WO2007124953A1

WO2007124953A1 - Method for space-resolved, nondestructive analysis of work pieces

Info

Publication number: WO2007124953A1
Application number: PCT/EP2007/003876
Authority: WO
Inventors: Ludwig Von Bernus; Michael KRÖNING; Andrei Bulavinov; Krishna Mohan Reddy; Olga Yastrebova; Vidaydhar Kudalkar
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2006-05-02
Filing date: 2007-05-02
Publication date: 2007-11-08

Abstract

The invention relates to a method for a space-resolved, nondestructive analysis of work pieces by means of at least one measuring sensor which is guided across a technical surface area of the work piece to be analyzed and is able to detect the presence of local material inhomogeneities, local material irregularities, and/or local material structure inside the work piece. The invention is characterised in that, starting from a start position, the at least one measuring sensor is positioned on the surface area of the work piece and a first ascertainable portion of volume of the work piece is detected, which is represented by a first measuring signal. By moving the measuring sensor in the longitudinal direction of the surface area of the work piece into a second position, a displacement path is detected, based on a comparison between the first measuring signal and a second measuring signal received from the second position, which represents a second portion of volume, wherein the first and second portion of volume overlap at least partially. Based on the displacement path, the relative position of the second position is detected in relation to the starting position on the surface area of the work piece.

Description

Method for spatially resolved, non-destructive workpiece inspection

Technical area

The invention relates to a method for spatially resolved non-destructive workpiece examination by means of at least one measuring sensor, which is guided over a technical surface of the workpiece to be examined and within the workpiece existing local material inhomogeneities, local material dances and / or local material structure is able to detect.

State of the art

For nondestructive workpiece inspection, a number of different measurement methods are available, such as ultrasonic, eddy current and magnetic field measuring method in which a suitably assembled test or measuring sensor is moved on the surface of the workpiece to be examined, to location-dependent information from the volume interior of the workpiece receive. Using the example of a known ultrasound test, the previous examination practice is to be explained in more detail, which, however, can also be transferred to other measuring or test methods in which, for example, appropriately designed eddy-current or magnetic sensors are used.

Thus, the ultrasonic wave testing method known per se is based on the pulse-echo principle in which ultrasonic wave transit times are measured between the event of the ultrasonic wave coupling over the workpiece surface and the ultrasonic wave reception after at least one single reflection event within the workpiece to be examined. The obtained in this way, from the respective Einkoppelort the ultrasonic transducer dependent measurement signals, one speaks in this context of time signals or A-pictures, provide information about the reflection behavior within the workpiece, respectively in the "direction of view" of the seated on the workpiece surface ultrasonic transducer, which applies to capture as possible the entire volume In order to be able to produce a local assignability between the individual time measuring signals recorded with the aid of the ultrasonic transducer and the position points on the workpiece surface where the measuring sensor for measuring signal recording is respectively positioned, it is necessary to additional position information of the measuring sensor relative to the surface of the workpiece to be examined during the measurement implementation.

Typically, for this purpose, the measuring sensor to be traversed over the surface of the workpiece to be examined is moved by means of mechanical systems in which displacement encoders are integrated which are capable of measuring the respective sensor position, which ultimately permits location-related measurement signal data acquisition. This, in turn, forms the basis for a spatially resolved measurement data evaluation and pictorial representation of the test or measurement results for the scanned area within the workpiece.

Hand-held tests are also used for determining the position of each measuring sensor in use Weggebersysteme with which a spatially resolved and ultimately pictorial representation of the measured signals can be obtained because in the example of the above-cited ultrasonic test itself the usual image reconstruction in the form of B-, C- and D-pictures only with knowledge of the respective Meßsensorposition is possible.

Such Weggebersysteme usually require a physical contact with the surface of the workpiece to be examined, for example by means of a rolling body, which is used for a similar purpose in known per se computer mice with integrated ball. Such or similar Distance measuring systems, however, entail additional expense, both constructively and financially. Non-contact path measuring systems are also known for detecting the position of a manually guided measuring sensor along the surface of a workpiece to be examined, in which the hand-held measuring sensor is detected optically by means of an image-processing camera unit or by means of a logger system based on radar or infrared technology. However, it is obvious that the cost factors associated with these systems also account for a considerable proportion of the total cost of such measurement system. Thus, typically accounts for 70% of the total system cost only on the handling technique that is not or only problematic in many cases due to space requirements. This may also be the reason that due to practical problems, implementing manual testing techniques, which typically make up 70% of all ultrasound examinations, can not enforce tracker systems or systems that can locate the position of the measurement sensor.

