| Magnetorheological fluid(MRF)is a widely used intelligent material in the field of vibration control.MRF zero-magnetic-field settlement will affect the vibration transmission of equipment using MRF.The effect is more significant after the equipment is been placed for a long time.That’s the reason why the transmission of elastic waves in the zero-magnetic-field subsidence MRF is studied,the characteristics will explore new developments and applications of MRFs in the field of vibration control.Based on the theory of porous medium and scattering of granular medium,a zero-magnetic-field MRF sedimentation layered structure vibration transmission model is constructed.Through numerical calculation and experimental verification.The transfer characteristics of elastic wave in the zero-magnetic-field sedimentation layered MRF is studied.This article focuses on the following aspects:First,the layered structure of MRFs with different settling time under zero-magnetic-field conditions was studied.Based on FLUENT simulation,the settlement characteristics of GH-MRF-250 MRF were analyzed,and the volume fraction-depth curves of ferromagnetic particles at different settlement times were obtained.The analysis results show that the original concentration zone is basically maintained at 0.25 after 7 days of settlement.After 15 days of sedimentation,a variable concentration zone with a volume fraction of 0.42 appeared,and after 30 days of sedimentation,a sediment zone with a volume fraction of 0.56 appeared.The timed quantitative sampling analysis method was used to carry out the MRF sedimentation layering experiment.The fitting results of the experimental data were consistent with the simulation results.According to the experimental results,the MRF was divided into high / low-density magnetics based on the volume fraction of 0.5.Secondly,the vibration transfer characteristics of the homogeneous MRF under zero-magnetic-field are studied.A high-density MRF vibration transfer model was established based on the porosity medium theory,and a low-density MRF vibration transfer model was established based on the scattering of granular medium theory.The volume fraction-vibration-level drop and layer thickness-vibration-level drop of high / low-density MRFs were obtained through numerical calculation.The curve analysis results show that the attenuation of elastic waves increase with the layer thickness and volume fraction of the MRF.A zero-magnetic-field homogeneous MRF vibration transfer experiment was performed to verify the accuracy of the high / low-density MRF vibration transfer model.Then,the vibration transfer model of the zero-magnetic-field MRF layered structure was established.Using the high / low density transfer model as the transfer matrix unit,a zero-magnetic-field MRF settlement layered structure vibration transfer model was established based on the transfer matrix method.Numerical calculations of the elastic wave level drop curves for different settlement times are obtained.The curve analysis results show that compared with the homogeneous MRF,the elastic wave attenuation tends to weaken first and then increase with the increase of the settlement time.Finally,the vibration transfer experiments of the zero-magnetic-field MRF sedimentation layered structure is carried out.An experimental platform for vibration transmission characteristics of MRF was set up,and experiments of 30 ～ 100 Hz elastic wave transmission of MRF with different settlement time in zero field were carried out.The analysis of experimental results shows that because the settlement time is too short,the 7-day settlement sample has a small change in the attenuation of the elastic wave compared to the homogeneous state.The 30-day settlement sample forms a complete settlement structure,and the elastic wave attenuation effect is better than the homogeneous state Change fluid has been enhanced.The experimental results agree well with the theoretical calculations,which verifies the accuracy of the theoretical model. |
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