Abstract Magnetorheological (MR) dampers are widely used for vibration isolation and the dynamic range is a key index to evaluate its performance. According to the vibration isolation theory, it is essential for the damper to maximize the damping force in resonance region and minimize the damping force in high-frequency excitation. However, for single-path MR dampers, achieving the goals of low field-off force and large dynamic range has conflicting requirements on the structural parameters. In this research, a dual paths MR damper has been proposed to overcome this problem. The proposed MR damper has two coaxial paths and the magnetic field strength in each path can be controlled separately. According to the flow state of the MR fluid, the working modes of the proposed MR damper are divided into three kinds and the corresponding mathematical models are driven. Based on the mathematical models, the effect of structural parameters on the dynamic range, maximum and minimum damping force is investigated. It is concluded that increasing the piston rod radius and piston length is an effective method to expand the dynamic range while maintain a small field-off damping force. The experimental results show that the proposed MR damper working mode can be controlled by the applied currents, the minimum force is obtained in the dual paths flow state while the maximum force is obtained in the inner path flow state. In particular, the dynamic range of the proposed MR damper is significantly improved to 93.3 and the filed-off damping force remains small compared to the previously reported MR damper.
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