In situ determination of the critical straining condition for solidification cracking during laser beam welding

In recent years, laser beam welding has found wide applications in many industrial fields. Solidification cracks are one of the most frequently encountered welding defects that hinder obtaining a safe weld joint. Decades of research have shown that one of the main causes of such cracks is the strain and the strain rate. Obtaining meaningful measurements of these strains has always been a major challenge for scientists, because of the specific environment of the measurement range and the many obstacles, as well as the high temperature and the plasma plume. By applying novel metrology based on optical flow (OF) algorithm, the critical strain conditions for solidification crack formation for the stainless steel 1.4828 in the immediate vicinity of the solidification front was identified. The developed two-dimensional technique allows for obtaining full strain distribution in the hot cracking critical zone.