Abstract
A pulse laser combined LWT technique with a two-stage reconstruction algorithm was proposed to realize rapid damage location, or even the evaluation of damage size for plate-like structures. Since the amplitude of Lamb waves in propagation is highly sensitive to damage, including inside damage, the change of the attenuation coefficient of Lamb waves in the inspection region was used as a damage index to reconstruct damage images. In stage one, the rough area of the damage was identified by a comparison of the amplitude of the testing signal data and reference data (undamaged state). In stage two, the damage image was reconstructed using an inverse approach based on the least-square method. In order to verify the effectiveness of the proposed rapid approach, experiments on an aluminum plate with a non-penetrating notch and a carbon fiber-reinforced plastic laminated plate with internal delamination induced by a low-velocity impact were carried out. The results show that the notch can be detected with accurate location, and the delamination image can be reconstructed successfully.
Highlights
To prevent fatigue, corrosion and aging failure in engineering structures, it is essential to develop various rapid non-destructive testing (NDT) technologies to estimate structural safety and integrity.Since plate or shell structures are widely used in aerospace, energy and chemical engineering fields, and they commonly have a very large size, it calls for a kind of NDT technique especially developed for those structures
According to the data-collecting scheme shown in Figure 3a,b (m = 24, n = 24), the pulse laser irradiated along the specified paths (B2→A2 and A2→B1), an An emissionemission (AE) sensor was placed in the appropriate location to receive wave signals
The suspected damage area was identified by a comparison which requires reference data was put forward
Summary
Corrosion and aging failure in engineering structures, it is essential to develop various rapid non-destructive testing (NDT) technologies to estimate structural safety and integrity. Different from the conventional CT technique that is to reconstruct cross-section pictures of a structure, the LWT technique is to reconstruct in-plane surface images of the plate or shell structures by manipulating numerous different rays of Lamb waves passing through the plane of interest. Reconstructed the damage region in two polymer composite plates using a Lamb wave tomography technique. Ng et al [22] proposed a two-stage imaging approach based on the cross-correlation analysis and Lamb wave diffraction tomography for quantitative imaging of damages in metallic plates. They successfully reduced the transducer number of the circular transducer network to 8 based on the proposed approach. The iterative reconstruction algorithm-based techniques have the disadvantage of the convergence problem and low computational efficiency.
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