Hat-Section Press Forming with Chevron Preforms Against Springback
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Solution Overview
Problem
Press-forming methods for hat-shaped cross-section products struggle to maintain accuracy of the flange angle due to springback, especially at the center and end portions, leading to reduced joint precision when forming products that curve along the longitudinal direction.
Innovation Solution
A two-step press forming method where the first step involves forming a preformed part with outwardly projecting chevron-shaped side walls and adjusting the angles and heights to counteract springback, followed by a second step that shapes the side walls to suppress wall curl and maintain flange angle accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If press-forming is performed using high-strength steel sheet, then the strength of the press-formed product is improved, but the angle of the flange portion changes due to springback and manufacturing precision deteriorates
Solution Approach 1:
The patent applies preliminary action by forming a preformed part in the first step with specific geometric features (tapered portions or outwardly projecting chevron-shaped bent portions) that anticipate and counteract the springback that will occur during final forming. This pre-forming creates initial stresses and shapes that compensate for the expected elastic recovery, allowing the final flange angle to achieve the target precision even when using high-strength steel sheets that exhibit significant springback behavior
2Ease of manufacture
If conventional press-forming methods are used, then the process is simple, but the angle accuracy of the flange portion deteriorates due to wall curl at the end portion side
Solution Approach 1:
The patent applies local quality by introducing specific geometric features only at critical locations where springback and wall curl occur most severely. The preformed part includes tapered portions or outwardly projecting chevron-shaped bent portions at the end portion side of the side wall, while other regions maintain conventional geometry. This localized modification targets the specific problem area without complicating the entire forming process, thereby improving angle accuracy at the flange portion while maintaining relative simplicity in manufacturing
3Manufacturing precision
If a preformed part with tapered portions is used, then the springback of the flange is suppressed, but the side wall develops wall curl that reduces flange angle accuracy
Solution Approach 1:
The patent applies inversion by reversing the conventional approach: instead of forming the side wall straight and then creating the flange angle, the preformed part intentionally includes outwardly projecting chevron-shaped bent portions that protrude outwardly from the side wall. These inverted geometric features counteract the wall curl tendency by pre-introducing compensating curvature, allowing the final forming to produce both a straight side wall and accurate flange angle simultaneously
4Shape
If press-forming is performed for products curving along the longitudinal direction, then the product achieves its curved shape, but the angle accuracy of the flange portion deteriorates at both center and end portion sides
Solution Approach 1:
The patent applies local quality by differentiating the preforming geometry between different regions of the curved press-formed product. The preformed part includes outwardly projecting chevron-shaped bent portions with specific angles and dimensions that are tailored to the local curvature requirements. At the end portion side where wall curl is more severe, the bent portions have greater projection, while at the center portion, the geometry is adjusted accordingly. This localized differentiation allows accurate flange angle formation across the entire curved structure
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 reduces the angle change of the flange portion due to springback, ensuring high accuracy and precision in the flange angle across the entire length, enabling accurate joining with other parts.
Implementation Method 1
the angle of the flange portion is changed due to springback after press-forming as the strength increases
Implementation Method 2
press-forming a press-formed product having a hat-shaped cross section
Data Source
Figure 1(a)~1(c)
Figure 2~3
Figure 4(a)~4(b)
AI summary
A press forming method according to the present invention press-forms a press-formed product 1 having a hat-shaped cross section curving along the longitudinal direction in a planar view into a target shape and includes: a first forming step of press-forming a preformed part 11 including a top portion 13 and flange portions 17 of the same shape as the target shape, and side wall portions 15 in an outwardly projecting chevron shape as compared with the target shape; and a second forming step of press-forming the preformed part 11 into the press-formed product 1 of the target shape. Each of the side wall portions 15 in the first forming step includes a side wall portion adjacent to top 15a, a side wall portion adjacent to flange 15b, and a bent portion 15c, and an angle formed by the side wall portion adjacent to top 15a and a horizontal plane is set to decrease toward an end portion from the center in the longitudinal direction.