PSI - Issue 80

Haomiao Fang et al. / Procedia Structural Integrity 80 (2026) 53–64 H. Fang et al./ Structural Integrity Procedia 00 (2025) 000 – 000

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Figure 9: Damage localization of scenario 2 based on different baseline-free techniques: (a) TR, (b) reciprocity, (c) IB, (d) the proposed K-SVD dictionary learning framework.

Figure 10: Damage localization of scenario 3 based on different baseline-free techniques: (a) TR, (b) reciprocity, (c) IB, (d) the proposed K-SVD dictionary learning framework.

As shown, the experimental comparison of localization results among different baseline-free techniques are illustrated in Figure 8, Figure 9, and Figure 10. The white circle represents the actual damage location, while the black cross indicates the prediction. It is evident that the proposed K-SVD baseline-free framework achieves the highest localization accuracy, while also exhibiting fewer and slighter adjacent artifact regions. With regards to TR, the predicted damage region (red region) is severely masked by the adjacent artifact region (yellow region) and the region closed to the sensors, which diminishes the effectiveness of the technique. Additionally, a significant localization error is observed in scenario 1, as shown in Figure 8 (a). The error is potentially caused by boundary reflections and inaccurate window selections. Despite the slight deviation observed in Figure 10 (b), the reciprocity approach demonstrates strong predictive performance across most damage scenarios. Additionally, the refined IB exhibits a significantly higher overall localization accuracies, although they are still severely masked by various artifacts. 4.3. Robustness validation The effectiveness and robustness of the proposed K-SVD baseline-free methodology is validated based on the damage detection under varying temperatures. Figure 11 (c) demonstrates the geometry diagram of M21-T800S composite coupon panel with the dimension of 300 mm × 225 mm and the thickness of 2.208 mm. A barely visible impact damage (BVID) is performed by the Drop Tower at the location of (115 mm, 97.5 mm), with the impact energy of 20J. The C-scan result is obtained by DolphiCam. The temperature is controlled by the environmental test chamber within the range of 20°C to 50°C, with a 5°C increment [28].