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| Author(s): |
Danilo Beli
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Mecânica |
| Defense date: | 2018-07-30 |
| Examining board members: |
José Roberto de França Arruda;
Renato Pavanello;
Gustavo Silva Wiederhecker;
Carlos De Marqui Junior;
Domingos Alves Rade
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| Advisor: | José Roberto de França Arruda |
| Abstract | |
The mechanical wave propagation in phononic crystals and metamaterials has been extensively investigated for noise and vibration attenuation, and for wave manipulation (e.g., energy focalization, guiding, harvesting and cloaking). Based upon and inspired by these extraordinary potentialities, this thesis investigates the wave propagation and dynamic behavior of rotating periodic structures, metamaterials with interconnected resonators, and metastructures with spatially correlated variability. First, the spectral element (SE) and wave finite element (WFE) methods are applied to rotating periodic structures, where the gyroscopic effect breaks the time-reversal symmetry, and, hence, the wave propagation symmetry. The Coriolis acceleration makes the band structure asymmetric and cause the natural vibration modes to split. These features are used to propose a mechanical circulator for elastic waves. From the numerical point of view, a WFE strategy is proposed, where the eigenvalue problem of the rotating structure is projected on a reduced, symplectic and well-conditioned wave basis. This approach can also be used for parametric analyses, such as Campbell diagram computations, as well as for uncertainty analyses of periodic structures with low computational cost. A metamaterial with interconnected resonators is then proposed. In this configuration, the translational and rotational motion of the resonator chain are coupled, which leads to a wide band gap at low frequency, without increasing the resonator mass. This mechanism is validated with experimental measurements on samples printed out using additive manufacturing. For the two-dimensional configuration, which is a plate with interconnected resonators, the flexural vibration can be localized in specific directions by using partial band gaps. Finally, the physical effects of spatial variability of the elastic properties in the dynamic response of phononic and metamaterial beams are analyzed. A high correlation between the spatial material distributions and the band gap performance is observed in both numerical and experimental models. In addition, the disorder can promote the widening or annihilation of the attenuation bandwidth and the wave trapping phenomenon. The results and analyses presented in this thesis can be extended to other periodic systems and can be used: I) from the physical point of view for vibration attenuation (e.g., rotordynamics and light structures) and for wave manipulation (e.g., nonreciprocal waveguiding, energy focalization, and wave trapping); II) from the numerical point of view, to save computational time in parametric and uncertainty analysis of periodic systems; and III) from the experimental point of view, to investigate periodic structures constructed by 3D printing (AU) | |
| FAPESP's process: | 14/19054-6 - Design of periodic structures with application to phononic crystals and acoustic metamaterials |
| Grantee: | Danilo Beli |
| Support Opportunities: | Scholarships in Brazil - Doctorate |