Press Forming Fold Structure for Crack-Resistant Stretch Flanges
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Solution Overview
Problem
Existing methods for manufacturing components with curved portions orthogonal to a top plate are prone to cracks in the stretch flange area due to material flow, which is only partially formed, leading to tensile stress and potential material thinning.
Innovation Solution
A method involving a first and second press mold configuration that forms a fold along the longitudinal direction of the flange portion, generating compressive stress to counteract tensile stress and inhibit crack formation, while allowing for the removal of excess material post-forming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If material is invited to flow into the inner circumference of the curved portion using a material inflow facilitating portion, then the curved portion can be formed, but cracks occur in the stretch flange area due to tensile stress
Solution Approach 1:
The patent applies preliminary anti-action by forming a fold in the extension portion before the main forming process. This fold creates compressive stress that counteracts the tensile stress generated during stretch flange formation, preventing crack occurrence while enabling the curved portion to be formed successfully
Solution Approach 2:
The patent changes the stress state parameter in the extension portion by introducing a fold structure. This transforms the stress distribution from purely tensile to a combination of compressive and tensile stresses, where the compressive stress from the fold balances the tensile stress during forming, thereby preventing material failure
2Ease of manufacture
If the extension portion is removed after forming, then subsequent processing becomes easier, but additional processing steps are required
Solution Approach 1:
The patent applies preliminary action by forming the fold structure in advance during the main forming process. This preliminary fold creation enables the extension portion to be easily removed in subsequent steps, as the fold already defines the separation line and reduces the effort needed for material removal
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 approach effectively reduces crack occurrence and maintains material thickness in the stretch flange area, enhancing the strength and ease of subsequent processing by relieving tensile stress and allowing for optional processing steps.
Implementation Method 1
In the flange portion having a shape curved to form the stretch flange, tensile stress is generated during its forming step, and cracks may occur. However, the aforementioned configuration makes it possible to obtain the following actions and effects. Specifically, the fold extends along a longitudinal direction of the outer-side edge of the flange portion and is thus curved in the same way as the flange portion. Therefore, the extension portion on the outer side relative to the fold is also a portion where the stretch flange is formed. Since tensile stress is also generated in the extension portion, as a reaction to this, compressive stress is generated in proximity to the fold. Compressive stress may relieve tensile stress in the flange portion.
Data Source
AI summary
Provided is a manufacturing method of a formed product by pressing a blank with a first press mold and a second press mold. The blank includes a top plate portion corresponding portion, a vertical wall corresponding portion, and an extension portion. The manufacturing method includes pressing the blank with the first press mold and the second press mold and forming a top plate portion, a vertical wall portion, and a flange portion while forming a fold on the extension portion. The flange portion is a portion that is formed of the extension portion and that extends from an outer-side edge of the vertical wall portion in a direction intersecting with the vertical wall portion, and the flange portion has a shape curved to form a stretch flange. The fold extends along a longitudinal direction of an outer-side edge of the flange portion.