Abstract
Vibration and noise control are among the classical engineering problems that still draw extensive research interest today. Multiple active and passive control techniques to resolve these problems have been reported, however, the challenges remain substantial. The recent surge of research activities on acoustic metamaterials for vibration and noise control are testimony to the fact that acoustic metamaterial is no longer limited to pure theoretical concepts. For vibration and noise control over an ultrawide frequency region, 3-D metastructures emerge as a novel solution tool to resolve this problem. In that context, the present study reports a novel proposal for 3-D monolithic phononic metastructures with the capability to induce low frequency ultrawide three-dimensional bandgaps with relative bandwidth enhancements of 157.6% and 160.1%. The proposed monolithic metastructure designs consist of elastic frame assembly that is connected with the rigid cylindrical masses. Such structural configuration mimics monoatomic mass-spring chain where an elastic spring is connected with a rigid mass. We develop an analytical model based on monoatomic mass-spring chain to determine the acoustic mode frequency responsible for opening the bandgap. The wave dispersion study reveals the presence of ultrawide bandgaps for both types of metastructures. The modal analysis shows distribution of vibration energy in the bandgap opening (global resonant mode) and closing (local resonant mode) bounding edges. We further analyze the band structures and discuss the physical concepts that govern such ultrawide bandgap. Vibration attenuation inside the bandgap frequency range is demonstrated by frequency response studies conducted by two different finite element models. Thanks to additive manufacturing technology, 3-D prototypes are prepared and low amplitude vibration test is performed to validate the numerical findings. Experimental results show the presence of an ultrawide vibration attenuation zone that spreads over a broadband frequency spectrum. The bandgaps reported by the proposed metastructures are scale and material independent. The research methodology, modelling and design strategy presented here may pave the way for the development of novel meta-devices to control vibration and noises over a broadband frequency range.
Highlights
metamaterials[15] with trampoline e ffect[23] have caught extensive attentions
We found that the ultrawide BGs are induced by the principle of mode separation or modal masses participation[31] where the global and local resonant modes and their localized vibrational energy in the unit cell structure is found responsible for opening and closing of the BG
The boundary of irreducible Brillouin zone is shown at the inset of band structure
Summary
metamaterials[15] with trampoline e ffect[23] have caught extensive attentions. Apart from these genetic algorithm and topology optimization approaches have been reported to optimize the physical structure and dynamical characteristics of metamaterials[17,24,25]. 3-D periodic structures consisting of multi-core materials are proposed to maximize the impedance mismatch in order to achieve wider BGs17,30 In such approaches, multi-material based prototyping and/ or adjusting the assembly phase of selective materials pose a significant challenge. The manufacturing of such smart devices is another problem that needs advanced technology In this regard, the present work proposes two phononic metastructure prototypes that consist of a single core structures (monolithic designs) and it is capable of inducing extremely wide low frequency three-dimensional BG. In both prototypes, the unit cell topology is realized by an external frame assembly connected with cylindrical masses at the middle points. One can observe an excellent agreement between the analytical and numerical models
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
