Full title: Optimization of coded excitations with Symmetry Analysis : Formalism and applications in NDT with perspectives in ultrasonic nonlinear imaging of bio-materials

Abstract: Ultrasonic imaging of material complexity is investigated theoretically and experimentally using the concept of symmetry analysis based signal processing, in symbiosis with the nonlinear elastic wave spectroscopy. These concepts have been tested experimentally on several complex media using an advanced electronic system. This system exploits the Time Reversal invariance, reciprocity and coded-excitation for an accurate extraction of the nonlinear signature of the medium under ultrasonic monitoring. Tested both in the context of the medical imaging of a tooth and in those of nondestructive testing (NDT) of aeronautic composites, the basis of a new tomography imaging of material complexity is described with the help of algebraic concepts describing the TR operators.