Two-Step Press Forming for Wrinkle-Free High-Strength Flanges
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional press forming methods struggle to suppress wrinkles and fractures in the flange portion of automotive parts made from high-strength steel sheets, particularly when thinning is required for weight reduction, as they concentrate compressive and tensile strains, leading to material defects.
Innovation Solution
A two-step press forming method is employed, where the first step forms a preformed part with a torsional shape to alleviate excess metal in shrink flange forming, and the second step forms the flange portion to address material shortages in stretch flange forming, dispersing strain concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If high-strength steel sheets are used for weight reduction, then weight decreases, but elongation deteriorates causing fracture during material processing
Solution Approach 1:
The press forming process is segmented into two distinct steps: first forming a preformed part with reduced flange, then forming the final shape. This segmentation allows different regions of the material to experience different strain conditions at different times, preventing simultaneous fracture in multiple areas.
Solution Approach 2:
The first forming step performs preliminary action by creating a preformed part with reduced flange before the final forming. This preliminary reduction of excess metal in the flange area prevents material accumulation that would cause wrinkles during the subsequent final forming step.
2Weight of moving object
If thinning of the sheet is performed for weight reduction, then weight decreases, but buckling and wrinkles occur during press forming
Solution Approach 1:
The forming process is divided into two steps where the first step addresses shrink flange forming and the second step addresses stretch flange forming separately. This segmentation allows precise control of material flow in each step, preventing wrinkles and maintaining surface quality on thin sheets.
Solution Approach 2:
The invention changes the forming parameters by introducing an intermediate preformed state with reduced flange. This parameter change in the forming sequence allows thin sheets to be formed without wrinkles by controlling material flow at each stage rather than attempting single-step forming.
3Ease of manufacture
If conventional press forming methods are used, then manufacturing simplicity is maintained, but wrinkles and fractures occur in the flange portion
Solution Approach 1:
The conventional single-step forming is segmented into two steps: first forming with reduced flange, then final forming. This segmentation resolves the contradiction by accepting increased process complexity in exchange for eliminating wrinkles and fractures in the flange portion.
Solution Approach 2:
The first forming step performs preliminary action by creating a preformed part with reduced flange. This preliminary reduction of excess metal prevents material accumulation that would cause wrinkles during final forming, thereby improving flange quality despite added process steps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively suppresses wrinkles and fractures in the flange by redistributing material flow, ensuring high-quality formation of press forming parts with convex and concave features.
Implementation Method 1
forming a blank made of a metal sheet into a preformed part; and forming the preformed part into a target shape
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A press forming method according to the present invention forms a press forming part, the press forming part including: a top portion 3 having a convex and concave outer edge part 11 in which a convex outer edge part 11a protruding outward in an in-plane direction and a concave outer edge part 11b recessed inward in the in-plane direction are continuous to each other via a connecting outer edge part 11c; and a flange portion 5 continuously formed on the convex and concave outer edge part 11 of the top portion 3. The press forming method includes: a first forming step S1 of forming a preformed part 15 including the flange portion 5 formed in the convex outer edge part 11a and including a torsional shape portion 17 having a torsional shape toward the concave outer edge part 11b so as to be formed in the connecting outer edge part 11c continuous from the flange portion 5; and a second forming step S3 of forming the preformed part 15 formed in the first forming step S1 into a target shape by forming the torsional shape portion 17 into the flange portion 5 and forming the flange portion 5 in the concave outer edge part 11b.