Dynamic Mechanical Properties And Application Of Magnetorheological Elastomer In Compressive Mode

In recent years,researchers have made great progress in the research of material proportion selection,preparation method and mechanism interpretation of magnetorheological elastomers(MRE).However,there are still many problems in the performance test and engineering application of MRE,which should be further studied and discussed.At present,the main research direction of the MRE mechanical model is its micro-dipole and viscoelastic mechanical models,and it mainly focuses on shear performance,the compression performance is less studied.In-depth study of the dynamic mechanical properties of MRE under various conditions is conducive to its better engineering applications,such as intelligent vibration and noise reduction,electromagnetic sensors and active control fields.For the influence of electromagnetic force on the MRE pressure in the compression mode,the paper firstly studies and analyzes the electromagnetic force,and establishes the parametric modified mechanical model of MRE which closer to the actual working condition based on the stress-strain relationship.In addition,a dynamic vibration absorber is designed and its damping performance is tested and studied,which verifies the validity of the modified mechanical model.The paper mainly carried out the following aspects:Firstly,the structure of the new test device is designed.For the problem of low precision of magnetic field regulation in traditional test equipment,a new test device is designed by using electromagnetic coil as magnetic field generator and S10 C steel as magnetic material based on the relationship between current and magnetic field,and the magnetic circuit simulation is carried out by JMAG-Designer electromagnetic finite element software.The results show that the magnetic induction intensity can basically reach the expected target of 0.5~1T,and the structure and magnetic circuit design of the test device are reasonable.Secondly,the silicone rubber-based MRE is prepared.Based on the principle of magnetic circuit design,the magnetic circuit of the mold is designed and calculated,and the simulation is carried out by JMAG software.The results show that the magnetic circuit design can meet the requirements of 1T magnetic induction.Using the designed preparation device,pre-structured and non-pre-structured silicone rubber-based magnetorheological elastomer samples with different volume fractions are prepared from the perspective of MRE preparation process.Then,a dynamic compression parametric modified mechanical model of the silicone rubber-based MRE is established.The Instron8801 electro-hydraulic servo fatigue tester is used to test the current-squeezing thickness-electromagnetic force relationship of the test device.Based on the measured data,the electromagnetic force between the two magnetic poles in the test device is identified by the least squares method.The mechanical model of force lays the foundation for the establishment of a MRE modified mechanical model.In addition,the microscopic mechanical model of MRE is studied.The factors that characterize the compressive modulus of the material and affect the magnetorheological effect of the material are explored.At the same time,the macroscopic mechanical model is studied and the viscoelastic and hyperelastic properties of the material are explored.The performance of the silicone rubber-based MRE is predicted.Based on the influence of electromagnetic force,the compression mode parameterized dynamic modified mechanical model which is closer to the actual working condition is established.Based on the measured data,the unknown parameters of the mechanical model are fitted.By comparing the curves of the parameterized mechanical model and the experimental data,it can be seen that the parameterized dynamic modified mechanical model can well describe the dynamic mechanical properties of the magnetorheological elastomer under the compression mode.Finally,the vibration damping properties of the silicone rubber-based MRE is tested.Based on the magnetron characteristics of the MRE and the working principle of the vibration absorber,the MRE dynamic vibration absorber is designed,and the main system vibration damping platform is built.By adjusting the control system of the vertical vibration platform,different external excitation frequencies are applied to the platform,and the acceleration transfer rate under different frequencies and currents are measured.The results show that the natural frequency range of the designed MRE dynamic vibration absorber is widened by adjusting the current.That is,the effective frequency band of the vibration absorber is broadened to 37.5~62 Hz,so as to track the external excitation frequency in real time and improve its vibration damping performance.During the test,the MRE samples with different iron content prepared in chapter 3 are replaced,and it is found that the iron content have an impact on the vibration damping performance of the vibration absorber,and the higher the iron content is,the more obvious the frequency shift characteristics are,and the better the vibration absorption performance is.In the paper,based on the influence of electromagnetic force on the compression force of MRE in compression mode,a parameterized modified model is re-established in the paper,which is conducive to its better engineering applications,such as intelligent vibration and noise reduction,electromagnetic sensor and active control,etc.In order to verify the rationality of the modified mechanical model,the vibration absorber is designed and its vibration damping performance is tested.