Propagation Characteristics Of Elastic Wave In Nonlinear Magnetoelectric Composite Structures

Magnetostrictive material is a kind of material with mutual conversion function of electromagnetic energy and mechanical energy,and it is defined as magnetic functional material which can produce large deformation under the external magnetic field.The giant magnetostrictive effect of magnetostrictive material can make a huge magnetoelectric effect in a nonlinear composite material composed of the magnetostrictive material and the piezoelectric material,so that it can be widely used in various ultrasonic devices,high-performance memory,new magnetoelectric devices and so on.Different from linear magnetoelectric composite materials,the dispersion characteristics of elastic waves propagating in composite structure may be more complicated and present many new physical phenomena due to the nonlinear characteristics of magnetostrictive material.Therefore,it is necessary to study the effect of external factors(such as external magnetic field)on the propagation characteristics of elastic wave in nonlinear magnetoelectric composite structure.Not only can it reveal the factors that affect the elastic waves propagating in nonlinear magnetoelectric composite structure,but it can also provide the theoretical reference for the application of nonlinear magnetoelectric sensors.The rare earth giant magnetostrictive material represented by Terfenol-D is different from the traditional magnetostrictive material,which has large saturated magnetostrictive strain and large magneto-mechanical coupling coefficient.In this paper,the propagation characteristics of elastic waves in nonlinear magnetoelectric structures composed of Terfenol-D and piezoelectric materials have been studied,mainly including:Propagation characteristics of SH wave and Love wave in nonlinear magnetoelectric layered composite structure.According to the nonlinear relationship between the material parameters of Terfenol-D and the external magnetic field,the constitutive relationship of the layered composite structure is obtained by the quasi-linear method.Combining with boundary conditions,the dispersion equations of SH wave and Love wave propagating in Terfenol-D layer/piezoelectric substrate are derived.The numerical results show that the larger the external magnetic field is,the greater the phase velocity of SH wave and Love wave in the magnetoelectric structure is,and the larger the BG wave velocity and shear wave velocity of Terfenol-D are.Propagation characteristics of Lamb wave and Rayleigh wave in nonlinear magnetoelectric composite plate.Considering the propagation of Lamb wave and Rayleigh wave in the plane,the dispersion curves of Lamb wave and Rayleigh wave in the bi-material structure composed of Terfenol-D and piezoelectric material are obtained by matrix analysis method.The numerical results show that the influence of external magnetic field on the displacement,stress,magnetic potential and potential of higher mode in composite structure is stronger than that of lower mode,and the attenuation velocity of elastic wave in the lower mode is stronger than that in the higher mode.Reflection and transmission of P wave and SV wave on the interface of nonlinear magnetoelectric materials.Based on the Christoffel equation in the magnetoelectric composite medium,the apparent velocity of the plane wave in Terfenol-D/piezoelectric material is derived firstly,and then the reflection and transmission of P and SV waves on the interface of Terfenol-D/piezoelectric material are analyzed by Snell theorem.The results show that the larger the external magnetic field is,the larger the reflection and transmission coefficient is,and the larger the critical angle of reflection and transmission is.