Stability and Flow Behavior of a Magnetorheological Lubricant in a Magnetic Shock Absorber

Interest in the use of field-responsive fluids in the automobile industry is growing in view of the increasing capabilities of electronic control in the vehicle's dynamic response. This is the case of magnetorheological fluids or lubricants (MRF). These are capable to change in very short times their rheological behavior upon application of modest magnetic fields. In the present work we describe a new formulation of a stable magnetic fluid that is checked both in a laboratory rheometer and in a commercial shock absorber. It is found that the yield stress can increase by several orders of magnitude when the magnetic field strength reaches a few hundred mT. Furthermore, friction tests carried out in a damper test machine showed that the shock absorber behaved very regularly when charged with the fluid under very different conditions of speed and amplitude of the forced oscillations produced and for various applied magnetic fields.