Selective generation of Lamb wave modes and their propagation characteristics in defective composite laminates

Abstract

Techniques for the generation of Lamb waves with purpose of non-destructive inspection (NDI) were brie y reviewed. An active excitation control circuit was designed and instrumented with an online damage diagnosis system, by which the desired fundamental symmetric Lamb mode, shear mode and antisymmetric mode can be selectively stimulated. A signal processing and identi cation algorithm in the timescale domain, using spectrographic analyses based on the wavelet transform technique, was developed to assist the wave signal interpretation. The proposed excitation methodology was applied to the study of the dispersion and propagation characteristics of Lamb waves in quasi-isotropic CF/EP composite laminates with delamination. For validation, numerical simulations were conducted in parallel with experimental investigations.

Detection of multiple low-energy impact damage in composite plates using Lamb wave techniques

“…As shown by Su and Ye in Ref. [31] it is valid to use the corrected signals to draw conclusions regarding the amplitude, since the excitation strains transmitted to the laminates are multiples of the applied voltage, which remained in the linear region of the PZT response. Therefore the behaviour of the signals is unaffected by the multiplication, and the responses plotted in Fig.…”

Lamb wave dispersion time-domain study using a combined signal processing approach

“…That can be achieved by implementing a time-scale domain mode separation algorithm based on wavelet transform (Se & Ye 2009). The possibility of installing a selective mode generation system is wittingly left aside because the reliability of that strategy can only be assured in laboratory conditions (Su & Ye 2004).…”

Reference-free crack detection under varying temperature

“…However, the majority of the past work has focused on selective generation of S 0 and A 0 modes (Giurgiutiu, 2005;Su et al, 2004;Wilcox et al, 2001;Yamanaka et al, 1991). For instance, by exciting PZTs A and D shown in Fig.…”

“…There is a large volume of literature that offers an excellent overview of recent developments in SHM and NDT (Adams, 2007;Blitz et al, 1996;Chang et al, 2003aChang et al, , 2003bCiolko et al, 1999;Doherty, 1987;Hellier, 2001;Montalvao et al, 2006, Popovics, 2004Sohn et al, 2004;Staszewski et al, 2004;Su et al, 2004Su et al, , 2006Van der Auweraer et al, 2003). Guided waves is one of the NDT techniques that have received a great deal of attention because they can propagate over considerable distances with little attenuation.…”