The next generation of higher efficiency vehicles will utilize lightweight materials to reduce the amount of power required for equivalent performance. The proposed project addresses engineering needs for this advancement by forming the basis of improved structural simulation methods in aluminum sheet metal forming. Application of modern state variable constitutive equations incorporating anisotropic effects in the yield shape and translation will be characterized to aluminum in more than one microstructural configuration. An anisotropic plasticity/viscoplasticity model with kinematic hardening, and a polycrystal model with slip-system hardening, intergranular hardening, and crystal lattice rotations will be used together. Finite strain validation is also emphasized in the project, using an integrated corotational formulation to maintain a consistent material referential where all the state variables exist, and the constitutive equations are evaluated. Innovative non-proportional biaxial sheer-extension testing at finite strain will be carried out to validate the strain measure of the corotational formulation, and investigate the models ability to accurately predict complex deformation histories. Microstructural investigation of the deformed test specimens will help define physically based coefficients and state variables (e.g. grain size and orientation, slip density, sub-grain) which can be introduced during Stage II developments. The combination of microstructural input variables, and the complexity of deformation paths in the biaxial tests will allow more thorough characterization for these materials than previously available.Commercial Applications:The constitutive modeling capability proposed in this project is important for the DoC and Partnership for the Next Generation of Vehicles program because it will reduce costs by replacing expensive tests with high quality computer simulation, and provide the basis for more accurate design prediction in forming. Constitutive model advancements will lead to easier and more concrete characterization of materials for structural simulation with increased levels of confidence. The fundamentals used here are applicable to essentially all types of metal deformation, giving the project large commercial scope in different industries.
