Double-gap bicone magnetorheology in steady shear under homogeneous magnetic and flow fields

Abstract

We design, fabricate, and test a double-gap bicone magnetorheological (MR) device to measure steady shear rheological properties ofMR fluids under saturating magnetic fields (i.e., large enough to saturate theMR fluids). The device is optimized using finite element method and computational fluid dynamics simulations so that homogeneous, saturating field strengths are reached while keeping a constant shear rate within the main shearing gaps. Experiments demonstrate that the flow curves in the saturation regime can be fitted to a viscoplastic Casson model in good agreement with MR fluids under much lower (nonsaturating) fields. Moreover, yield stress data follow a linear dependence on volume fraction at low particle loadings, in agreement with existing theoretical models.