| description abstract | Abstract. Tunable elastic metamaterials based on dynamic vibration absorber (DVA) concepts typically achieve frequency adjustment by varying a single resonator parameter, resulting in limited tuning range or bandwidth expansion. In contrast, this study introduces a fundamentally different reconfigurable mechanism based on threaded coupled dual-beam resonators with a shared tip mass mounted on a homogeneous host beam, enabling a dual-parameter coupled tuning strategy. Unlike conventional approaches that modify either stiffness or mass independently, the proposed design simultaneously and continuously modulates the effective bending stiffness and mass distribution of the resonator through coordinated adjustment of beam length and moment of inertia. This coupled mechanism produces a substantially amplified shift of the local resonant (LR) band gap while preserving structural compactness and passive operation. Furthermore, gradient LR metamaterials are systematically constructed by spatially programming the dual-tunable parameters along the beam, enabling broadband vibration attenuation that surpasses the bandwidth limitations of uniform configurations. The band gap behavior of infinite periodic systems and the transmission characteristics of finite structures are rigorously analyzed using spectral element and finite element methods, followed by experimental validation. The results demonstrate a maximum 5.7-fold shift in band gap center frequency and up to 191% higher relative bandwidth compared to corresponding uniform configurations, achieving approximately 500-Hz coverage within the sub-kilohertz regime. The proposed mechanism establishes a new paradigm for tunable LR metamaterials by enabling wide-range, continuous, and passive band gap reconfiguration without altering the host structure, offering significant potential for adaptive vibration control and wave manipulation in engineering systems. | |
