Pattern recognition of weld defects detected by radiographic test

In recent years there has been a marked advance in the research for the development of an automatized system to analyze weld defects detected by radiographs. This work describes a study of nonlinear pattern classifiers, implemented by artificial neural networks, to classify weld defects existent in radiographic weld beads, aiming principally to increase the percentage of defect recognition success obtained with the linear classifiers. Radiographic patterns from International Institute of Welding (IIW) were used. Geometric features of defect classes were used as input data of the classifiers. Using a novel approach for this area of research, a criterion of neural relevance was applied to evaluate the discrimination capacity of the classes studied by the features used, aiming to prove that the quality of the features is more important than the quantity of features used. Well known for other applications, but still not exploited in weld defect recognition, the analytical techniques of the principal nonlinear discrimination components, also developed by neural networks, are presented to show the classification problem in two dimensions, as well as evaluating the classification performance obtained with these techniques. The results prove the efficiency of the techniques for the data used. (C) 2004 Elsevier Ltd. All rights reserved.