Abstract:
The monotonic response of natural rubber (NR) and high damping rubber (HDR) as
revealed through recent experiments are critically examined and reported here in. In
understanding the mechanical behavior of rubbers, attention is mostly paid to the
compression and shear regime. In studying the mechanical test results in the
compression and shear regime, the existence of Mullins' effect, strain-rate
dependency, hystersis and residual strain effects in all the specimens was noted. In
NR, the extent of these effects is found to have an inherent relation with the presence
of microstructural voids. The presence of all these effects is also found to be
significant in HDR. In addition, the strain-rate dependent high initial stiffness feature
at low compressive strain levels was also evident. However, in considering a strainrate
dependent response, equilibrium and instantaneous responses are defined rateindependent
responses. In the constitutive model, these responses are uaually
modelled using a hyperelasticity law. In this context, the current work is carried out
using finite element modeling of the rate independent elastic behavior of NR and
HDR subjected to compression, shear and their combinations.
To this end, several constitutive models based on phenomenological motivation were
thoroughly studied. An improved hyperelasticity model was utilized to formulate the
finite element coding for representing the rate-independent nonlinear elastic
responses including high initial stiffness characteristics of rubber materials. In doing
this an explicit analytical expressions for the second Piola-Kirchhoff stress tensor and
the Cauchy stress tensor have been formulated for the distortional part of the
hyperelasticity model. The Lagrangian elasticity tensor has also been formulated for
the distortional part of the hyperelasticity model to implement in a general-purpose
finite element code. The elastic equilibrium and instantaneous responses of NR and
HDR under compression and shear have been simulated using material parameters
identified from the available experimental observations. The numerical simulation
results have been compared with the available experimental observations to discuss
the adequacy of the developed finite element procedure in simulating quasiincompressible
response of NR and HDR under uniaxial compression and simple
shear deformation. To this end, the simulation results have been verified with
available analytical solution for the elastomeric rubber bearing with different shape
factors. Numerical expeirments have been performed for simultaneous action of
compression and shear. Finally, the possibility of modeling and analyzing the fullscale
bridge seats and base isolation bearings have been investigated at different
deformation modes by utilizing the developed finite element procedure. In this
process, the numerical results have been compared with the available analytical
results.
