Magnetorheology in unsteady fields: From uniaxial DC to rotating AC fields

Abstract

Magnetorheological fluids structured under precession fields are thoroughly investigated. Having complete dynamic triaxial magnetic field control, we are able to study both the structural and magnetorheological response via videomicroscopy and rheometry integration for a wide range of magnetic field configurations, once previously limited to traditional uniaxial fields. Optimal precession fields for driving the formation of more robust particle structures enhancing yield stress response are identified. It is believed that structural reinforcement comes from chain coarsening through lateral chain coalescence and particle compactness within the structures such that a lower energy configuration is found for certain field configurations. Particle level simulations supplement our understanding of lateral chain coalescence and structure strengthening.