PSI - Issue 57

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Boris Spak et al. / Procedia Structural Integrity 57 (2024) 445–451 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The material behavior under quasi-static loading is obtained from tension tests in compliance with the standard DIN EN ISO 6892-1 (2020) with dog bone specimen manufactured according to German standard DIN 50125 (2016). In order to assess the impact of anisotropy, specimen were manufactured in rolling direction at an angle of 0 °, as well as at an orientation of 45 ° and 90 ° with respect to the rolling direction. For each direction three specimen were tested. The experimental results are presented in fig. 1. The mechanical properties are summarized in table 2. As ca n be seen, the anisotropy is pronounced insignificantly, with merely the Young’s modulus exhibiting a slightly higher value for specimen at an angle of 90 °. Consequently, for the subsequent process simulation of robot-assisted roll forming, a single flow curve is used as input to model the constitutive behavior.

Fig. 1. Experimental results from quasi-static tension tests for aluminum alloy EN AW-7475 T761 for specimen in different orientation to rolling direction (specimen enumeration running from one to three at angles of 0 °, 45 ° and 90 °, respectively). The process simulation is carried out using the commercial implicit finite element solver of LS-Dyna®. The initial set up of the model is presented in fig. 2, left. The sheet with a length of l = 300 mm and a width of w = 78 mm is positioned between two rolls, modelled as rigid bodies. The upper roll has a n arbitrary chosen radius of r = 6 mm for this study. Proper boundary conditions are applied at the left hand side of the sheet to keep it fixed during the roll forming operation. The contact is assumed to satisfy ideal rolling conditions, therefore only sliding of rolls along the sheet in the local direction z r and rotation about this same axis at the local angle φ r are permitted with a negligible

Fig. 2. Finite element model ofthe process simulation. Left: Initial set up with sheet material, upper and lower rolls and boundary conditions. Right: Local coordinate system, sheet dimensions and close up meshing with hexahedron elements in the forming region with expected high degree of plastic deformation.