The full wavefield detection method based on guided waves can efficiently detect and locate damages relying on the collection of large amounts of wavefield data. The acquisition process by scanning laser Doppler vibrometer (SLDV) is generally time-consuming, which is limited by Nyquist sampling theorem. To reduce the acquisition time, full wavefield data can be reconstructed from a small number of random sampling point signals combining with compressed sensing. However, the random sampling point signals need to be obtained by adding additional components to the SLDV system or offline processing. Because the random sparse sampling is difficult to achieve via the SLDV system, a new uniform sparse sampling strategy is proposed in this paper. By using the uniform sparse sampling coordinates instead of the random spatial sampling point coordinates, sparse sampling can be applied to SLDV without adding additional components or offline processing. The simulation and experimental results show that the proposed strategy can reduce the measurement locations required for accurate signal recovery to less than 90% of the Nyquist sampling grid, and the damage location error is within the minimum half wavelength. Compared with the conventional jittered sampling strategy, the proposed sampling strategy can directly reduce the sampling time of the SLDV system by more than 90% without adding additional components and achieve the same accuracy of guided wavefield reconstruction and damage location as the jittered sampling strategy. The research results can greatly improve the efficiency of damage detection technology based on wavefield analysis.

As a new kind of elastic materials, elastic wave metasurface has great research significance in the field of elastic wave regulation. However, most of the researches on elastic wave metasurface are guided by traditional Generalized Snell’s Law (GSL), and the effect of higher order diffraction waves caused by structural periodicity is not considered. Under the action of higher order diffraction wave, the incident wave will produce more complex transmission phenomenon when passing through the metasurface, and the angle of transmission does not conform to GSL in some cases. In order to verify whether the modified GSL theory considering the higher-order diffraction term is still applicable to the regulation of solid elastic waves, this paper designs a helical metasurface based on the elastic wave theory of plate-beam structure, which is composed of helical lines of different lengths, and uses this structure to explain the complex transmission phenomenon of elastic wave metasurface. Finally, the asymmetric transmission, modal separation and waveguide of Lamb waves in thin plates are realized by combining the theory with structural design, which proves that the structure has great application potential in ultrasonic detection and other fields.

This paper proposes a phase-reversal method (PRM) for damage imaging in plate structures. The PRM is a novel Lamb-wave-based method that mainly focuses on phase spectrum information of scattering waves reflected from a defect. The PRM reverses the phase angle along the propagation path by using the inverse Fourier transform first, and then the reversal reconstruction of the wave field in the frequency domain is performed for damage imaging. The proposed method analyzes the scattered wave field without using the baseline data and structural parameters. Moreover, dispersion characteristics and anisotropy are not involved in the process of damage positioning, thus making the PRM suitable for damage monitoring of composite laminates. To improve the PRM accuracy further, a combined addition and multiplication method of the correlation coefficient (CAMM) is proposed, which can reduce the effects of phase and noise artifacts and distortion. The results of the finite element simulations and experiments show that the combination of the PRM and CAMM methods can accurately locate damage in composite structures. Therefore, the PRM and CAMM methods have great application potential in damage imaging in composite laminates.

Lamb waves exhibit multimode and dispersive characteristics, which mask crucial damage information and deteriorate damage localization resolution in structural health monitoring. This article aims to enhance damage detection capability through multi-mode fusion imaging by developing an advanced signal processing approach. A computationally efficient Particle Swarm Optimization-enhanced Orthogonal Matching Pursuit (PSO-OMP) algorithm with physics-guided over-complete dictionaries is proposed to separate overlapping wave packets of A₀ and S₀ modes and compensate dispersion effects. Numerical simulations demonstrate that the proposed method achieves superior wave packet arrival time accuracy (errors < 2%) compared with conventional MP and OMP algorithms, while maintaining robust performance under various noise conditions. Experimental validation using a sparse array of piezoelectric wafers confirms successful mode separation and dispersion compensation. Comparative analysis reveals that the multi-mode fusion imaging significantly outperforms single-mode imaging, achieving 23.8% improvement in damage localization accuracy and effective artifact suppression. This work contributes to the field of structural health monitoring by establishing an effective multi-mode imaging framework, enabling more accurate and reliable damage assessment in plate-like structures.

Based on the Generalized Snell’s Law (GSL), combined with the elastic wave propagation theory in the thin plate and beam structure, a new type of elastic wave metasurface is constructed. The metasurface structure realizes the design of equal gradient of transmitted wave phase according to the difference of the length of different helical curved beams. Through this structure, the transmission wavefront of the Lamb wave in the thin plate is controlled, and acoustic phenomena such as negative refraction and asymmetric transmission are realized, which proves the accuracy of the GSL theory and the feasibility of the structure. And on this basis, the use of the design of symmetrical attachment to the metasurface solves the problem of destroying the plate structure in the traditional elastic wave metasurface, and provides an effective new idea for the elastic wave metasurface.