| Phononic crystal is a kind of functional composite material with periodic structure,which has a band gap characteristic capable of suppressing the propagation of elastic waves in frequency range of band gap.With the rise of intelligent phononic crystals,magnetoelectroelastic materials,as functional materials with two or more properties of piezomagnetism,piezoelectricity and elasticity,are introduced into phononic crystals to form magnetoelectroelastic phononic crystals.Due to the multiple characteristics of magneto-electro-mechanical coupling,mutual conversion of magnetic energy,electrical energy and mechanical energy can be achieved.Therefore,magnetoelectroelastic phononic crystals have shown rich research value and broad application prospects in the fields of vibration and noise reduction,signal control,magnetoelectric sensors,and electronic communication.The propagation behavior of elastic wave and magneto-electro-mechanical coupling characteristics are the key issues affecting the design and application of magnetoelectroelastic phononic crystal devices.So,elastic wave band gaps of one-dimensional and two-dimensional magnetoelectroelastic phononic crystals are systematically studied,and the magnetoelectric coupling problem of multilayer magnetoelectric composites is explored.Specific research contents are as follows:(1)The magnetostrictive material is introduced into the rod and beam structures commonly used in engineering applications,and the theoretical model of band gap characteristics of magnetoelastic phononic crystal rod and beam with magnetostrictive material is established by using the plane wave expansion method.Firstly,considering the nonlinear mechanical-magneto-thermal coupling constitutive relation of magnetostrictive materials,the propagation behavior of longitudinal wave in rod-shaped magnetoelastic phononic crystals is studied,and the influence of operating temperature,external magnetic field,prestress and demagnetization effect caused by structure size on band structure is analyzed.It is found that temperature has a significant effect on the position and width of bandgap,especially for high-order bandgap.The width of the first four band gaps presents a wavy curve with the change of material filling fraction and successively appears corresponding order peaks,whose amplitude is affected by magnetic field,prestress and temperature.Subsequently,the size-dependent behavior of bending wave propagation in magnetoelastic phononic crystal nanobeam is investigated,and the influence of surface effect on band structure in different structure sizes is discussed.It is found that the effect of surface effect on band gap cannot be ignored when the structure size of phononic crystal beam is reduced to nanometer scale.The position and width of band gap with surface effect are higher and wider than those without surface effect.Surface elasticity and surface piezomagnetic energy are the main factors affecting band gap.The nonlinear variation of band gap with magnetic field and prestress is also discussed.(2)Firstly,for the propagation behavior of elastic waves in layered magnetoelectroelastic phononic crystals,the dispersion relation of SH wave propagating perpendicular to interface layer is derived by using transfer matrix method.The effects of elastic/elastic,piezoelectric/elastic,piezoelectric/ piezomagnetic and magnetoelectroelastic/elastic on band gap characteristics are numerically analyzed.It is found that band gap obtained by considering the piezoelectric effect is higher than that without piezoelectric effect,the piezomagnetic and magnetoelectroelastic coupling effects can also regulate band gaps.Subsequently,considering the strong magnetoelectric coupling in piezoelectric/magnetizing layered phononic crystals,a two-dimensional nonlinear magneto-mechanical-thermal coupling theoretical model of multilayer magnetoelectronic composites is established.The influence of amplitude and direction of magnetic field and prestress on magnetoelectric coefficient is analyzed,and the regulating effect of working temperature on magnetoelectronic effect is discussed.The maximum magnetoelectric conversion performance can be obtained by loading magnetic field and prestress at an optimal direction angle.It is shown that the resonance frequency shift of high frequency magnetoelectronic coefficient is caused by the "(35)E effect" induced by magnetic field,prestress and temperature.(3)For the plate-like phononic crystals,a magnetic-elastic coupling theoretical model of band gap characteristics is established.Firstly,the propagation behavior of longitudinal wave in magnetoelastic phononic crystal thin plate is studied.It is found that the loading mode,direction and amplitude of magnetic field have a significant effect on band structure.When magnetic field is loaded in x-y or x-z planes,respectively,the optimal angles of magnetic field corresponding to the maximum bandwidth can be obtained at 45° and 0°,respectively.Meanwhile,there is a competitive relationship between the prestress and magnetic field on band gap,applied a proper prestress can weaken the influence of magnetic field.Then,the evolution of Lamb band gap in Trampoline type(pillars and holes)and pillars only type magnetoelastic phononic crystal plates is studied,the important role of Trampoline effect on band structure and eigenmode is discussed.It is found that the generation and close of band gap can be strongly dependent on Trampoline effect,geometric parameters,magnetic field and prestress.In addition,Trampoline effect can increase band width and obtain band gap in a larger ranger of magnetic field.(4)In practice,the mechanical properties of magnetostrictive materials are inevitably affected by hysteresis effect.Therefore,the band gap characteristics of elastic waves considering the action of hysteresis effect and magnetic-mechanical coupling are studied for two-dimensional magnetoelastic phononic crystals.The hysteresis phenomena of magnetostrictive material coefficients varying with the applied magnetic field are discussed.The effects of two magnetic field loading paths caused by hysteresis effect on band structure are investigated.It is found that the loading path and amplitude of magnetic field as well as pre-stress have a significant effect on the generation and close of band gap.Compared with the magnetic field decreasing path,a higher frequency band gap can be obtained by applying a magnetic field through the increasing path.In addition,unlike the anti-plane z mode wave,the band gap of in-plane x-y wave is more concentrated on high-frequency region.In summary,this paper studies the elastic wave propagation behavior of several kinds of magnetoelectroelastic phononic crystal structures,explores the effect of external magnetic field,prestress,temperature and other factors on band gap,and further improves the mechanical-magneto-thermal coupling theoretical model of magnetoelectronic coupling effect for multilayer magnetoelectronic composites.These results provide an important theoretical guidance for the application of magnetoelectroelastic composite materials in the field of elastic wave and vibration control,and contribute to the structural design and performance optimization of new magnetoelectric functional devices. |
