Ultrasonic Inspection of Weld Defects Using Total Focusing Method

Abstract

AbstractUltrasonic arrays have been widely employed in industrial applications because of their ability to perform quick inspections for detection and characterization of flaws. The total focusing method (TFM) is an advanced ultrasonic imaging technique that utilizes the full matrix capture (FMC) data of the phased array elements to generate a high-resolution image by focusing on every image pixel in both transmission and reception. In this work, the time of flight framework involved for the TFM post-processing is illustrated for an angular wedge configuration. Further, the TFM algorithm is extended for imaging using multiple direct and half-skip wave modes by taking into account the wave mode conversions in the specimen. The implications of the mode conversions on the TFM images are analyzed, and the challenges posed on the TFM, specific to weld inspection, are explained in detail. In this work, experimental studies are performed on weld specimens with five common weld defects using the TFM algorithm. FMC data is acquired from the ultrasonic instrument and is post-processed to get the TFM images. The TFM results of weld defects show high resolution, better defect detectability, and easy visualization of defects compared to phased array sector scan images.KeywordsUltrasonic arraysFull matrix captureTotal focusing methodAngular wedgeWeld inspection