Development And Performance Sutdy Of A New Magnetorheological Grease Damper

In the filed of structural vibration control,smart base-isolation technology in structural control have become one of the research hotspots because of its effectiveness in response reduction without requiring high power sources.On the other hand,MR dampers have been used extensively in the studies and applications of smart base-isolated structures because of their attractive advantages,such as high-dynamic range and rapid response speed.Nowadays,many kinds of MRD have been developed.However,the existing MRD was developed based on unidirectional output and cannot solve the problem of settlement of magnetorheological fluid.In face,the earthquake is not limited to a single direction.Aiming at the shortcomings of the existing magnetorheological damper,this paper proposed a new type of magnetorheological damper with bidirectional output,and analyzed its parameters.The ANSYS Workbench was used to analyze the influence of parameters on the magnetic filed and damping force.The optimization of the damper was studied from the magnetic circuit-damping channel and the damping channel-magnetic circuit respectively;The performance of the damper was tested by hydraulic servo actuator.The parameters of the Bouc-Wen model were identified by experimental data.The identified mechanical model was combined with the smart base-isolation structure to compare the damping effect of smart base-isolation structure?common isolation structure and passive isolation structure.The main research content of this article is as follows:(1)A new magnetorheological fluid damper with bidirectional output is proposed,and the influence of damper magnetic field parameters is analyzed.By setting the chute and the magnetorheological fluid,the damper achieves a bidirectional output and avoids the long-term settling of the magnetorheological fluid.Based on Maxwell's electromagnetic field theory,the influence of magnetic field parameters on the magnetorheological fluid damper was analyzed using the ANSYS Workbench platform.The research shows that the new damper proposed inthis paper is reasonable in structure,and the coil is separated from the magnetorheological fluid to facilitate the repair and replacement of the coil.The thickness of the damper,the diameter of the core,the number of turns and the magnitude of the current affect the magnetic induction at the gap.Large,the ratio of the thickness of the magnetic block to the core diameter should not exceed 2.5.(2)The parameters of the magnetorheological fluid damper proposed in this paper were analyzed,and the damper magnetic circuit and fluid optimization process were proposed.The genetic algorithm was used to optimize the damper parameters by the ANSYS Workbench platform.The analysis shows that after the magnetorheological fluid yields,the damping force was positively correlated with the magnetic field strength and area of the magneto-rheological fluid.Before the magnetorheological fluid yields,the groove diameter and groove spacing have a greater influence on the damping force.When the groove diameter was increased by 100% and the gap thickness was varied by 400%,the damping force became41.7% and 30%,respectively.(3)The performance of the hysteretic behavior of the new magnetorheological grease damper was tested.The hydraulic servo actuator was used to study the actual influence of loading amplitude,frequency and current on the performance of magnetorheological grease damper.Based on the Bouc-Wen model,the model was identified by least squares method.The analysis results show that the Bouc-Wen model can effectively describe the mechanical properties of the damper.The new magnetorheological fluid damper proposed in this paper has good mechanical properties.(4)The damping effect of the intelligent isolation structure with two-way magnetorheological grease damper was studied.Taking a five-layer isolated structure as an example,the pseudo-negative stiffness control algorithm was used to analyze the numerical analysis with MATLAB,and the analysis results were compared with the passive isolation structure of passive isolation structure,passive off and passive on.The analysis results show that compared with passive on passive isolation structure,the intelligent isolation structure did not significantly amplify the seismic response of the superstructure;compared with the passive off-isolated passive isolation structure and the common isolation structure,the intelligent isolation structure The displacement of the isolation layer can be effectively limited,that is,the intelligent isolation structure can effectively reduce the displacement of the upper structure without effectively amplifying the displacement of the isolation layer.