Impact behavior of a novel magnetorheological energy absorber based on wedge-shaped squeeze flow model

Magnetorheological (MR) energy absorbers (MREAs) have been extensively investigated as a means of dissipating impact energy and decreasing injury as well as used in a wide range of applications. When applied as an accidental collision buffer, however, problems can arise owing to the inertia of the sudden impact. In this study, a novel MREA with a gradient resistance gap structure working in a wedge-shaped squeeze flow model of a high-viscosity linear polysiloxane-based MR fluid was developed. The MREA has a continuously changing working gap and internal magnetic flux density gradient distribution representing a wedge-shaped structure. A Power-Law model inclusive of fluid minor losses (PLM)- of the damping force of an MREA with a wedge-shaped resistance gap was built to study the impact behavior. A second model also considered the effects of inertia (PLMI). The wedge angle was defined to quantitatively and comprehensively characterize the effects of the wedge-shaped resistance gap because of its significant influence on the dynamic characteristics. Two MREAs with wedge-shaped and equidistant working gaps were fabricated and tested using a drop tower facility with a mass of 600 kg. The experimental results show that the maximum damping force of the MREA with a wedge-shaped resistance working gap reached to as high as 235.8 kN and the dynamic range is increased by 6.5% compared to that with an equidistant working gap. The relative errors of the peak force for impact velocities between 2.8 and 4.2 m s −1 with no applied current were 1.84%–3.67% (PLM) and 0.63%–1.91% (PLMI), and with 3 A applied current were 2.35%–4.99% (PLM), and 1.24%–2.72% (PLMI), demonstrating that the PLMI-based model is capable of accurately predicting the dynamic behavior of the MREA.