Plastic deformation behavior in laser bending of elastic pre-loaded metal plate

Laser bending of elastic pre-loaded metal plates is promising due to many advantages, such as high forming precision and avoidance of plastic instability. To reveal the plastic deformation behavior of the plate, the deformation process is investigated through theoretical analysis and finite element (FE) simulations. The FE model is verified via forming experiments. The results show that the yield strength of the metal material decreases faster than the elastic modulus with the rising temperature of the plate during laser scanning. Then, the equivalent stress which is calculated to be proportional to the elastic modulus overtakes the yield strength in some regions of the plate, so that the plastic deformation occurs. The amount of the plastic deformation inside the plate can be estimated by an analytical formula derived in theory, and it depends on both pre-stress field and peak temperature field. Larger pre-stress and higher peak temperature bring about larger plastic strain. Because of this, for a point of any segment whose midperpendicular is the scan path in the present forming model, the closer position is to the scan path the larger x-axis direction plastic strain it would generate inside.