Application of a filtering method for the estimation of effective transmission condition parameters from ultrasonic data

In a recently completed thesis work, a filtering strategy combining both iterations of a Levemberg-Marquardt descent method with a gradient-free Kalman filtering approach has been developed. First evaluations of the algorithm have been carried out in order to reconstruct the pre-deformation of a plate geometry from guided wave ultrasound data. In this context, the main objective of the proposed work is on the one hand to consolidate the knowledge and implementation of the proposed approach, and to confirm its efficiency and interest in other ultrasonic NDT configurations. A particular application case of interest in the framework of this work will be the reconstruction of the Effective Transmission Conditions (ETCs) parameters that can typically represent: a delamination defect between two layers of a composite material, an imperfect bonding between an ultrasonic sensor and the inspected part, or an interface presenting a roughness of characteristic dimensions lower than the minimum wavelength used for the control. In practical industrial cases, the parameters of these ETCs are difficult to obtain. Thus, the interest of setting up a filtering process is to offer, in complex cases, an automatic calibration of the effective parameters of these models.