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Experimental and numerical study of acoustic wave propagation
Impakt-Echo. Experimentelle und numerische Untersuchungen akustischer Wellenausbreitung
: Algernon, D.; Schubert, F.; Wiggenhauser, H.

Al-Qadi, I. ; American Society for Nondestructive Testing -ASNT-, Columbus/Ohio:
NDE Conference on Civil Engineering: A joint conference of the 7th Structural Materials Technology (SMT) : NDE/NDT for highways and bridges and the 6th International Symposium on NDT in Civil Engineering (NDE-CE). August 14 - 18, 2006, St. Louis, Missouri
Columbus: ASNT, 2006
ISBN: 1-57117-157-6
Structural Materials Technology (SMT) <7, 2006, St. Louis/Mo.>
International Symposium on NDT in Civil Engineering (NDE-CE) <6, 2006, St. Louis/Mo.>
Fraunhofer IFAM ()

Impact echo is an acoustic NDT method successfully used for the investigation of concrete structures. For the interpretation of the measurements a detailed investigation of the acoustic wave propagation is highly relevant. This paper describes useful techniques for that purpose. By using a scanning laservibrometer it is possible to obtain a visualization of sound waves propagating along the surface of a concrete specimen. The interaction of the sound waves with tendon ducts as well as their behaviour when reaching the backwall of the specimen are investigated. Impact-echo measurements in transmission arrangement, in which the transducer is placed on the opposite side to the excitation, enable further investigation of the so-called geometry effects, which disturb the signals obtained from structures with limited dimensions. In order to visualize the surface wave propagation an arrangement showing the instantaneous wave field on all planes of the specimen in phase with the excitation is used. Time slices then show the instantaneous wave field for all points on the surface of the specimen. The experimental results are compared with numerical simulations.