关键词: 盒形件多道次变薄拉深模拟, Levy-Mises增量理论, 毛坯尺寸预测, 流动规律

Abstract: The finite element simulation of box-shaped parts is usually modeled by shell unit. The applicability of the thin shell unit in multi-pass deep-drawing forming, and multi-step ironing process conditions is questionable because they ignore the thick-directional stresses in the calculation. This paper takes 3003H14 high box as the research object, and uses Dynaform and LS-DYNA finite element software to conduct numerical simulation. The simulated results of shell element and solid element are compared and the instantaneous constitutive relationship coefficients of Levy-Mises increment theory are analyzed. Then the influence law of element type on simulation calculation accuracy of multi-pass thin sheet deep drawing is obtained by the above methods. The development of the blank size prediction software for the box-shaped parts drawing process is achieved by training the established box-shaped parts drawing blank size calculation program using the sample data of blank sizes from actual engineering. In addition, after the modeling method was clarified, the mechanism of material thinning and thickening during the ironing process of the sheet is studied in combination with the solid unit finite element simulation results, and the material flow law is revealed. The study shows that the solid unit simulation calculation results are closer to the actual one. If the percentage difference of the theoretical deformation thickness of the billet unit before and after the process is used as a measure of the degree of deformation, when the degree of deformation is 0-11.1%, the difference between the two unit calculations is 0.5%-27.8%. When the deformation degree varies from 24.2% to 34.9%,the calculated difference is 44.4% to 79.3%. After the multi-stage ironing draws, the thickness of the metal material has occurred in the rounded corners of the flange and the long side and the short side. The thinned region occurs in the bottom round of the bottom,and both of the long side and the short side area are thinned under the limitation of the mold. After multiple thinning and drawing, the thickening area of the metal material mostly occurs on the flange and the rounded corners at the junction of the long and short sides.Under the restrictive effect of the mold, the thinning area mostly occurs at the bottom rounded corners, and both of the long and short sides are thinned. Except for process one, the average thickness of the straight wall on the long side of each process is 1.00%-2.02%larger than the ideal value of the process design, and the average thickness of the straight wall on the short side is 0.86%-12.90%smaller than the ideal value of the process.

Key words: multi-step ironing process simulation of box-shaped parts, Levy-Mises incremental theory, prediction of blank size, metal flow law