Elastomer materials as part of the polymer group are used in a large number of different applications. Components made of elastomers, such as seals, can be found in tires of automobiles, commercial vehicles and aircraft. Elastomers are also used for sealings in machines that are exposed to high dynamic loads. This class of materials is characterized in particular by its time-dependent, frequency-dependent and temperature-dependent behavior. Due to the time dependence, the behavior is called viscoelastic. The material behavior can be determined experimentally depending on the influencing factors. The frequency-temperature equivalence discovered by Williams, Landel and Ferry is used here. With the help of suitable material models, the viscoelastic behavior can be simulated with computer support. The numerically efficient and realistic modeling of viscoelasticity is one of the current difficulties in material modeling today.Rheological material models made up of classic spring and damper elements are well established. Many of these elements are required for a model for a realistic illustration of elastomers’ behavior. By using fractional derivatives, a new rheological element is created, which enables a more precise mapping of the material behavior and fewer elements overall are required for a model. The use of fractional material models is not supported by commercial finite element programs, only that of the classic material models.In this thesis we therefore build a classic viscoelastic and a fractional viscoelastic material model using finite elements. The two models are parameterized for this on the basis of experimental data. It is shown that both material models can simulate the real material behavior. Both models are compared with each other in terms of accuracy, stability, complexity and computational efficiency. Various load cases are simulated for this purpose. The implementation takes place via the UMAT interface of the FEM program Abaqus. It is possible there to implement and expand own material models.In order to reduce the numerical effort, a similarly formulated model is set up on the force-displacement level and compared with the results of the finite element formulations. In this way, the complexity of the simulation can be reduced and at the same time a realistic mapping of the material behavior can be made possible. We show that the finite element formulations and the models on the force-displacement level deliver consistent results and we provide parameter studies and dynamic load cases. Since the simulation of the material models with force-displacement formulation is not carried out by an external finite element program but by a dedicated framework, the simulation can be expanded in a modular manner.

Modelling the Dynamic Behaviour of Elastomers Using Fractional Viscoelastic Material Formulations

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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