Experimental, theoretical, and numerical investigations have been carried out to evaluate resonant frequency and stiffness of a magnetic bead chain in the magnetic field. Chains formed on a solenoid coil were vibrated by the sinusoidal wave and impulse wave to deduce resonant frequency. It showed weak dependency on the magnetic flux density and the bead diameter, because both the equivalent stiffness and the chain length were large in accordance with the increase of the magnetic flux density. These characteristics were confirmed by theoretical considerations based on an assumption of potential energy minimization and a numerical calculation with the Distinct Element Method. Stiffness of the chain was directly measured by observation of chain deflection in inclined gravitational field and the results agreed with the dynamically deduced characteristics. It was concluded that the resonant frequency was 20–60 Hz and the static stiffness at the top of the chain was 10−4 – 10−2 N/m. The investigation is expected to be utilized for the improvement of the two-component magnetic brush development subsystem in electrophotography.
Nobuyuki Nakayama, Hiroyuki Kawamoto, Satoshi Yamada, "Resonance Frequency and Stiffness of Magnetic Bead Chain in Magnetic Field" in Journal of Imaging Science and Technology, 2003, pp 408 - 417, https://doi.org/10.2352/J.ImagingSci.Technol.2003.47.5.art00007