Rheological synergistic effects of electric and magnetic fields in iron particle suspension

The effects of electric field and/or magnetic field on the rheological property of iron suspension were studied by use of parallel-plate rheometers developed for electro-magnetorheological (EMR) measurements. The EMR effect, which is defined as an increase in the shear stress under combined fields, was dependent on the strength and direction of the fields. In particular, significant synergism was found in the EMR effect when the electric and magnetic fields were applied in parallel. Observation of the suspensions solidified in parallel field and crossed field conditions revealed different structures of aggregated particles for these combined fields. The parallel field induced many chains along the field, while the crossed field induced a network structure. It is concluded that the synergistic EMR effect in parallel field is due to the increase in the number of particle chains bridging the plates.