Hat-Section Press Forming Using Twisted Side Wall Preforming
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Solution Overview
Problem
Existing press forming methods for automotive parts with hat-shaped cross sections face challenges in preventing fractures and wrinkles, particularly in high-strength steel sheets, due to limitations in applicability, versatility, and surface accuracy requirements.
Innovation Solution
A two-stage press forming method that includes a first process to preform a twisted side wall portion with a specific torsion amount, generating in-plane shear deformation to reduce line length differences between web and flange portions, and a second process to form the final product, ensuring the web and flange portions are concavely curved in the height direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If high-strength steel sheets are used for body parts, then weight reduction is achieved, but forming defects such as fractures and wrinkles occur
Solution Approach 1:
The patent divides the press forming process into two distinct stages: a first forming process that creates a preformed part with reduced curvature, and a second forming process that achieves the final curved shape. This segmentation allows each stage to optimize for different requirements, preventing forming defects in high-strength steel sheets
Solution Approach 2:
The first forming process performs preliminary shaping by creating a preformed part with reduced curvature before the final forming. This preliminary action prepares the material in a more favorable state for the second forming process, reducing the risk of fractures and wrinkles when forming the final curved shape
2Strength
If a folding portion is added to increase stiffness, then resistance against shrinking force increases, but the technique has limited applicability to certain part shapes
Solution Approach 1:
Instead of adding a folding portion at the end portion, the patent applies local quality changes by reducing curvature specifically at the concave curved portion where it is most needed. This localized approach provides the necessary stiffness and control without the geometric constraints of a folding portion, enabling broader applicability to various part shapes
3Manufacturing precision
If beads are added to suppress wrinkles, then wrinkle occurrence is reduced, but the technique requires additional structural elements that increase complexity
Solution Approach 1:
The patent changes the curvature parameter of the concave curved portion to create a preformed part with reduced curvature. This parameter change inherently suppresses wrinkle formation by reducing the excess material that would otherwise require beads for control, thereby simplifying the overall structure and eliminating the need for additional bead elements
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 fractures and wrinkles in the press-formed product by inducing shear deformation, allowing for the formation of automotive parts with high surface accuracy and reduced line length differences, thereby enhancing the press formability of hat-shaped cross-sectioned products.
Implementation Method 1
A two-stage press forming method that includes a first process to preform a twisted side wall portion with a specific torsion amount, generating in-plane shear deformation to reduce line length differences between web and flange portions
Data Source
AI summary
A press forming method forms a press-formed product having a hat-shaped cross section and includes: a first forming process of press-forming a preformed part in which a portion corresponding to web corresponding to a web portion, and a portion corresponding to side wall corresponding to a side wall portion and including a twisted side wall portion of a twisted shape along the longitudinal direction, are formed, the preformed part including a portion corresponding to concave curve corresponding to the concave curved portion; and a second forming process of press-forming the preformed part into the press-formed product. The twisted side wall portion at the first forming process is twisted such that an angle between the twisted side wall portion and the portion corresponding to web is smaller on an end portion side than at a longitudinal center of the portion corresponding to concave curve.