Abstract
Hole-flanging which is the manufacturing operation used to form an integral collar around the periphery of a hole in a metal sheet is investigated. In this work, a 2-mm-thick 1000 series aluminium alloy sheet which is widely used in industrial applications was considered. The process is studied by means of numerical simulations and compared with experimental data. Three-dimensional elastic-plastic finite element models using various anisotropy assumptions (i.e., isotropy, normal, and orthotropic anisotropy) and based on isotropic yield criterion (von Mises) and anisotropic yield criterion (Hill 1948) were used. For the orthotropic anisotropy assumption, two approaches were tried to identify the r values, (i.e., the direct measurement of strains and the fitting of stress-strain curves). Experiments were conducted to assess the numerical accuracy of the different anisotropy assumptions. The study focused on the comparison of the geometrical and forming parameters predicted by the different models. It was found that the model based on the orthotropic anisotropy assumption with r values determined by fitting the stress-strain curves precisely predicts the experimental results (e.g., circularity error, thinning, punch load, critical value of the clearance-thickness ratio). However, a numerical model based on the normal anisotropy assumption can also be pertinent to accurately predict the forming parameters (e.g., punch load and critical value of the clearance-thickness ratio). In conclusion, the use of the Hill 1948 yield criterion can lead to accurate results for the majority of geometrical and forming parameters allowing accurate designs of many parts obtained by the hole-flanging process.
Published Version
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