Modeling and testing of magnetorheological energy absorbers considering inertia effect with non-averaged acceleration under impact conditions

The quasi-static model, without considering the inertia effect, is usually used to design and evaluate magnetorheological energy absorbers (MREAs). Although the quasi-static model is generally acceptable to describe the behavior of MREA operated at low velocity and low frequency, it is not sufficient to predict that under high-speed impact conditions. For this situation, we develop an analytical model inclusive of fluid Inertia as well as Minor losses based on the Bingham-plastic model (called BPIM model). In particular, instead of using area-averaged acceleration (assuming fluid acceleration uniformly distributes over the flow cross-sectional area), we directly take the non-averaged acceleration to analyze fluid inertia. Then, the governing equation is obtained from Navier-Stokes equations and continuity equation, in which the time-related term representing inertia effect is no longer neglected. In addition, the expression of damping force is derived by solving the initial-value problems obtained from the governing equation, boundary conditions and initial conditions using the method of separation of variables. Further, the influence of inertia effect and minor losses on MREA force is quantitatively analyzed. Besides, the MREA coupled with disc springs as the storage element is presented, and the nonlinear model of disc spring is employed. To validate the theoretical model, two identical MREAs are fabricated, and a high-speed drop tower is set up to test the two MREAs placed in parallel. It is shown that the BPIM model is capable of well predicting the dynamic behavior of the MREA.