Laser Induced Phased Arrays (LIPA) to detect nested features in additively manufactured components

Abstract

Additive manufacturing (AM) has the capability to build complex parts with internal features, which have many advantages over conventionally manufactured parts. This makes AM an alternative for advanced manufacturing sectors. AM components suffer from defects due to the lack of understanding in the build process. This makes the adaptation of AM in safety-critical industries, such as aerospace, problematic. The current AM work flow calls for costly off-line inspections to qualify components as defect-free. The layer by layer nature of the AM provides an opportunity for an on-line inspection to take place. This can provide early detection of defects as well as information for optimization and repair of the build. Laser Induced Phased Arrays (LIPA) present themselves as a viable remote, non-destructive, ultrasonic technique capable of being implemented as part of an on-line inspection of AM. Lasers are used to generate and detect ultrasound and a phased array is synthesized in post-processing. This paper demonstrates the capability of LIPA to successfully detect and locate features within AM components off-line. Cylindrical features as small as 0.2 mm in diameter and 26 mm above the inspection surface were detected using LIPA and verified using X-ray computed tomography (XCT). Keywords: Additive manufacturing, Laser Induced Phased Array, Non-destructive, Non-contact, Selective laser melting, Geometrical accuracy