Application Of Magnetic Materials In Phononic Crystals

Metamaterials(MMs)can exhibit unnatural properties,even far beyond those found in nature,through artificial design of the periodic structure.This emerging class of materials has diverse application potentials in many fields.In recent years,phononic MMs or phononic crystals(PCs)engineered to manipulate the propagation of elastic waves have received significant interest because of their broad range of applications including acoustic cloaking,wave filtering,noise reduction and vibration control.Phononic crystals(PCs)is a kind of phononic MMs with periodic structure.A part of conventionally designed and fabricated PCs can hardly have tunable acoustic properties,which may limit their applications.As a consequence,how to conduct tunable and active PCs is very promising.In our study,multiphysics finite element modeling methods are used to investigate deformation pattern and band structure of the phononic crystal with periodically distributed magnetic-hard particles.In order to reduce computational cost and obtain general properties,unit cells are used,which apply periodic boundary conditions(PBC)on the edges of unit cells.Based on the study of particle distribution,particle’s volume ratio,particle magnetic flux density and other factors,several feasible material design schemes were obtained and compared with the deformation mode driven by uniaxial compression.A simple magnetic dipole model is used to analyse the difference between these two cases.The analysis results show that there are two main factors affecting the deformation mode of materials: one is the interaction of magnetic particles,the other is the magnetic torque given by the external magnetic field.Moreover,the wave propagation of the unit cells with different deformation modes under magnetic field are also simulated.The numerical results demonstrated that large deformation of the structure under magnetic field can change the position and width of the band gap,which is beneficial for design of active PCs excited by magnetic field.Besides,in order to simulate the dynamics behavior of the magnetic-hard material,LAMMPS,a classical molecular dynamics simulation code is extended.Lattice model is used to simulate the elastic matrix and dipole model is adopted to calculate the magnetic interaction between particles.Detachment mechanism is found during the uniaxial stretch test with different initial magnetic moment.