Directed energy deposition on sheet metal forming for reinforcement structures

Abstract

While incremental forming processes can inexpensively create complex geometries from sheet metal, they struggle with adding sharp out of plane features for stiffness enhancement. With the implementation of directed-energy deposition (DED), an additive manufacturing process that locally deposits metal onto metallic substrates, reinforcement structures can be formed on the sheet metal. Furthermore, a design engineer may take advantage of the high residual stresses of DED to directly alter shapes in the substrate metal sheet. This hybrid forming-deposition process, as well as the application of local reinforcement, requires a good understanding of the process mechanism to predict expected shapes and minimize undesired deformations. In this work, numerical approaches are applied to evaluate heat transfer, thermal stress, and buckling of thin sheets under the stresses of deposition. These results are compared to analogous experiments conducted on an open-architecture laser-powder DED machine. The results of the thermal-mechanical analysis resemble the deformation trends observed in the experiments. However, the small-displacement formulation in the simulation used for ease of convergence does not fully capture the magnitude of the observed deformations. Nevertheless, the simulations effectively illustrate the effect of different scan strategies on the final deformed shape of the sheet metal.