Finite element analysis of the effects of process parameters on maximum and residual stress in aluminum cup forming

This study investigates the effects of thickness reduction ratio (TRR), die angle, and friction coefficient on maximum stress, residual stress, and plastic deformation during AA1100 aluminum cup ironing using finite element analysis supported by experimental observations. A three-factor, three-level design generated 27 simulation combinations, and mesh verification identified a 1.00 mm element size as an efficient and stable configuration. The results show that maximum stress ranged from 348.99 to 363.00 N/mm², while residual stress ranged from 119.11 to 163.33 N/mm². ANOVA screening identified TRR as the dominant factor for maximum stress with a contribution of 84.21%, followed by die angle at 9.82%, whereas friction had only a minor effect. For residual stress, TRR and friction were the most influential parameters. Increasing TRR also increased the mean maximum equivalent plastic strain from 0.3980 at 20% TRR to 0.5915 at 30% TRR, while the mean residual stress decreased, indicating that active forming stress, accumulated plastic strain, and post-forming stress follow different response patterns. Experimental results supported the physical consistency of the model through forming-force and dimensional comparisons. Hardness increased from 44.3 to 52.0 BHN after ironing, while metallographic and SEM observations showed deformation-related morphological changes. These findings indicate that TRR primarily governs deformation severity and maximum stress, whereas friction is more relevant to the post-forming stress state. The results provide a practical basis for selecting ironing parameters according to the targeted mechanical response, although direct experimental measurement of residual stress is still required.