Microstructural Stability of Magnetorheological Fluids Based on Magnetic Energy Analysis

The minimum point determination method of the magnetic energy surface has been proposed on the basis of magnetic dipole theory in our study. This method can effectively explain the behaviors that the polydisperse magnetorheological fluids (MRFs) can form more complex chain-like structures and the magnetic energy of the particle system will decrease with the formation of the aggregations. The minimum points on the magnetic energy surface of two-particle and three-particle system are observed, and several kinds of stable microstructures are obtained by analyzing these points. Finally, both the stability and evolution mechanism of these microstructures have been explored based on the concept of the magnetic energy barrier. The results demonstrate that a minimum point on the magnetic energy surface of the particle system corresponds to a type of stable microstructure, and the migrations between the minimum points in the systematic magnetic energy phase space can be accounted for the mutual evolutions of these stable microstructures. The microstructural stability depends on the magnetic energy barrier height. For this reason, the microstructural evolution is more likely to appear when the barrier height is relatively low. In the case of sufficient perturbation, the particle system always evolves into the state with lower magnetic energy.