Optimization of laser bending process parameters for enhanced bending angle and residual stress control in St12 steel sheets: Experimental investigation and FEM simulation

Laser bending has emerged as an efficient technique for bending sheet metals without the need for mechanical force or hard tooling. This study investigates the bending angle and residual stress in ST12 steel sheets under direct CO2 laser irradiation. Finite element simulations, experimental investigations, and statistical analysis were employed to systematically examine the influence of laser power (1600–2400 W), scanning speed (65–93 mm/s), and the number of passes (1–5) on the bending process. Seventy-five numerical simulations and a subset of 15 experiments – selected via the Central Composite Design (CCD) method – were conducted to optimize process parameters and validate the simulation model. ANOVA identified the number of passes as the most significant factor; additionally, higher scanning speeds reduced both the bending angle and residual stress, whereas increased laser power had the opposite effect. Notably, higher compressive residual stresses, resulting primarily from multiple passes, help mitigate the spring-back effect, thereby enhancing the final form accuracy of the bent sheet. Simulation outcomes, validated with a maximum error of 6.48%, were used to determine the optimal conditions (2400 W, 65 mm/s, and five passes) for achieving the desired bending performance. Overall, this research advances our understanding of laser bending phenomena and provides practical guidelines for optimizing sheet metal forming processes.