Experimentally validated broadband self-collimation of elastic waves. (15th February 2021)

• Record Type: Journal Article
• Authors: Jo, Soo-Ho; Xia, Yiwei; Moura, Adriane G.; Yoon, Heonjun; Shin, Yong Chang; Erturk, Alper; Youn, Byeng D.
• Is Part Of: International journal of mechanical sciences. Volume 192(2021)
• Publication Date: 2021-02-15
• Subjects: Self-collimation -- Equi-frequency contour -- Phononic crystal -- Anisotropy -- Broadband; Mechanical engineering -- Periodicals; Génie mécanique -- Périodiques; Mechanical engineering; Maschinenbau; Mechanik; Zeitschrift; Periodicals; 621.05
• DOI: 10.1016/j.ijmecsci.2020.106131
• Languages: English
• ISSNs: 0020-7403

Abstract

Highlights: Material property requirement to enable rectangular-like and parallel-line-like equi-frequency contours (EFCs) is newly proposed. Adjoining the frequency ranges of two EFCs achieves the broadband self-collimation. Broadband self-collimation of an anisotropic phononic crystal is experimentally validated. Abstract: One extraordinary phenomenon exhibited by phononic crystals (PnCs) is that they can manipulate oblique incident waves in a target direction via proper refraction, commonly called wave self-collimation. Although prior studies have demonstrated self-collimation of electromagnetic and acoustic waves, only a few studies have examined elastic waves in this context. If a PnC is designed to represent rectangular-like and/or parallel-line-like equi-frequency contour (EFCs), elastic waves can be self-collimated in either horizontal or vertical directions. However, in the existing literature, there is no theoretical rationale for realizing rectangular-like and/or parallel-line-like EFCs; besides, broadband self-collimation of elastic waves has not yet been explored. Therefore, we propose to derive the material property requirement for an anisotropic PnC to exhibit rectangular-like EFCs (a range of low frequencies) and parallel-line-like EFCs (a range of high frequencies) in the case of elastic waves. Furthermore, by inherently adjoining two frequency ranges of the rectangular-like and parallel-line-like EFCs at a certain frequency, broadband self-collimation covering the entire range of frequencies can be achieved. With the designed anisotropic PnC that fulfills the proposed material property requirement, self-collimation for S0 Lamb waves is numerically simulated and experimentally demonstrated over a broad range of frequencies. Graphical abstract: Image, graphical abstract