Wave propagation in a phononic material with periodic bilinear elastic layers

Abstract

This presentation discusses how bilinear elastic layers influence wave propagation in phononic materials. Bilinear elastic layers have been shown to produce wave propagation phenomenon such as shock waves, non-reciprocity,phase-reversal effects, and harmonic generation. Here, we examine how a propagating wave through a periodic array of linear elastic layers coupled with springs that exhibit bilinear stiffness can be tuned with the stress state of the excited wave. Using time-dependent finite element simulations, we study the interactions of bilinear springs and phononic materials, analyzing how the tensile or compressive stress state influences dispersion, band gaps, and energy transfer between frequencies. We select excitation waveforms to exploit the bilinear stiffness to fundamentally change the shape of the propagating wave. Results demonstrate phase-reversal effects, attenuation of tensile strain, and cumulative displacement offsets. To experimentally probe these results, bilinear stiffness couplings are physically realized by fabricating samples with prescribed delaminations between stiff and soft materials so the samples exhibit higher stiffness in compression than tension. Single layered samples are experimentally studied using both propagating waves and resonant methods. The nonlinear response from delaminations may be used to control frequency energy transfer and wave transformation for applications such as blast mitigation and passive mechanical sensing.