Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Break of reciprocity principle due to localized nonlinearities in concrete
We have shown here that the well known elastic nonlinear properties of concrete have important effects on the reciprocity principle. While distributed nonlinearity and/or damage have little influence on reciprocity between signals from one source to a receiver and viceversa, the result becomes more complex when localized damage is present. In such cases, nonlinear indicators of the reciprocity break can be introduced, either from the signals themselves (R is defined as a difference between signals) or from the nonlinearity of the sample (indicator k). Both seem to be correlated not only to the presence of localized damage, but also to its position, since the larger the asymmetry (between transducers and defect positions), the higher both reciprocity indicators. Exploiting the linear correlation between non-reciprocity and asymmetry into a quantitative analysis is the next step to define a Nonlinear Reciprocity Ultrasonic Tomography technique for location of cracks in concrete. Data on other samples show that the method could indeed be applied to detect also closed cracks and simulations indicate the feasibility also on 2-D and 3-D samples, provided a large number of transducers is used. Of course, comparison of the efficiency in crack location using other linear or nonlinear methods will be required to prove the usefulness of the proposed approach. The topic is under study and it is not within the scope of the present contribution, also due to the nature of the considered crack. Finally, it is important to mention the role of the coda of the signals. Here, only a small time window has been used around the first arrivals. Coda contains much more information, resulting from more complex propagation paths and including reflections and transmission from the crack. While here it is more difficult to define the asymmetry of the transducers with respect to the crack, the signals could provide a stronger mean to define an efficient imaging procedure, with perhaps a reduced number of transducers.
Break of reciprocity principle due to localized nonlinearities in concrete
We have shown here that the well known elastic nonlinear properties of concrete have important effects on the reciprocity principle. While distributed nonlinearity and/or damage have little influence on reciprocity between signals from one source to a receiver and viceversa, the result becomes more complex when localized damage is present. In such cases, nonlinear indicators of the reciprocity break can be introduced, either from the signals themselves (R is defined as a difference between signals) or from the nonlinearity of the sample (indicator k). Both seem to be correlated not only to the presence of localized damage, but also to its position, since the larger the asymmetry (between transducers and defect positions), the higher both reciprocity indicators. Exploiting the linear correlation between non-reciprocity and asymmetry into a quantitative analysis is the next step to define a Nonlinear Reciprocity Ultrasonic Tomography technique for location of cracks in concrete. Data on other samples show that the method could indeed be applied to detect also closed cracks and simulations indicate the feasibility also on 2-D and 3-D samples, provided a large number of transducers is used. Of course, comparison of the efficiency in crack location using other linear or nonlinear methods will be required to prove the usefulness of the proposed approach. The topic is under study and it is not within the scope of the present contribution, also due to the nature of the considered crack. Finally, it is important to mention the role of the coda of the signals. Here, only a small time window has been used around the first arrivals. Coda contains much more information, resulting from more complex propagation paths and including reflections and transmission from the crack. While here it is more difficult to define the asymmetry of the transducers with respect to the crack, the signals could provide a stronger mean to define an efficient imaging procedure, with perhaps a reduced number of transducers.
Break of reciprocity principle due to localized nonlinearities in concrete
Brechen des Reziprozitätsprinzips während der Ortung von Nichtlinearitäten in Beton
Scalerandi, M. (Autor:in) / Bruno, C.L.E. (Autor:in) / Gliozzi, A.S. (Autor:in) / Bocca, P.G. (Autor:in)
Ultrasonics ; 52 ; 712-719
2012
8 Seiten, 10 Bilder, 1 Tabelle, 38 Quellen
Aufsatz (Zeitschrift)
Englisch
Nonlinear response spectrum for systems with localized nonlinearities
| British Library Conference Proceedings | 1996