Electro-mechanical vibration control of functionally graded marine risers by a piezoelectric meta-structure design

In this paper, a novel electro-mechanical meta-riser structure is designed aiming to suppress its vibration and wave propagation. The riser is made of porous functionally graded material (FGM), and is periodically attached with piezoelectric layers, each of which is connected with a multi-mode resonant shunt circuit to trigger multiple locally resonant (LR) band gaps (BGs). The periodically varying rigidity due to piezoelectric layers can also generate Bragg scattering (BS) BGs, resulting in a hybrid meta-structure. A point defect is introduced into the system by removing a certain piezoelectric layer. Theoretical analysis and finite element (FE) simulation both demonstrate the superior vibration control effect of the present meta-structure. Owing to the presence of defect, the riser presents a remarkable vibration response within the original BS BGs, reflecting the vibration energy localization and enabling energy harvesting by meta-structure designs. Different circuit designs and parameters can be used to regulate LR BGs, while the particular material composition of the riser will contribute to enhancing the BS BG performance. This study can provide a technical scheme for the vibration and elastic wave control of marine riser structures, and lay a theoretical foundation for the vibration energy harvesting by utilizing dynamical meta-structures.