Plates with periodic cavities show excellent vibration attenuation characteristics. This behavior can be attributed to the presence of frequency bandgaps on account of interference between the incident wave and the reflected wave from the cavities. The present work investigates the vibration attenuation/bandgap characteristics of plates with varying shapes of periodic cavities, such as square, circular, vertical rectangle, and horizontal rectangle, through experiments and simulation. Vibration responses of different periodic plates have been studied by carrying out frequency sweep on a vibration shaker. The investigation has been restricted to flexural vibrations of the plates, which are the predominant mode of vibration in many practical vibration scenarios. The frequency bandgaps, observed through the experiment, have been compared with the numerical simulation by harmonic analysis and by carrying out dispersion analysis on a unit cell of the periodic structure using Floquet–Bloch theory. Dispersion curves of the periodic plates yielded bandgaps, which were observed to be in agreement with the bandgaps from the experiment. The effect of variation in the aspect ratio of the cavities, that is length-to-width ratio, on the bandgaps has also been examined. It has been demonstrated that by suitable selection of the shape/size of the periodic cavity, desired vibration attenuation bandgaps can be realized for a 2-dimensional structure.

Periodic structures have been studied extensively for their wave-filtering capabilities as they exhibit frequency band-gaps. The band-gap characteristics of flexural periodic structures, consisting of periodic cavities, depend on the geometry (shape and size) of cavities. The present work brings out experimental and numerical investigation of the effect of geometry of periodicity on the vibration characteristics of one-dimensional periodic structures. A procedure for prediction of the experimentally observed frequency band-gaps, with the help of eigenfrequency analysis, has been presented. Further, a novel concept of ‘real’ and ‘pseudo’ band-gaps has been theorized. Based on the experimental and numerical results, the best configuration of a periodic structure for maximum vibration attenuation has been arrived at. The work can find application in the design of frames and channels, made of periodic structures, where periodicity can be introduced to reduce vibration transmission in desired frequency bands. It can also reduce the requirement of extensive prototype trials for the selection of suitable periodic geometry.

Vibration attenuation is an important factor while designing rotating machinery since frequency lying in the range corresponding to natural modes of structures can result in resonance and ultimately failure. Damping dissipates energy in the system, which reduces the vibration level. The mitigation of vibrations can be achieved by designing the base frame with periodic air holes. The periodicity in air holes result in vibration attenuation by providing a stop band. A finite element-based approach is developed to predict the modal and frequency response. The analysis is carried out with different shapes of periodic cavities in order to study the effectiveness of periodic stop bands in attenuating vibrations. The amount of mass removed due to the periodic cavities is kept constant. It is seen that better attenuation is obtained in case of periodic cavities compared to a uniform base frame. Among the different geometries tested, rectangular cavities showed better results than circular and square cavities. As a result, it is seen that waves propagate along periodic cells only within specific frequency bands called the “Pass bands”, while these waves are completely blocked within other frequency bands called the “Stopbands”. The air cavities filter structural vibrations in certain frequency bands resulting in effective attenuation.

Vibration attenuation in acoustic-metamaterial plates assembled from a periodic arrangement of unit cells with a cavity containing local resonator system is presented. Each cell incorporates a base aluminum plate with vertical rectangle-shaped cavities containing a viscoelastic membrane supporting a mass forming a local resonator system. These acoustic-metamaterial structures exhibit stop-band behavior due to Bragg scattering and local resonance. Floquet–Bloch approach and eigenvalue analysis is used to identify the stop bands for metamaterial unit cells. The dispersion analysis predictions are validated experimentally by studying the vibration responses of different acoustic-metamaterial plates excited by an electrodynamic shaker over a frequency range of 8−4000 Hz. The attenuation regions observed in the finite element simulation results have been compared to that of the experiments. The obtained results show the potential of FE simulation to predict the metamaterial plate attenuation with reasonably good accuracy. The viscoelastic material properties also affect the attenuation region, as observed while comparing experimental results for different viscoelastic materials. These results show the effectiveness of acoustic-metamaterial plates to provide broadband vibration attenuation.