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Modular System for Custom tailored Ultrasonic Inspection Author: Siegmar Schulz, KRAUTKRÄMER GmbH & Co. oHG, D-Hürth Co-Author: Klaus Volkmann, KRAUTKRÄMER GmbH & Co. oHG, D-Hürth Contact

As in other areas of technology, the PC has a lasting influence in the field of NDT. Ultrasonic test systems change and become components in a higher level system.
The two different component designs on the right are an example of this. Fig. 1 shows a PC card for the PCI bus. All components of a state-of-the-art ultrasonic flaw detector are contained on this card. After parameterization using a PC, a maximum of 8 such cards are able to work independently in one computer at a very high pulse repetition frequency without loading the CPU.

Fig 1: USPC 2100 PC Board

Fig 2: USLT 2000 PCMCIA Card

Fig. 2 shows an ultrasonic flaw detector as a PCMCIA plugin card. This module turns any notebook into a high performance ultrasonic flaw detector.
The computer industry supplies the right package for every application - whether it be a Desktop PC in the lab or a 19" industrial PC in a rolling mill.

The systems can be universally used for different test tasks; the configuration to the different methods for testing, recording and evaluation is made by the "Client/Server" software concept.

Fig. 3 shows that the application software no longer consists of a single package, which is difficult to test and maintain with changes. The software consists of a server developed together with the hardware which then remains unchanged. The server supplies the complete hardware operation quickly and has a plausibility check via a standardized interface. The client, a compact program written in a high-level language such as Visual Basic, requests the services of the server in order to display and further process them in an own environment tailored to the test task.

Fig 3: Client/Server Structure

This link, which is the foundation for many applications in the "World of Windows" (e.g. EXCEL and ACCESS are "clients"), is the basis for the application examples described in the following text.

The inspection of laser beam welded gear wheels shows the modular design.

As shown in Fig. 4, the gear wheel is lowered into an immersion tank and tested in one revolution. An unrolled presentation of the result is made and one track is allocated to each test channel. An evaluation of the flaw lengths is made online according to the applied specifications so that an Accept/Reject indication occurs when the gear wheel is withdrawn and the grip is able to deposit the part in the corresponding bin.

Fig 4: Gear Wheels

Fig 5: UltraPROOF

Fig 7: C-scan

Fig 6: Camshaft testing

The testing of hard soldered camshafts is an application by which a similar test method is linked to another evaluation.

The camshafts consist of a steel tube and casted cams which are hard soldered. Immersion testing is not carried out in the usual way by immersing the complete part in the coupling fluid but by flooding the vertically positioned camshaft and feeding the probe vertically into the tube (Fig. 6). The points to be tested are scanned spirally. The result of the test is displayed as a C-scan - an unrolled presentation of the cam´s inner side (Fig. 7). Good bonding areas are marked in green and insufficient bonding areas are marked in red.

The bonding surface of the largest individual flaw and the sum of all flaws is given as a percentage of the total bonding surface in an automatic evaluation of each cam. Due to modular design, the same components can be used for an entirely different test task.

When testing components from the aircraft industry, the testing device must, depending on the size of the component, be brought to the test object. Even here, there is a test movement divided into two axes and the result displayed as a C-scan.

Fig. 8 shows a lightweight X-Y scanner attached to the surface of the test object (in this case part of an aircraft fuselage) with vacuum suction pads. Ultrasonic and position data are fed to the PC during travel and a C-scan produced in which structural changes in the material are considerably better recognizable than in an A-scan of a normal ultrasonic flaw detector.

Fig 8: Portable Scanner

Fig 9: Portable PC

The ultrasonic card (Fig. 1) integrated into the PC can be used for normal testing without scan movement as shown in the example of the sound velocity measurement. For cost reasons, safety parts in the automotive industry, such as drag bearings or brake clasps, are increasingly being casted. Due to the fact that graphitization and the sound velocity are connected, information can be obtained via the ultrasonic test about the applicability of the part.

Fig 10: Steering Knuckle made of Cast Iron

Fig 11: Evaluation

A problem which can be solved by matching software: ultrasonics normally measures the time of flight in the material; the wall thickness can be calculated with a known sound velocity or vice versa. In the case of casted parts, the tolerance for the material thickness is too great so as to specify it as constant. Therefore a thickness measurement of the part must be made before the time of flight. The measurement is carried out in a water tank using the through-transmission mode. Firstly, the water path is measured without the part, then the remaining water path and the time of flight are measured with the part. The sound velocity can be determined (with dependence on thickness) with a little bit of calculation.

The last example shows the automated measurement and filing of probe data. Within the framework of measurement device certification even ultrasonic probes have to be inspected at regular intervals in order to guarantee test results.

If users apply large numbers of probes, e.g. in testing machines, then the manual test will quickly become incoherent. In this case, automatic process control is of help via the PC which guides the user through the test sequence step for step (Fig.12), prepares the necessary information using text and graphics and stores the test results in a user-friendly database.

Fig 12: Test Sequence

Fig 13: 13 Data Acquisition

These different application examples were made with the same ultrasonic equipment and a software matched within broad limits. The object is to consistently apply the client/server architecture so that the user is in a position to match the software without having to be a software developer!

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