A NOVEL APPARATUS FOR RHEOLOGICAL MEASUREMENTS OF ELECTRO-MAGNETO-RHEOLOGICAL FLUIDS

A parallel-plate rheometer equipped with electrodes and magnetic coils was developed for rheological measurements of electro-magneto-rheolog ical (EMR) fluids which respond to both electric and magnetic fields. The effects of electric and magnetic fields perpendicular to the direc tion of shear flow were examined. It has been found that the shear str ess of the fluid depends not only on the strength of the fields but al so on the order of application. The apparent viscosity of the EMR flui d under shear flow increased when the electric and magnetic fields wer e applied simultaneously. The increase in viscosity was lower when onl y an' electric or magnetic field was applied. The dependence of EMR fl uid behavior on the external field conditions is discussed in terms of the difference between cluster structures induced by electric and/or magnetic fields.