Issue 78

C. Vendittozzi et alii, Fracture and Structural Integrity, 78 (2026) 519-540; DOI: 10.3221/IGF-ESIS.78.30

Accordingly, the following comparison should be read as a phenomenological interpretation of the measured FBG response, not as an externally validated reconstruction of the flight or ground-operation sequence. Dataset A (Fig. 6). During inter-event intervals, the four signals remain relatively clustered and follow a common slow trend. In contrast, Events 1–3 correspond to rapid increases in oscillation amplitude and marked divergence among channels, indicating short-duration, highly dynamic load-transfer interactions within the instrumented landing-gear structure. Following each event, the traces reconverge and resume the same underlying trend observed before and between events. This recovery behavior suggests that, within the FBG response, Events 1–3 behave as transient high-energy interactions followed by partial return toward the pre-event strain pattern. Because no independent operational marker is available, these events are not assigned to specific touchdown, braking, or maneuver phases.

Figure 6: Dataset A: Baseline-normalized response expressed as microstrain (S1–S4). The conversion restores the strain variations to an interpretable scale, enabling identification of three dominant FBG-derived high-energy event candidates. Shaded regions denote Events 1–3.

Figure 7: Dataset B: Baseline-normalized response expressed as microstrain (S1–S4). The conversion restores the strain variations to an interpretable scale, enabling identification of three dominant FBG-derived high-energy event candidates. Shaded regions denote Events 1–3.

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