RMS of Lamb wavefield interacting with delamination - numerical

In this work, we have generated a large dataset of 475 cases of a full wavefield of propagating Lamb waves in a plate made of carbon fibre-reinforced plastic (CFRP). The time-domain spectral element method was used for simulation of Lamb wave interaction with delamination. It should be added that despite the utilisation of the parallel code of the spectral element method which was run on the Tesla K20X GPU card, the computation of the dataset took about 3 months. For each case, single delamination was modelled by using the method of splitting nodes between appropriate spectral elements. It was assumed that the composite laminate is made of eight layers of a total thickness of 3.9 mm. The delamination was modelled between the third and fourth layer. Zero-volume delamination was assumed in the model. Delamination spatial location was selected randomly so that the interaction of guided waves with delamination is different for each case. It includes cases when delamination is located at the edge of the plate which is the most difficult to identify by signal processing methods. Additionally, the size of the delamination was randomly simulated by selecting the ellipse minor and major axis from the interval 10-40 mm. Also, the angle between the delamination major axis and the horizontal axis was randomly selected. Guided waves were excited at the plate centre by applying equivalent piezo-electric forces. The excitation signal had a form of sinusoid modulated by Hann window. It was assumed that the carrier frequency is 50 kHz and the modulation frequency is 10 kHz. The output from the top and bottom surfaces of the plate in the form of particle velocities at the nodes of spectral elements were interpolated on the uniform grid of 500x500 points by using shape functions of elements. It essentially resembles measurements acquired by the scanning laser Doppler vibrometer in the transverse direction (perpendicular to the plate surface). The root mean square (RMS) of the wavefield acquired at the bottom surface of the plate is given in this data set.