Design Of Elastic Metamaterials Research Articles

Deep learning for the design of phononic crystals and elastic metamaterials

Abstract The computer revolution coming by way of data provides an innovative approach for the design of phononic crystals (PnCs) and elastic metamaterials (EMs). By establishing an analytical surrogate model for PnCs/EMs, deep learning based on artificial neural networks possesses the superiorities of rapidity and accuracy in design, making up for the shortcomings of traditional design methods. Here, the recent progresses on deep learning for forward prediction, parameter design, and topology design of PnCs and EMs are reviewed. The challenges and perspectives in this emerging field are also commented.

Design of elastic metamaterials with ultra-wide low-frequency stopbands via quantitative local resonance analysis

Elastic metamaterials (EMMs) with engineered bandgaps have numerous applications in medical, transport, and aerospace domains due to their extraordinary performance in manipulating elastic waves. Nevertheless, developing an efficient method to guide designs of EMMs with low-frequency and wide frequency stopband is still a challenging problem in this field. In this paper, a quantitative local resonance analysis scheme is proposed for efficient design of three-dimensional (3D) latticed EMMs with broad and complete wave attenuation band at low frequency. To acquire a low starting frequency, a diatomic mass spring analytic model is applied to guide the modification of structure and adjustment of geometrical parameters of the EMM, and thus its effective stiffness and mass values affecting the starting frequency are altered desirably. With the aim of enlarging stopband, a strategy to analyze stopband formation mechanism is proposed by virtue of modal superposition principle. Dominant vibration modes developed on the EMM are found with modal superposition principle and these modes are further characterized with the aid of a quantitative local resonance measurement method aiming at exploring vibration features on the EMM. Upon the revealing of wave attenuation mechanism, we show the low-frequency stopband for the EMM can be widened via altering vibration characteristics of dominant modes that are responsible for stopband closing. The proposed new analysis scheme as well as the EMM structure facilitate the development of structure designs for elastic wave attenuation.

A design of elastic metamaterials with multi-negative pass bands

In this paper, an elastic metamaterial is proposed by integrating a two-dimensionally periodic honeycomb lattice and tetrachiral metamaterial inclusions for low-frequency wave applications. Plane wave propagation in infinite periodic cells is investigated through using Floquet–Bloch principles and the finite element method. Two separate negative pass bands induced by different mechanisms appear in the band structures of wave propagation in the proposed elastic metamaterial. The working mechanisms of those two negative pass bands are revealed though analyzing the eigenmodes of the unit cell and the dynamic effective material properties. Numerical examples validate the proposed model and show that negative refraction of elastic waves in the elastic metamaterial has been obtained. The design concept of this type of elastic may be of use for the design of broadband flat lenses for elastic wave focusing.

Optimum design of elastic metamaterials based on a high-frequency homogenization method for the elastodynamic equation

Optimum design of elastic metamaterials based on a high-frequency homogenization method for the elastodynamic equation

Analytic model of elastic metamaterials with local resonances

A unified analytic model for effective mass density, effective bulk modulus, and effective shear modulus is presented for elastic metamaterials composed of coated spheres embedded in a host matrix. The effective material properties are derived directly from the averages of local momentum, stress, and strain defined in a single doubly coated sphere. It is shown that the effective material parameters predicted by the proposed model are in excellent agreements with the coherent-potential approximation results at low filling fractions where the anisotropy of periodic structures can be neglected for elastic waves. The advantage of the proposed method is that it can reveal clearly the physical mechanism for negative effective material parameters induced by the resonant effect. It is found that negative effective mass density is induced by negative total momentum of the composite for a positive momentum excitation. Negative effective bulk modulus appears for composites with an increasing (decreasing) total volume under a compressive (tensile) stress. Negative effective shear modulus describes composites with axisymmetric deformation under an opposite axisymmetric loading. Numerical examples are also given to illustrate these mechanisms. These findings may be useful in design of elastic metamaterials.