| The purpose of this research is to develop a fully-tabulated, anisotropic, asymmetric, strain rate, and temperature dependent material model for solid finite elements. Physical testing of several metallic materials has shown to have anisotropic (or orthotropic) characteristics. While many material models in finite element codes currently have anisotropic options, they tend to focus on material forming applications -- not crash and impact analysis. Unlike most anisotropic forming material models, this model has: rate dependency, temperature dependency, tabulated hardening (as opposed to parameterized inputs), associated flow, and the ability to maintain numerical stability for large deformations.;The implementation of this anisotropic model is an extension of the currently existing Generalized Yield Surface (GYS) variant of the Tabulated Johnson-Cook material model. This new model builds upon the previously available features of both of these well-established material models. Strain rate and temperature dependencies are utilized as independent tabulated values. Yield curves for tension, compression and shear are also tabulated and independent. Isotropic failure is retained from the Tabulated Johnson-Cook model as a function of triaxiality, Lode parameter, strain rate, temperature and element size. Lastly, tabulated plasticity for tension and compression allows the user to specify yield stress in the 0-degree, 45-degree, 90-degree, and thickness directions (as a function of strain rate). Therefore, this model applies to thick orthotropic metallic plates as it is assumed that a thickness direction can be recognized in the structure (although no plane state of stress is assumed) and that the response under 135-degree and 45-degree are identical. Due to the fully tabulated nature of the material law, rate and temperature dependency and asymmetry are all orthotropic in nature which is a unique feature of this current approach.;Physical testing (tension and compression) of Al-2024 and Ti-6Al-4V specimens were used to validate the development of this material model. Using a single material model for each metal, the author was able to replicate test results in each specimen direction. Lastly, this model was used to simulate ballistic impacts of a 0.25 inch Ti-6Al-4V plate and compared to other models with comparable inputs. |
