Nondestructive testing of additively manufactured material based on ultrasonic scattering measurement

Abstract

To improve ultrasonic testing capability for additively manufactured materials, extreme value statistics is employed to calculate the experimental confidence bounds of structural noise, which can be treated as time-dependent thresholds for ultrasonic C-scan image segmentation. A 316L stainless steel sample manufactured by selective laser melting is used for ultrasonic scattering measurements with a focused transducer. Compared with the fixed threshold used in the traditional C-scan image segmentation, the time-dependent threshold can effectively distinguish the flaw echoes from the background of structural noise. The optical microscopy measurement results show that the present method can avoid both missed detections and false positives.