DE10258336B3 - Non-destructive testing of components with monolithic and sandwich regions, e.g. aerospace parts, whereby transmission testing with water jet coupling is used with amplification adjusted for the different and transition regions - Google Patents

Abstract

Method for non-destructive testing of components in which a component (1) to be tested is transmission tested with ultrasound probe heads (2, 3) coupled to it from either side using a liquid jet (6, 7). The amplification of the probe heads can be adjusted over a dynamic range of more than 60 dB. When testing components that have both monolithic (1a) and sandwich (1b) regions a low amplification is used for the monolithic region, a higher amplification for the sandwich region and the amplification is varied from high to low or vice versa for the transition region. An Independent claim is made for a device for non-destructive testing of components with both monolithic and sandwich areas.

Description

TECHNICAL TERRITORY

The invention relates to a method and a non-destructive device Material testing using Ultrasound, in which a component to be checked is transmitted through an arrangement of ultrasound heads that moved on a predetermined path relative to the component and by means of a jet of liquid can be acoustically coupled to the component.

STATE OF THE ART

For non-destructive material testing of components with ultrasound it is known this by means of an arrangement of ultrasound heads to scan through, the ultrasound heads on a predetermined Path moved relative to the component and by means of a liquid jet be acoustically coupled to the component.

So is from the DE 40 07 956 C2 an ultrasound probe assembly for non-destructive material testing is known, in which an ultrasound probe is coupled by means of a feed chamber to a jet nozzle, which generates a free liquid jet for acoustic coupling of the probe to the workpiece.

From the DE 40 15 847 C2 is an ultrasonic test head arrangement for the non-destructive testing of adhesive or adhesive connections between sound-conducting plates, in particular sheets, known, which contains a sound transmitter and a sound receiver for sounding through the component to be checked in the transverse direction. Here, too, the sound coupling of the test heads should take place with the aid of a liquid free jet generated by a jet nozzle assigned to the test heads. The aim of the known arrangement is to reliably check components produced by large-area adhesive or adhesive connections of single or multiple duplicated plate parts for adhesive homogeneities. This is done by sonication of the component by means of a test head in the form of a highly damped low-frequency shock wave transducer with an increasingly lower dimensioned sound frequency of less than 2 MHz for components with a thickness between 1.5 mm and 5.0 mm between 1 MHz and 0.5 MHz.

From the DE 32 03 862 C2 it is known to test components with an irregular cross-sectional profile, ie, for example, a component with an outer skin and T-beams, using ultrasound without destruction. For this purpose, a special arrangement and alignment of two test heads is provided, the measured values of which are evaluated in the course of a difference formation process.

From the journal "Materialprüfung", 37 (1995) 11-12, pages 469 - 472, W. Hillger, "Imaging Ultrasonic testing for sandwich components "is a process for ultrasonic testing of honeycomb sandwich components known in which to examine the Honeycomb sandwich components in the form of samples with different Dimensions or core material thicknesses and densities as well as different Cover skin materials are available, Ultrasonic probes are used become. Dependent on the respective sandwich component shape becomes the respective transmission frequency spectrum of the ultrasound probe in question optimized by choosing the pulse duration, with depending on the thickness of the honeycomb and the top layer of the sandwich frequency spectra can result which are between 0.3 and 1.4 MHz depending on the component.

PRESENTATION THE INVENTION

The object of the invention is to specify a method and a device with which in reliable in one operation and it is easy to test components that are both monolithic Have areas as well as areas with a sandwich structure.

For example, the monolithic areas be formed by a pure CFRP laminate, while the sandwich areas for example areas with honeycomb cores can be used as honeycomb materials such as Nomex or aluminum honeycomb can be used. During monolithic areas a relatively good one Show sound transmission there is very high sound attenuation in the sandwich areas, where the sound transmission over the The core of the sandwich structure only very poorly, for example only zonally via the honeycomb bridges.

According to the invention, the posed Procedural task by a non-destructive process Materials testing with the features of claim 1 or claim 2 or of Claim 3 solved; device-wise the task set by a device for non-destructive Materials testing solved with the features of claim 18.

Advantageous further developments are in the respective subclaims specified.

In the following, embodiments of the Invention explained with reference to the drawing.

It shows:

1 a schematic side cross-sectional view of a probe assembly for non-destructive material testing of a component with ultrasound; and

2a ) and b) Longitudinal sections through ultrasonic probes, as used in the 1 shown arrangement can be used, according to two embodiments.

