A Hyper-Viscoelastic Polyurethane-Based Multistage Vibration Isolator: Constitutive Modeling and Shock Attenuation Performance

To address the insufficient damping and instability tendency of metal coil spring isolators subjected to intense impact loading, a multi-stage vibration isolation configuration integrating polyurethane, springs, and eddy current dampers is proposed. Dynamic models for both single-stage and multi-stage isolation systems are formulated, and a corresponding simulation model is developed in MATLAB R2023b/Simulink to investigate the peak suppression and attenuation characteristics of the multi-stage isolation under impact. To characterize the nonlinear finite deformation and time-dependent response of polyurethane, a hyperelastic-viscoelastic constitutive model is established by coupling the Ogden hyperelastic model with a generalized Maxwell viscoelastic model, with model parameters identified through quasi-static compression and stress relaxation tests. Drop impact experiments are performed to compare the displacement response, top- and bottom-plate peak accelerations, and vibration isolation rate between a polyurethane-spring-eddy-current multi-stage isolator and a spring-spring-eddy-current multi-stage isolator. The results demonstrate that the multi-stage structure enables staged dissipation of the impact energy, substantially reducing both the peak acceleration and the displacement stroke of the isolated mass. Under all drop test conditions, the polyurethane-based multi-stage isolator yields lower top-plate output peak acceleration and higher isolation rate than its all-spring counterpart, confirming its superior isolation performance. Envelope fitting of the simulation-based output acceleration with experimental inputs reveals that the all-spring multi-stage isolator exhibits a higher attenuation rate and equivalent damping ratio, whereas the polyurethane-based isolator achieves more effective suppression of the output peak level under severe impact conditions.