An orthotropic elastoplastic constitutive model for lattice materials

High-fidelity finite element modeling of large-scale lattice-filled structures remains prohibitively expensive due to immense computational demands. To address the persistent challenge of balancing accuracy and efficiency in predicting mechanical behavior of lattice systems, this study proposes an orthotropic elastoplastic constitutive model for lattice materials based on the Hill yield criterion. A cross-scale methodology is developed to predict the elastoplastic responses, enabling highly efficient evaluation of large-scale lattice-filled structures. First, the Hill criterion is extended to formulate an orthotropic elastoplastic constitutive model, with the corresponding constitutive parameters determined through four standard experiments. A predictive framework is thus constructed to assess the elastoplastic properties of lattice materials, facilitating cross-scale mechanical performance prediction from the unit cell level to the full-scale structure. Validation against experimental data and high-fidelity mesoscopic simulations demonstrates that the proposed method accurately predicts the elastoplastic behavior and effectively captures the anisotropic characteristics. A significant advantage of this approach is its computational efficiency, improving by about two orders of magnitude while maintaining high engineering accuracy. Furthermore, the framework is highly adaptable, allowing for customization to various lattice topologies by substituting of unit-cell property databases, which provides an efficient and reliable solution for analyzing large-scale lattice structures in practical engineering applications.