Pressed Component Forming With Ridgelines to Prevent Flange Cracking
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Solution Overview
Problem
Existing methods for manufacturing vehicle body frame components with high tensile strength materials face issues with sporadic stretch flange cracking due to fluctuations in material movement during bending, especially in mass production, and often result in surface defects and increased costs.
Innovation Solution
A method involving press forming with a die structure that includes ridgelines on the lower die and pad to control material movement, applying out-of-plane deformations, reducing sporadic stretch flange cracking by stabilizing material movement through controlled bending and unbending resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If pad bending-based method is used to avoid cracking when press forming high tensile strength materials, then cracking is avoided, but stretch flange cracking frequently occurs at flange end of curved portion
Solution Approach 1:
The method applies preliminary bending to the flange portion before main forming, creating a pre-formed shape that prevents stretch flange cracking during subsequent pressing operations. This preliminary action prepares the material in advance to avoid cracking issues.
Solution Approach 2:
The forming process is divided into multiple stages: first bending the flange portion to a predetermined shape, then performing main forming. This segmentation of the forming process allows each stage to address specific requirements, preventing cracking while achieving the final shape.
2Reliability
If method in PTL 1 is used to improve stretch flange cracking by allowing material movement under pad, then cracking is reduced, but moving amount fluctuates due to friction changes, causing sporadic cracking
Solution Approach 1:
The flange portion is bent to a predetermined shape before main forming, establishing a stable initial configuration. This preliminary action ensures consistent material distribution and movement characteristics during subsequent pressing, eliminating fluctuations caused by friction changes.
Solution Approach 2:
The method changes the forming sequence and material state parameters by pre-bending the flange portion. This parameter change transforms the material configuration before main forming, ensuring stable and predictable material movement behavior throughout the process.
3Reliability
If method in PTL 2 is used to avoid stretch flange cracking by forming bead and steps, then cracking is prevented, but cost increases and surface defects occur
Solution Approach 1:
The flange portion is bent to a predetermined shape as a preliminary step before main forming. This approach avoids the need for complex bead and step formations while still preventing stretch flange cracking, thereby reducing manufacturing cost and avoiding surface defects.
Solution Approach 2:
The method extracts and eliminates the unnecessary bead and step forming steps from the process, keeping only the essential flange portion bending. This simplification reduces manufacturing complexity and cost while maintaining the effectiveness of preventing stretch flange cracking.
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
Stable production of L- or T-shaped components with reduced sporadic stretch flange cracking and lower costs, even with high tensile strength materials, by controlling material movement during bending using ridgelines on the die and pad.
Implementation Method 1
applying an out-of-plane deformation (having a mountain-shaped cross section) on the metal sheet portion by the sandwiching
Implementation Method 2
the moving amount and the moving rate of a portion sandwiched by the die (lower die) and the pad during the forming are governed by a frictional force between the die (the pad or the punch) and the blank material
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
Provided is a technology capable of simply and more stably suppressing stretch flange cracking in a curved portion. A material is press formed into a component shape including a top sheet portion (2) including a curved outer peripheral edge portion (2a) curved in such a manner as to be recessed inward, a vertical wall portion (3A) continuous with the curved outer peripheral edge portion (2a), and a flange portion (4A) continuous with the vertical wall portion (3A). In a state where a lower die (20) and a pad (30) sandwich a sandwiching region (P) that is a region including at least a part of a region corresponding to the top sheet portion (2), an upper die (40) is moved in a pressing direction to perform bending while moving the sandwiched material to the vertical wall portion 3 side. A surface of the lower die (20) that sandwiches the sandwiching region (P) is provided with one or more ridgelines (20a) for forming bends. The ridgelines (20a) are set at positions such that, in a state where the bending is complete, the position of the top sheet portion (2) is located on the vertical wall portion (3) side rather than the positions of the ridgelines (20a).