The Use of Eddy Current Testing for Defect Detection in Additive Manufactured Metals

Abstract

The non-destructive method of electromagnetic eddy current testing is investigated using mirrored D-shaped coils and a giant magneto resistor sensor. An AC current between 1 – 5 kHz was sent through the coil wires generating a magnetic field oriented as if it were a single solenoid. Various samples were measured consisting of aluminum, copper, and brass, each type of metal had a sample with a 5/32th diameter hole, a 5/16th diameter hole, and a thin 0.18 mm depth surface crack. The sample defects under examination were used to mimic defects that would be present in the metal additive manufacturing process, specifically laser powder bed fusion methods. Although the defects under consideration are considerably larger than those encountered in the additive manufacturing process, the following research serves as a proof of concept that higher sensitivity sensors could be achieved. A linear actuator was used to create 1D scans of the surfaces of the metals, to detect the various defects. Tests were conducted for each defect type, along with detecting the large and small holes beneath another ‘defect-free’ sample to mimic the subsurface flaws.