A Study On The Dynamic Characteristics Of A Magneto-Rheological Damper Featuring Piston Non-Magnetised Paths

The MR damper with both the magnetizable and non-magnetised flow paths improves the damping properties by slowing down the radical change of damping force in the low-velocity region,and helps vehicles achieve better ride comfort.Major work is summarized as follows:(1)The friction characteristics were tested and analysed.Dynamic characteristics of MR damper featuring non-magnetised paths in piston were analysed.The relationship between damping force and excitation current,piston velocity,temperature of magneto-rheological fluid was discussed.By introducing the concept of dynamic damping ratio,the dynamic characteristics were further analyzed.(2)The variation and mechanism of friction force was analysed by electromagnetic simulation of the magnetic circuit.The method to reduce the friction force and the phenomenological model of friction force were given.An efficient mathematical model for rod load was established.The rod loads under each current and each excitation velocity were calculated.The influence of the local head loss on damping force was analysed.The calculated damping forces by Bingham constitutive model,Eyring constitutive model and modified Bouc-Wen phenomenological model respectively were compared with each other.(3)The variation of magneto-rheological ratio of MR fluid under high shear rate and low shear rate was analysed.The influence of magneto-rheological ratio on dynamic damping ratio of MR damper was studied.The effects of the components of MR fluid on the magneto-rheological ratio were studied by experiments.The force-velocity characteristic with respect to structural parameters was studied.The sensitivity of mechanical properties of MR damper to structural parameters was analysed.The influences of the width of the annular path and the length of the MR effect area of the annular path on the dynamic damping ratio of the MR damper were studied.(4)The vibration governing equation of quarter vehicle integrated with MR damper was established.The ride comfort of MR damper featuring non-magnetised paths was compared with that of the MR damper without non-magnetised paths.The vibration isolation performances of two MR dampers were investigated involving the sky-hook control scheme.