A combined sonic crystal rod of Bragg type with ability of vibration reduction in broad frequency band

Abstract

One dimensional sonic crystal (SC) rod has apparent band gaps in which longitudinal wave and bending wave can be suppressed distinctly. However, each single SC rod�s band gap width is comparatively narrow and the low frequency vibration cannot be reduced generally. For this reason, a combined SC rod is proposed. The combined SC rod consists of three SC rods, each of which has the same periodical structure of typical Bragg type. The transfer matrix of the combined SC rod is deduced and the theoretical results are acquired by means of numerical calculation. Finite element analysis and experiments are carried out. Our results show that: in the combined SC rod, the bending wave can be transformed into the longitudinal wave and therefore the vibration reduction effect can be found in two kinds of band gaps. At the same time the ability of vibration suppression in low frequency range, which is similar to the effect of vibration isolation of traditional �spring-oscillator� system, also can be realized. Additionally, the material arrangement has obvious influence on the performance of the single and combined SC rods. The vibration reduction when the external excitation is loaded on the softer end is obviously stronger than when loaded on another end. The structure and the analysis results of the combined SC rod can be beneficial to the engineering application of SC structures