Experimental Study of Lamb Waves Propagation inside an Impact Damage in the Size of the Used Wavelength

Abstract

The present work is an experimental study of Lamb waves propagation in an aluminum plate with an impact damage in the size of the S0 mode wavelength. The aim of this study is to visualize the wavefield near the defect in the case of extreme diffusion, as well as the interference of the modes inside of it and their transformation. The results were obtained by applying the continuous wavelet transform (CWT) on the wavefield data recorded by two ultrasonic scanning techniques: the air coupled ultrasonic (ACU) and the Laser doppler vibrometry (LDV), to obtain a C-scan and a B-scan of the plate respectively. Space-wavenumber representations showed the behavior of Lamb waves in the plate as well as the reduction in thickness of the impacted area. The width of the latter could be estimated and the modes present at each position of the plate could be identified.

Impact Damage Detection in Laminate and Honeycomb CFRPs using Lamb Wave Ultrasonic Sensing

“…Due to low attenuation these waves can ACOUSTIC METHODS cover extensive areas, that is extremely important in aircraft industry, where the area of CFRP skins can be very large. Lamb wave ultrasonic methods are widely studied for the detection of impact damages in composites [26,27]; the optimal networks of transducers are investigated [28][29][30]. However, the physical mechanism of Lamb waves propagation is quite complex [31,32] requiring consideration of many factors such as the stability of the adhesive layer and the degradation of its properties [33,34], temperature deviations [35,36], sensor failure [37], etc.…”