Experimental Identification of the B-spline Model of Isotropic Viscoelastic Materials

Purpose A nonlinear, model-based, material identification procedure is proposed. The procedure makes it possible to identify the complex elastic E ( ω ) tensile modulus and the G ( ω ) shear modulus of isotropic, viscoelastic materials, from experimental measurements made on material beam specimens. Methods A mixed experimental-numerical technique is proposed to estimate the beam specimen input-output, frequency dependent, transfer ratio in a wide frequency range, requiring forced harmonic and creep relaxation dynamical measurements. The analytical frequency transfer function is also found, by modeling the full mechanical test system. An algebraic, iterative E ( ω ) and G ( ω ) material parameter identification procedure is described, and a B-spline fitting procedure is adopted to obtain the continuous E ( ω ) and G ( ω ) model. The contribution of the experimental noise can be filtered by means of properly choosing the B-spline fitting parameters. Results The identification of a known material model from numerically simulated data with added random noise is reported, and some results concerning the experimental identification of the unknown model of some materials are also reported and discussed. Conclusions A novel technique for the experimental parametric identification of the material model of isotropic viscoelastic materials in a wide frequency range is proposed. An iterative, algebraic numerical procedure is proposed to identify the complex value of the material parameters at the experimental test frequencies, and a B-spline continuous complex fit of the material parameters is obtained. Material consistency constraints are taken into account. The proposed procedure does not require optimization nonlinear techniques to be used. Some application cases are proposed to outline the effectiveness and robustness of the proposed technique.