PRESENTATION OF PREFERRED EMBODIMENTS

In the 1 The device shown for non-destructive material testing with ultrasound comprises an ultrasound head arrangement 4 . 5 , the two ultrasound heads facing each other 2 . 3 contains, which are preferably designed here as an identical pair of probes. These are used to scan through a component 1 in a direction substantially transverse to its extent, the ultrasound head assembly 4 . 5 on a given path relative to the component 1 is moved. To do this, either the component 1 held stationary and the ultrasound head arrangement 4 . 5 relative to the component 1 be moved, the ultrasound head assembly 4 . 5 can be held stationary and the component 1 can be moved relative to it, or it can both the component 1 as well as the ultrasound head assembly 4 . 5 be moved, for example in the case of a rotationally symmetrical component 1 which is rotated around its axis during the ultrasound head assembly 4 . 5 is moved radially to it. The ultrasound heads 2 . 3 are each by means of a liquid jet 6 . 7 acoustically to the component 1 coupled.

In the 2a ) and b) a cross-sectional view of the ultrasound head arrangements shown in two embodiments 4 . 5 each include a pressurized water jet nozzle 102 ; 202 with a circular cylindrical, in a jacket tube 104 ; 204 , which can consist of acrylic glass, for example 106 ; 206 and one at the downstream end of the flow chamber 106 ; 206 - for example by screw connections - fixed nozzle insert 108 ; 208 , which can also be made of transparent material and with a to the central axis A - A of the flow chamber 106 ; 206 coaxial, cylindrical, but in diameter compared to the flow chamber 106 ; 206 reduced nozzle outlet channel 110 . 210 is provided. The ultrasound probe associated with the probe assembly 2 . 3 is directly on the insert 108 ; 208 opposite, sealed end of the flow chamber 106 ; 206 arranged.

On the front face of the insert 8th is a bulge inward into the flow chamber 6 protruding airflow nose 114 . 214 formed the nozzle outlet channel 110 . 210 encloses slightly in the inflow area and runs concentrically to the central axis A - A. The pressurized water supply to the jet nozzle 2 takes place via a in the flow chamber 106 ; 206 near the airflow nose 114 ; 214 opening opening 116 ; 216 , which is aligned exactly radially to the central axis AA, that is to this centrically and perpendicularly.

For individual, sensitive regulation of the liquid pressure conditions in the jet nozzle, this is a separate one between the pressurized water supply line 118 ; 218 and inlet opening 116 ; 216 effective, variably adjustable pressure control valve 120 ; 220 assigned.

At the in 2 B ) probe assembly shown, in contrast to that in 2a ) probe assembly shown the flow chamber 206 in the transition area between the cylindrical prechamber section and insert 208 to the outlet duct 210 frustoconically tapered and the inlet opening 216 is arranged in the outlet channel side end section of the cylindrical flow chamber section.

A particularly high free jet coupling quality results when the jacket tube 104 ; 204 the jet nozzle 102 ; 202 about 1.5 times as long as the insert 108 ; 208 and the diameter of the flow chamber 106 ; 206 about 2.5 times the size of the nozzle outlet channel 110 ; 210 is and the distance of the flow bead 114 ; 214 about 5 mm from the inner tube wall and its axial length is 4 mm.

The component 1 has differently structured areas, namely a monolithic area 1a and a sandwich area 1b , The monolithic area 1a can be formed, for example, by a CFRP laminate, whereas the sandwich area 1b through respective surfaces forming shells 1c and an intermediate core 1d , about a honeycomb core can be formed.

The material testing of the component 1 is carried out according to specified component-specific test specifications, for example the monolithic area 1a for a porosity of more than 5% and for delamination of more than 5 mm in diameter, the sandwich area 1b in the connection between shell 1c and core 1d checked for delamination of more than 15 mm diameter or similar.

The reinforcement of the test heads is used to carry out the material test 2 . 3 adjustable over a wide dynamic range, with material testing of the monolithic range 1a of the component 1 the probes 2 . 3 operated with a relatively low gain, whereas for material testing of the sandwich area 1b of the component 1 the probes 2 . 3 operated with a relatively high gain. At the transition from the monolithic area 1a to the sandwich area 1b and / or vice versa, the gain is changed depending on the type of component area to be tested 1a . 1b , so that in one operation an examination of both the monolithic area 1a as well as the sandwich area 1b of the component 1 can be done.

