Measurement of the Rheological Properties of Magnetorheological Fluids Using a Double Concentric Halbach Cylinder Array

A new experimental setup for measuring rheological properties of magnetic fluids at variable magnetic flux density B with increased homogeneity is described. The proposed setup is mounted on a commercial strain-controlled ARES rotational rheometer. The magnetic flux is generated via two concentric Halbach cylindrical arrays made from permanent NdFeB magnets. The use of permanent magnets overcomes some of the disadvantages of electromagnets (e.g., excessive heating of the coils, formation of large radial stray fields, cost of electricity, cooling, etc). The performance of the new setup is tested for a magnetorheological fluid in both steady and oscillatory shear regimes.