Keywords: elastomers, hyperelasticity, large strain viscoelasticity, time convolution integral, strain rate dependency, hysteresis, stress relaxation, styrene-butadiene rubber.

The aim of this paper is to investigate the possibility of the convolution integral model (CIM) to predict the behaviour of the elastomeric material of a rail pad subjected to low strain rate compression loads in different regimes. Special attention is devoted to the possibility of the model describing the following phenomena: hyperelasticity; a hysteretic load-deformation loop; and strain rate dependency. Samples made of the styrene-butadiene rubber material are tested in a low strain rate domain with constant strain rate compression (different values of strain rate are used) and a stress relaxation regime with alternating loading/unloading and relaxation regions. Results of experiments are used for: 1) identification of appropriate hyperelastic part of the CIM; 2) searching of constants of the CIM; 3) validation of the CIM. It is shown that the CIM (in the configuration, used in this paper) cannot successfully predict the experimental data at wide range of strain rates. It is found that the CIM shows satisfactory prediction of the loading part of a stress relaxation experiment but fails in the prediction of unloading part. The reasons of inaccuracies of CIM prediction are studied and possible solutions are suggested.

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