The large dynamic range over which the gain of the probes 2 . 3 is adjustable is necessary agile to the monolithic area 1a and the sandwich area 1b of the component 1 to be able to test in one operation, since the ability to transmit ultrasound for the monolithic area 1a and the sandwich area 1b considerable, namely by several orders of magnitude. The test heads are preferably reinforced 2 . 3 Adjustable over a range of more than 60 dB, advantageously over more than 80 dB, possibly over more than 100 dB.

The reinforcement of the test heads 2 . 3 becomes at the transition from the monolithic area 1a to the sandwich area 1b and / or vice versa adjusted by 20 to 60 dB, typically by 30 to 40 dB. This adjustment at the transition from the monolithic area 1a to the sandwich area 1b and / or vice versa plus a setting option for the basic reinforcement of the test heads 2 . 3 makes the aforementioned large adjustability of more than 60 dB to possibly more than 100 dB necessary. The change in the gain of the probes 2 . 3 at the transition from the monolithic area 1a to the sandwich area 1b and / or vice versa can be erratic or gradual.

Typically, the probes 2 . 3 operated at a significantly lower frequency than their actual nominal frequency. The test heads can for example have a nominal frequency between 4 and 20 MHz, in particular typically a nominal frequency between 8 and 12 MHz. The probes 2 . 3 are typically operated at a frequency that is a factor of 2 to 4 below the nominal frequency. In particular, the test heads 2 . 3 be operated at a frequency which is a factor of 4 to 20, preferably 4 to 8, below the nominal frequency. In the exemplary embodiment described here, the nominal frequency of the test heads is 2 . 3 over 8 MHz and the probes 2 . 3 are operated at a frequency of 2 to 4 MHz.

In the illustrated embodiment, the component 1 by means of an arrangement of two opposing ultrasound heads 2 . 3 transmitted through, one of which is operated as a transmitter and the other as a receiver. It can either always be the same, for example the ultrasound head 2 as the transmitter and the other, for example the ultrasound head 3 operated as a receiver, or the ultrasonic heads 2 . 3 can be operated alternately as transmitter and receiver or as receiver and transmitter.

In 1 are just the component 1 who have favourited Ultrasound Head Assembly 4 . 5 and robot manipulators 9 . 10 to move the ultrasound head assembly 4 . 5 relative to the component 1 shown, but not the amplifier devices for generating the ultrasound frequencies for the ultrasound heads 2 . 3 and also not the means for supplying the liquid for generating the liquid jets 6 . 7 for acoustic coupling to the component 1 , As such, they are known in the art.

In the test method explained above, there is a point in time and / or a place at which a change in the gain during the transition from a monolithic region 1a to a sandwich area 1b and / or vice versa, preferably by comparing a current position of the ultrasound heads 2 . 3 in relation to the component 1 with stored data of a two- or three-dimensional construction model of the component to be tested 1 certainly. For this purpose, the test device according to the invention has at least one suitable position sensor, at least one data processing device with storage means in which the data of the construction model of the component 1 are stored, as well as a control device which is connected to the data processing device and / or the position sensor and the ultrasonic test heads or their control device and which can initiate or effect the change in the gain of the test heads.

Device and method for non-destructive Materials testing with ultrasound, as described above, allow automated exam of monolith and sandwich structures in one pass, so that a reliable, Fast and always reproducible material testing, especially of highly stressed ones and / or particularly critical components in vehicle construction in which Aerospace, energy technology and other fields allows becomes.

