Two-Step Flange Forming for Wrinkle- and Fracture-Free Press Parts
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Solution Overview
Problem
Existing press forming methods struggle to suppress wrinkles and fractures in the flange portion of automotive parts made from high-strength steel sheets, especially when sheet metal thinning is applied for weight reduction.
Innovation Solution
A two-step press forming method is introduced, where the first forming step creates a preformed part with a torsional shape portion that alleviates excess metal in shrink flange forming, and the second forming step further processes the preformed part to suppress fractures in stretch flange forming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If high-strength steel sheets are used for automotive parts, then weight reduction is achieved, but elongation decreases leading to fracture during material processing
Solution Approach 1:
The flange portion is divided into multiple zones based on wall depth: a first flange portion in a first curved portion (large wall depth) and a second flange portion in a second curved portion (small wall depth). This segmentation allows different forming approaches for different regions, preventing fracture in high-strength steel sheets by accommodating varying material flow requirements across the flange.
2Weight of moving object
If sheet metal thinning is applied for weight reduction, then weight decreases, but buckling and wrinkles occur during press forming
Solution Approach 1:
Different wall depth portions of the flange are formed with different local qualities: the first flange portion (large wall depth) undergoes shrink flange forming while the second flange portion (small wall depth) undergoes stretch flange forming. This local differentiation prevents wrinkles and buckling by matching the forming method to the specific geometric and material requirements of each region.
3Manufacturing precision
If a two-step forming method is used to suppress wrinkles and fractures in the flange, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The forming process is segmented into two steps: first forming the preformed part with the first flange portion in the first curved portion, then forming the second flange portion in the second curved portion. This segmentation enables precise control over material flow in different flange regions, achieving high manufacturing precision while maintaining reasonable process complexity through systematic division of the forming sequence.
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
This method effectively suppresses the occurrence of wrinkles during shrink flange forming and fractures during stretch flange forming, achieving a high-quality press forming part with no defects in the flange portion.
Implementation Method 1
press forming method for forming a press forming part from a metal sheet
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A press forming method according to the present invention forms a press forming part 1, the press forming part 1 including a top portion 3, a side wall portion 5 continuous from the top portion 3 and having a recessed portion 7 in which a bottom edge, which is a side portion on an opposite side of the top portion in a side view, is recessed toward the top portion 3, and a flange portion 9 formed outward on the bottom edge of the side wall portion 5, in which the flange portion 9 undergoes stretch flange forming and shrink flange forming, the method including: a first forming step S1 of forming a preformed part 23, the preformed part 23 including the side wall portion 5, the flange portion 9 formed on a bottom edge of a portion having a large wall depth, and a torsional shape portion 25 formed continuously from the flange portion 9; and a second forming step S3 of further processing the preformed part 23 including processes of forming the torsional shape portion 25 into the flange portion 9 and forming the flange portion 9 in the second curved portion 19 continuous from the inclined side portion 13 and in the recessed side portion 15 having a small wall depth so as to achieve formation of a target shape.