The Research Into Full-Size Intelligent MR Damper

Over the past three decades, the development of intelligent control technique opens up new areas for vibration control of civil engineering. The application of intelligent materials and smart devices is the outstanding sign for structure intelligent control system. The intelligent materials mostly include ER/MR fluids, shape memory materials, piezoelectric materials, magnetostriction materials and retractable/inflatable polymeric colloid etc al. The active control and variable damped devices modulated by electricity, magnetism or temperature and so on could be manufactured by using the intelligent materials. Because of the merits such as large force capacity, low power requirement and prompt response, they will be the new generation of the active control and variable damped devices. MR damper is one of the most excellent semi-active control devices. Due to their mechanical simplicity, high dynamic range, low power requirements, large force capacity, and robustness, a great deal of interest has been generated around the world.The focus of this dissertation is to develop a fundamental study to the large-scale MR dampers—2T-MR damper developed by us. Above all, the conditions of study and application of MR damper are summed up and the work of this dissertation is mentioned. In the next place, the rheological mechanics and constitutive relation and preparation requirements are introduced. The more rational style and inner structure of MR damper is chosen according to the comparison of the MR dampers anciently developed. Then the MR damper is designed initially applying the parallel-plate models. In the course of the design, it is discussed that the working gap of MR fluid exerts influence on two key indexes of the damp force and dynamic range and the optimum gap size is calculated. The design methods of magnetic circuits and accumulator are advanced in the meantime. Thirdly, the quasi-static experiments of the 2T-MR damper are conducted. Experimental results for the variable input current tests, amplitude-dependent tests, frequency-dependent tests, response time tests are presented. The experimental results are then compared with theoretical results obtained using previously developed quasi-static models. The relationships between the MR fluid yield stress and input current are estimated. Some phenomena observed during the experiment are also discussed, and possible explanations are given. Although useful for MR damper design, quasi-static models are shown to be insufficient to describe the MR damper nonlinear force-velocity behavior under dynamic loading, thus, more accurate dynamic models are presented and the influences of parameters on the models are discussed in Chapter 4. Based on theexperiments data, the parameters are identified by using the damped least square method namely L-M method. At last, the finite element model of the magnetic circuit is analyzed recurring to professional magnetic circuit analysis soft. The analysis results contain magnetic field in different currents, conditions of magnetic saturation and leakage and the magnetic flux density along the working gap of MR fluid. In order to make the MR damper more efficient, Optimum designs for the damper are described in virtue of the variety of the materials and structure.The study of this dissertation aims to lucubrate the dynamic characteristics of MR damper. The parameters identification method for dynamic models and the optimum method for magnetic circuits are presented. It is all setting stage for the better designed MR dampers.