The optical and acoustic metagratings have addressed the limitations of
low-efficiency wave manipulation and high-complexity fabrication of
metamaterials and metasurfaces. In this research, we introduce the concept of
elastic metagrating and present the theoretical and experimental demonstration
of locally resonant elastic metagrating (LREM). Remarkably, the LREM, with
dimensions two orders of magnitude smaller than the relevant wavelength,
overcomes the size limitations of conventional metagratings and offers a unique
design paradigm for highly efficient wave manipulation with an extremely
compact structure in elastic wave systems. Based on a distinctive elastic
impedance engineering with hybridization of intrinsic evanescent waves, the
proposed LREM achieves wide-angle perfect absorption. This tackles a
fundamental challenge faced by all elastic metastructures designed for wave
manipulation, which consists in the unavoidable vibration modes in finite
structures hindering their implementations in real-world applications