FEA of an Essentially Nonlinear Elastomeric Spring for a Nonlinear Energy Sink, Numerical Optimization and Performance Evaluation for Civil Structures

Abstract

This study is conducted with the intention of contributing towards development of a transformable regime for Non Linear Energy Sinks used as Dynamic Vibration Absorbers for vibration mitigation in civil structures. It primarily deals with the finite element analysis of a hyper-elastic polyurethane foam under compression which behaves as an essentially nonlinear spring in a Nonlinear Energy Sink (NES). Previous studies have used Mooney-Rivlin model for compressive strains up to 40% for hyperelastic materials with geometric nonlinearities. Mooney-Rivlin model has the limitation that it can only be used to accurately simulate strains up to 50% and cannot accurately predict the 3 regions (linear, collapse and compaction) in an elastomeric compression. This study builds on the previous works by conducting an FEA analysis of a geometrically nonlinear hyperelastic material upto compressive strains of 80% using Ogden model. A FEA simulation in ABAQUS is conducted for a truncated cone shaped elastomer under compression. Initially a widely used strain energy density-based model for elastomers in compression, Ogden, is evaluated under different strain energy potential orders. Secondly, height of the truncated cone is varied to document the effect of geometric parameter on stiffness under compressive loading. In the final phase, the force-displacement curve obtained from these studies is imported into ETABS as a characteristic of a nonlinear link. This link is attached to a 10-storey rigid frame structure whose story displacement plots are compared with and without the link to exhibit the effectiveness of this nonlinear spring element in mitigation of structural vibrations. The results demonstrate that the 3rd order Ogden model can be used for simulating large compressive deflections, up to 80% strain, in hyper-elastic polyurethane foam. It makes evident that the force-displacement graph of the material

exhibits nonlinear behavior in 3 regions (linear, collapse and compaction) in force- deflection graph which can be utilized in applications as an essentially nonlinear

spring in NES and finally that this type of device can mitigate the story displacement in civil structures.