Experimental and numerical simulation of the hemming process of an aluminum sheet

http://link.aip.org/link/?APCPCS/712/1001/1International audienceHemming is a mechanical joining method that is typically used to connect two sheet metal components, such as inner and outer panels of automobile doors or hoods. Hemming generates defects like outer sheet size reduction (called roll-in), cracks and sheet metal springback. This affects the final dimensions of the hemmed part and can cause problems in the assembly stage or damage the product appearance. Hemming process control is currently experience-oriented and die design is based on trial-and-error. Therefore, developing predictive modeling capability and establishing die and process design guidelines are helpful to a better process understanding and control. FE simulations of the hemming process are realized at PSA Peugeot Citroen with the explicit code OPTRIS using under-integrated shell elements. Whereas they give a good estimation of the roll-in for steel sheets, the estimation is inaccurate for aluminum sheets. The article describes an analytical model and an implicit FE-model based on plane strain elements (FORGE2((R))). The simulations are applied to an aluminum sheet assumed to be isotropic with an isotropic hardening law determined from tensile tests. The results given by the analytical model and the FE-codes are then compared to the experimental observations. The element types as well as the material models used are then discussed and evaluated. Solutions for improving the hemming modeling are finally propose