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

This paper investigates the influence of static and dynamic structures on R heology in a model magnetorheological fluid. Dynamic structures generated u nder shear an studied using first a rotational rheometer then an optical im age processing system. A microscope allowed us to visualize the different p atterns thus generated and compare these results to the measurements obtain ed with the rheometer. It also enabled us to analyze the various initial st atic structures formed by an externally applied magnetic held. Besides the well known column-dominated and bent-wall dominated static structures we we re able to observe novel, concentric, ring like formations under shear. A d ynamic 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.