Patent Application
20090257660
This application claims priority to German patent application No. 10 2008 015 235.8, filed Mar. 20, 2008 and German patent application No. 10 2009 005 111.2, filed Jan. 19, 2009. The complete disclosure of the above-identified priority applications is hereby fully incorporated herein by reference.
The invention relates to a method for inspecting component surfaces by means of a scanning test system.
With the non-destructive testing of a component, in the case of a scanning method, a probe has to be moved along the component surface, for instance for ultrasound or eddy current testing, in order to be able to test the points to be tested at the correct distance and angle, so that the surface to be tested is completely covered.
With certain manufacturing methods, for instance sintering or forming by bending or as a result of abrasive wear on components which were already in use, individual different shape deviations appear. If the shape deviations are not taken into account during the scanning test, reliable inspection of the components by means of a scanning method is no longer possible with sufficient accuracy.
As a result of the individual nature of shape deviations, a shape measurement of the components is necessary.
One previous solution consists in determining the shape prior to the testing using a separate measuring system, for instance by a sheet-of-light imaging method with an optical system.
In a further step, reference points must ensure that the measured shape can be assigned to the positioning of the scanning system in respect of the position and the orientation. The disadvantage with this procedure is that the additional steps take time, i.e. reduce the throughput of the test system and that a relatively large additional outlay is necessary for a separate shape measuring system.
In the case of ultrasound immersion testing, optical shape measurement is also only feasible outside the dip tank.
It is also known to measure the component shape with the same scanning system, mechanism and sensor system with which the inspection takes place. It is advantageous here that no expensive additional hardware is necessary. If additional sensors, which can be actuated by the same electronics system, are needed however, the material outlay increases. The disadvantage is the significant expenditure of time taken to measure the shape. The speed is generally determined by the operating speed of the scanning mechanism, so that approximately double the time outlay occurs overall.
There is the possibility of accurately measuring the deviation from the component surface during the scanning process and immediately using this information to control the scanning mechanism. To this end, an extremely rapid control loop consisting of surface measurement, measuring evaluation and motor control would be necessary however. The disadvantage here is that very minimal reaction times result in large positioning errors and thus in an unreliable inspection. Conventional motor controls are also designed to follow previously known paths.
According to various embodiments, the shape of a test sample can be measured using the same scanning system, mechanism and sensor system, saving almost all the time taken for additional scanning movements.
According to an embodiment, a method for inspecting component surfaces by means of a scanning test system may comprise the steps of:—activating the test system such that an estimation of the component shape is drawn up based on a known region of the component surface,—preparing the estimation at the edge of the known region at least for a part of the edge,—using the estimation to calculate a path for the scanning system,—implementing an inspection when scanning along the path, and—measuring a deviation from the true component shape so that the exact shape of the component is known along this path.
According to a further embodiment, both the inspection and also the determination of the component shape may take place using the same sensors. According to a further embodiment, with the inspection, a repetition of individual scanning lines may take place with a large deviation between the estimation and actual shape. According to a further embodiment, a dynamic selection of the shape model can be performed. According to a further embodiment, a known region may consist of several unrelated parts. According to a further embodiment, a known region, which has a rectangular shape, can be extended on one or two sides. According to a further embodiment, a linking of a test sample movement and component shape can be performed in the case of a cylindrical tube for instance. According to a further embodiment, an estimation of the component shape for the points next to be inspected may take place. According to a further embodiment, a smoothing of the estimated component shape may take place by means of low pass filtering. According to a further embodiment, a plausibility check of the estimated component shape may take place in order to test a curvature. According to a further embodiment, estimation may take place with a priori knowledge.
According to another embodiment, a handling system for inspecting component surfaces implementing a scanning test, may comprise a sensor for scanning across the component surfaces, wherein the handling system is operable to be activated such that a known subregion of the component surface is retraced, an estimation at the edge of the known region is performed at least for one part of the edge, this estimation for the calculation of a path being used for the scanning test and the inspection is implemented when scanning along this path.
According to a further embodiment, the system may be operable to detect a movement of the test sample during the inspection of a component surface. According to a further embodiment, the test sample may be a cylindrically rotating shaft.
Embodiments are described below with reference to schematic figures which do not restrict the invention.
According to various embodiments, an estimation of the component shape is used instead of the actual component shape in order to control the scanning system.
The estimation is to be drawn up sufficiently closely to the true shape so that the inspection can be implemented with the required accuracy. It is advantageous if the complete component shape or an estimation of the complete component shape is not needed at the start of the inspection. It is instead sufficient to estimate the component shape before tracing a scanning curve within the region of this scanning curve.
Based on a known region, the method creates an estimation for the component shape at the edge of the known region and/or at least for a part of the edge of the known region. The path is then calculated for the scanning mechanism using this estimation. During the scanning process along this path, the inspection is implemented and the deviation from the true component shape is measured at the same time so that the exact shape of the component is then also known exclusively along this path.
For a small region of the component surface, it is thus only necessary at the start of an inspection to determine the shape in advance using one or a few scanning lines for instance.
The starting point is the knowledge of the true shape for a segmented component. A global, partial or local shape model can be used for estimation purposes, for instance a plane, cylinder or sphere segment.
A global and/or a partial shape model describes the shape of the test sample overall, and/or in large regions, i.e. the design of the model depends on the test sample. As many types of deformations are considered in order to create a global shape model, a local shape model is generally easier to manage.
One possible use of a global shape model exists in respect of controlling the curvature, by comparison with a priori knowledge.
Based on this known region 4, estimations and corrections are already plotted in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 015 235.8 | Mar 2008 | DE | national |
| 10 2009 005 111.2 | Jan 2009 | DE | national |
