Application of Damage Detection of Metal Structure Lamb Wave Modal Superposition Imaging Based on Scanning Laser Vibration Measurement

Metal structural plates are extensively used in various engineering structures due to their high strength, high-temperature resistance, toughness, and plasticity. However, they are susceptible to damage from external loads and impacts over time. The current Lamb wave detection methods suffer from dispersion and multimodal effects, leading to ineffective identification of damage information. In this paper, we investigate Lamb wave propagation in steel structure plates with flat-bottomed holes using a sinusoidal modulation five-peak wave signal. Finite element numerical models are developed, and an experimental platform is constructed using steel and aluminum boards. Experimental data is collected using a Scanning Laser Doppler Vibrometer (SLDV, PSV-500, Polytec Inc., Baden-Württemberg, German). The results demonstrate that, under the same frequency, the damage reflection energy for different modes is distinct. By fusing the data from the two modes, more accurate damage imaging results are obtained in the frequency-wavenumber (f-k) domain compared to single-mode imaging. Furthermore, experiments are conducted to locate damage in a steel board with a through hole and an aluminum plate with double flat-bottomed holes, confirming the feasibility of the proposed algorithm in isotropic plates.