Simulation of Elastomeric Parts

Concerning the simulation of elastomeric parts, Fraunhofer LBF differentiates between system simulation and the simulation of local stresses in a part.

For a reliable simulation of the behavior of the entire system, the model must guarantee a precise depiction of the transfer behavior of the elastomeric component over the entire strain spectrum containing stress amplitudes and frequencies. Separated into the areas of application: “driving dynamics/structural durability” and “NVH” and because of the different frequency and amplitude ranges Fraunhofer LBF uses different modeling approaches and machines for the characterization.

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The typical test setups used are described under the topic Characterization of Elastomeric Parts. Depending on the type of bearing (pure elastomer bearing or hydro bearing), the measured data is parameterized in different types of models. The goal is an exact as possible depiction of the real transfer behavior of the bearing component over the entire frequency and amplitude range. The image above shows a possible modelling approach for a hydro bearing. The parameterized and verified models of the elastomer components can then be integrated into the simulation of the entire system, for example, of an entire vehicle, as it is depicted in the image below.

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By utilizing appropriate material models and determining the necessary characteristic material values, elastomeric parts can also be simulated via the finite element method. Through this approach, as a matter of principle, the transfer behavior as well as the expected vibration resistance of a part can be calculated. It cannot be denied that the quality of the results obtained does not yet reach the standards of typical FEM calculations of metal components. The reason for this is the significantly more complex material behavior based on the temperature dependency of the material properties of the base material, the dampening material properties and the resulting temperature increase, as well as the complex failure mechanics. A concept for the temperature dependent service life time prediction compiled in a research project is depicted in the figure.

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Models with physical parameters are applied for the model based design and optimization of complex vibration control technology systems in the vibro-acoustic frequency range. For this, the description based on fractional derivative has proven itself as a reliable method. This approach shows high calculation efficiency, especially for the system simulation of active and passive measures needed to minimize vibrations in the time range. Another substantial advantage of this modelling approach lies within the parameterization via the characteristic values "stiffness" and "loss angle". These values can be taken directly from the experimental characterization. With this, the LBF offers a holistic range of services ranging from the experimental characterization to the numeric description. It is our pleasure to support our customers with the modeling and simulation of dynamic systems.

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The complex interactions of mechanical and electrical effects in dielectrical elastomers generally require numeric simulation models for detailed examinations because analytical approaches can only be solved with simplified assumptions. At Fraunhofer Institute for Structural Durability and Systems Reliability LBF, we work with multi physical models, finite-element-models (FEM) in particular, to calculate the electromechanical behavior of dielectrical elastomers with complex geometries. Models with microscopically refined level of detail of the layer, as well as macroscopic models with homogenized characteristic material values are used here. These models can assist in the purposeful optimization of, for example, electrode structure, and the optimization of dielectric elastomeric converters regarding their layer thickness, material properties, geometry, and mechanical boundary conditions.