Non-invasive, non-destructive characterization of subsurface weld defects via directed ultrasound

Directed ultrasound is employed to identify defects in subsurface welded joints and to characterize the defects as either inclusions or voids. We scan over the welded joint with a single ultrasound transducer, which transmits an ultrasound burst, and then we measure the burst after it reflects from the subsurface weld defects. In contrast with existing ultrasound characterization techniques we do not require a mechanical connection between the ultrasound transducer and the welded specimen, which facilitates implementation in the field. We utilize a correlation envelope to identify and locate defects in the presence of noise, and we distinguish between voids and inclusions based on phase change in the measured burst after reflection from a weld defect. We demonstrate the directed ultrasound technique for identifying subsurface defects in a tungsten alloy with a square joint. In contrast with X-ray imaging techniques, which cannot penetrate tungsten alloys, we identify, locate, and characterize known defects at depths of >10 mm. This directed ultrasound technique enables non-invasive, non-destructive inspection of a wide range of materials, and finds application in numerous applications including welding, printed circuit board fabrication, and sintered 3D printing.