Parametric identification of a transmission line model forin situdamage characterization in lap joints

Abstract

This paper presents an in situ damage identification method to characterize the thickness and location of a notch in a one-dimensional lap joint. The approach uses the propagation of flexural waves generated by a piezoceramic (PZT) to evaluate the global reflection coefficient of a complex structure such as a lap joint. A transmission line model (TLM) is used to describe the theoretical reflection coefficient from healthy and damaged lap joints. Parameters from the lap joint are identified in two steps from the experimental measurement of the reflection coefficient. The first step is a calibration step which gives, for the healthy lap joint, the length of the lap joint and distance between the measurement point and the lap joint. The identification of these parameters is performed by minimizing a cost function evaluated for different combinations of parameters. The second step allows us to obtain the parameters associated with the notch, which are its location and thickness. Several cases of healthy and damaged lap joints are conducted and very good results are achieved for the identification of the parameters.

Subspace model identification of guided wave propagation in metallic plates

“…Lessening the dependence on the orthodox physical principles and adopting numerically friendly assumptions, semiphysical or parametric models have been strategically considered. For example, a parametric model with complex modulus is identified by a least squares solution [8]; a heuristic transmission line model is proposed for modeling wave propagation along lap joints [9]. There is an interesting task of estimation of a transfer function, between white-noise excitation and propagating waves in a thin aluminum strip [10]; the estimated transfer function is a data-fitted auto-regressive with exogenous input (ARX) model and thus considered a data-driven black-box model not directly related to the underlying physical principles of wave propagation.…”