Particle-based simulation of sheared magnetorheological fluids

Magnetorheological fluids (MRF) belong to the class of smart materials as their rheological behavior can be reversibly changed by a magnetic field. Current MR applications include controllable dampers, e.g., for shock absorbers or seat suspensions, human prostheses and clutches. In this work, the mechanisms of shear stress transmission in MRF are investigated on particle-level by means of numerical simulations.

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With a particle-based simulation approach, three aspects of magnetorheological fluids (MRF) are addressed: The role of the hydrodynamic drag model for the resulting shear stress in the simulation, the shear stress transmission and the structure formation of the suspended particles.
To investigate the influence of the hydrodynamic drag law on the computed shear stress, different one-way coupled and two-way coupled drag models are compared. An easy-to-check criterion for the applicability of the commonly used one-way coupled discrete element model is derived.
For an adequate modeling of shear stress in particle-based simulations, the particle-wall interaction is crucial. Using a physically motivated wall model, the experimental shear stress behavior is reproduced. On the basis of systematic simulations, possibilities for shear stress enhancement are discussed.
To assess the mechanisms of shear stress transmission, the structure formation of the suspended particles is analyzed. For each of the different structure types observed in the simulations, a corresponding failure mechanism is reported. The particle-based approach allows for a detailed description of the failure process.