In situ measurements and simulation of residual stresses and deformations in additively manufactured thin plates

In this work, the residual stresses and deformations developed during and after laser powder bed fusion (L-PBF) manufacture of thin quasi-2D metallic plates were investigated. Such thin structures are particularly susceptible to effects of residual stress development. A finite element analysis of the L-PBF process was validated with in situ force measurements for the first time for a thin horizontal plate. The predicted forces developed reached a steady growth rate in the corners of the sample of 4.25 N per layer deposited, compared to 3.1 to 3.6 N per layer measured by in situ load cells. The evolution of deformation and residual stress in a different configuration, thin vertical plates, during and after removal of support structures, was also studied numerically and experimentally. Here, the finite element results showed good qualitative and quantitative (to within about 30% on average) agreement for residual deformations and final geometries of the thin vertical structures when compared with stereoscopic digital image correlation measurements. The results from the simulations showed that through-thickness stresses and shear stresses are negligible, while in-plane stresses grow in magnitude during the build process and the subsequent cooling period but are relaxed when the supporting structures are severed and the built plates removed from the base-plate, leaving tension in first built layers and compression in the last built layers. The models provide a tool for designing support structures and processes for release of the structures from their supports and substrates.