Topological design of hexagonal lattice phononic crystals for vibration attenuation combined fast plane wave expansion method with elite seed strategy genetic algorithm

The characteristics of manipulating elastic wave propagation in phononic crystals (PnCs) have been applied in various fields. A triangular element discrete method for two-dimensional (2D) hexagonal lattice PnCs is proposed, which combines with the fast plane wave expansion method (FPWEM) to obtain the band structure. As compared to the finite element method (FEM), time consumption is one order of magnitude faster while ensuring accuracy. To design the wider band gap (BG) of PnCs, the elite seed strategy genetic algorithm (ESS-GA) is used to optimize the topology of PnCs for in-plane mode and out-of-plane mode, and based on this, the proposed method is first applied to optimize hexagonal lattice PnCs, which is extended to the BG design of mixed mode. The relationship between the optimized individual under different propagate modes, and the volume fraction of PnCs at each BG is explained, physical mechanism of optimized unit cells is also estimated through iso-frequency contours and dynamic effective mass. The numerical and experimental results of a hexagonal lattice composed of optimized unit cells indicate that elastic waves can be suppressed within the BG, fully demonstrating the effectiveness of the method. In addition, this method is expected to explore its potential applications in the reverse design of PnCs.