Development of a novel compact magneto-rheological impact damper featuring shear-mode twin-tube structure

Magnetorheological impact dampers (MRIDs) have been widely investigated as an effective strategy for mitigating the harmful effects of impact shocks and vibrations. However, flow-mode MRIDs suffer from strong velocity sensitivity and high off-state forces, whereas conventional shear-mode designs deliver low velocity sensitivity at the expense of limited load capacity. To address this trade-off, this study proposes a novel shear-mode twin-tube MRID that increases the effective shear-activated magnetorheological fluid (MRF) volume within a confined envelope. Magnetic coils are placed between two concentric annular channels spanning the long operational stroke to improve magnetic-field utilization and dissipation efficiency without enlarging the package. The work comprises development of a quasi-static force model for shear-mode behavior, a FEM-based, performance-index driven multi-objective optimization of the magnetic circuit and geometry for impact requirements, and fabrication of an optimized prototype. Comprehensive cyclic loading experiments were performed to characterize damping force performance under varied coil currents and frequencies. Results show good agreement between model and measurements, pronounced field-dependent force generation with modest velocity sensitivity, and tunable increases in energy dissipation as current is raised. Subsequent drop-weight tests further demonstrate the effective impact mitigation capability of the proposed MRID under practical impulsive loading environments.