and the bottom, respectively the cover element—in the case that it, itself, functions as a bottom—in order to prevent a loss of peening material at the lateral contact surfaces. A peening chamber arrangement of this kind is able to be implemented very simply when the sonotrode is designed in accordance with at least one of the claims 1 through 7. The advantages described therein also apply analogously to the peening chamber arrangement according to the present invention.
Another advantageous embodiment of the present invention provides for the wall to have at least one further wall portion that is designed as a guide element attached to the wall portion which moves together with the cover element. A wall portion of this kind make it possible for a simple adaptation to be made to the distances and deflection angles of the peening material. Since it is also provided in accordance with the present invention for the additional wall portion to be adjustable in its position and fixable in the adjusted position, an especially rapid and simple option for adapting the peening chamber arrangement to components having a broad array of surface geometries may be readily implemented. Special advantages are able to be realized in that the additional wall portion, designed as a guide element, for example, is attached directly to the wall portion to be moved together with the cover element. In this context, screw connections, for example, are suited as a simple and cost-effective option for adjusting the wall portion and fixing it in position. Also, conceivable, however, are other connection types and positioning options that are familiar to one skilled in the art.
To ensure an optimal and direct control of the intensity and duration of the surface peening, it proves to be advantageous for a first device for ascertaining an impact frequency and/or an impact intensity of the peening material to be accelerated within the peening chamber to be provided, which is preferably to be mounted on the component on a side facing away from the cover element. Especially suited for this purpose are devices which include induction sensors, sound sensors or the like, designed as vibration sensors, for example. Placing the device on the component on the side facing away from the cover element makes it possible for the device to be simply and variably positioned, on the one hand, and protected from mechanical damage by the peening material, on the other hand. Moreover, it is conceivable for the first device to be used to determine the total energy transmitted via the peening material to the component.
Since it is not always possible for a closed chamber to be provided for complex components, the present invention provides a second device for the postmetering of the peening material to be accelerated within the peening chamber. This makes it possible to maintain a constant total quantity of peening material, even in the case of a possible loss caused by escaping of the same out of the peening chamber, and to thereby ensure a reproducible process monitoring and control. The second device may be controlled, in particular, with the aid of the above described first device for determining an impact frequency and/or impact intensity of the peening material to be accelerated within the peening chamber, so that, in this manner, an especially precise control of the quantity of peening material, acceleration intensity and duration is made possible. Accordingly, in the case that too small a quantity of peening material impinges on the surface of the component, peening material may be postmetered until the desired level is reached again.
An especially uniform and reproducible result of the surface peening may be ensured by operating the cover element at an oscillation of a predefined frequency, in particular of 20 kHz or less. The oscillation excitation is preferably carried out essentially in a rectangular and/or trapezoidal waveform. In contrast to the related art, where the peening material can only be accelerated by adapting the amplitude of the oscillation excitation, the high edge steepness of a rectangular, respectively, trapezoidal waveform makes it possible for the acceleration of the peening material to be adjusted in an especially simple and variable process and independently of the amplitude.
Other advantages and features of the present invention and details pertaining thereto are derived from the following description of a preferred exemplary embodiment, as well as in light of the drawings. They show in:
In a schematic sectional view,
In addition to wall 20, chamber wall 21 of peening chamber 14 includes a guide element 22 that is coupled to wall 20 and, in the present case, is adjustably connected thereto by articulation. It would likewise be conceivable, however, for guide element 22 to be mounted immovably, so that cover element 18, respectively wall 20 that is moved together therewith, vibrates relative to guide element 22.
Moreover, the peening chamber arrangement has a device 24 for postmetering peening material, as well as a device 26 for determining an impact frequency and impact intensity of peening material 12 on a component 28 to be surface-peened.
Component 28 itself, which is exemplarily a rotor blade in the illustrated embodiment, is configured at an open top side 30 of peening chamber 14. In the present case, the merely schematically illustrated sonotrode 16 is designed as an ultrasonic sonotrode and, on the bottom side of cover element 18, includes a multiplicity of vibration exciters 32, which are designed as column-shaped, ultrasonic piezoactuators, essentially having a basic cylindrical design. In addition, vibration exciters 32 are connected to a base plate 34, which is designed to be plane-parallel to cover element 18. For the sake of clarity, sonotrode 16 is shown without outer cladding.
For the surface peening of component 28, peening material 12 introduced into peening chamber 14 is accelerated in a pulsed manner by cover element 18 of sonotrode 16 which is vibrating with a specific oscillation frequency and oscillation waveform toward component 28 and forms a spray of shot within peening chamber 14. On the one hand, wall 20, which is secured peripherally around cover element 18, directs peening material 12 at component 28 and, on the other hand, it enhances the stability of vibrating cover element 18. With the aid of guide element 22 that is attached to wall 20 and is variable in its angular position, peening material 12 may be variably deflected and adapted to the surface geometry of the particular component.
To ensure a reproducible surface peening and an optimal process monitoring and control, a device 26 for determining the frequency and intensity of peening material 12 impacting on the side of component 28 facing peening chamber 14, is located on the top side of component 28. For example, the frequency, amplitude or excitation waveform of sonotrode 16 may be modified as a function of the ascertained measured values of this device 26. Moreover, in the case of a loss of peening material 12—which may occur, for example, across an intermediate space 36 between guide element 22 and component 28—it is possible to maintain a constant quantity of peening material 12 within peening chamber 14 during the entire peening process by controlling device 24 for postmetering peening material 12. This is particularly advantageous in terms of being able to process a broad array of components having complex geometries, without having to undertake expensive and complex adaptations of the peening chamber arrangement to the surface geometry of the particular component.
In a diagram as a function of time,
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 036 519.4 | Aug 2006 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE2007/001361 | 7/31/2007 | WO | 00 | 2/3/2009 |
