Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Non-linear frequency domain techniques for processing impact-echo signals for distributed damage in concrete
The concrete deterioration processes of alkali-silica reaction (ASR), delayed ettringite formation (DEF) and freeze-thaw cycles all produce distributed damage in the form of microcracking which results in loss of strength or stiffness. Ultrasonic stress waves are the basis for nondestructive test methods for measurement of this type of distributed damage. Conventional ultrasonics-based test methods such as impact-echo have characterized the damage in terms of changes in the attenuation factor, or pulse velocity, which are obtained by processing the signal in the time domain. However, these are inherently linear dynamics method while the development of microcracks gives rise to nonlinear dynamics. One approach to signal processing in the frequency domain calculates the Q-factor. However, this is essentially a linear dynamics method. Two nonlinear approaches are proposed here. One involves calculating the deviation of the peak from the shape of an ideal Lorentzian function model. The other calculates the second order nonlinear harmonic coefficient. Examples of these methods are given using data from laboratory specimens which have been damaged by DEF.
Non-linear frequency domain techniques for processing impact-echo signals for distributed damage in concrete
The concrete deterioration processes of alkali-silica reaction (ASR), delayed ettringite formation (DEF) and freeze-thaw cycles all produce distributed damage in the form of microcracking which results in loss of strength or stiffness. Ultrasonic stress waves are the basis for nondestructive test methods for measurement of this type of distributed damage. Conventional ultrasonics-based test methods such as impact-echo have characterized the damage in terms of changes in the attenuation factor, or pulse velocity, which are obtained by processing the signal in the time domain. However, these are inherently linear dynamics method while the development of microcracks gives rise to nonlinear dynamics. One approach to signal processing in the frequency domain calculates the Q-factor. However, this is essentially a linear dynamics method. Two nonlinear approaches are proposed here. One involves calculating the deviation of the peak from the shape of an ideal Lorentzian function model. The other calculates the second order nonlinear harmonic coefficient. Examples of these methods are given using data from laboratory specimens which have been damaged by DEF.
Non-linear frequency domain techniques for processing impact-echo signals for distributed damage in concrete
Nichtlineare Frequenzbereichstechnik zur Verarbeitung von Impaktechosignalen für die Schadensverteilung in Beton
Livingston, Richard (Autor:in) / McMorris, Nicolas (Autor:in) / Lijeron, Cintia (Autor:in) / Amde, Amde (Autor:in)
2009
6 Seiten, 2 Bilder, 10 Quellen
(nicht paginiert)
Aufsatz (Konferenz)
Datenträger
Englisch
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