Inspection of thick welded joints using laser-ultrasonic SAFT

A Review of Non-Destructive Testing (NDT) Techniques for Defect Detection: Application to Fusion Welding and Future Wire Arc Additive Manufacturing Processes

“…Use on a rough surface for a later inline application still has to be tested. To overcome this, Levesque et al [ 60 ] showed in a later publication the possibility of using LU for defect analysis of thick welded structures (butt welds). Since similar surface roughness and geometry problems are expected here as in the previous investigations, a comparison can be made to the applicability of LU to WAAM structures.…”

“…For this purpose, a pulsed laser with a pulse width of 9 ns and a frequency of 100 Hz, placed at a distance of 50 mm behind the welding torch and 4.5 mm behind the melt pool, generated the sound waves in ablation mode, and a laser detector received the excited sound waves. The synthesis Aperture Focusing Technique (SAFT) [ 55 , 60 , 66 , 67 ] was adopted to acquire images by means of longitudinal sound wave velocities. Although the depth position of the defects was estimated inaccurately (around 5% deviation) due to the difference between the applied room temperature and the true value for the ultrasonic waves, it was successfully shown that LU is capable of detecting defects in real time as well as during the welding process.…”

The Progress in Photoacoustic and Laser Ultrasonic Tomographic Imaging for Biomedicine and Industry: A Review

“…In this case, the temporal shape and the amplitude of the pulse are fixed, and can be optimized for the particular task. The surface absorption in the investigated medium can be used, for example, in non-contact LUI applications [55]. The temporal shape and the amplitude of the probe pulse here may depend on a particular point of the sample where the light pulse is absorbed.…”

“…In recent years, imaging of solids has drawn much research attention [55,120]. While nondestructive testing and evaluation of objects with complex shapes have numerous practical applications, they pose a significant challenge.…”

“…LUT was applied to the immersion ultrasound profilometry of solid samples [52,53], measurements of internal geometry of solid samples with complex external surface [54], inspection of thick welded joints [55], and evaluation of internal structure of rock samples [56] and biological objects [45,[57][58][59][60][61] (often in combination with PAT). These applications will be reviewed, in more detail, below.…”