A submodeling technique for incorporating sheet metal forming effects in an AA5083 FPV structure

While the first generation of floating photovoltaics (FPV) was designed for operation in freshwater reservoirs, the technology is currently expanding to marine territories. In this paper, an FPV structure made from formed aluminum alloy sheets in AA5083-H111 is subject to a multi-stage numerical investigation in LS-DYNA. Quasi-static directional tensile experiments and disc-compression tests are conducted to characterize the plastic anisotropy of the rolled aluminum sheets. An anisotropic yield criterion with associated flow rule and combined isotropic-kinematic strain hardening is employed to simulate the drawing and springback of a subsection of the full structure, obtaining predictions of residual stresses, effective plastic strains, thickness change, and the process-induced geometrical imperfections. In order to analyze the performance of the formed structure under operational loads, a novel approach for submodeling that overcomes the usual requirement of precise geometric compliance enables driven variables to be obtained from a global service load model that is based on the idealized computer-aided design. The method is used to analyze geometrical, mechanical, and material-related process effects on operational stresses that are important to consider in fatigue analysis. Residual stresses were confirmed to significantly affect fatigue, while the stress increase often seen as a result of material thinning was essentially eliminated by the redistribution of internal forces. Furthermore, a parametric investigation showed that the magnitudes of the residual stresses largely depend on the alloy's kinematic hardening properties, emphasizing the importance of proper plasticity models.