A controllable MRF damper with a liquid spring device

The goal of this research is to study the feasibility of incorporating a liquid spring in a magnetorheological fluid (MRF) damper as a semi-active suspension system for use on heavy, off-road vehicles. The damping force for the suspension system is generated by a field-controllable MRF damper utilizing a flow-mode external valve. The restoring spring force is created by compressing silicone fluid in a sealed control volume achieved by a relative displacement between a fixed chamber and a piston. The MRF damper-liquid spring suspension system generates the force characteristics of a conventional suspension system at off state (no magnetic field applied). However, when the magnetic field is applied, more damping force is produced. Individual components of the device are characterized separately for their specific force outputs. Performance characterization of the MRF damper-liquid spring suspension system is performed on a hydraulic dynamometer. The force-displacement results are presented.;A phenomenological model is developed to predict the performance of the system at different operating conditions and is compared to the experimental results. In the range of the experiments conducted, the liquid spring shows a linear characteristic, comparable to the conventional helical springs and is capable of generating high forces for relatively small displacements. The MRF damper generates high damping forces for relatively low power consumptions. The device produces the desired force-displacement characteristics over a range of input conditions. The phenomenological model developed is in close agreement with the experimental results. This study provides the proof that a passive liquid spring can be used in conjunction with an MRF damper as a semi-active suspension system.;A study to characterize three novel MR fluids using a commercially available fluid MRF 132AD as a benchmark, is also conducted as a part of this research work. The rheological property changes in these fluids are measured and reported at various magnetic field intensities, shear rates and strain amplitudes. The rheology of the fluids is measured and documented under both rotational and oscillatory shear conditions. The novel MR fluids exhibit stable rheological properties comparable to the commercial fluid, and are stable under continuous deformation over a period of time. The novel MR fluids exhibit desirable rheological properties such as, low viscosity and high yield stress.