Material model robust identification procedure from dynamical measurements made on a flexible specimen-frame system

A procedure for the identification of the material model of beam specimens by means of harmonic force and displacement measurements in flexural condition is presented. Input-output frequency response function (FRF) evaluations are used in standard DMA instruments to estimate the material stress–strain frequency response function. Nevertheless, the contribution of the instrument frame model coupling and of the inertial contribution of the excitation moving substructure to the input–output FRFs can make such estimates meaningless in most practical applications, especially if a wide excitation frequency range is taken into account. In this work the instrument frame model contribution is estimated by means of doing calibration measurements on some reference beams and processing them by a procedure based on optimization algorithms. A signal processing-based procedure is also proposed to identify the optimal frame model rational function fit by eliminating computational and noise related contribution. The identified rational frame model is used to obtain the material model in the frequency domain being filtered from the contribution of the experimental system. The proposed technique robustness is tested on some numerical model cases. The same technique is then applied to some dynamical measurements made on specimens of different materials. The results are shown and critically discussed.