Press Forming of Convex-Concave Flanges Without Wrinkles or Fractures
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Solution Overview
Problem
Existing press forming methods struggle to suppress wrinkles and fractures in the flange portion of press forming parts, especially when forming parts with convex and concave outer edges.
Innovation Solution
A two-step press forming method is employed, where the first step forms a preformed part with a torsional shape portion that alleviates excess metal in shrink flange forming, and the second step forms the flange portion in the concave outer edge part, dispersing strain and preventing material shortage-induced fractures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high-strength steel sheet is used for weight reduction, then the strength of the automotive part is improved, but the elongation decreases leading to fracture during material processing
Solution Approach 1:
The forming process is segmented into two distinct steps: a first forming step that creates a preformed part with controlled material distribution, and a second forming step that achieves the final target shape. This segmentation allows the high-strength steel sheet to be formed without excessive strain in a single step, preventing fracture while maintaining the required strength.
Solution Approach 2:
The first forming step performs a preliminary action by creating a preformed part with a specific material distribution pattern before the final forming. This preliminary action pre-distributes the material to reduce strain concentration during the second forming step, enabling the use of high-strength steel sheets without fracture.
2Weight of moving object
If thinning of the sheet is performed for further weight reduction, then the weight of the automotive part is reduced, but the likelihood of buckling and wrinkles increases
Solution Approach 1:
The forming process is divided into two steps that separately address different regions of the sheet. The first forming step focuses on the flange portion to control material distribution and prevent wrinkles, while the second step forms the top portion without causing buckling, enabling thin sheet formation with maintained surface quality.
Solution Approach 2:
The first forming step creates a preformed part with locally optimized material distribution, particularly in the flange portion. This local quality control ensures that thin sheets have sufficient material density in critical areas to resist buckling and wrinkles during the final forming step.
3Manufacturing precision
If a wrinkle suppression pad is used to hold down the inside of the product, then wrinkles inside the product are suppressed, but the technique cannot be applied to shapes with wrinkles or fractures in the flange portion itself
Solution Approach 1:
The forming process is segmented into two steps with different focus areas. The first forming step specifically addresses the flange portion to prevent wrinkles and fractures during material distribution, while the second step forms the top portion. This segmentation enables the technique to handle flange portion defects that the single-step pad method cannot address.
Solution Approach 2:
The first forming step performs a preliminary action on the flange portion to establish proper material distribution and prevent wrinkles and fractures before the main forming operation. This preliminary flange formation enables the subsequent formation of complex top portions without the limitations of using a wrinkle suppression pad throughout the entire process.
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 in the first forming step and fractures in the second forming step, resulting in a high-quality press forming part with reduced defects.
Implementation Method 1
a torsional shape portion having a torsional shape toward the concave outer edge part so as to be formed in the connecting outer edge part continuous from the flange portion
Data Source
AI summary
A press forming method forms a press forming part including: a top portion having a convex and concave outer edge part where a convex outer edge part protruding outward in an in-plane direction and a concave outer edge part recessed inward in the in-plane direction are continuous to each other via a connecting outer edge part; and a flange portion continuously formed on the convex and concave outer edge part, and includes: forming a preformed part including a flange portion formed in the convex outer edge part and including a torsional shape portion having a torsional shape toward the concave outer edge part so as to be formed in the connecting outer edge part continuous from the flange portion; and forming the preformed part into a target shape by forming the torsional shape portion into the flange portion and forming the flange portion in the concave outer edge part.