Search

Considering the nonlinear coupling behavior of magnetostrictive material, the modulation of Lamb wave bandgaps in magneto-elastic phononic plates composed of Terfenol-D pillars on a silicon matrix is investigated by the finite element method. By the introduction of holes, two schemes, i.e., the pillars only case for scheme-I and the trampoline (pillars and holes) case for scheme-II, are considered for exploring the effect of magnetostriction and trampoline on band structures. Numerical results show that the edges of bandgaps shift toward higher frequencies and the relative bandwidth enlarges as the magnetic field increases. The greater the compressive pre-stress applied, the greater the magnetic field at the open or closed points of the bandgap required. Compared to scheme-I, we find that the existence of holes for scheme-II can cause the closing of the higher branches' bandgaps and the generation of a new bandgap, and larger relative bandwidth of the bandgap and wider range of the required magnetic field can be observed due to the trampoline effect. Meanwhile, the height of the pillar is a key parameter for generating or vanishing bandgaps. According to the displacement distribution of eigenmodes, it can be seen that the opening or closing of the bandgap is controlled by the coupling between Lamb modes of the plate and resonant modes of the pillars, which is induced by the combined effect of trampoline, magnetic field, and pre-stress as well as geometry parameters. These results give guidance for active controllability of Lamb wave propagation and intelligent regulation of phononic devices in complex environments. [ABSTRACT FROM AUTHOR]

In this paper, a novel type of cross‐like holes phononic crystal with excellent band gap characteristics, machinability and stability is optimized and designed based on genetic algorithm. The improved genetic algorithm is used to enlarge the band gap in the low frequency range, and the transmission spectrum of the structure is calculated by finite element method. In addition, the magnetorheological elastomer was introduced to optimize the spatial magnetic field distribution and study the influence of magnetic field on the band gap. This work provides useful guidance for the topological design of other types of intelligent phononic crystals. [ABSTRACT FROM AUTHOR]

The aim of this article is to present a three-dimensional (3D) simulation based on Voronoi tessellation, used to assess the strain dependence of the superconducting critical properties of inhomogeneous polycrystalline Nb3Sn at the microstructural level. To support this objective, we first present a polycrystalline model with equiaxed grains used to analyze the relationship between the polycrystalline structure and the strain response. We analyze the Young's moduli of Nb3Sn at different temperatures with random and preferential polycrystalline orientations, and the relation between the Young's modulus of polycrystalline Nb3Sn and spontaneous tetragonal transformation is discussed. The results indicate that the elastic properties (Young's modulus, stress/strain field) of polycrystalline Nb3Sn are mainly associated with ambient temperature and phase transition and are affected by the grain orientation. Meanwhile, an estimation-based model for the superconducting critical properties of single-crystal Nb3Sn is proposed. This model is based on changes in the electron density of states and phonon frequency induced by strain. The results calculated by the estimation-based model are consistent with the experimental data and the values calculated according to first principles. The change in the strain-induced superconducting properties of polycrystalline Nb3Sn is analyzed by combining the numerically simulated strain field of the polycrystal with the estimation-based model of single-crystal Nb3Sn. Compared to ideal single-crystal Nb3Sn, the superconducting critical temperature of the polycrystalline Nb3Sn superconductor has a higher strain sensitivity, which is related to the non-uniformity of the strain field of the polycrystal. [ABSTRACT FROM AUTHOR]