The transient response of magnetorheological actuator/ fluid in shear mode on the rapid change of magnetic field: effect of shear rate

The semi-active (S/A) control can be easily applied to the magnetorheological (MR) actuators. The S/A control with MR actuator exhibits a significant improvement of suspension systems performance. However, the performance of the S/A control is significantly influenced by the transient response (response time) of the actuator. The currently published designs of MR damper achieved great transient behaviour (response time roughly 1.2 ms). It can be stated that the response time of MR fluid itself is probably close to the response time of the current designs of the MR actuator. The response time of MR fluid can be divided into (i) hydrodynamic response time, (ii) particle structure development response time, and (iii) rheological response time. In our research, we experimentally determined the rheological response time of MR fluid and measured the effect of shear rate. We developed a unique shear mode rheometer that allows rapid change of magnetic field in the gap. The response time of MRF 132-DG was determined based on the transfer function between the measured magnetic field and shear stress in MR fluid. The rheological response time (63.2 %) achieved a value of 0.66 ms for magnetic flux intensity of 12.5 kA/m and shear rate 40 s(exp -1). As the shear rate increases, the response time decreases.