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Understanding and analysing the complex phenomena related to elastic wave propagation has been the subject of intense research for many years and has enabled application in numerous fields of technology, including structural health monitoring (SHM).

We study the propagation of in-plane elastic waves in a soft thin strip, a specific geometrical and mechanical hybrid framework which we expect to exhibit a Dirac-like cone. We separate the low frequencies guided modes (typically 100 Hz for a 1-cm-wide strip) and obtain experimentally the full dispersion diagram. Dirac cones are evidenced together with other remarkable wave phenomena such as negative wave velocity or pseudo-zero group velocity (ZGV). Our measurements are convincingly supported by a model (and numerical simulation) for both Neumann and Dirichlet boundary conditions. Finally, we perform one-way chiral selection by carefully setting the source position and polarization. Therefore, we show that soft materials support atypical wave-based phenomena, which is all of the more interesting as they make most of the biological tissues.

A timely evaluation of the noise that surrounds us, how we hear it, and what we can do about it, Marcia Jenneth Epstein gives us the impetus and the tools to understand the sounds and noise that define our daily lives. This is a groundbreaking interdisciplinary study of how auditory stimuli impact both individuals and communities.

Elastic waves involving mechanical particle motions of solid media can couple volumetric and shear deformations, making their manipulation more difficult than electromagnetic waves. Thereby, circularly polarized waves in the elastic regime have been little explored, unlike their counterparts in the electromagnetic regime, where their practical usage has been evidenced in various applications. Here, we explore generating perfect circular polarization of elastic waves in an isotropic solid medium. We devise a novel strategy for converting a linearly polarized wave into a circularly polarized wave by employing an anisotropic medium, which induces a so-far-unexplored coupled resonance phenomenon; it describes the simultaneous occurrence of the Fabry-Pérot resonance in one diagonal plane and the quarter-wave resonance in another diagonal plane orthogonal to the former with an exact 90° out-of-phase relation. We establish a theory explaining the involved physics and validate it numerically and experimentally. As a potential application of elastic circular polarization, we present simulation results demonstrating that a circularly polarized elastic wave can detect an arbitrarily oriented crack undetectable by a linearly polarized elastic wave. The authors introduce a method for non-destructive testing based on circularly polarized ultrasound in solids, enabled by metamaterials, allows for detecting internal defects regardless of their orientation. This innovation will redefine ultrasonic non-destructive examination.

Elastic waves and their associated devices offer versatile platforms for sensing, metrology, and information processing. The rise of topological materials has enabled unprecedented control of elastic waves in solids, giving rise to elastic wave topological insulators (EWTIs) that host defect‐immune, high‐fault‐tolerance edge states. However, most existing studies remain confined to monolayer configurations, which limit elastic wave propagation and device performance to 2D planes. In contrast, the more promising and practical regime of multilayer elastic wave devices has received little attention. In this work, we experimentally demonstrate a class of bilayer elastic wave topological insulators (BLEWTIs) with high‐fault‐tolerance. By introducing the layer degree of freedom, BLEWTIs exhibit four distinct topological phases, in contrast to the two found in monolayer EWTIs. This enables the construction of multiple types of domain walls with diverse transmission behaviors, such as layer beam splitting. Consequently, we realize high‐fault‐tolerance interlayer converters and beam splitters operating along the normal direction of the 2D plane—features impossible to achieve in monolayer systems. Our findings pave the way for advanced elastic wave applications, including layer‐selective emitters and splitters and multi‐path topological routing, marking a significant step toward the development of compact, high‐performance electromechanical and optomechanical devices. Bilayer elastic wave topological insulators are experimentally realized, introducing the layer degree of freedom to access four topological phases. This enables diverse domain walls and transmission behaviors, including interlayer conversion and beam splitting. The approach achieves high‐fault‐tolerance converters and splitters along the normal direction, opening avenues for layer‐selective emitters, multi‐path topological routing, and compact, high‐performance elastic wave devices.

