Title: ULTRASONIC-BASED DEFECT IDENTIFICATION IN TIMBER USING UNIFORM MANIFOLD APPROXIMATION AND PROJECTION (UMAP)
Abstract:Naturally occurring strength-impacting defects in timber, such as grain deviation and knots, are common in commercial timber.Additionally, defects caused by the environment such as fungal decay and te...Naturally occurring strength-impacting defects in timber, such as grain deviation and knots, are common in commercial timber.Additionally, defects caused by the environment such as fungal decay and termite damage are also attributed to strength reduction which can lead to the failure of structural timber.This work provides a demonstration, of applying Uniform Manifold Approximation and Projection (UMAP), a novel feature extraction tool, for the purpose of identifying such defects in structural timber, with the use of an ultrasonic-based examination of the test specimens.Two case studies are presented, the first demonstrating UMAP's capability in identifying grain deviation and knots in timber, and the second, showing its ability to distinguish healthy sections from that with known internal damage.In both case studies, 54kHz pressure waves were transmitted transversely through pre-defined sections of known damage state and were analysed with UMAP -producing highly favourable clustering and data separation between defect states, compared to wavelet packet decomposition, a state-of-the-art signal analysis framework.The key contributions of the study are -UMAP is successfully applied for the first time for damage identification in commercial bare timber, and it is demonstrated to be able to identify signals sent through sections of different defect types.This demonstration in this area opens the door to future works, which may then scrutinise in-depth material-specific factors for the aim of defect characterisation in timber and timber composites using UMAP.Read More