Effect of pressure on the physical properties of magnetorheological fluids
To date, several applications of magnetorheological (MR) fluids are present in the industrial world,nonetheless system requirements often needs better material properties. In technical literature a previous workshows that MR fluids exhibit a pressure dependency called squeeze strengthen effect. Since a lot of MR fluidbased devices are rotary devices, this paper investigates the behaviour of MR fluids under pressure when arotation is applied to shear the fluid. The system is designed in order to apply both the magnetic field and thepressure and follows a Design of Experiment approach. The experimental apparatus comprises a cylinder inwhich a piston is used both to apply the pressure and to shear the fluid. The magnetic circuit is designed toprovide a nearly constant induction field in the MR fluid. The experimental apparatus measures the torque as afunction of the variables considered and the yield shear stress is computed. The analysis of the results showsthat there is a positive interaction between magnetic field and pressure, which enhances the MR fluidperformances more than twice.