FEM simulation of the deformation field during the laser forming of sheet metal

A laser beam can be used as a flexible sheet metal forming tool. Its mechanism is the forming caused by thermal stresses resulting from the irradiation of laser beam scanning. Because of the complexity of this process, numerical simulation becomes necessary for its analysis. In this paper, the deformation field during the laser bending of sheet metal is studied using the 3D thermoelastoplastic finite element method. Considering the coexistence of the temperature and stress arising and dropping during the laser forming, a handling technique for the transitional zone between the elastic zone and plastic zone is adopted. In order to increase the accuracy of calculation, the reduced integration method is applied in the calculation. The results show that: (i) the laser bending process may be divided into two stages: in the first stage, a small counter-bending away from the laser source appears, and in the second stage, a bending angle facing the laser source is just formed finally; (ii) the counter-bending angle away from the laser source in a narrow sheet is greater than that in a wide sheet, i.e. the wider the sheet, the smaller the counter-bending angle; (iii) in the zone being passed through by the laser beam and its neighbouring zone, the stresses change severely with time and place. The form of the displacement field and its change obtained from the FEM simulation calculation is identical with the observed results from experiments, and the calculated bending-angle also agrees well with the experimental data.