Measuring the Depth of Subsurface Defects in Additive Manufacturing Components by Laser-Generated Ultrasound

Abstract

A new method to measure the depth of subsurface defects in additive manufacturing components is proposed based on the velocity dispersion analysis of Lamb waves by the wavelet-transform of laser ultrasound. Firstly, the mode-conversion from laser-generated surface waves to Lamb waves caused by subsurface defects at different depths is studied systematically. Secondly, an additive manufactured 316L stainless steel sample with six subsurface defects has been fabricated to validate the efficiency of the proposed method. The measured result of the defect depth is very close to the real designed value, with a fitting coefficient of 0.98. The defect depth range for high accuracy measurement is suggested to be lower than 0.8 mm, which is enough to meet the inspection of layer thickness during additive manufacturing. The result indicates that the proposed method based on laser-generated ultrasound (LGU) velocity dispersion analysis is robust and reliable for defect depth measurement and meaningful to improve the processing quality and processing efficiency of additive/subtractive hybrid manufacturing.

Advanced Characterization and On-Line Process Monitoring of Additively Manufactured Materials and Components

“…Interestingly enough, authors contributed to demonstrating how more 'classic' nondestructive testing techniques can also well give invaluable insights into the problem of defect characterization [12], thereby complementing the high-end (but somehow expensive) characterization techniques.…”

Debonding Detection in Aluminum/Rigid Polyurethane Foam Composite Plates Using A0 Mode LAMB Wave EMATs

“…However, PZTs are inconvenient for automatic detection as coupling agents are required. Laser beams can also be used to generate Lamb waves, but the high cost and large size of the laser generation devices make field application difficult [ 16 , 17 ]. EMATs are extensively used to generate Lamb waves because of the advantages provided by requiring no coupling agent, being noncontact, and enabling convenient detection [ 18 ].…”