Impact Performance of Magnetorheological Fluids

As part of an emerging effort in what is now termed the area of mechamatronics (Browne et al., 2004), an effort was begun to assess the suitability of magnetorheological (MR) material-based devices for impact energy management applications. A fundamental property of MR materials is that their yield stress alters almost instantaneously (and proportionally) to changes in the strength of an applied magnetic field. Based on this property, MR-based devices, if found suitable, would be desirable for impact energy management applications because of attendant response tailorability. However, it was identified that prior to adopting MR-based devices for impact energy management applications several key issues needed to be addressed. The present study focuses on one of the most significant of these, the verification of the tunability of the response of such devices at stroking velocities representative of vehicular crashes. Impact tests using a free-flight drop tower facility were conducted on an MR-based energy absorber (shock absorber) for a range of impact velocities and magnetic field strengths. Results demonstrated that over the range of impact velocities tested — 1.0—10 m/s — the stroking force/energy absorption exhibited by the device remained dependent on, and thus could be modified by, changes in the strength of the applied magnetic field.