Hat-Shaped Metal Member Two-Stage Forming Springback Control
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Solution Overview
Problem
Existing methods fail to effectively improve the shape freezing property of hat-shaped cross section members with bent portions in the longitudinal direction, particularly those with flange portions positioned outside, as they suffer from significant springback and hanging down issues in three-dimensional shapes.
Innovation Solution
A two-stage forming method is employed, where the die shoulder radius is set to a range of 1.1 to 3.5 times the initial radius, with the first stage using a larger radius to manage tensile stress and the second stage using the initial radius to minimize compressive stress, thereby reducing springback and improving shape accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional single-stage forming method is used, then the manufacturing process is simple, but the shape freezing property deteriorates due to significant springback and hanging down in the longitudinal direction
Solution Approach 1:
The forming process is divided into two distinct stages: a first forming stage that creates initial deformation, and a second forming stage that achieves the final precise shape. This segmentation allows each stage to be optimized independently, with the first stage handling rough shaping and the second stage correcting springback and achieving dimensional accuracy, thereby resolving the contradiction between manufacturing precision and process complexity.
Solution Approach 2:
The first forming stage performs preliminary deformation on the metal sheet before the final forming stage. By pre-deforming the material in a controlled manner with specific tool radii, the process prepares the material state for the second stage, enabling better shape freezing property and reduced springback in the final product while maintaining a manageable two-stage process structure.
2Manufacturing precision
If existing forming methods from JP-A-2004-181502 or JP-A-2007-21568 are applied, then certain shape properties are improved, but they are not applicable to hat-shaped members with flange portions positioned outside
Solution Approach 1:
The two-stage forming method with specific die radius relationships (R1 > R0 in first stage, R1 = R0 in second stage) is designed to be universally applicable to hat-shaped cross-section members with flange portions positioned outside. The method addresses the specific geometric constraints of this configuration while maintaining a systematic approach that can be adapted to various dimensions and specifications, thereby achieving both shape accuracy and configurational adaptability.
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 drastically decreases hanging down caused by springback in the longitudinal direction, enhancing the shape freezing property of metal members with vertical wall portions and flange portions connected to them.
Implementation Method 1
a first stage forming in which the hat-shaped cross section member is formed by a die having a die shoulder radius R1 larger than a die shoulder radius R0
Implementation Method 2
springback ascribable to residual stress occurs, and as indicated by a dotted line in Fig. 2, hanging down in three-dimensional directions occurs in the longitudinal direction based on the bending point
Data Source
Figure 1~2
Figure 3~4B
Figure 5
AI summary
When forming a hat-shaped cross section member having, on its cross section perpendicular to its longitudinal direction, vertical wall portions (1b and 1b) on both sides, flange portions (1a and 1a) on both sides connected to the respective vertical wall portions (1b and 1b), and a top sheet portion (1c) connected to the vertical wall portions (1b and 1b) on both sides, and having a bent portion (2) bent in the longitudinal direction with the flange portions (1a and 1a) positioned outside by using punches (5) and dices (4), a dice shoulder radius of the dice (4) for obtaining the final shape of the hat-shaped cross section member is set to R0, the hat-shaped cross section member is formed by the dice (4) having a dice shoulder radius R1 larger than the dice shoulder radius R0, and then the hat-shaped cross section member is formed by the dice (4) having the dice shoulder radius R0. By performing the forming at two stages as above, stress relaxed in a compressing direction acts in the flange portions (1a and 1a) in the final shape, and thus the balance of tensile-compressive stresses can be minimized.