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Ultrasonic Testing of Rails Including Vertical Cracks - Numerical Modeling and Experemental Results

: Schubert, F.; Köhler, B.; Sacharova, O.

Chimenti, D.E.; Thompson, D.O.:
Review of Progress in Quantitative Nondestructive Evaluation. 18B
New York, London: Plenum Press, 1999
ISBN: 0-306-46139-0
Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE) <25, 1998, Snowbird/Utah>
Conference Paper
Fraunhofer IZFP ()

The good qualitative agreement between the measurements and the numerical simulations for the different testing situations shows the accuracy of the developed numerical code. By the help of the simulations, all mode conversions at the crack and rail surfaces were cleared up leading to a better understanding and inerpretation of the recieved signals. A significant attenuation of the rail bottom echo for the three different crack locations were found for both, shear and longitudinal waves. The most important difference between the two wave modes is the fact the interaction between primary shear wavefront and crack or rail surfaces does not produce new echoes in the A-scan like head-waves or secondary echoes as descriebed for the P-wave. It should be mentioned that the method using piezoelectric shear wave transducers is unpracticable for fast testing of resl rails in railway tracks due to coupling-problems. But this can be solved bhy using EMA-transducers. Further investigations should i nvolve more realistic crack geometries and various crack parameters such as width, length, depth, orientation, surface roughness and so on, different frequencies and moreover, shear waves with a polarization plane perpendicular to the rail cross-section. The latter problem can be treated with a special three-dimensional EFIT model that consists of only one grid cell in the direction of the longitudinal rail axis if a strip-like transducer is still taken as a basis. a broader future perspective of the investigations should involve a classification of typical rail defects in the pulse-echo mode of ultrasonic testing.