THIS COMMUNICATION IS CANCELLED: Compared performances of Levenberg-Marquardt-like methods vs Genetic Algorithm ones for elastic constants evaluation of orthotropic materials in a non principal coordinate-system

The evaluation of the elastic properties of an orthotropic material has widely been studied and reported in many papers. In the case of composite materials the principle symmetry axes correspond to those of the sample, and nine constants have to be determined. But in the case of anisotropic polycristals, such as austenitic stainless steel welds, it is not the always the case. Then, the characterization of the elastic properties of the material from time of ultrasonic velocities measurement requires to recover the nine elastic constants allowing to express the stiffness tensor in the material's principal coordinate system but also the three Euler angles related to the sample's coordinate system with respect to the materials one. Moreover, the complexity in the inversion process increases and classical algorithms are often trapped by local minima of the objective function. In this paper, the performances of a classical local inversion algorithm will be compared, on simulated data, with the ones of a Genetic Algorithm. The influence of several parameters, such as noise or initialisation set will be studied and discussed.