FINITE ELEMENT MODELING OF THE ROLLING BEHAVIOR OF A POLYURETHANE SPHERE FOR LOW-COST SEISMIC ISOLATION APPLICATIONS

This paper presents the experimental test and finite element modeling of the rolling behavior of a very hard (95 Shore A) polyurethane elastomeric sphere that can be used to construct low-cost seismic isolation systems. A small-amplitude rolling test was performed at the component level on a polyurethane sphere to validate the finite element simulations. The considered material model parameters were based on those presented by the authors in a previous study. The constitutive model was based on the parallel rheological framework considering three mechanisms: one mechanism representing the equilibrium behavior of the material (modeled with a hyperelastic constitutive law), and two mechanisms representing the rate-dependence at two different time scales (modeled as a hyperelastic spring in series with a nonlinear viscoplastic dashpot element). The results showed a good overall agreement between the rolling test and the numerical simulation; however, better material characterization is required to improve the results in terms of the energy dissipated and the shape of the hysteretic loops. Moreover, additional numerical simulations need to be conducted to understand the deformation mechanism within the ball, and thus select appropriate testing protocols for calibrating new material parameters.