Forming of aluminum alloys at elevated temperatures – Part 2: Numerical modeling and experimental verification

The temperature-dependent Barlat YLD96 anisotropic yield function developed previously [Forming of aluminum alloys at elevated temperatures – Part 1: Material characterization. Int. J. Plasticity, 2005a] was applied to the forming simulation of AA3003-H111 aluminum alloy sheets. The cutting-plane algorithm for the integration of a general class of elasto-plastic constitutive models was used to implement this yield function into the commercial FEM code LS-Dyna as a user material subroutine (UMAT). The temperature-dependent material model was used to simulate the coupled thermo-mechanical finite element analysis of the stamping of an aluminum sheet using a hemispherical punch under the pure stretch boundary condition. In order to evaluate the accuracy of the UMAT’s ability to predict both forming behavior and failure locations, simulation results were compared with experimental data performed at several elevated temperatures. Forming limit diagrams (FLDs) were developed for the AA3003-H111 at several elevated temperatures using the M-K model in order to predict the location of the failure in the numerical simulations. The favorable comparison found between the numerical and experimental data shows that a promising future exists for the development of more accurate temperature-dependent yield functions to apply to thermo-hydroforming process.