Damage characterization using reverberant decays

Classical wave experiments on chaotic scattering

“…where ν is the number of channels and Γ is the average decay rate. This was first derived in acoustics by Schröder [60] and later by Burkhardt [61,62,63]. This differs from (18) due to the assumed lack, in acoustics, of significant losses into the source and detection channels.…”

Power Variances and Decay Curvature in a Reverberant System

“…In a recent series of papers by Burkhardt and co-workers [27,28], it has been suggested that the decay curvature is a product of variation amongst modal decay rates, even between modes at almost the same frequency. Inasmuch as a simple perturbative estimate for the modal decay rate suggests that the decay rate should depend on the details in the shape of the associated eigenmode, one expects random #uctuations in these modal decay rates.…”

“…( t)/3n#2, i.e., the decay commences at the average rate. Burkhardt has suggested [28] that the parameter n, inasmuch as it is related to the number of a distinct sites at which dissipation is signi"cant, might correlate with the presence of localized damage. In any case, the model gives a plausible form for the curvature.…”

Structural Damage Characterization Using Free Decays

“…More recently, the author has presented an additional decay technique, more suitable to structural applications, which identi"es and characterizes non-uniform damage distributions in visco-elastic solids. This technique relies on a non-exponential, transient decay model for non-proportionally damped systems [6]. While adding considerable complexity, non-exponential decays also present an opportunity because, when properly modelled, they can be used to inversely determine damage characteristics as demonstrated in ultrasonic systems [6].…”

“…This technique relies on a non-exponential, transient decay model for non-proportionally damped systems [6]. While adding considerable complexity, non-exponential decays also present an opportunity because, when properly modelled, they can be used to inversely determine damage characteristics as demonstrated in ultrasonic systems [6]. This paper extends the ultrasonic technique to the identi"cation and characterization of structural damage which increases dissipation, such as corroded or loosely fastened connections, by exploiting the characteristics of non-exponential decays.…”