Experimental application of the V.F.M. to the identification of material properties using vibrating plate

The paper presents a novel procedure to derive both stiffness and damping parameters from forced vibrating isotropic plates. The theory assumes that displacement and curvature fields are measured on the whole surface of the plate using a suitable optical technique. These data are processed with the Virtual Fields Method (VFM). In the case of an elastic isotropic material with viscous damping, the method leads to a linear system of equations valid for any excitation frequency. So the identification is possible out of resonance. A particular experimental set up is used for excitation and measurement of the kinematic fields. Measurement of the slope fields are taken at two times : in phase and at π/2 lag, using a phase shifting treatment of images of the plate taken with a CCD camera triggered by the excitation. First results of measurements and identifications are presented.