Efficient modelling of nonlinear ultrasonic NDT systems

Most of the Ultrasonic Systems modelling techniques for Non Destructive Testing (NDT) applications assume that the system under study is linear: actually in a number of cases the system can show, to some extent, non-linear characteristics. In some circumstances the non-linear behavior leads to significant differences between the real response and the one modelled under the hypothesis of linearity. Efficient methods for non-linear systems characterization and parametrization are assuming an increasing importance in the NDT field. By modifying the standard pulse-compression procedure, Farina proposed a very efficient and easy to implement method to estimate the parameters of a generalized Hammerstein model, which describes a large class of nonlinear systems in the case they do not exhibit hysteresis. In the present paper we propose the results of our study on the application of this method for modeling Non Linear Systems in the specific case of Ultrasonic NDT. A survey of the method and the results of a number of laboratory experiments are reported.