STUDY OF SHEET METAL FORMING STRATEGIES OF FREE-FORM GEOMETRY PARTS BY NUMERICAL SIMULATIONS

ABSTRACT: Sheet metal forming (SMF) is a key manufacturing process extensively used for producing complex components in various industrial sectors. The current study presents a comprehensive numerical investigation into the effects of forming strategy and free-form surface geometry on the quality and deformation behavior of sheet metal components produced by stamping and multi-point forming (MPF) processes. Finite element simulations were systematically conducted to evaluate the main quality indicators, including wrinkling severity, springback displacement, and thickness non-uniformity, under various forming strategies (pure stamping/MPF and hybrid strategies) and different surface configurations. Statistical analysis confirms that the forming strategy and surface geometry significantly affect wrinkling and springback, with negligible impact on thickness. In addition, the numerical results prove that the forming strategy is the dominant governing factor in controlling material flow behavior, deformation stability, and overall forming quality, whereas surface geometry critically dictates strain path evolution and stress distribution. Hybrid forming strategies were found to significantly deteriorate wrinkling, springback, and in general, thickness distribution, mainly when applied to complex hybrid free-form surfaces, especially ruled geometries. In contrast, pure forming strategies effectively promote membrane-dominated deformation, resulting in superior wrinkling suppression and reduced residual stress gradients. However, among the explored configurations, the stamp punch–MPF die hybrid strategy exhibited the most favorable performance in terms of thickness uniformity. These findings establish a reliable numerical framework and practical design guidelines for optimizing forming strategies and surface geometries, thereby enhancing dimensional accuracy, structural reliability, and process robustness in advanced free-form sheet metal forming applications.