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Numerical analysis of multistep ironing of thin-wall aluminium drawpiece

This work presents results obtained from numerical analysis of ironing with use of finite element mesh. The base drawpiece, that was a starting point in the analysis, includes a full history of deformation that resulted from simulations of preceeding operations, that is drawing and redrawing. Such a complex approach allows for a complete analysis of each successively conducted process. In the case of materials of thicknesses smaller than 0.250 mm, work hardening is a significant aspect which determines further plastic working of the element. Local work hardening allows for carrying stresses that are necessary to form material in following operations. Numerical simulations of ironing cylindrical elements formed from stripes are highly problematic due to difficulty in defining base material. Such simulations require a reological model of the material including a forming limit curve and a hardening curve. The numerical analysis was carried out for ironing a side wall of a drawpiece from a thin aluminium stripe. The analysis was conducted in Dynaform 5.9.1 with LS-Dyna solver. The material used in the analysis was 3104 aluminium alloy in H19 temper of original thickness 0.250 mm. The final thickness of a wall after ironing is smaller than 0.100 mm. The process of increasing height of a side wall at the cost of reduction in its thickness was conducted in 3 stages. It was a consequence of a degree of reduction in thickness, which was calculated. The data resulting from each individual operation were imported as input data to the analysis of a following operation. The study was carried out in 2 stages. In the first one, the material model was optimised taking into account the problematic character of ironing. The second stage was the analysis of results from the simulation. The state of deformation and stress in the numerical model was analysed. Then, the results were compared to the physical process which is currently used in the industry. The compared results embraced: reduction in thickness of a wall, localisation of the transition to a thin wall of a drawpiece, geometry of a drawpiece.