a b s t r a c tThree-dimensional (3D) phononic band gap structures are formed using identical inertial amplification mechanisms. The resonance and antiresonance frequencies that characterize the first vibration stop band of the building block mechanism are obtained analytically and by finite element method. The mechanism is optimized to yield wide vibration stop bands in two different 3D structures, namely, an octahedron and a 2 Â 3 array of octahedrons. Furthermore, these structures are manufactured using a 3D polymer printer and their experimental frequency responses are obtained. Structural damping is added to the finite element model in order to match the resonant peak magnitudes of the numerical and experimental frequency response results. It is demonstrated that the 3D structures are capable of isolating excitations in longitudinal and two transverse directions in a very wide frequency range.

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In this work, we study the thermo-mechanical behavior of metallic structures designed to significantly change shape in response to thermal stimuli. This behavior is achieved by arranging two metals with different coefficient of thermal expansion (CTE), Aluminum and Titanium, as to create displacement-amplifying units that can expand uniaxially. In particular, our design comprises a low-CTE bar surrounded by a high-CTE frame that features flexure hinges and thicker links. When the temperature increases, the longitudinal expansion of the high-CTE portion is geometrically constrained by the low-CTE bar, resulting in a large tangential displacement. Our design is guided by theoretical models and numerical simulations. We validate our approach by fabricating and characterizing individual units, one dimensional arrays and three-dimensional structures. Our work shows that structurally robust metallic structures can be designed for large shape changes. The results also demonstrate how harsh environmental conditions (e.g., the extreme temperature swings that are characteristic of extraterrestrial environments) can be leveraged to produce function in a fully passive way.

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This paper investigates effects of inertial amplification mechanisms on the phononic band structure of infinitely periodic simple cubic (SC) and body centered cubic (BCC) lattices. First, these three-dimensional lattices are formed using mass and spring elements. Then, dispersion curves of these lattices are obtained. Consequently, inertial amplification mechanisms are embedded around each spring in these lattices and their dispersion curves are calculated again. When compared to the cases in which inertial amplification was not used, phononic band gaps are obtained at much lower frequencies.