Press Forming Tool for Wrinkle- and Fracture-Resistant Flanges

The press forming process is divided into two distinct stages: initial forming with a lower pad to create basic geometry, and subsequent forming with a lower die to complete the flange portions. This segmentation allows each stage to be optimized independently - the first stage prepares the material without causing fractures, while the second stage completes the forming with proper strain distribution, thereby enabling the use of high-strength steel sheets that would otherwise fracture during single-stage forming.

The initial forming stage performs preliminary action by creating the basic geometry of the press forming part including the top portion and side wall portion before the final forming stage. This preliminary forming prepares the material in a controlled manner, reducing strain concentration in critical areas before the second forming stage completes the flange portions, thus preventing fractures in high-strength steel sheets.

The two-stage forming process segments the deformation history to control material flow and strain distribution. The initial forming stage with the lower pad creates the basic shape with controlled thinning, while the subsequent forming stage with the lower die completes the flange portions with optimized strain distribution. This segmentation prevents excessive localized thinning that would lead to buckling and wrinkles in thinned high-strength steel sheets.

The invention changes the forming parameters by using different tool configurations for different stages: a lower pad for initial forming and a lower die for subsequent forming. This parameter change allows optimization of the forming process for thinned materials, controlling material flow and strain distribution to suppress buckling and wrinkles while maintaining weight reduction benefits.

The invention segments the forming process into two stages with different tool configurations. The first stage uses a lower pad for initial forming, and the second stage uses a lower die specifically for forming the flange portions. This segmentation allows the process to address both internal wrinkle suppression and flange portion forming, making the technique versatile for complex geometries that were previously无法 handled.

The initial formed shape acts as an intermediary between the blank and the final formed part. The lower pad creates this intermediate shape that prepares the material for the subsequent forming stage. This intermediary shape allows controlled material flow and strain distribution, enabling the final forming stage to create flange portions without wrinkles or fractures, thus extending the technique's applicability.