The evaluation of some mechanical properties of materials by means of an identification method of a nonlinear dynamical system

• A new identification procedure developed by the author is proposed.
• The procedure is useful for evaluating material properties at high strain rates.
• It is based on the (appropriately extended) rheological Zener model.
• Some results from computer simulations and an application for polyurea are presented.

The determination of the dynamic properties of materials is a complicated process. Ordinary static tension or compression tests often reveal a dependence between the elastic properties and the deformation velocity (which in such tests has an initially fixed constant value). This means that the rheological model of materials may be complicated, often going beyond the generally used linear viscoelastic model.The identification method presented in this paper can be helpful in determining the form of the rheological model of a material. The method consists in an appropriate analysis of the load-deformation dependences determined for a wide range of velocities of the motion of a concentrated mass attached to a flexible element made of the tested material.The method is based on the rheological Zener model appropriately extended to enable the evaluation of mechanical material properties also at high strain rates. Therefore a solid fraction, a nonlinear spring function and a nonlinear damping function are additionally included in the model. The forms of the functions are not fixed a priori, but are developed by the presented method.The method was verified on a numerical example as well as on a real material object.