Laser bending of metal sheet and thermal stress analysis

• Self-annealing effect of recently formed tracks influences stress levels.
• Sharp change of displacement across laser scanning tracks takes place.
• Ferritic–pearlitic microstructures are transformed to martensite in the surface region.
• Austenitic phase is concentrated in dendrites and the ferritic phase remains in interdendritic regions.
• High pressure nitrogen as assisting gas causes nitride compound formation.

Laser bending of a steel sheet is examined. Temperature and stress fields are predicted using the finite element code in line with the experimental conditions. The predictions of surface temperature, bending angle, and residual stress formed at the laser scanned surface are validated with the experimental data. Morphological and metallurgical changes in the laser treated region are investigated by incorporating the optical and electron scanning microscopes, energy dispersive spectroscopy, and X-ray diffraction. It is found that predictions of surface temperature, bending angle, and residual stress agree well with the experimental data. The self-annealing effect of the recently formed laser scanning tracks influences stress fields and displacement in the workpiece. Although high pressure nitrogen assisting gas is used in the experiments, the formation of few scattered cavities is observed along the laser scanning tracks at the surface because of the evaporation.