In a second embodiment of a method according to the invention for non-destructive material testing using ultrasound, in which essentially the device described above can be used, a component to be checked is used 1 also by means of an arrangement of ultrasound heads 2 . 3 passes through on a given path relative to the component 1 moved and by means of a jet of liquid 6 . 7 acoustically to the component to be tested 1 be coupled. The reinforcement of the ultrasound heads 2 . 3 is in turn adjustable over a wide dynamic range. For material testing of a monolithic area 1a of the component 1 become the ultrasound heads 2 . 3 as with the first embodiment operated with a relatively low gain (see above). For material testing of an area constructed as a sandwich structure 1b of the component 1 the ultrasound heads 2, 3 are operated with a relatively high gain (see above). In a first step, the monolithic area is checked 1a of the component 1 with the low gain. The gain is then dependent on the type of component area to be tested 1a . 1b changed, ie here: increased (see above). The area constructed as a sandwich structure is then checked in a second step 1b of the component 1 with the high gain (see above). In this way, the component is checked in two steps 1 performed that both monolithic areas 1a as well as sandwich areas 1b having. The procedure can of course also be reversed, that is to say the sandwich areas must first be checked 1b and then testing the monolithic areas 1a , In this variant of the method, the reinforcement of the ultrasound heads does not have to be changed during a transition from a monolith to a sandwich area or permanently adapted to the nature of the respective component areas. Rather, the entire component is first run with the lower gain and then with the high gain, or vice versa. When using several different test heads, which have the required reinforcement, ie a low and a high gain, the testing of the different component areas can even be carried out in one operation.

In a third embodiment of a method according to the invention for non-destructive material testing using ultrasound, in which essentially the device described above can be used, a component to be checked is used 1 also by means of an arrangement of ultrasound heads 2 . 3 passes through on a given path relative to the component 1 moved and by means of a jet of liquid 6 . 7 acoustically to the component to be tested 1 be coupled.

For material testing of both monolithic areas 1a as well as sandwich areas 1b of the component 1 become the ultrasound heads 2 . 3 , which have a logarithmically resolving ultrasound receiver, are operated only with a relatively high gain of more than 60 dB (for example 70 to 100 dB or more) at a substantially constant frequency and are moved over the component in one operation. Measurement data acquired by the logarithmically resolving ultrasound receiver over an entire logarithmic ultrasound reception spectrum are stored in a storage means of a data processing device. Despite the constant frequency and high amplification (which is much higher than necessary for the monolithic areas), the ultrasound receiver is able to resolve the entire ultrasound echo spectrum for both monolithic areas and sandwich areas with sufficient accuracy.

To check the monolithic areas 1a of the component 1 only upper measured value ranges of the stored, recorded ultrasound reception spectrum are then evaluated. And to check the sandwich areas 1b of the component 1 only lower measured value ranges of the stored, recorded ultrasound reception spectrum will be evaluated in each case.

Due to the logarithmic resolution, the Differences between an echo from a monolith and a sandwich area Naturally so big that for the purpose of a visual display they are not uniform in a common measurement image (e.g. on a monitor of the data processing system), in which a certain echo intensity is usually a certain one Color is assigned, can be displayed. Because the echoes are off a monolith area of course always of the same order of magnitude can move they are easily displayed and evaluated in a single measurement image become. The same applies to the echoes from the sandwich areas. So there are usually two different measurement images for evaluating the respective different Component areas (monolith or sandwich areas) required. For one However, the specific location of the component to be considered is factual evaluated the data of the same measured value, however different measured value ranges can be considered.

Reference signs in the claims, the The description and the drawings serve only for a better understanding of the Invention and are not intended to limit the scope.

Designate it:

1

component

1a

monolithic Area

1b

Sandwich area

1c

Bowl

1d

core

2

ultrasound probe

3

ultrasound probe

4

Ultrasound transducer assembly

5

Ultrasound transducer assembly

6

liquid jet

7

liquid jet

9 10

Robot manipulators

102; 202

Pressure water-jet nozzle

104; 204

casing pipe

106; 206

lead chamber

108; 208

Nozzle insert

110; 210

Nozzle outlet channel

114; 214

Umströmungsphase

116; 216

inlet opening

118; 218

Pressurized water supply line

120; 220

Pressure control valve

Claims (31)

