Phenomenological studies on magnetic and mechanical remanence effects in magnetorheological fluids

Although magnetorheological fluids (MRF) have been used in science and engineering for many decades and several products based on this technology are known, there is still no consistent routine that properly takes into account major effects in the material. The aim of this work is to establish a series of steps, from the preparation of the fluid through the demagnetization routine to the choice of the angular evaluation point, which will allow to achieve stable and reproducible results regarding the material’s response to magnetic fields and mechanical actuation. As a major result of this work, a general demagnetization routine and a method for subsequent reproducible evaluation accounting for the long-term time-dependent behavior of the MRF were identified. Our efforts are aimed at exploring the following targets and questions: how can a stable initial state be ensured? Why is the initial measurement of MRF commonly hardly reproducible? How can reproducible measurements for characterizing the material be obtained? For each of these items, we developed procedures or suggest measures and discuss to what extent they solve the underlying issues and what had to be left for future investigations.