Bent Member Manufacturing Using Segmented High-Strength Steel
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Solution Overview
Problem
Conventional press forming methods for high-strength steel sheets with tensile strength greater than 590 MPa often result in defects such as wrinkles and cracks, especially when forming complex curved parts, and struggle to achieve both high strength and complex shapes while reducing weight.
Innovation Solution
A method involving two blanks with a side-bend outline corresponding to the target curved part shape, where the blanks are bent and joined using a die to form the desired shape without drawing, stretch forming, or stretch flanging, reducing plate thickness and eliminating the need for reinforcing parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If high-strength steel sheets with tensile strength greater than or equal to 590 MPa are used to reduce weight, then weight reduction is achieved, but drawing ability, stretch forming ability, and stretch flanging ability are reduced causing wrinkles and cracks
Solution Approach 1:
The blank is divided into a plurality of bent portions, each bent along different folding lines to form different curved surfaces. This segmentation allows each portion to be bent independently along its folding lines, avoiding the need for complex drawing and stretch flanging operations that would cause wrinkles and cracks in high-strength steel sheets.
Solution Approach 2:
Instead of forming curved parts by drawing and stretching the steel sheet (conventional approach), the invention inverts the approach by bending the steel sheet along pre-determined folding lines. This reverse approach avoids the harmful drawing and stretch flanging processes that cause defects in high-strength materials.
2Shape
If conventional press forming is used to form complex curved parts, then complex shapes can be obtained, but wrinkles occur in planar sections and cracks occur in vertical walls and flanges
Solution Approach 1:
Folding lines are determined in advance based on the target curved part shape, and the blank is designed with these folding lines marked. The bending operations are then performed sequentially along these pre-determined folding lines, ensuring that each bend is controlled and predictable, thereby preventing wrinkles and cracks before they occur.
Solution Approach 2:
The invention changes the forming parameters by specifying bending angles and folding line positions that are optimized for high-strength steel sheets. By controlling the bending parameters (angle, position, sequence) rather than using conventional drawing parameters, the process achieves complex curved shapes without causing defects.
3Shape
If the shape of curved parts becomes more complex, then functional requirements are met, but the ability to obtain curved parts by conventional press forming is reduced
Solution Approach 1:
Complex curved shapes are achieved by dividing the blank into multiple bent portions, each with its own folding lines. This segmentation transforms a single complex forming operation into multiple simpler bending operations, making it feasible to manufacture complex shapes in high-strength steel sheets that would otherwise be impossible to form.
4Ease of manufacture
If low-strength steel sheets are used to achieve complex curved shapes, then formability is improved, but part strength becomes insufficient requiring additional reinforcing parts which increases weight
Solution Approach 1:
The invention changes the material parameter by using high-strength steel sheets (tensile strength ≥ 590 MPa) instead of low-strength sheets. By combining this material parameter change with the bending process parameter changes (folding lines, bending angles), the invention achieves both high strength and complex curved shapes without requiring additional reinforcing parts.
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
Enables the production of high-strength, complex curved parts with reduced weight and minimal defects, such as wrinkles or cracks, by reflecting the target shape in the blank outline and using a die to form the parts without excessive deformation.
Implementation Method 1
a method involving two blanks with a side-bend outline corresponding to the target curved part shape, where the blanks are bent and joined using a die to form the desired shape without drawing, stretch forming, or stretch flanging
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A curved-part forming method includes a bending process in which blanks 1 and 2 having a curved outline corresponding to a curve of a curved part 30 in a longitudinal direction is bent into a sectional shape corresponding to a division portion of a sectional shape of the curved part, and a joining process in which two (or three of more) portions 10 and 20 obtained by the bending process are joined together. In a conventional forming method, when single high-strength steel sheets are used are materials, forming into desired curved parts cannot be achieved by one-piece press forming; or, when single low-strength steel sheets are used as materials, forming into curved parts can be achieved, but the parts lack strength. Therefore, the parts have insufficient strength, as a result of which weight is increased due to an increase in the number of reinforcing parts.