Electro-rheological cylinders used as impact energy absorbers

Smart fluids, that is, electro-rheological (ER) and magneto-rheological (MR) fluids have been studied widely in vibration control, seismic isolations, and rotation transmission, where the velocity is low and the motions are periodic. However, very few investigations concern about the dynamic response and energy absorption of ER dampers under impact loadings. To explore the feasibility of using ER cylinders as impact energy absorbers, two different ER fluids were first characterized by using a capillary rheometer with rectangular duct. Then, a double-ended ER cylinder with two parallel annular ducts was designed, and its performance in response to a mass impact was tested. The experiments show that a typical dynamic response of the ER cylinder consists of three distinct stages, namely, an initial shock stage, a transition stage, and a stable flow stage. Afterwards, the dynamic response is analyzed theoretically, in which the contact between the impinger and the piston rod, the viscous and ER effects as well as the inertia and response time of the ER fluid are considered. It is revealed that, the controllability of the ER impact energy absorber greatly depends on the impact velocity and ER fluids yield stress, and that when the impact velocity increases, its controllability deteriorates due to viscosity and response time.