A NEW ANALYSIS OF THE SYMMETRIES OF AN AN ISOTROPIC ELASTIC-MATERIAL - EXAMPLE FROM ULTRASONIC MEASUREMENTS

When the material symmetries ave unknown, experimental techniques give the stiffness tensor C only in the specimen base B-0 which is not rel ated to the possible symmetry directions. At first we suggest the use of a pole figure to reveal the symmetries of the tensor C. The intrins ic function F(C, B) allows us to determine the tensor C-sym, invariant by the symmetry group Sym, closest to C and its associated base B-sym . For each symmetry level we can choose the one which minimizes the di screpancy between C and C-sym. An ultrasonic experiment is explained a nd the full analysis is applied to an oak specimen.