Shock load mitigation using magnetorheological energy absorber with bifold valves

Abstract

Magnetorheological energy absorbers (MREAs) have been identified as a candidate for tunable impact energy absorber applications, meaning those in which a high shock load is applied during a short time period. In this study, we focused on the theoretical analysis, design and laboratory implementation of a compact high force MREA for shock and impact loads. This study included the design and fabrication of a flow-mode bifold MREA (magnetorheological energy absorber) that operates under piston velocities up to 6.71 m/s and the development of a hydro-mechanical analysis to predict MREA performance. Experiments were conducted both in the laboratories at UMCP (sinusoidal excitation) and at GM R&D (drop tower tests), and these data were used to validate the analysis. The hydro-mechanical model for the MREA was derived by considering lumped hydraulic parameters which are compliances of MR fluids inside the cylinder and flow resistance through the MR bifold valves. The force behavior predicted by the hydro-mechanical analysis was simulated for two classes of inputs: sinusoidal displacement inputs, and shock loads using a drop tower. At UMCP, sinusoidal inputs ranging up to 12 Hz with an amplitude of 12.7 mm were used to excite the MREA using three different MR fluids, each having an iron volume fraction of nominally 35%, 40% and 45%. Subsequently, drop tower tests were conducted at GM R&D by measuring MREA performance resulting from the impact of a 45.5 kg (100 lb) mass dropped onto the MREA shaft at speeds of 1, 2 and 3 m/s. Comparison of the simulations with experimental data demonstrated the utility of the hydro-mechanical model to accurately predict MREA behavior for the specified ranges of sinusoidal and shock classes of inputs.