Experimental and numerical modeling of buckling instability of laser sheet forming

New experimental results show that laser bending can be extended to generate a bending angle not only towards but also away from the laser beam, giving more flexibility to the process. In order to explain this buckling instability, a series of experiments have been carried out with real-time measurement of the bending angle for different materials, thicknesses, scanning speeds, laser beam diameters and laser powers, pre-bending conditions, and cooling conditions. Furthermore, a 3-D FEM simulation has been performed that includes a non-linear, transient, indirect coupled, thermal–structural analysis accounting for the nonlinear geometric and material properties. The buckling deformation, bending angle and distribution of stress–strain and temperature, as well as residual stresses, have been obtained from the simulations. The bending angle is affected by the temperature distribution and gradient, the mechanical and thermal properties of the sheet metal material, and the process parameters, such as the laser power, the laser beam diameter, the scanning speed, the material, the sample geometry, and other bending conditions. The buckling mechanism can be illustrated by the simulation results.  2002 Elsevier Science Ltd. All rights reserved.