Hat-Section Press Forming With Wavy Preform to Suppress Spring-Back
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Solution Overview
Problem
Existing press forming methods for vehicle frame components with curved shapes prone to cracks, wrinkles, and dimensional inaccuracies due to material stress differences and spring-back, especially with high-strength steel sheets.
Innovation Solution
A two-step press forming process involving a first stretch forming step to create a wavy shape on the metal sheet followed by a second bending step to form the desired component shape, with controlled line length differences and amplitude adjustments to minimize material stress and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high strength steel sheet is used to achieve vehicle lightweighting and collision safety, then material strength increases, but ductility decreases causing large spring-back and forming defects
Solution Approach 1:
The patent applies preliminary action by performing a first forming step before the final forming step. In this first forming step, a preliminary formed body is created with a predetermined angle θpa that is larger than the final required angle θp. This preliminary deformation pre-stretches the material and reduces spring-back in the subsequent forming operation, enabling accurate formation of high strength steel sheets.
Solution Approach 2:
The patent changes geometric parameters to solve the contradiction. Specifically, it introduces a preliminary formed body with angle θpa > θp, and controls the curvature radius R1 in the curved portion to be 50mm or more. These parameter adjustments optimize the stress distribution and reduce spring-back, maintaining forming accuracy while using high strength materials.
2Productivity
If simple press forming is applied to curved components, then production efficiency is maintained, but cracks and wrinkles occur due to material stress differences
Solution Approach 1:
The patent segments the forming process into two distinct steps: a first forming step that creates a preliminary formed body with specific geometric parameters, and a second forming step that achieves the final component shape. This segmentation allows each step to be optimized independently - the first step prepares the material to prevent defects, while the second step achieves the final shape, thereby maintaining both productivity and reliability.
Solution Approach 2:
The first forming step serves as a preliminary action that creates optimal material conditions before final forming. By forming the preliminary body with angle θpa > θp and controlled curvature radius R1, the material is pre-conditioned to resist cracking and wrinkling during the subsequent forming operation, ensuring high component quality.
3Device complexity
If conventional forming methods are used for curved portions, then process simplicity is maintained, but dimensional accuracy deteriorates due to spring-back and stress differences
Solution Approach 1:
The patent introduces a preliminary formed body as an intermediate stage that compensates for spring-back before final forming. The preliminary body has angle θpa > θp and curvature radius R1 ≥ 50mm, which are specifically designed to offset the elastic recovery that occurs during forming, thereby achieving high dimensional accuracy in the final component.
Solution Approach 2:
The patent changes key geometric parameters - introducing preliminary angle θpa > θp and controlling curvature radius R1 ≥ 50mm - to compensate for spring-back. These parameter modifications are integrated into the forming process design, achieving high dimensional accuracy while maintaining reasonable process complexity.
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
Reduces forming defects such as cracks, wrinkles, and dimensional inaccuracies, while suppressing spring-back in components with hat-shaped cross-sections featuring curved portions towards flanges.
Implementation Method 1
When producing such a vehicle frame component from a flat metal sheet by press forming, a crack or a wrinkle may be formed on a part of the component
Implementation Method 2
problems may occur such as lowered dimensional accuracy due to elastic recovery in formed product after release
Data Source
Figure 1A~1C
Figure 2A~2K
Figure 3~4
AI summary
Provided is a press forming technology capable of reducing forming defects in a formed component having a hat-shaped cross-sectional shape and including a shape curved in such a manner as to protrude toward a flange portion as seen in a side view. The technology includes a first forming step (9A) of press forming a metal sheet (10) into an intermediate formed product (40) that includes a wavy shape including uneven shapes continuous along a longitudinal direction in a vertical wall portion forming position (13) and a flange portion forming position (14), an amplitude of the uneven shapes in a sheet thickness direction increasing toward a position corresponding to a boundary between the vertical wall portion (3) and the flange portion (4), and a second forming step (9B) of performing bending on the intermediate formed product (40). A longitudinal line length at the position corresponding to the boundary between the vertical wall portion (3) and the flange portion (4) in the intermediate formed product (40) is set to coincide with or approach a longitudinal line length at the boundary between the vertical wall portion (3) and the flange portion (4) in the press-formed component shape (1).