Frank Schubert: A Modeling Platform for Ultrasonic Immersion Testing of Polycrystalline Materials ..
Channel: NDT.net
Date: 2014-12-04

Ultrasonic immersion testing with conventional focused and unfocused transducers represents one of the most important measurement set-ups in nondestructive testing. In order to optimize the relevant UT configuration for specific materials and flaws a detailed understanding of the interaction between ultrasonic waves and specimen is essential. This includes the excited wave field in water, reflection and transmission at the surface, mode conversion between pressure and shear waves, shortening of the focal length in solids, interaction with the microstructure of the material, interaction with defects, reflections at the back wall including multiple reflections between top surface and back wall as well as the propagation path back to the transducer. Most of these aspects are in general guided by wave physics. This is of particular importance if the dominant wavelengths of the ultrasonic pulse are comparable to the lateral size of the flaw and/or the grain size of the microstructure. In the present work we present a numerical wave-physical modeling platform for ultrasonic immersion testing based on the Elastodynamic Finite Integration Technique (EFIT). Besides the characteristics of the transducer like diameter, focal length, frequency, pulse form, tilting angle etc., the platform is able to model the most important flaw geometries like cracks, notches, flat bottom holes, voids, inclusions, delaminations etc. Moreover, complex polycrystalline microstructures based on random isometric and textured Voronoi tessellations can be included and their frequency-dependent influence on the wave field can be studied. Numerical results of typical immersion testing applications are presented in terms of time-resolved wave front animations and pulse-echo A-Scans. These findings are briefly discussed and compared to experimental data. Read More at http://www.ndt.net/search/docs.php3?id=16826&content=1