Laser induced phased arrays for remote ultrasonic imaging of additive manufactured components

Laser Induced Phased Arrays (LIPAs) use laser ultrasonics to generate and detect ultrasound, synthesising an ultrasonic phased array in post processing. Full Matrix Capture (FMC) is done by scanning the laser generation and detection beams at every possible combination with respect to position. The acquired data are used to synthesise a focus at every point in the section imaged, using the Total Focusing Method (TFM). The result is greatly improved imaging quality compared to conventional laser ultrasonic imaging. As the technique is remote and couplant free it lends itself well to extreme environments, such as the Additive Manufacturing (AM) process. We will present remote ultrasonic TFM images of additive manufactured components made of aluminium, using Selective Laser Melting (SLM). LIPAs were synthesised under the base plate of the built, to demonstrate the capability for in situ process monitoring. The aluminium built incorporated six side through holes of 0.5-1mm diameter size, in its design, in order to simulate process occurring defects. These were located as deep as 25mm below the surface of the component and were successfully imaged using LIPAs. TFM images from transducer based phased arrays will also be presented to complement the analysis.