An eddy current effect on the response time of a magnetorheological damper: Analysis and experimental validation

This work proposes a new magnetorheological (MR) damper which can produce sufficient damping force within a few millisecond. Firstly, damping force mechanisms of MR damper are analyzed by deriving several equations representing the flow motion. Then, the eddy current analysis of several different core materials is undertaken since it most significantly influences to the time delay of MR damper. After analyzing several candidates of the magnetic core material, the soft magnetic composite (SMC) is selected which has relatively high electric resistivity. In addition, the inner surface of the housing is machined to have many grooves around the housing to reduce the eddy current magnitude. After confirming that the proposed MR damper causes a very small eddy current distribution, two MR dampers are designed and manufactured by considering the order of the influence level of the factors determined on the basis of Taguchi method. The field-dependent damping force to the step input current is then measured in time domain and the response time of MR damper is calculated. It is shown through experimental tests that very fast response time of MR damper can be achieved by reducing the eddy current around the magnetic field zone. (C) 2019 Elsevier Ltd. All rights reserved.