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In the underwater sonar or similar devices where the high pressure field is required, the concentrating and black hole like structures have important applications in harvesting energy systems of elastic waves. In this work, a new kind of active elastic metamaterials with cavities and an acoustic concentrator are presented. By the feedback control gain of piezoelectric diaphragms, we can obtain both the controllable effective bulk modulus and density within a wide frequency range. Based on the coordinate transformation method and by the feedback control on the periodic arrangement of acoustic cavities, an acoustic concentrator with multilayered alternative homogeneous materials can be achieved. Numerical results show that the acoustic wave is perfectly limited within the core region of the concentrator, which can enhance the acoustic energy. These characteristics with the tunable effective bulk modulus and density within a very wide frequency range are expected to be helpful for the design of practical acoustic concentrators. [ABSTRACT FROM AUTHOR]

Dislocation behavior is a critical feature in describing the reliable properties of structures and materials. As a new kind of smart material, multiferroic solids have special applications on the coupling systems of mechanical, electric, and magnetic fields. Then, the moving dislocation in multiferroic solids has special interests for strength characteristics. In the present work, the moving edge dislocation is studied by the eigenstrain theory. The explicit solutions are derived and can be reduced to the piezoelectric and even pure elastic materials as the special cases. [ABSTRACT FROM PUBLISHER]

A screw dislocation in a functionally graded magnetoelectroelastic material is investigated. The material properties exponentially changing along bothxandydirections are considered and the mechanical–electric–magnetic coupling is discussed. Closed-form expressions for the mechanical, electric and magnetic components are derived using the general stress function method. The solutions can be applied as a fundamental result and reduced into the classic and piezoelectric cases. The study puts forth a direct way for screw dislocation analysis in inhomogeneous structures with multifield coupling. [ABSTRACT FROM AUTHOR]

In this paper, the band gap properties of the periodic structures of bar system, which include the rod-joint, truss, and frame structures, are studied using spectral element method (SEM). The spectral equations of the rod, beam, and joint elements are established and the spectral equations of the whole structures are further assembled. The frequency responses of the whole structures are calculated and the results are compared with those calculated by the finite element method (FEM). It can be observed that the SEM is more accurate in high frequency ranges. The band gap properties of the three types of periodic structures are studied, respectively. Furthermore, the effects of structural length, unit cell number, structural configurations, load conditions, and structural damping on the band gap properties are investigated. [ABSTRACT FROM PUBLISHER]