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Experimental characterization of sensors for elastic guided waves based on 3D laser vibrometric measurements and the reciprocity relation

 
: Koehler, B.; Schubert, L.; Barth, M.; Windisch, T.

European Federation for Non-Destructive Testing -EFNDT-:
10th European Conference on Non-Destructive Testing, ECNDT 2010. CD-ROM : 7.-11.06.2010, Moskau
Moskau, 2010
10 pp.
European Conference on Non-Destructive Testing (ECNDT) <10, 2010, Moskau>
English
Conference Paper
Fraunhofer IZFP ()

Abstract
The development of new Non-destructive testing (NDT) and structural health monitoring (SHM) concepts initiated the development and application of new types of sensors and transducers. So, for structural health monitoring with guided elastic waves a variety of piezoelectric transducers were proposed. Examples are disc, foil and fiber transducers. A reliable characterization of these transducers in its various application conditions is necessary, because the transducer performance will depend on a number of factors. Among them are the way of mounting the transducer (e.g. attached or embedded), the type and thickness of a glue layer and also the structure the transducers are mounted to. Analytical and numerical modeling of the transducer behavior is helpful for characterizing the transducer's behavior, but has also its limitations. Within this paper a basic application of the reciprocity relation exerted to surface waves was demonstrated. Based on a well-designed experiment and carefully consideration of proper chosen input signals a good agreement between measurements and reciprocity related derivations can be achieved. The incorporation of laser-vibrometry enables new possibilities for characterizing sensors and actors used in NDT and SHM systems. Besides the evaluation of the valid scope of the presented relation it is also possible to characterize a transducer's sensitivity and its angular dependencies. Further studies will concentrate on the magnitudes of the determined signals to complete the model. Summing up and as shown in figure 6, reciprocity applied to surface waves is feasible and benefits a SHM sensor system's design.

: http://publica.fraunhofer.de/documents/N-186324.html