Une nouvelle analyse des sym\'etries d'un mat\'eriau \'elastique anisotrope. Exemple d'utilisation \`a partir de mesures ultrasonores

This note deals with stiffness tensors measured from anisotropic linear elastic materials, whose symmetry is unknown. Their possible symmetries (exact or approximative) are revealed by a pole figure. An intrinsic function allows one to obtain a stiffness tensor which posses the chosen symmetry, the nearest from the measured tensor, and its associated natural symmetry basis. For each symmetry level, a distance between these tensors is given. The measurement of the stiffness tensor is done with an ultrasonic direct contact method. It is applied onto a 26 faces oak specimen.