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Based on the combination of the high bearing capacity of a slender Euler beam before buckling and low stiffness in the postbuckling range near the critical condition after loading, a novel quasi-zero stiffness (NQZS) isolator with enhanced vibration isolation capability is proposed using slender beams as positive stiffness elements. The proposed NQZS isolator can obtain a much large range with ultralow system stiffness maintaining the bearing capacity. Its vibration isolation performance was robust to equilibrium position deviation, which is essential for engineering practice. The correctness of the theoretical analysis was confirmed by the agreement between the experimental and theoretical results. [ABSTRACT FROM AUTHOR]

An effective methodology is proposed to evaluate the boundary stiffnesses of beams with generally restrained edges. The boundary conditions at the ends of the beams are implemented by the penalty method. The unified Jacobi polynomials are introduced to represent the assumed mode shape functions of the beam. Hamilton’s principle with the assumed mode method is employed to derive the equation of motion of the beam with generally restrained boundaries. Subsequently, a novel approach is proposed to evaluate the boundary stiffnesses of the beam using the measured natural frequencies of the beam by vibration experiments. The accuracy of this method is verified by comparing the results with the previously published literature, the finite element method (FEM), and the vibration experiments. The effects of the types and values of the boundary spring stiffnesses on the vibration properties of the beam are also discussed. The calculation method in this research can provide an effective prediction technique for the boundary stiffnesses of engineering structures with generally restrained edges. [ABSTRACT FROM AUTHOR]

A periodic elastic metamaterial plate is designed by the locally resonant band-gap mechanism. Based on the Floquet–Bloch wave theory, the band-gap structures of the elastic metamaterial plate are calculated using the finite element method, and validated by the spectral element method and the vibration experiment. The band-gap characteristics are optimized by an effective asymptotic optimization method to determine the target band-gap ratio. This optimization method can be targeted at specific frequency band to realize the superior vibration reduction capacity by optimizing the structural parameters. This article provides a useful reference for optimizing the vibration band-gap characteristics of elastic metamaterial plates. [ABSTRACT FROM AUTHOR]

Inspired by the Stewart platform, the theoretical model of a double-layered Stewart platform with local oscillators is proposed and its performance is studied based on numerical simulations and experimental methods. To validate the performance of the proposed technique we perform a vibration experiment, where the vibration isolation performance is estimated based on the ADAMS software. From the experimental analysis, we study the influence of the model parameters on the vibration isolation performance and highlight the advantages of the proposed double-layered platform over the traditional single-layered ones. The experimental results demonstrate that the oscillators can effectively suppress the transmissibility near the resonant frequency, which benefits the vibration isolation performance of the system. A double-layered Stewart platform with local oscillators is designed and manufactured. The advantages of the proposed platform over the single-layered ones are highlighted. The oscillators can effectively suppress the transmissibility near the resonant frequency. The proposed platform has better low-frequency vibration isolation performance. [ABSTRACT FROM AUTHOR]

Hierarchical periodic elastic metamaterial beams which can enhance the band-gap properties are designed by effectively combining the Bragg-scattering and locally resonant mechanisms. The frequency responses of the hierarchical periodic elastic metamaterial beams are calculated using the spectral element method (SEM). The correctness and feasibility of the present numerical method are verified by the vibration experiment. It is found that the design of the hierarchical periodicity can obtain more and broader band-gaps because the Bragg-scattering and locally resonant band-gaps can be generated simultaneously. The present results can provide a useful aid for the vibration reduction design of the elastic metamaterial structures in multi-frequency ranges. [ABSTRACT FROM AUTHOR]