High viscosity linear polysiloxane magnetorheological fluid (HVLP MRF) was demonstrated with excellent suspension stability. Such material is suitable for application in the magnetorheological energy absorbers (MREAs) under axial impact loading conditions. On this basis, a new energy absorber incorporating a radial valve with high magnetic field utilization and a corrugated tube is proposed. In energy absorption applications where the MREA is rarely if ever used, our MREA takes the ultra-stable HVLP MRF as controlled medium in order for a long-term stability. For MREA performing at very high shear rates where the minor losses are important contributing factors to damping, a nonlinear analytical model, based on the Herschel-Bulkley flow model (HB model), is developed taking into account the effects of minor losses (called HBM model). The HB model parameters are determined by rheological experiments with a commercial shear rheometer. Then, continuity equation and governing differential equation of the HVLP MRF in radial flow are established. Based on the HB model, the expressions of radial velocity distribution are deduced. The influences of minor losses on pressure drop are analyzed with mean fluid velocities. Further, mechanical behavior of the corrugated tube is investigated via drop test. In order to verify the theoretical methodology, a MREA is fabricated and tested using a high-speed drop tower facility with a 600 kg mass at different drop heights and in various magnetic fields. The experiment results show that the HBM model is capable of well predicting the impact behavior of the proposed MREA.

High-viscosity linear polysiloxane-based magnetorheological fluid features its excellent suspension stability. Few reports could be found for magnetorheological energy absorbers using such highly viscous but highly stable magnetorheological fluids as the controlled medium. This study presents a design strategy for the high-viscosity linear polysiloxane-based magnetorheological fluid-based magnetorheological energy absorber with multi-stage radial flow mode. The design strategy is based on the Herschel-Bulkley flow model incorporating minor losses proposed in our prior work. The optimal geometrical parameters were obtained by gradually reducing the number of unknown variables. By analyzing the effect of thicknesses of baffle and outer cylinder and number of coil turns on magnetic circuit, the distribution of magnetic flux in the effective region of magnetorheological valve was optimized. Furthermore, a magnetorheological energy absorber was fabricated and tested using a high-speed drop tower facility with a 600 kg mass. The maximum nominal impact velocity was 4.2 m/s, and the applied current varied discretely from 0, 1, 2, to 3 A. Comparison of our Herschel-Bulkley flow model with measured data was conducted via analysis of peak force, dynamic range, and maximum displacement that indicate the performance of magnetorheological energy absorber. The results validated the effectiveness of the design strategy for the high-viscosity linear polysiloxane-based magnetorheological fluid-based magnetorheological energy absorber.

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Accurate theoretical models play a key role in the development of magnetorheological energy absorbers (MREAs). Traditionally, the apparent slip caused by non-uniformity interface (i.e., the separation of carrier fluid and magnetic particles at the wall) of the working medium is often ignored for simplifying theoretical models. However, the apparent slip influence the cross-sectional flow and decreased the theoretical accuracy of the damping force for MREA applied in the impact absorption area. In this study, a dynamic model with apparent slip boundary condition for radial-flow-based MREA was proposed. The effect of apparent slip layer thickness on the dynamic behavior of an MREA was qualitatively and quantitatively compared in terms of the following three aspects: (1) with the Power-Law constitutive model, theoretical models of the dynamic characteristics of the magnetorheological fluid (MRF) squeeze and MREA are presented based on the apparent slip boundary condition with the MRF behavior of the Navier–Stokes equation; (2) the accuracy of the theoretical model to predict MREA peak force and boundary velocity with different slip-layer thicknesses; and (3) global agreement of the dynamic force and range curves between the modeling and experimental results. The results show that the absolute values of the relative errors in the two models with a 2- and 0-µm thick slip layer were less than 3.73 and 7.41%, respectively, and that a 2-µm thickness can help predict the actual dynamic characteristic more efficiently under accidental collision loading conditions.