Presentation of the invention

In many cases, the material and workpiece inspection are required for holistic volume detection of the workpiece to be examined as well as for a pictorial representation of the test or measurement results for each scanned or scanned workpiece area location information with which the respective measurement signals are to be included. It is therefore the object to realize the position detection of each measuring sensor used relative to the surface of the workpiece to be examined in the simplest and most cost-effective manner possible. For example, hitherto known displacement sensor systems which detect the position of measuring sensors have to be replaced by more cost-effective solutions, which, however, likewise enable an exact position detection of the respective measuring sensor.

The solution of the problem underlying the invention is specified in claim 1. The concept of the invention advantageously further-forming features The subject of the dependent claims and the explanations with reference to the exemplary embodiments.

According to the invention, a method for spatially resolved non-destructive workpiece inspection by means of at least one measuring sensor, which is guided over a technical surface of the workpiece to be examined and existing within the workpiece, local material inhomogeneities, local material dances and / or local Matehalgefüge able to detect, is designed such starting from a starting position at which the at least one measuring sensor is positioned on the surface of the workpiece and a first volume region of the workpiece which can be detected by the measuring sensor, which is represented by a first measuring signal, by moving the measuring sensor along the workpiece surface into a second position, a movement trajectory based on a comparison of the first measurement signal with a second measurement signal obtained at the second position, which represents a second volume region, wherein the first and second te volume range at least partially overlap, is determined. By determining the movement trajectory, the spatial relative position of the second position on the workpiece surface relative to the starting position is determined and thus a relative location information of the individual measuring locations at which the workpiece is examined with the aid of the measuring sensor is obtained.

The solution according to the method thus requires no additional systems or additional sensors whose task is the location of the measuring sensor in use, as is the case in the prior art. In contrast, the method according to the solution makes use of the measuring signals already obtained for the purpose of workpiece inspection, which are additionally evaluated by means of suitable algorithms for geometry calculations. It is thus possible, based on simple trigonometric relationships on the surface of the workpiece, to make changes in position of the measuring sensor on the basis of different viewing angles of at least one defect located within the workpiece, for example in the form of a material inhomogeneity or material dancings. For example, in the case of workpiece examination by means of ultrasound measurement, the ultrasonic waves emitted by an ultrasound transducer are reflected back to the ultrasound transducer seated on the surface of the workpiece on a material dancer formed, for example, by material rupture. Based on the variable measurement signals, which come from one and the same defect within the workpiece and are obtained from different positions on the workpiece surface, the positional offset between the two measuring positions on the surface of the workpiece to be examined can be determined. By using efficient computer structures, for example in the form of highly integrated components and the use of optimized calculation algorithms, the measurement signals obtained for workpiece examination can be evaluated in almost real time, ie even with rapid sensor movement in terms of their information content about position and position change. The location information can be stored together with the detected measurement signals and made available for subsequent evaluation.

Thus, in the workpiece examination by means of ultrasound measuring technology, so-called time signals or A-pictures or reconstructed pictures, so-called C- or sector images can be evaluated via fast signal processors to obtain the required location information. For this serve primarily reflection events on discrete scatterers within the workpiece, for example in the form of defects, in addition, however, the acoustic noise contained in the received signal for location determination due to the location information contained in the noise is possible.

Due to the measuring system independence, the method according to the solution can be applied both to non-destructive workpiece investigations by means of ultrasound technology and by means of eddy current or magnetic field measurement technology. For certain material groups, the method can also be transferred to microwave measurement technology. Brief description of the invention

The invention will now be described by way of example without limitation of the general inventive idea by means of embodiments with reference to the drawings. Show it:

1a, b schematically and experimentally determined cross-sectional representation through a workpiece in a first position,

Fig. 2a, b schematized and experimentally determined cross-sectional view through a workpiece in a second position, as well

Fig. 3a, b experimentally determined time signals at two different positions of a workpiece.

Ways to carry out the invention, industrial usability

FIG. 1 a shows a schematic cross section through a workpiece 1 in which local material inhomogeneities 2 are present at different points. On the surface 3 of the workpiece 1, a measuring sensor 4 is shown in a first position X1. In the sector image (C-frame) shown in FIG. 1b, the defects represented diagrammatically in FIG. 1a are shown in the form of experimentally determined reflection events ZB1 to ZB4. Furthermore, in the sector image gem. Fig. 1 b, the rear wall R and a side edge K of the through-sounded workpiece as pictorially representable measuring signals.