Process for non-destructive material testing with ultrasound, in which a component to be checked ( 1 ) by means of an arrangement of ultrasound heads ( 2 . 3 ), is transmitted through on a given path relative to the workpiece ( 1 } moved and by means of a liquid jet ( 6 . 7 ) acoustically to the workpiece ( 1 ) are coupled, characterized in that - the reinforcement of the test heads ( 2 . 3 ) is adjustable over a wide dynamic range of more than 60 dB; and - one component inspection ( 1 ) that covers both monolithic areas ( 1a ) as well as sandwich areas ( 1b ) exhibit; - the reinforcement of the test heads ( 2 . 3 ) at the transition from a monolithic area ( 1a ) to a sandwich area ( 1b ) and / or vice versa is adjusted by 20 to 60 dB; - whereby for material testing of a monolithic area ( 1a ) of the component ( 1 ) the probes ( 2 . 3 ) operated with a low gain and for material testing of an area constructed as a sandwich structure ( 1b ) of the component ( 1 ) the probes ( 2 . 3 ) are operated with a high gain. Process for non-destructive material testing with ultrasound, in which a component to be checked ( 1 ) by means of an arrangement of ultrasound heads ( 2 . 3 ) is transmitted through, which is on a predetermined path relative to the component ( 1 ) moved and by means of a liquid jet ( 6 . 7 ) acoustically to the component ( 1 ) are coupled, characterized in that - the reinforcement of the ultrasound heads ( 2 . 3 ) is adjustable over a wide dynamic range of more than 60 dB; and - a test of components in two work steps ( 1 ) that covers both monolithic areas ( 1a ) as well as sandwich areas ( 1b ) exhibit; - the reinforcement of the test heads ( 2 . 3 ) to check a monolithic area ( 1a ) on the one hand and for checking a sandwich area ( 1b ) on the other hand and / or vice versa is adjusted by 20 to 60 dB; - whereby for material testing of a monolithic area ( 1a ) of the component ( 1 ) the probes ( 2 . 3 ) operated with a low gain and for material testing of an area constructed as a sandwich structure ( 1b ) of the component ( 1 ) the probes ( 2 . 3 ) are operated with a high gain. Process for non-destructive material testing with ultrasound, in which a component to be checked ( 1 ) by means of an arrangement of ultrasound heads ( 2 . 3 ) is transmitted through, which is on a predetermined path relative to the component ( 1 ) moved and by means of a liquid jet ( 6 . 7 ) acoustically to the component ( 1 ) can be coupled, characterized in that for material testing both monolithic areas (1a) and sandwich areas ( 1b ) of the component ( 1 ) Ultrasound heads ( 2 . 3 ) which have a logarithmically resolving ultrasound receiver, are operated only with a relatively high gain of more than 60 dB at a substantially constant frequency and are moved over the component in one operation; Measurement data recorded by the logarithmically resolving ultrasound receiver over an entire logarithmic ultrasound reception spectrum is stored in a storage means of a data processing device for checking the monolithic areas ( 1a ) of the component ( 1 ) only upper measured value ranges of the stored, recorded total ultrasound reception spectrum are evaluated, and for checking the sandwich areas ( 1b ) of the component ( 1 ) only lower measured value ranges of the stored, recorded total ultrasound reception spectrum are evaluated. Method according to one or more of the preceding claims, characterized in that the reinforcement of the test heads ( 2 . 3 ) is adjustable over a range of more than 80 dB. Method according to one or more of the preceding claims, characterized in that the reinforcement of the test heads ( 2 . 3 ) is adjustable over a range of more than 100 dB. Method according to one or more of the preceding claims, characterized in that the reinforcement of the test heads ( 2 . 3 ) at the transition from a monolithic area ( 1a ) to a sandwich area ( 1b ) and / or vice versa by 30 to 40 dB. Method according to one or more of the preceding claims, characterized in that the change in the gain of the test heads ( 2 . 3 ) at the transition from a monolithic area ( 1a ) to a sandwich area ( 1b ) and / or vice versa. Method according to one or more of the preceding claims 1-10, characterized in that the change in the gain of the test heads ( 2 . 3 ) at the transition from a monolithic area ( 1a ) to a sandwich area ( 1b ) and / or vice versa. Method according to one or more of the preceding claims, characterized in that the test heads ( 2 . 3 ) are operated at a frequency significantly lower than their actual nominal frequency. Method according to one or more of the aforementioned Expectations, characterized in that the test heads have a nominal frequency between 4 and have 20 MHz. Method according to one or more of the aforementioned Expectations, characterized in that the test heads have a nominal frequency between Have 8 and 12 MHz. Method according to one or more of the preceding claims, characterized in that the test heads are operated at a frequency be below the nominal frequency by a factor of 2 to 4. Method according to one or more of the aforementioned Expectations, characterized in that the test heads are operated at a frequency, which is a factor of 4 to 20 below the nominal frequency. Method according to one or more of the aforementioned Expectations, characterized in that the nominal frequency of the probes above 8 MHz is and that the probes with operate at a frequency of 2 to 4 MHz. Method according to one or more of the preceding claims, characterized in that the component ( 1 ) by means of an arrangement of two ultrasound heads facing each other ( 2 . 