A new model for electro-elastic Bernoulli–Euler beams of centrosymmetric cubic materials is proposed, which incorporates microstructure and flexoelectric effects. The wave equations and boundary conditions are derived simultaneously through a variational approach based on Hamilton’s principle. The new beam model is then applied to predict elastic wave band gaps in a periodic electro-elastic composite beam structure. Bloch’s theorem and the transfer matrix method for periodic structures are used to solve the wave equations and determine band gaps. The current model reduces to its flexoelectric and classical elastic counterparts as special cases. To illustrate the new model, the effects of microstructure, flexoelectricity, beam thickness, unit cell length and volume fraction on band gaps are investigated through a parametric study. The numerical results show that the microstructure and flexoelectric effects lead to increased band gap frequencies, and these two effects are important when the beam thickness is at the submicron and micron scales. In addition, it is found that the unit cell length and volume fraction can significantly affect the band gap size at all length scales. These findings indicate that band gap frequencies and size can be tailored by adjusting the microstructural and material parameters.

Due to the special ability of wave manipulation, elastic wave metamaterials have many interesting applications in mechanical engineering, vibration and sound isolation. This work proposes a movable metamaterial driven by nonlinear elastic waves with stop band and nonreciprocal crawling. Inspired by stop band properties, the metamaterial employs a periodic structure of nonlinear diatomic chain. A defect mass is introduced near the wave source to break the periodicity and symmetry, which leads to the nonreciprocal propagation of nonlinear elastic waves. With the asymmetric friction, the nonreciprocal and one-directional crawling of the metamaterial can be observed, which behaves as a movable mechanical diode. Furthermore, theoretical analysis is performed to derive the band structure and crawling velocity, which are supported by experiments. This research wishes to introduce nonlinear elastic wave metamaterials into new designs of robotics.

A wind-wave generation model over an ice-covered sea is proposed. The wind velocity over the ice upper surface is decomposed into the mean velocity profile of the boundary-layer flow and small perturbations, while the ice cover is modelled as a viscoelastic layer, with the water part modelled as an inviscid fluid. The present model is based on two-dimensional linear flow-instability theory, with no-slip boundary conditions at the air–ice interface, and both normal and shear stress boundary conditions matched on the air–ice interface. It is shown that the model converges to the field and experimental data for open-water cases. The ice elasticity is found to be the critical factor for generating wind waves, and the generation of flexural-gravity waves and elastic waves in ice is analyzed.

The author introduces the technical principles of elastic wave CT method and seismic imaging method, taking the detection results of a dangerous road in southern Shaanxi as a research example. The application effect of comprehensive geophysical methods in solving engineering exploration problems was analyzed and studied, and the two methods were mutually verified, improving the accuracy of interpretation. The results show that the elastic wave CT method and seismic imaging have high recognition and resolution ability in the detection of dangerous roads in goaf collapse areas, and are effective technical methods to solve such geophysical exploration problems.

For effective maintenance and failure prevention of mine tailing in geo-resource field, it is essential to assess porosity in both partially and fully-saturated tailing dams. This study aims to evaluate sand-hematite mixtures’ porosity, considering various hematite content (HC) and saturation levels, using electrical resistivity and elastic wave velocity as geophysical methods. Hematite powder is mixed with sand particles in a weight ratio of 0 to 30%. The experimental setup includes a specially designed cell equipped with a bender element (BE), piezo disk element (PDE), electrical resistivity probe (ERP), and time domain reflectometry (TDR) probe at the top and bottom. Additionally, a porous stone disk connected to a silicon tube regulates the water level in the cell. Test results reveal significant variations in dielectric constant and electrical resistivity within the water level range of 0.250 m to 0.200 m. Elastic waves show changes at the water level of 0.200 m due to hematite and capillary effects. For porosity evaluation, the electrical resistivity-based method proves more reliable than the elastic wave-based method, considering error norms influenced by various factors. This integrated experimental framework provides an effective tool for assessing porosity in tailing materials, contributing to enhanced geotechnical monitoring and sustainable resource management.