Modelling the viscoplastic properties of carbon black filled rubber A finite strain material model suitable for Finite Element Analysis

Sammanfattning: An increased environmental awareness, legal demands and the large part of total costs attributable to fuel cost are all incentives for the automotive industry to reduce fuel consumption. The optimal driveline to enable this reduction depends on the operational conditions and the available infrastructure. Moreover, special care is needed when developing the driveline isolators, since the demands on noise, vibration and harshness (NVH) are the same regardless of driveline. To this end, computer aided calculations can be used in order to evaluate a large number of configurations. However, these calculations are only, at best, as good as the material models employed. In the foreseeable future, rubber with reinforcing fillers will be used in vibration isolators in order to obtain the desired properties of these components. However, the stiffness and damping of rubber with reinforcing fillers are highly non-linear functions, and the available material models in commercial software and in the literature are often insufficient. Therefore, a finite strain viscoplastic material model is derived in the time domain and implemented as a user defined material model in Abaqus Explicit. The model captures the strain amplitude and frequency dependency of the storage and loss modulus for a carbon black filled natural rubber. The model is accurate over a wide range of shear strain amplitudes and frequencies, 0.2-50 % and 0.5-20 Hz, respectively, using only 5 material parameters. In addition, the model correctly captures the response from bimodal excitations. The implementation in Abaqus Explicit enables component characteristics to be evaluated early in the development phase, with material parameters derived from simple test specimens. The improved accuracy of simulations of these components can aid engineers develop more optimized solutions faster than with conventional methods.