Debonding localization in connected panels using nonlinear pseudo-forces across higher to sideband harmonics
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Given the critical importance of structural integrity and safety, there is a significant demand for localising local debondings in connected panels. The existing linear pseudo-force (LPF) approach regards local damage as virtual forces applied exclusively to the damage regions, enabling the localisation of damage. However, this model fails to account for nonlinearities arising from the contact behaviour of “breathing” debondings. To address this limitation, this study extends the concept of LPF to the nonlinear pseudo-force (NPF). Superior to the existing LPF model, the NPF model is capable of extracting both linear and nonlinear damage features, producing a more comprehensive approach to localising debondings in connected panels. The NPFs are reconstructed from nonlinear operating deflection shapes (ODSs) across higher to sideband harmonics. Damage indices (DIs) are established using NPFs associated with successive higher harmonics or neighbouring sideband harmonics. Peaks arising in the DIs can distinctly characterise the spatial features of debondings. The approach is experimentally verified on a laminated panel with a “breathing” debonding mechanism, as measured by laser scanning. Additionally, the approach is experimentally validated for its applicability to bolted panels with debondings caused by local bolt looseness. The results confirm that the NPF approach effectively characterises the locations and sizes of debondings in both laminated and bolted panels.