PSI - Issue 77

Andrzej Katunin et al. / Procedia Structural Integrity 77 (2026) 18–25 Author name / Structural Integrity Procedia 00 (2026) 000–000

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To estimate the accuracy of quantification, the hit/miss metric, introduced by Amerei et al. (2025), was applied. This metric allows determination of the amount of area of identified damage that coincides with a true damage location, ℎ , and the amount of area that is not coinciding with the true damage location, , based on the following relations: ℎ = ∩ ∙ 100% , (5) = ( ∪ )\ ∙ 100% , (6) where and denote identified area of damage (represented by red line in Fig. 5) and true area of damage (represented by black line in Fig. 5), respectively. This metric provides more realistic estimation of quantification accuracy than comparison of the areas of identified and true damage areas. The acquired results for the investigated scenarios are presented in Table 1.

Table 1. The results of accuracy estimation for quantified damage. Scenario ℎ , % miss , % 10% 92.80 18.98 25% 94.10 12.52 50% 98.06 21.61

The results of accuracy estimation demonstrates high precision in determining the true area of damage, indicating coincidence with a true damage for the scenario with the flattest damage less than 8%, and for the scenario with the deepest damage less than 2%. However, some minor overestimations are observable in all considered scenarios (see Fig. 5 and Table 1), which result from the excitation parameters and the applied processing procedures. 4. Conclusions The non-destructive SHVT technique provides a unique possibility of performing thermographic inspections without external heat source, the thermal excitation is performed by conversion of local stresses due to mechanical vibration to internally generated heat due to the self-heating effect appeared in viscoelastic materials. This study demonstrates that detection of damage using SHVT technique is possible while heating up a tested composite structure by less than 2°C for a short period of time, which confirms its non-destructive and non-invasive character. The proposed processing algorithm, based on selection of the best raw thermogram, and then, filtering and fusion of consequent thermograms acquired after the selected one using DWT-based fusion procedure, ensures enhancement of the acquired thermograms that make it possible to quantify damage due to measurement noise suppression and edge sharpening. The results of damage quantification demonstrate high accuracy in estimating of damage area, which was quantitatively confirmed by calculating hit/miss metrics for the investigated scenarios. The proposed approach demonstrated high sensitivity of SHVT technique even to small damage, often being the most problematic in the practical inspections. Acknowledgements The publication is supported by the rector's pro-quality grant. Silesian University of Technology, grant no. 10/060/RGJ25/2061. References

Amraei, J., Katunin, A., Wachla, D., Lis, K. 2025. Damage assessment in composite plates using extended non-destructive self-heating based vibrothermography technique. Measurement 241, 115670.