Study On Parameters And Vibration Reduction Principle Of Eddy Current Damper

Eddy current tuned mass damper（eddy current TMD）is a TMD which adopts eddy current damping unit,which has the advantages of simple structure,high reliability,good durability and convenient maintenance.However,due to the low efficiency of eddy current damping and limited cognition of the parameters affecting the damping coefficient,it is difficult to adjust the damping coefficient.Although some improvements have been made in the engineering field,the significant degree of the influence of the relevant parameters has not been studied,and it is rarely used in the structural vibration reduction of large-scale projects.Therefore,the paper studies the relevant parameters of the eddy current damping unit in theory,simulation and test verification,and analyzes the influence of different geometric parameters,position parameters and motion parameters on the eddy current damping coefficient in detail.On this basis,the response surface design method is used to quantify the significant degree of the influence of the three key parameters of the eddy current damping unit,and explores the significance of the three key parameters in theory The vibration reduction principle of eddy current TMD.The main contents and research results of this paper are as follows:（1）The theoretical calculation and Simulation of the magnetic field distribution outside the rectangular permanent magnet are carried out,and the finite element simulation results are compared with the theoretical calculation results to verify the effectiveness of the finite element method,which provides a prerequisite for the accurate calculation of the eddy current damping coefficient.（2）Based on the assumption that the external magnetic field distribution of rectangular permanent magnet is uniform and the conductor plate is infinite and only on the projection plane of permanent magnet,the theoretical calculation formula of eddy current damping coefficient is derived.According to the theoretical calculation formula and the structure of the eddy current damping unit,several parameters which may affect the eddy current damping coefficient are simulated.The results show that: in order to improve the utilization rate of the permanent magnet,the poles of the permanent magnet should be staggered,and the best magnet spacing is 0.5 times of magnet width.The size of the permanent magnet perpendicular to the moving direction of the conductor plate should be increased to give full play to the positive coupling between magnets.The eddy current damping coefficient can be significantly improved by placing a permanent magnet iron plate and magnetic plate,but the change of plane size and thickness has little effect.There is an optimal plane size of the conductor plate,and the thickness should not exceed 11 mm.The smaller the magnetic gap,the better.（3）Based on the conclusion of the finite element simulation of eddy current damping coefficient,a set of experimental model of single degree of freedom system is designed,and the influence of different conductor plate materials and thickness,copper magnetic gap,magnet spacing and the presence or absence of magnetic plate on eddy current damping coefficient is studied through orthogonal experiment.The results show that the finite element simulation values are in good agreement with the experimental values.（4）On the basis of finite element simulation and experimental analysis,response surface design method is used to optimize the design of different copper plate thickness,copper magnetic gap and magnet spacing.The results show that the order of influence significance is as follows: Copper magnetic gap is the largest,copper plate thickness is the second,and magnet spacing is the smallest.（5）The change of displacement response coefficient with frequency ratio of single degree of freedom system under different damping ratio is explored.Under different frequency ratios,the dynamic response of the structure is determined by stiffness,mass and damping respectively.The operating frequency range of the dynamic vibration absorber can be adjusted by changing the mass ratio after adding the dynamic vibration absorber.After adding a certain amount of damping,it becomes a tuned mass damper,its operating frequency range increases,and the formulas of optimal frequency ratio and optimal damping ratio are derived.