High-speed videomicroscopy and magnetorheology under triaxial unsteady magnetic fields.

Abstract

We describe a custom-built device that is capable of superimposing triaxial unsteady magnetic fields on a sample at the same time that its microstructure is visualized using a high-speed camera and its rheological properties are measured with a commercial rheometer. The device reaches field strengths up to 5 kA·m^{-1}, frequencies up to 4 kHz, and its functionality is evaluated by testing magnetorheological fluids under steady shear flow and field transients. Striking differences are found at small Mason numbers by changing the field configuration.