Fully Noncontact Hybrid NDT for 3D Defect Reconstruction Using SAFT Algorithm and 2D Apodization Window

• Published in: Sensors (Basel, Switzerland) Vol. 19; no. 9; p. 2138
• Main Authors: Selim, Hossam, Trull, José, Delgado Prieto, Miguel, Picó, Rubén, Romeral, Luis, Cojocaru, Crina
• Format: Journal Article Publication
• Language: English
• Published: Switzerland MDPI AG 08-05-2019; Multidisciplinary Digital Publishing Institute (MDPI); MDPI
• Subjects: 3D reconstruction; Algorithms; Aluminum; Apodization; Defects; Física; Image enhancement; Laser ultrasonics; Lasers; Làsers; NDT; Noncontact transducers; Nondestructive testing; Propagation; Quality control; SAFT; Sidelobes; Signal processing; Synthetic aperture; Synthetic apertures; Ultrasonic imaging; Ultrasonic transducers; Ultrasonic waves; Ultrasons; Ultrasound; Wave propagation; Wavelet transforms; Weighting function; Àrees temàtiques de la UPC; United States > US; Spain; noncontact transducers; synthetic aperture; 3D reconstruction; apodization; defects; SAFT; weighting function; laser ultrasonics; NDT
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s19092138

Nondestructive testing of metallic objects that may contain embedded defects of different sizes is an important application in many industrial branches for quality control. Most of these techniques allow defect detection and its approximate localization, but few methods give enough information for its 3D reconstruction. Here we present a hybrid laser-transducer system that combines remote, laser-generated ultrasound excitation and noncontact ultrasonic transducer detection. This fully noncontact method allows access to scan areas on different object's faces and defect details from different angles/perspectives. This hybrid system can analyze the object's volume data and allows a 3D reconstruction image of the embedded defects. As a novelty for signal processing improvement, we use a 2D apodization window filtering technique, applied along with the synthetic aperture focusing algorithm, to remove the undesired effects due to side lobes and wide-angle reflections of propagating ultrasound waves, thus enhancing the resulting 3D image of the defect. Finally, we provide both qualitative and quantitative volumetric results that yield valuable information about defect location and size.