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Sampling phased array application for immersion technique

: Kudalkar, V.N.; Kröning, M.; Reddy, K.M.; Bulavinov, A.

Volltext urn:nbn:de:0011-n-511591 (84 KByte PDF)
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Erstellt am: 18.7.2008

Indian Society for Non-Destructive Testing:
NDE 2006. Seminar on Non-Destructive Testing & International Exhibition. CD-ROM : NDE in Knowledge Society, Hitex Exhibition Center, Hyderabad, India, December 7-9, 2006
Hyderabad: Indian Society for Non-Destructive Testing, 2006
Seminar on Non-Destructive Testing (NDE) <2006, Hyderabad>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer IZFP ()
phased array; ultrasonic testing

The principles of phase controlled excitation and processing of ultrasonic signals are used in nondestructive testing and medical diagnostics. A phased array system is a multi channel ultrasonic system, which uses the principle of a time-delayed triggering of the transmitting transducer elements, combined with a time - corrected receiving of detected signals. The main advantage of the phased array systems is their ability to vary the angle of insonification in the inspection object (sweeping and focusing of the sound beam).
A new phased array technique - sampling phased array (SPA) was developed in the Fraunhofer-Institute for non-destructive testing (IZFP), which uses a patented technology. Conventional phased array requires several shots at different angles to cover the entire section. In contrast, in the sampling principle, the same can be achieved with a single insonification (single shot). For this, it is necessary to calculate the to and fro travel times for different points inside the test specimen. Faster inspection speeds with simultaneous enhancement of information content (qualitative and quantitative), fast 2D and 3D imaging in real time, cost reduction are some of the important advantages of SPA technique.
The ultrasonic testing of steel billets is typically carried out in a water bath to achieve maximum sensitivity and high eproducibility. Inline inspection takes place with the movement of steel billet along its longitudinal axis. This approach can be extended to examination of rods, pipes and other cylindrical structures. In immersion technique, the sound has to travel through two different media. The sound paths in each medium are straight-lines but at interface between different media, refraction causes ray direction to change.
In present work we present the results for billets and rods. For planar interface, Taylor series expansions for travel times can be used which involve velocities in different media and their even order moment. This gives accurate results for small offset to depth ratio. For curved interfaces, forward ray tracing can be used with generalized 2D interpolation
to find travel times.