Forming quality and residual stress analysis of Al2024-T351 perforated sheets with laser annulus and strip peening

Abstract

Laser peen forming (LPF) is a precision forming technique that uses nanosecond pulsed laser-induced shock waves to bend, shape, align, and restore components with remarkable precision. This study has developed a novel process approach by combining laser annulus and strip peening to enhance the consistency of the forming curvature in perforated sheets and maximize their structural performance. The study compared and analyzed the forming effectiveness of two peening strategies (laser strip peening, laser annulus and strip peening) under different peening sequences. Then, a thorough analysis of residual stresses following the bending deformation of sheets from diverse specimens was carried out using numerical models. The results showed that the radius of curvature of the perforated sheet decreased as the peening sequence increased. The laser annulus and strip peening process could not increase the degree of deformation of the perforated sheet compared to strip peening under the same peening sequence, but it could decrease the deviation of the hole edge. In addition, the laser peening strategy with one peening sequence in the annular area and three peening sequences in the strip area could further improve the consistency of single curvature forming. The distribution of residual stresses around the holes varied significantly across specimens subjected to the laser annulus and strip peening process. The compressive residual stress (CRS) surrounding the hole was lower for perforated sheets treated with one peening sequence in the annular area and three peening sequences in the strip area. This was mainly due to the greater bending moment generated by the strip peening, resulting in a more pronounced release of compressive stress around the hole.