Design optimization of a bi-fold MR energy absorber subjected to impact loading for skid landing gear applications

Dynamic range is an important characteristic index to evaluate the performance of magnetorheological energy absorbers (MREAs). In high-speed impact, the dynamic range may fall into the uncontrollable zone due to the increase in the off-state damping force. This is attributed to the transition of the flow from laminar to turbulent state. Thus, it is important to design optimize the MREA to maintain high controllability. To accurately evaluate the damping force, Bingham plastic model with minor loss factors (BPM) has been utilized to formulate the problem. The magneto-static analysis of the MREA valve has been conducted analytically and using magnetic finite element analysis in order to obtain the induced magnetic flux in the MR fluid active gap region against the applied current. Then, using BPM, a design optimization problem has been formulated to optimally design a bi-fold MREA to maximize its dynamic range at an impact velocity of 5 m s−1 while satisfying the constraints. Both genetic algorithm and sequential quadratic programming methods are utilized to capture the accurate global optimal solution. Finally, the performance of the optimized bi-fold MREA is evaluated first under different impact velocities, input currents, and then compared with that of equivalent single-flow path MREA.