H J Liu, Y Q Ni and J M Ko.pdf

Design and Testing of ER/MR Dampers for Vibration Mitigation H. J. Liu*, Y. Q. Ni and J. M. Ko Department of Civil and Structural Engineering The Hong Kong Polytechnic University Kowloon, Hong Kong P. R. China * Permanent address: Department of Aircraft Engineering, Northwestern Polytechnical University, Xi’an, P. R. China. Abstract Semi-active structural vibration control using electro/magneto-rheological (ER/MR) dampers has recently attracted extensive interest because it combines the advantages of passive devices with the benefits of active control. This paper describes the design and vibration testing of a low-force ER damper and a high-force MR damper, which are developed for the experimental studies of semi- active vibration control of a stay cable and a system of coupled adjacent buildings respectively. The ER and MR dampers are designed using the shear-mode and the fixed-mode of the fluid respectively. Dynamic characteristics of the built ER damper are tested at different electric field strengths and varying displacement amplitudes. The hysteresis loops of restoring force versus displacement and velocity are experimentally obtained via periodic vibration testing under a series of exciting frequencies. Then the Bingham model and a hysteretic biviscous model for the ER damper are established in which the model parameters are determined from the testing data. A comparison between the experimental hysteresis loops and those predicted using the established hysteretic biviscous model shows that the developed model captures the nonlinear damping behavior of the damper quite accurately. 1 Introduction Controllable fluids such as electro-rheological (ER) and magneto-rheological (MR) fluids have recently attracted extensive interest because of their quick response, reversible changes in behavior when subjected to electric field or magnetic field. They exhibit rapid transition from a free-flowing state to a semi-solid