High-Speed Mathematical Modelling of Ultrasound Propagation in Cladded and Welded Components Using Gaussian Beam Superposition
M. Spies, FhG-IzfP, Saarbrücken, Germany
ABSTRACT
To ensure safe operation, nuclear power plants have to be inspected periodically. Ultrasonic constitute a commonly applied non-destructive inspection technique, which however, suffers from the complex structure of the relevant components. Also, the performance of the various tests during shutdown is extremely costly due to the time the nuclear unit is out of service. In view of these aspects, mathematical modelling has evolved as a new important tool providing assisting analysis and optimised experimental set-ups. In inspecting cladded and welded components the prediction of ultrasonic signals is aggravated by the presence of curved interfaces as well as of the anisotropic and inhomogeneous microstructures. Thus, many modelling techniques suffer from large computation times, a problem that is even more critical when in-homogeneity has to be accounted for. In this contribution a computationally fast and simple ultrasonic modelling code based on the superposition of Gaussian beams (GB) is presented. This approach - formulated recently for anisotropic materials - is applied to the clad- component and weld geometries, in particular accounting fir the propagation through the isotropic/anisotropic layers and the reflection/refraction process at the plane and/or curved interfaces. In describing piston transducers, a ten-term Gaussian beam solution is used, where each beam function is furnished ith coefficients fixing the beam waists and their position. Verification is performed for single-layer, plane-surface configurations using both experimental and theoretical results. The latter are obtained using the Generalised Point Source Synthesis method. Examples are presented for plane and curved two-layered configuration of different material combinations as well as for several weld geometries. The GB-method allows for a fast evaluation of the sound fields generated by commercial angle beam transducers in the various configurations. Emphasis is put on (quasi-) longitudinal wave propagation accounting for both the reflected and the transmitted wave modes.
Publication Source: First International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurised Components , 20 - 22 October 1998, Amsterdam, Netherlands. Held by the Joint Research Centre of the European Commission. Publisher:Woodhead Publishing Limited
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