A periodic array of resistive inductive (RL) shunted piezoelectric (PZT) patches is applied to achieve tunable low-frequency locally resonant (LR) band gaps in a flexible isotropic beam. Each pair of surface-bonded PZT patches is linked to an independent RL circuit. All the circuits are the same and are tuned synchronously. A transfer matrix methodology is used to calculate the frequency range and attenuation properties of the LR band gap. Two main differences are found between the LR band gaps induced by shunting circuits and traditional oscillators. Antoniou's circuits are used to produce large ideal inductances necessary for low eigenfrequencies. The theoretical results are experimentally validated by measuring the harmonic response of the beam. Significant attenuation in the low-frequency LR band gap is observed.
The effect of periodic arrays of feedback shunted piezoelectric patches in the flexural wave attenuation of phononic beams is analyzed theoretically and experimentally. A numerical model based on transfer matrix methodology is developed to predict the transmission of vibration and the frequency ranges of the band gaps. Broadband vibration attenuations are observed in or out of the band gaps. The proposed concept is validated on a suspended epoxy beam driven by a shaker, and the experimental results are presented in terms of the vibration transmissions recorded using two accelerometers placed on both sides of the beam.
On the basis of the relationship of material damping and stress amplitude proposed by Lazan, the formulae of energy dissipation in per unit volume of concrete filled steel tube and reinforced concrete subjected to normal stress are presented. In the process of finite element analysis, the proposed formulae are applied by an iterative algorithm to calculate the material damping of the frame structures made of different materials, i.e. concrete filled steel tube column steel beam frame, reinforced concrete column steel beam frame and steel frame, respectively. In addition, a comparison of the material damping values of the three different frames is conducted, showing that even in the elastic state, the material damping values of the three different structures are not always constant and they increase in a nonlinear way with the increase of the stress amplitude; the performance of the energy dissipation of the concrete filled steel tube and reinforced concrete are better than that of steel, and the performan...
With each unit cell replaced by a system of finite freedoms of motion, two_dimensional phononic crystals can be simplified to an infinite discrete periodic system. Therefore, the elastic wave band structures of the two_dimensional phononic crystals can be calculated with a straightforward lumped_mass approach, whose computational cost is much lower than the well_known plane wave expansion(PWE) method. The numerical results of the two methods are in reasonable agreements. As the well_known Gibbs oscillations in the PWE can be eliminated with the lumped_mass method, this new approach is insensitive to the sharp variation of elastic constants on the interfaces inside the phononic crystals. Furthermore, the lumped_mass method can also be used to calculate the band structures of two_dimensional phononic crystals with arbitrary unit shapes easily.
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