3 ) is transmitted through, of which ner ( 2 ) as transmitter and the other (3) as receiver. Method according to one or more of the preceding claims, characterized in that the component ( 1 ) by means of an arrangement of two ultrasound heads facing each other ( 2 . 3 ) is transmitted through, which are operated alternately as transmitter and receiver or as receiver and transmitter. A method according to claim 1, characterized in that a point in time and / or place at which a change in the gain in the transition from a monolithic area ( 1a ) to a sandwich area ( 1b ) and / or vice versa, by comparing a current position of the ultrasound heads ( 2 . 3 } in relation to the component ( 1 ) with stored data of a two- or three-dimensional construction model of the component to be tested ( 1 ) is determined. Device for non-destructive material testing with ultrasound, with an arrangement of ultrasound heads ( 2 . 3 ) to scan through a component to be checked ( 1 ) that are on a given path relative to the component ( 1 ) movable and by means of a liquid jet ( 6 . 7 ) acoustically to the component ( 1 ) can be coupled, characterized in that - the reinforcement of the test heads ( 2 . 3 ) is adjustable over a wide dynamic range of more than 60 dB; and - for one-step inspection of components ( 1 ), both monolithic areas ( 1a ) as well as sandwich areas ( 1b ), the reinforcement of the test heads ( 2 . 3 ) at the transition from a monolithic area ( 1a ) to a sandwich area ( 1b ) and / or vice versa can be adjusted by 20 to 60 dB dB; - whereby for material testing of a monolithic area ( 1a ) of the component ( 1 ) the probes ( 2 . 3 ) can be operated with a low reinforcement and for material testing of an area constructed as a sandwich structure ( 1b ) of the component ( 1 ) the probes ( 2 . 3 ) can be operated with a high gain. Apparatus according to claim 18, characterized in that the reinforcement of the test heads ( 2 . 3 ) is adjustable over a range of more than 80 dB. Apparatus according to claim 18 or 19, characterized in that the reinforcement of the test heads ( 2 . 3 ) is adjustable over a range of more than 100 dB. Device according to one or more of claims 18 to 20, characterized in that the reinforcement of the test heads ( 2 . 3 ) at the transition from a monolithic area ( 1a ) to a sandwich area ( 1b ) and / or vice versa is adjustable by 30 to 40 dB. Device according to one or more of claims 18 to 21, characterized in that the reinforcement of the test heads ( 2 . 3 ) at the transition from a monolithic area ( 1a ) to a sandwich area ( 1b ) and / or vice versa can be changed by leaps and bounds. Device according to one or more of claims 18 to 21, characterized in that the reinforcement of the test heads ( 2 . 3 ) at the transition from a monolithic area ( 1a ) a Sanwich area ( 1b ) and / or vice versa is gradually changeable. Device according to one or more of claims 18 to 23, characterized in that the test heads ( 2 . 3 ) can be operated at a significantly lower frequency than their actual nominal frequency. Device according to one or more of claims 18 to 24, characterized in that the test heads have a nominal frequency between 4 and 20 MHz. Device according to one or more of claims 18 to 25 characterized in that the test heads have a nominal frequency between Have 8 and 12 MHz. Device according to one or more of claims 18 to 26, characterized in that the test heads ( 2 . 3 ) can be operated at a frequency that is a factor of 2 to 4 below the nominal frequency. Device according to one or more of claims 18 to 27, characterized in that the test heads ( 2 . 3 ) can be operated at a frequency which is a factor of 4 to 20, preferably 4 to 8, below the nominal frequency. Device according to one or more of claims 18 to 28, characterized in that the test heads ( 2 . 3 ) have a nominal frequency of over 8 MHz and that the test heads can be operated with a frequency of 2 to 4 MHz. Device according to one or more of claims 18 to 29, characterized in that an arrangement of two ultrasound heads ( 2 , 3) for sonication of the component (1), an ultrasound head ( 2 ) can be operated as a transmitter and the other ultrasound head as a receiver. Device according to one or more of claims 18 to 30, characterized in that an arrangement of two mutually opposite ultrasound heads ( 2 . 3 ) to scan through the component ( 1 ) is present, with the ultrasound heads ( 2 . 3 ) can be operated alternately as transmitter and receiver or as receiver and transmitter.