Numerical And Theoretical Studies On Mechanical Properties Of Eddy Current Damping-rack And Gear Damper

As a new type of damping,eddy current damping has been widely used in vibration control fields such as vehicle braking,aerospace,and machining.Compared with the traditional viscous liquid damping,eddy current damping is non-contact,long life,less maintenance and easy to adjust and install.Therefore,the eddy current damper can fundamentally solve the oil leakage problem of the viscous liquid damper.In recent years,the research group of Professor Chen Zhengqing of Hunan University has applied for a series of patents of eddy current damping,which greatly improve the energy consumption density of eddy current damping,and have gradually been applied to large structures in civil engineering.The research group has proposed a new eddy current damper and the mechanical performance is systematically studied by theoretical analysis,electromagnetic finite element numerical simulation and prototype test in this article.The main work content and results are as follows:.(1)The mechanical properties of ECD-RGD are studied by theoretical analysis.A simplified calculation formula for the mechanical properties of ECD-RGD was deduced based on the assumption of uniform magnetic field and ignoring magnetic flux leakage.According to results of finite element simulation,the accuracy of the simplified calculation formula is analyzed and we found that the simplified calculation values match well with the electromagnetic finite element simulation values at low speed.Compared with air gap and back iron plate,the accuracy of simplified calculation formula is more sensitive to the position and number of permanent magnets.The established nonlinear mathematical model of ECD-RGD can simulate its nonlinear mechanical properties at high speed;The calculated values of modified formula matches well with the electromagnetic finite element simulation values in the whole process.(2)An electromagnetic finite element model is established by an electromagnetic finite element software called COMSOL Multiphysics,and its mechanical characteristics is performed.Then the effect of each main design parameter on the mechanical characteristics of the damper is studied,including the thickness of conductive plate,the material of conductive plate,the thickness of back iron plate,the thickness of distance between magnet and conductive plate,the number of permanent magnets and the position of permanent magnets.The results show that as the thicknessof conductive plate increases,the linear damping coefficient will increase,but its maximum damping force will decrease significantly;the thickness of back iron plate has little effect on the damping force;as the thickness of air gap decreases and the number of permanent magnets increases,the damping force will increase obviously.(3)A prototype of Eddy Current Damping-Rack and Gear Damper was designed and made to verify the reliability of the numerical simulation.The electromagnetic finite element simulation results match well with experimental results.