Elastic Wave Propagation In Layered Magneto-Electro-Elastic Composites With Imperfect Interface

Magneto-electro-elastic (MEE) solids are a class of new composites consisting of piezoelectric and piezomagnetic phases. Due to possessing coupling effects between mechanical deformation, electric field and magnetic field, such composites can be used as magnetoelectric controllers, sensors, transducer, microwave devices as well as other electric products, and so on. The layered structures are basic configurations for these magneto-electric components and many applications are associated with elastic wave propagation in such composite structures. So several problems of elastic wave propagating in layered transversely isotropic MEE composites is investigated in this dissertation, and the imperfect bonding that sometimes exists in devices is considered. Based on the theory of MEE constitutive relations, the analytical solutions of the problems are derived and a lot of numerical examples are given. The results can provide a theoretical basis for the applications of MEE composites and structures to engineering.SH wave propagation in piezoelectric/piezomagnetic coupled structures with imperfect interface is studied. Two kinds of configurations are considered, i.e. piezoelectric layer/piezomagnetic substrate and the reverse configuration. According to the existence conditions for SH wave in MEE composites, the exact dispersion relation is obtained and the effects of the electro-magnetic boundary conditions, interface imperfection, geometry and material properties on the dispersion behaviors are then discussed. The results show that the layer material properties and electro-magnetic boundary conditions play a dominant role in the dispersion relation. The wave speed decreases due to the interfacial imperfection. Moreover, the weaker the bonding interface is, the smaller the phase velocities of SH wave are. The phase velocity of the first mode may be smaller than the B-G surface wave velocity of the layer material in certain region of wave number. The smaller the ratio of thickness of the layer to the substrate is, the larger the phase velocity of SH wave propagating in the corresponding structure.Lamb wave propagation in piezoelectric/piezomagnetic bi-material plates with imperfect interface is investigated. For the plane strain problem, the interfacial property can be described by the normal and the tangential stiffness coefficients. The influences of the electro-magnetic boundary conditions, interface imperfection, geometry and material properties on the dispersion behaviors are discussed, respectively. The results show that the first two modes are determined by the electric and magnetic boundary conditions, respectively, and the third mode has nothing to do with the electro-magnetic boundary conditions. The wave velocity for the perfect interface is the largest, the sliding interface is secondary and the unbonded interface is the smallest for a given wave number. Compared with the tangential interface imperfection, the dispersion characteristic is sensitive to the normal interface imperfection. The thickness ratios of the two layer and the piezoelectric properties have great effect on the dispersion properties.Wave propagation along axis of piezoelectric/piezomagnetic layered cylinder with imperfect interface is studied. The radial and the axial stiffness coefficients are used for expressing interface characteristic and the influences of the electro-magnetic boundary conditions, interface imperfection and geometry on the dispersion relations are discussed, respectively. The results show that the electro-magnetic boundary conditions and the axial imperfection have no effect on the phase velocity of the first mode, but have great effect on the second mode. The influence of the radial imperfection on the dispersion properties is larger than that of axial imperfection. The ratio of inner to outer radii of piezoelectric layer can evidently change the dispersion curves.The propagation of Lamb waves in an infinite MEE plate under a biasing electric field is studied. The phase velocity and stress field of the symmetric and antisymmetric wave modes are obtained. The effect of biasing electric field on phase velocity, the mechanical displacements, electric and magnetic potentials and stress fields are discussed, respectively. The results show that the biasing electric field has significant effect on the phase velocity. The phase velocity of Lamb wave will decrease when we apply a negative biasing electric field to the MEE plate, and the time delay can be obtained, which is very useful in engineering. The biasing electric field has slight effect on the mechanical displacements, electric and magnetic potentials and stress fields for both symmetric and antisymmetric Lamb wave modes.