Analysis Of Guided Waves In Multilayered Magneto-electro-elastic Media In Quasi/non-quasi Static Conditions

Dispersion(Propagation and Attenuation)characteristics of guided waves in piezoelectric/piezomagnetic/magnetoelectric multilayered media are crucial to their characterization,functional optimization,device development,material identification and non-destructive testing.The research on this topic can also provide a theoretical reference for the further development of new composite materials.In this thesis,the classical elastic wave theory based on quasi-static assumption of piezoelectric/piezomagnetic/magnetoelectric multilayered media is systematically studied.Then,the coupled electromagnetic-elastic wave theory in the non-quasi-static condition is further developed.Firstly,the quasi-static elastic wave theory of piezoelectric/piezomagnetic/ magnetoelectric multilayered media with general configuration of arbitrarily anisotropic materials is reviewed and deduced.It is based on the quasi-static hypothesis,which assumes the electric and magnetic fields are non-coiled and uncoupled static fields and simplifies the derivation process as well as the governing equations.The derived theory can be applied to the frequency range of traditional elastic waves,and has the advantages of uniform formulation,high efficiency,and clear physical meaning.Based on this theory,the FORTRAN computer program is compiled to calculate the slowness curves in the piezoelectric/piezomagnetic/ magnetoelectric multilayered media.The variation of the propagation velocity of the guided wave in these media with the propagation direction is analyzed.Secondly,the quasi-static hypothesis is abandoned to establish coupled electromagnetic-elastic wave theory in piezoelectric/piezomagnetic/magnetoelectric multilayered media.On the basis of non-quasi-static conditions,electric and magnetic fields are considered as mutually-induced dynamic fields,which are described by the Maxwell's equations.The theory is applicable not only to the low frequency domain of the traditional elastic waves,but also to the high frequency range of the electromagnetic waves.In the derivation of the coupling theory,the redundancy of the Maxwell's equations and the elimination of redundant equations in the case of harmonic solutions are discussed in detail.For each layer in the system media,the state equations of coupled electromagnetic-elastic waves within the framework of state space formalism are derived,which is further nondimensionalized for obataining its solutions.For the multilayered system,the method of reverberation-ray matrix is introduced to obtain the dispersion relation of the coupled electromagnetic-elastic waves.Based on the derived formula,the FORTRAN computer program is compiled to calculate the dispersion curves of coupled electromagnetic-elastic waves in piezoelectric,piezomagnetic and magnetoelectric multilayered composite media in non-quasi-static state conditions.The calculated results are further compared with the counterpart results in the quasi-static approximation to explore the influence of the inductive coupling between the electric field and the magnetic field on the dispersion characteristics of guided waves in piezoelectric,piezomagnetic and magnetoelectric multilayered media.Referring to numerical examples,the influence of boundary conditions on the guided wave propagation and attenuation characteristics in various composite media is also analyzed.