COMPUTATION OF MODEL PARAMETERS FOR APPLICATION IN FEA OF RUBBER

Four models describing pure elastic behaviour of rubber are compared. These are Neo-Hooke, Mooney-Rivlin, van der Waals (Kilian) and Ogden models. This paper examines whether and under what conditions it is possible to predict experimental stress-strain curves using these models. Stress-strain curves are derived from uniaxial and pure shear (biaxial) tests using specimens of SBR rubber vulcanizate, cross-linked to level of 50-degrees Sh A. Both, uniaxial and pure shear tests are carried out in extension and compression, covering a wide range of deformation. Analyses approved that by using Kilian and Ogden models it is possible to predict actual behaviour of rubber submitted to uniaxial and pure shear loads, for the entire range of applied deformation. Neo-Hooke and Mooney-Rivlin models satisfy only in compression and moderate extension. The analysis pointed out that the influence of approximation range of deformation (measured as extension (compression) ratio) on the amount of model parameters is very strong. They are calculated by means of linear and non-linear regression.. These results are approved by means of FEA simulation of axial loading of two real rubber products, and they are compared with results of loading experiment. In this analysis the ABAQUS software package is used. All considered models are implemented in this software as subroutines.