A modified sequential algebraic algorithm applied to identify rough acoustic impedance profiles in slender structures

This paper develops and examines a modified technique for identifying damage in slender structures. An algorithm, called modified sequential algebraic algorithm, is presented to solve the longitudinal acoustic wave propagation problem in inhomogeneous media. This method accurately predicts the echo generated by the inhomogeneities when the acoustic impedance variation profile in the damaged part of the structure is non-smooth. For these cases, the available algorithms fail to provide the actual regressive wave component. In the following, a stochastic optimization scheme, the differential evolution method, is applied to solve the inverse problem. Numerical examples with smooth and non-smooth impedance profiles are considered. It is shown that, for smooth profiles, both the available techniques and the modified algorithm succeed in identifying the actual damage. Nevertheless, in situations where a rough profile is to be reconstructed, only the modified algorithm succeeds. The technique is found to be robust with respect to additive noise in the signals.