In the present study, a modular mass oscillator elastic metasurface (MMEM) is proposed to manipulate the wavefield of flexural waves by assembling and replacing mass-oscillator-like functional units. Based on the bandgap analysis of phononic crystals, the MMEMs were found to achieve a full 2 π range of phase shift with relatively high transmission using functional unit arrangements of varying sizes (masses). According to the generalized Snell’s law, the modulation of abnormal refraction, lens focusing, and beam self-acceleration can be realized. To broaden the operating frequency domain, we present the idea of a multiple mass oscillator array design, which can control flexural waves at broadband frequencies of 13–41 kHz by adding/removing mass oscillators within a functional unit. This study presents a method to realize tunable metasurfaces and provides an innovative concept for broadening the operating frequency of elastic metasurfaces.

Uncertainty propagation, one of the structural engineering problems, is receiving increasing attention owing to the fact that most significant loads are random in nature and structural parameters are typically subject to variation. In the study, the collocation interval analysis method based on the first class Chebyshev polynomial approximation is presented to investigate the least favorable responses and the most favorable responses of interval-parameter structures under random excitations. Compared with the interval analysis method based on the first order Taylor expansion, in which only information including the function value and derivative at midpoint is used, the collocation interval analysis method is a non-gradient algorithm using several collocation points which improve the precision of results owing to better approximation of a response function. The pseudo excitation method is introduced to the solving procedure to transform the random problem into a deterministic problem. To validate the procedure, we present numerical results concerning a building under seismic ground motion and aerofoil under continuous atmosphere turbulence to show the effectiveness of the collocation interval analysis method. uncertainty propagation, interval analysis, Taylor series expansion, Chebyshev polynomial, Pseudo excitation method PACS number(s): 02.30.Mv, 02.50Ey, 02.60Gf, 02.70.Jn Citation:Qi W C, Qiu Z P. A collocation interval analysis method for interval structural parameters and stochastic excitation.

Considering the manufacturing difficulty and tunability, a one-dimensional phononic crystal-type metastructure is proposed in this paper. By adjusting the distance between the mass oscillators installed on the connecting bar, that is, changing the length of the phononic crystal unit, the phase shift of the flexural wave can span over a full range of 0–2π and then the phenomena such as abnormal refraction, beam focusing, and self-acceleration can be realized based on the generalized Snell’s law. In addition, the method of multiple mass oscillator array design is used to broaden the operating frequency domain by increasing or decreasing the number of mass oscillators. This proposed method provides an innovative concept for realizing broadband tunable metastructures and has potential applications in the fields of vibration control, energy harvesting, and noise isolation.

No abstract

Inspired by the studies on defects in nondestructive monitoring techniques, we propose a new type of metasurface with single-groove array to manipulate Lamb waves in plate structures along arbitrary trajectories. Because of the interaction between the groove and the Lamb waves, the phase of a transmitted wave varies with the groove position. We manipulated a transmitted wave by optimizing the groove position on the metasurface and realized abnormal refraction, self-accelerating acoustic beams, and source illusion devices. The numerical results confirmed the broadband and robustness of the metasurface in terms of its wave manipulation capability, providing a basis for the design of wave control devices. The proposed method has potential applications in the fields of structural nondestructive testing, vibration control, and signal modulation.