An investigation of the electromagnetic coupling problem by means of a rational framework and selected experiments
To analyze electromechanical interactions, electromagnetic coupling models are required. Identifying a suitable electromagnetic coupling model for a given application is a challenging task since there exists a multitude of different models in the literature and not all of these models are equivalent. This thesis proposes a theoretical framework for the evaluation and comparison of electromagnetic coupling models. This includes the investigation of the interaction between coupling models and constitutive theory. It is shown that the electromagnetic force model influences the entropy principle, but is not affected by it for simple material responses. However, the electromagnetic energy model is subject to restrictions by the second law of thermodynamics and therefore influenced by the force-model choice. Hence, the electromagnetic force model must be investigated first. In order to determine the limitations of the most popular force models, their theoretical predictions are compared to experimental results. To this end, three experiments are evaluated. The first two experiments encompass the force measurement of magnets that are immersed in ferrofluid and the measurement of moments between non-coaxial permanent magnets. Both experiments were designed and conducted in this work. For the corresponding theoretical investigations, an efficient finite element method in curvilinear coordinates is developed. The method is also used to evaluate the third experiment, which was conducted in the literature. In the experiment, the local deformation of an oil drop subjected to an electric field is investigated. The theoretical predictions of the considered force models are compared to the experimental data. The evaluation shows that the generalized \textsc{Lorentz} model is the only electromagnetic force model to correctly predict the results of all three aforementioned experiments. All other considered electromagnetic force models show significant differences between their prediction and the experimental results in at least one of the three experiments.
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