If the measuring sensor 4 is now displaced along the surface 3 of the workpiece 1 into a position 2 as shown in FIG. 2a, the relative position of the individual defects 2 changes to the newly positioned measuring sensor 4. The sector image recorded by the measuring sensor 4 is shown in FIG. 2b. It can be seen from the sector image according to FIG. 2b that all the reflection images have a changed spatial position to the position sensor located in position 2. For example, the measuring sensor 4 in position 2 no longer detects the defect 1 (see ZB1), whereas a new defect ZB5 is detected in the sector image according to position 2. The reflected in position 1 reflex events ZB2 to ZB4, but also found in a different position in the sector image in position 2, serve as a basis for the calculation of the position position of the measuring sensor 4 in position 2.

The test signal example illustrated in FIGS. 1 and 2 is intended to clarify that stationary, local reflectors present within the workpiece serve to determine the position of the measuring sensor. Nevertheless, it is possible to obtain location information also from the remaining noise signal with optimized methods of image and signal processing. Reference is made to Figures 3a and b, which represent an acoustic background signal at two different positions on a workpiece. The abscissa corresponds to a distance measure measured from the surface of the workpiece in the depth of the workpiece, along the ordinate are shown according to receiving amplitudes. Nevertheless, location information for determining the position of the measuring sensor can be extracted on the basis of the noise signal which can be detected differently between the two positions.

By using the method according to the invention, there are basically two advantages. On the one hand, the method according to the solution also makes it possible to carry out an imaging quality similar to that achievable with previously automated tests, even when the workpiece inspection is carried out manually. In particular, under difficult conditions, by which the installation of manipulators are not permitted or limited by access times, for example in nuclear facilities due to prevailing radiation protection regulations or underwater tests or much more, can be a quick, easy to carry out manual test with quantifiable, ie pictorial results as a viable alternative be used. On the other hand, the solution according to the method helps to significantly reduce costs due to unnecessary encoder or positioning systems.

LIST OF REFERENCE NUMBERS

1 workpiece

2 defect

3 surface

4 Measuring sensor R Back K edge

For example, 1 to ZB5 detected reflection events

Claims

claims

1. A method for spatially resolved non-destructive workpiece inspection by means of at least one measuring sensor, which is guided over a technical surface of the workpiece to be examined and within the workpiece existing local material inhomogeneities, local material dances and / or local material structure is able to detect, characterized in that starting from a starting position at which the at least one measuring sensor is positioned on the surface of the workpiece and a first volume region of the workpiece detectable by the measuring sensor is represented by a first measuring signal, by moving the measuring sensor along the workpiece surface in a second position a movement trajectory, on the basis of a comparison of the first measurement signal with a second measurement signal obtained at the second position, which represents a second volume region, wherein the first and second volume regions at least partially overlap, is determined, and that based on the movement trajectory, the relative position of the second position relative to the starting position on the surface of the workpiece is determined.

2. The method according to claim 1, characterized in that by repeated execution of the displacement of the at least one measuring sensor on the surface of the workpiece and the respective determination of the movement trajectory between two positions, at each of which at least partially overlapping volume regions representative measuring signals are obtained, a plurality are obtained by Bewegungsstrajektorien, based on which the local position of the measuring sensor is determined on the surface of the workpiece relative to the starting position.

3. The method according to claim 1 or 2, characterized in that the measuring sensor, an ultrasonic transducer, preferably a piezoelectric or an electromagnetic ultrasonic transducer (EMUS), an eddy current sensor, a magnetic field sensor and / or a Mikrowellenmesstechnischer sensor are used.

4. The method according to any one of claims 1 to 3, characterized in that for determining the location of the at least one measuring sensor on the surface of the workpiece measuring signals from at least two different positions are used that in the presence of at least one detectable by the measuring sensor stationary material inhomogeneity and / or local Materialungänze and / or local material structure containing at least two measurement signals location-dependent location information about the material inhomogeneity and / or local material dances and / or local material structures that are subjected to a Geometrieberechnung.

5. The method according to claim 4, characterized in that the geometry calculation is used as part of image processing in which the individual measurement signals are evaluated as image signals representing sectional or volume images.

6. The method according to any one of claims 1 to 5, characterized in that measurement signal components which are not derived from stationary material inhomogeneities and / or local material dances are used for determining the location of the at least one measuring sensor.

7. The method according to any one of claims 1 to 6, characterized in that the at least one measuring sensor is moved manually or robot-assisted along the surface of the workpiece to be examined.

8. The method according to any one of claims 1 to 7, characterized in that using the ultrasonic measurement by means of at least one ultrasonic transducer obtained time signals, so-called A-pictures, and / or sector images, so-called B-pictures, are used for location.

9. The method according to claim 8, characterized in that an evaluation of the B-pictures for determining the position of the measuring sensor on the surface of the workpiece is carried out in real time or almost in real time.