Effect of elastic prestress on the laser peen forming of aluminum alloy 2024-T351: Experiments and eigenstrain-based modeling

Laser peen forming is a viable means for flexible shaping and adjusting of metal plate. The prestress is effective and useful to improve its formability. Experiments and numerical modeling are performed to investigate the effect of elastic prestress on the deformed shape generated by laser peen forming of aluminum alloy of 2024-T351. The experiments with prestressing laser peen forming are implemented in one direction of square samples by applying simple bending. A newly developed eigenstrain-based modeling procedure is introduced to simulate the prestress effects on the bending deformation and residual stresses. The boundary conditions of displacement are proposed to define in the explicit model to include the prestress effect. The numerical model is validated to be an effective and efficient tool for the predictions of deformed shape and residual stresses. Both experiments and model predictions provide that the radius of curvature in the direction of prebending can be greatly decreased by the increase of prebending curvature because much more in-plane plastic strains are generated during laser shocking. The scanning strategy is one important factor to generate the difference of bending in two directions besides prebending and spatial decay of shock pressure. The compressive residual stresses are observed to generate both at the top and at the bottom surfaces of samples. The increase of prebending curvature can increase the compressive residual stresses values at the top surface. And laser peen forming both with and without prestress is observed to have little effect on the surface roughness.