Christian Leppin

Texture Based Finite Element Simulation of a Two-Step Can Forming Process

Aluminum sheets used for beverage cans show a significant anisotropic plastic material behavior in sheet metal forming operations. In a deep drawing process of cups this anisotropy leads to a non-uniform height, i.e., an earing profile. The prediction of this earing profiles is important for the optimization of the forming process. In most cases the earing behavior cannot be predicted precisely based on phenomenological material models. In the presented work a micromechanical, texture-based model is used to simulate the first two steps (cupping and redrawing) of a can forming process. The predictions of the earing profile after each step are compared to experimental data. The mechanical modeling is done with a large strain elastic visco-plastic crystal plasticity material model with Norton type flow rule for each crystal. The response of the polycrystal is approximated by a Taylor type homogenization scheme. The simulations are carried out in the framework of the finite element method. The shape of the earing profile from the finite element simulation is compared to experimental profiles.

Formability Prediction Of Aluminum Sheet In Automotive Applications

In the following paper, a full mechanical characterization of the AA6016 T4 aluminum alloy car body sheet DR100 is presented. A comprehensive experimental program was performed to identify and model the orthotopic elasto‐plastic deformation behavior of the material and its fracture characteristics including criteria for localized necking, ductile fracture and shear fracture. The commercial software package MF GenYld + CrachFEM in combination with the explicit finite element code Ls‐Dyna is used to validate the quality of the material model with experiments, namely, prediction of the FLD, deep drawing with a cross‐shaped punch and finally, analysis of a simplified hemming process using a solid discretization of the problem. The focus is on the correct prediction of the limits of the material in such processes.

Stress-strain characterization and damage modeling of glass-fiber-reinforced polymer composites with vinylester matrix

Beyond a certain loading threshold, glass-fiber-reinforced polymer composites with vinylester matrix can show considerably nonlinear deformation behavior due to damage of the matrix material. To model such nonlinear deformation properties, we follow the approach of a fully anisotropic damage model suggested by Govindjee et al. (Govindjee S, Kay GJ and Simo JC. Anisotropic modelling and numerical simulation of brittle damage in concrete. International Journal for Numerical Methods in Engineering 1995; 38(21): 3611–3633). In addition, the inter-fiber fracture criterion introduced by Puck (Puck A. Festigkeitsanalyse von Faser-Matrix-Laminaten: Modelle für die Praxis. München, Germany: Hanser Fachbuchverlag, 1996) is used for the damage function that defines the damage initiation and the material strength. A particular procedure is chosen to identify the material properties to validate the model: three glass-fiber-reinforced polymer laminates with different layups are tested in tension under different loading orientations, assuming laminate theory to be reasonably well fulfilled. Finally, further experiments are compared with corresponding simulation results to demonstrate the performance of the model.