Towards quantification of hidden corrosion using D-Sight non-destructive testing technique

Hidden corrosion, not detected timely, may significantly affect the durability and integrity of aircraft structures; therefore, improvement of non-destructive testing (NDT) techniques is of high importance for reliable and safe aircraft operation. One of the commonly used NDT techniques for the detection of such a type of corrosion is the D-Sight technique, which gained wide appreciation in the aerospace sector due to its ability to perform low-cost and fast inspections of wide areas. One of the drawbacks of the method is its qualitative character, which makes it difficult to quantify corroded spots and track corrosion growth during operation. The following study aims to present recent advances in the enhancement of this technique by using advanced image processing, numerical simulations, and validation studies using reference methods (classical metrology, and digital image correlation) to make this method suitable for quantification of areas affected by hidden corrosion and monitoring its growth between periodic NDT inspections. The studies are performed on test specimens that simulate hidden corrosion and verified on results of D-Sight inspections of the Polish Air Force military aircraft. The results demonstrated good performance in identification and quantification hidden corrosion spots on D-Sight images. The approach can be used for supporting aircraft inspectors in analysis of inspection results of aircraft under operation that require periodic non-destructive testing.