Rheological behaviour of iron-silicone fluid mixtures used in magnetic slip clutches

The rheological behaviour of electrolytic iron powder of <37 ¿¿m and 37¿¿50 ¿¿m diameter mixed with silicone carrier fluids of 20, 50 and 100 cstokes kinematic viscosity, used in magnetic fluid clutches, is investigated through viscometric and rheometric experiments for volume fractions ranging from 5 to 33% empirical equations are given to represent the behaviour. It is shown that these non-Newtonian mixtures are yield pseudoplastics at low shear rates tending to Newtonian behaviour at high shear rates. A special viscometric fixture was devised to measure the interacting effect of volume fraction and transverse magnetic induction on apparent viscosity. It is found that, when the volume fraction is half its maximum possible value, the percentage variation of apparent viscosity is highest under magnetic induction. The temperature effect on viscosity of the iron/silicone mixtures is determined and segregated.