A transformer model for detection of stiffener disbonding in stiffened aluminium panel using Lamb wave

Stiffened panels are widely used in a range of engineering domains to enhance load-bearing capacity, reduce buckling, and improve overall structural integrity. Stiffener disbonding is a common failure mode, making it essential to detect these disbonds before they reach a critical level that could lead to structural failure. In this work, a transformer architecture has been implemented to detect the presence and extent of disbonding between the stiffener and the host aluminium plate. The research uses a dataset of Lamb waves obtained from an experimental setup with four types of specimens, ranging from no disbonding to disbonding of varying widths induced by Teflon strips. The problem is framed as a multi-class classification task with labels representing different disbonding levels. The transformer model utilizes a self-attention mechanism to analyze the Lamb wave responses and ascertain the presence and extent of disbanding. Operating in encoder-only mode, the tailored transformer accepts Lamb wave responses as input and outputs a class probability score for each of the four predefined disbonding levels using a softmax activation function. The developed model has been able to predict the state of the stiffened panels with an accuracy of 100%. To demonstrate the effectiveness of the transformer model, it has been compared to the convolutional neural network (CNN) model. When tested on an unseen noisy dataset, the transformer model achieved an accuracy of 100%, outperforming the CNN model, which achieved an accuracy of 89%.