A shape memory alloy-based tunable phononic crystal beam attached with concentrated masses

Shape memory alloys (SMAs) in phononic crystals (PCs) or metamaterials mostly serve as smart inserts or local resonators to generate tunable bandgaps for other structures. In this letter, we address the method for creating tunable bandgaps in structures made of SMA. Specifically, we consider concentrated masses, realized by steel balls, as attachments on a SMA. To provide a design guideline, we derived the closed - form bandgap formula of the proposed SMA PC beam. As the bandgap order increases, the coefficient of the nth Bragg bandgap width decreases. In addition, the practical final beam enlarges bandgap edges than ideally infinite PCs or metamaterials. Our experimental results on the PC beam with different sizes of the steel ball arrays agree with the analytical predictions of the bandgap behaviors. With the bandgaps formed by the steel balls and the shape memory effect, wide tunability of the bandgaps are achieved on the SMA beam. (C) 2019 Elsevier B.V. All rights reserved.