A finite element material modeling technique for the hysteretic behaviour of reinforced rubber

Reinforced rubber is thanks to its elastic and dissipative properties found in industrial applications such as isolators, flexible joints and tires. Its dissipative propertied comes from material related losses which have the effect that energy invested when deforming the material is not retained when returning it back to its initial state. The material losses are in turn caused by interactions in the material on a level below the micro scale. These interaction forms a macro stress strain response that is dependent on both strain amplitude, strain rate and temperature. It is thus a challenge to accurately model components made of reinforced rubber and and features of interest related to them, such as the rolling resistance for a tire. It is also difficult to device general design guide lines for such components due to rubbers many and complex dependencies and a simple accurate phenomenological model for modeling these properties are highly sought for in industry today. This thesis presents a method for modeling the strain amplitude and strain rate behavior for cyclically loaded rubber along with a method of choosing its material parameters. The proposed modeling technique results in a model with the same frequency dependency over all strain rates. An approximation which is shown to be valid over a few decades of strain amplitudes and rates and is believed useful for many industrial applications. The material model presented can in addition be implemented in commercial FEsoftwares by using only pre-defined material models. This was achieved by implementation of the overlay method. The thesis also presents a method for how to implement the modeling technique in simulations with purpose to determine the rolling resistance of a truck tyre.