Influence on rheology of static and dynamic structures in model magnetorheological fluids

This paper investigates the influence of static and dynamic structures on Rheology in a model magnetorheological fluid. Dynamic structures generated under shear an studied using first a rotational rheometer then an optical image processing system. A microscope allowed us to visualize the different patterns thus generated and compare these results to the measurements obtained with the rheometer. It also enabled us to analyze the various initial static structures formed by an externally applied magnetic field. Besides the well known column-dominated and bent-wall dominated static structures we were able to observe novel, concentric, ring like formations under shear. A dynamic yield stress analysis was conducted for each type of structure along with a statistical approach to further characterize and differentiate the various types of magnetic particle arrangements.