MRF in a plate-plate magnetorheometer

Particle-based simulations are a suitable tool to gain insight into the microstructural behavior of a magnetorheological fluid (MRF). For the application of MRF in clutches, the amount of torque transmission is a matter of particular interest. Concerning the contact between iron particles and clutch walls, several questions arise: Is a higher wall roughness beneficial for torque transmission? What is the influence of wall magnetism on torque transmission? What are the mechanisms on particle scale that lead to increased torque transmission? Inspired by a previous experimental study, we performed three-dimensional simulations based on the Discrete-Element-Method (DEM) with different wall roughnesses and different magnetic conditions to investigate the mechanisms of shear stress transmission at particle level. The simulations show that a higher wall roughness leads to higher torque transmission only in the case of non-magnetic walls. For ferromagnetic walls, no influence of wall roughness on torque transmission is observed. This is in qualitative agreement with the experimental results.