Design of a magnetorheological damper with enhanced effective length ratio and reduced area ratio for low off-state damping and wide dynamic range

This paper presents a novel magnetorheological damper (MRD) specifically designed for shock mitigation applications. The proposed design achieves a low off-state damping force and a wide controllable dynamic range, which are critical for semi-active shock mitigation control systems. Based on the Bingham plastic (BP) model, the relationships among off-state damping force, dynamic range, and structural parameters were derived, providing clear design guidelines. Following this analysis, a new MRD configuration was developed by reducing the piston effective area and extending the effective magnetic field length. Comparative simulations with a conventional MRD revealed that the proposed design effectively reduces the off-state damping force and significantly improves the utilization of the magnetic circuit. A prototype was fabricated and tested under both sinusoidal and impact excitations. The simulation results demonstrate that the off-state damping force was reduced by >69% while the controllable dynamic range increased by approximately 88% compared with the conventional design at 6 m/s. Experimental results up to 4.5 m/s confirm the trends predicted by simulation. These findings confirm that the proposed MRD has superior adaptability for shock mitigation systems in aerospace and defense applications.