Study On Optimization Design And Applications Of Magnetorheological Plastomers

Magnetorheological plastomer(MRP)is a new type of magnetically sensitive soft material,which is usually composed of magnetic particles and a non-magnetic plastomer.Its mechanical properties and electrical properties can be controlled by magnetic fields.In the absence of a magnetic field,MRP can be changed to any shape and maintain this shape after removing the external force,exhibiting plastic behavior.At the same time,the internal magnetic particles can move under the action of a magnetic field to form a chain or network structure,and maintain this structure after removing the magnetic field.So,MRP has a high magnetorheological effect and magnetoresistance effect and there is no problem of particle sedimentation,which makes it has broad application prospects in areas sush as vibration control,intelligent actuators,sensors,etc.In addition,the particle microstructure in MRP can be controlled by a magnetic field,which is helpful to the study of the relationship between macroscopic mechanical properties and microstructure.Therefore,the research on MRP has important practical and theoretical significance.Until now,preliminary research has been made on the testing of MRP's properties and particle microstructure calculation,but there is no research on the optimization and application of MRP.At the same time,more words are needed to further improve the testing and characterization of MRP,and strengthen the mechanism study of interaction between particles and the matrix.In view of the shortcomings of current research,the normal stress of MRP in the process of oscillating shearing is first tested in this paper,and the relationship between macroscopic mechanical properties and microstructure is studied.Then for the lack of optimization of material properties,hollow glass balls reinforced MRP and graphite reinforced MRP were prepared and their mechanical and electrical properties were tested.Finally,a noval energy absorber with MRP as buffer medium was designed.The details are as follows.1.Normal stress in MRP under shear mode.Firstly,the normal stress in MRP under different shear modes was tested.It was found that the normal stress oscillated with the oscillation of shear strain,and the amplitude was related to that of the shear strain.The test results under the step shear mode show that the shear itself also generates normal stress in the MRP and the stress magnitude becomes proportional to the stress,called the Poynting effect.Particlelevel dynamics simulations were used to calculatethe particle microstructure,magnetic induced normal stress,and structural strain under different sinusoidal shear strains.The results show that the particle microstructure strain is much smaller than the shear strain and there is a phase difference between the two strains.The results of experimental tests and numerical calculations show that the Poyntings effect and the change of magnetic induced normal stress with microstructure are the main reasons for the normal stress change.2.Strengthening effect of hollow glass particles on magnetic induced mechanical properties of magnetorheological plastomer.For the optimization design of MRP,hollow glass powders(HGPs)were added to improve the mechanical properties of MRP.The test results show that the addition of hollow glass spheres not only increases the initial shear modulus of MRP,but also greatly enhances its magnetic induced properties.Using the equivalent inclusion theory,the relationship between the MRP magnetic induced shear modulus and the content of iron particles/HGPs was established.The theoretical fitting results are in good agreement with the experimental results.The addition of non-magnetic HGPs can replace part of the iron powder particles and achieve the same mechanical properties,which can not only reduce the overall density of the material but also reduce the cost of material preparation.3.Preparation of GMRP and its Magneto-mechanical-electrical coupling performance.The MRP with graphite flakes was prepared and its mechanical properties and electrical properties were tested.It was found that the addition of graphite flakes effectively improved its magnetic induced mechanical properties and greatly improved the conductivity of MRP.As the magnetic field increases,the MRP resistance decreases by at least three orders of magnitude.At the same time,adding graphite can increase MRP conductivity by 8000 times.A particle-particle resistance model was further proposed to establish the relationship between magnetic field,particle spacing variation and electrical properties.The relationship between resistance and magnetic flux density was also deduced.The fitting results of the model agree well with the experimental results.Finally,using the magnetic field controllability of MRP'resistance,a magnetic switch was designed.4.A novel energy absorber based on the magnetorheological plastomer.Finally,a new magnetorheological energy absorber with MRP as a buffer medium was designed and tested for its buffering performance.Firstly,the mechanical properties of MRP in shear and compression mode under magnetic field were studied.Then,a new type of magnetorheological energy absorber was designed.The side of the piston is parallel to the side of the inner liner and is inclined so that the distance between the pistons decreases as the piston moves down.At the same time,the internal magnetic field distribution of the energy absorber was calculated by finite element analysis.The lower rod of the piston is made by the non-magnetic stainless steel so that the magnetic field at the piston gap increases as the piston descends.This design can improve the utilization of the entire buffer stroke and reduce the amplitude of the pulse force during impact.The test results show that the energy absorption process is relatively stable throughout the entire buffering process and meets the design requirements.In the drop hammer test,the speed of the piston can be reduced from 3.4 m/s to 0 within 13 ms and the maximum damping force does not increase with the drop weight.The maximum damping force can reach to 8 kN.Switching on the current can increase the energy absorption rate and the energy absorption rate increases from 4.1 J/mm to 5.1 J/mm.