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| Periodic elastic structures, also known as phononic crystals (PCs), have shown many exceptional elastic-wave characteristics. In particular, complete phononic band gap (PBG) in the structure that forbids the propagation of acoustic waves in certain frequency range has demonstrated the possibility of manipulating the acoustic energy flows in diverse ways. The complete PBGs have been found for various forms of elastic waves in distinct PC structures, such as bulk waves in bulk PCs, surface waves in semi-infinite PCs, and Lamb waves in PC plates. In this paper, the band structures in a homogeneous plate with periodic truncated cones for the square lattice based on finite element method (FEM) are investigated. The radius of the truncated cone is gradually reduced from the lower base to the upper base. Compared to the classical stubbed phononic plates, a considerable enlargement of the bandwidth by a factor of 2.04 is obtained by varying the semiangle of the truncated cone, while the truncated cone's weight is only 65.19% of that of the cylinder of the stubbed case. Moreover the relative bandwidth is also enlarged by a factor of 1.68. We show that this band gap enlargement is due to the acoustic waves of different wavelengths is localized at the different parts of the truncated cone. These characteristics of elastic or acoustic waves suggest potential applications in aerospace. |
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| Keywords:phononic crystal; periodic truncated cone; Local Resonance Broadband Gap |
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