• Poelman, Gaétan
• Kersemans, Mathias
• Van Paepegem, Wim
• Hedayatrasa, Saeid
• Segers, Joost

Abstract

Local Defect Resonance (LDR) is exploited for non-destructive testing (NDT) by using ultrasonicvibrations to get a localized resonant activation of defected zones. The LDR technique relies on thelocal stiffness difference between the defect and the sound material. Analyzing the structure’sdisplacement field at this localized resonance frequency reveals the defect’s location and providesinformation about the defect’s characteristics, i.e. geometry, size and depth.In this study, the opportunities and limitations of linear LDR for NDT of materials are investigated in aparametric way. Both finite element simulations and experiments (using scanning laser Dopplervibrometry) are performed for aluminum alloy and carbon fiber reinforced polymer coupons with flatbottom holes and delaminations ranging in both depth and diameter. The resonance frequencies aswell as the associated defect-to-background ratios are parametrically evaluated.For shallow defects, a clear LDR is observed caused by the strong local stiffness reduction at the defect.On the contrary, deep defects are associated with a limited stiffness decrease that results in theabsence of LDR behavior.The local stiffness reduction at damages is further exploited using a weighted band power calculation.It is shown that using this technique, deep defects can be detected for which no LDR behavior wasobserved.

Topics

• impedance spectroscopy
• polymer
• Carbon
• experiment
• simulation
• aluminium
• defect
• activation