Abstract
Metamaterials are materials having artificially tailored internal structure and unusual physical and mechanical properties. Due to their unique characteristics, metamaterials possess great potential in engineering applications. This study proposes a tunable metamaterial for the applications in acoustic isolation. Therefore, a stopband in the dispersion curve can be created because of the energy gap. For the conventional metamaterial, the stopband is fixed. Although the metamaterial with tunable characteristics has been proposed in the literature to extend its working stopband, the efficacy is usually compromised. In this study, cantilevers of tunable shape memory materials (SMM) via controlled phase transformation are incorporated into the metamaterial plate. Its theoretical finite element formulation for determining the dynamic characteristics is established. The effect of the configuration of the SMM cantilever absorbers on the metamaterial plate for the desired stopband in wave propagation is simulated by using finite element model and a commercial multi-physics software. The result demonstrates the tunable capability on the stopband of the metamaterial plate under different activation controls of the SMM absorbers, and shows the ability to trap the vibration at the designed frequency and prevent vibration wave from propagating downstream in different absorber arrangements and alloy phases. It should be beneficial to precision machinery and defense industries which have desperate need in vibration and noise isolation.
Highlights
The sub-wavelength characteristic structure to provide the resonance with the incident wave-like excitation can offer unique dynamic properties which are impossible to be obtained from natural materials, such as negative mass density, negative material modulus, negative refractory index and negative Poisson’s ratio, etc
The sound transmission loss through a proposed tunable acoustic metamaterial plate design incorporating extrinsically added shape memory alloy (SMA) resonance units has been investigated by using finite element simulation
The finite element analysis for an air duct divided by the metamaterial plate was carried out to calculate the sound transmission loss through the plate
Summary
The better control in vibration and noise gains more and more attentions both environmentally and industrially. According to the mass law in acoustics, to increase the sound transmission loss for achieving better noise isolation, the use of thicker insulation is unavoidable [1]. The sub-wavelength characteristic structure to provide the resonance with the incident wave-like excitation can offer unique dynamic properties which are impossible to be obtained from natural materials, such as negative mass density, negative material modulus, negative refractory index and negative Poisson’s ratio, etc. These unique properties can reflect on the material’s superior performances on electromagnetic shielding, acoustic isolation
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