Press-Molded Curved Wall Forming to Suppress Spring-Back
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Solution Overview
Problem
The manufacturing of elongated structural components for automotive bodies, such as roof rails, faces challenges with spring-back and shape fixability due to residual stress and bending issues when high tensile sheet steel is cold pressed, leading to difficulties in achieving the desired shape.
Innovation Solution
A manufacturing method involving a two-stage press process where the first process forms an intermediate component with specific step projections, and the second process narrows these projections to reduce residual stress and bending, using a press apparatus with tailored molds to adjust the angles and widths of the steps to suppress bending and improve shape fixability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high tensile sheet steel is cold pressed to manufacture curved configuration elements, then manufacturing cost is suppressed and strength is increased, but spring-back occurs and shape fixability deteriorates
Solution Approach 1:
A step is formed in advance in the vertical wall portion before final shaping. This preliminary step structure allows residual stress to be released in a controlled manner during subsequent pressing, preventing spring-back and improving shape fixability while maintaining the strength benefits of high tensile sheet steel
Solution Approach 2:
The pressing process is divided into multiple stages: first forming a step in the vertical wall, then removing the blank and performing final pressing. This segmentation allows controlled stress release and prevents the spring-back that would occur in a single-step pressing operation
2Manufacturing precision
If a step is applied to suppress opening-out, then shape fixability is improved, but bending occurs in curved walls and desired shape cannot be formed
Solution Approach 1:
The step is positioned specifically in the vertical wall portion at a predetermined distance from the top plate, not uniformly throughout. This localized step placement allows stress control in critical areas while preserving the curvature and shape of other portions of the configuration element
3Manufacturing precision
If flange is bent back to reduce residual stress, then shape fixability is improved, but deviatoric residual stress arises and bending occurs in pressed component
Solution Approach 1:
The blank is removed from the mold after the step is formed, allowing the structure to be released and stress to redistribute. This extraction and re-positioning enables controlled stress release without creating the deviatoric residual stress that would result from constrained bending operations
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
The method effectively suppresses bending and residual stress in the final component, ensuring better shape fixability and dimensional precision, thereby improving the manufacturing efficiency and quality of elongated structural components.
Implementation Method 1
a first press device presses a blank BL to form an intermediate formed component 30
Implementation Method 2
the projection width of steps 36a, 36a' formed in a first process is narrowed in a second process, thereby reducing residual stress in a vertical wall 4a, 4b
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A pressed component manufacturing method of the present disclosure includes a first process of pressing a blank to form an intermediate formed component configured including a top plate, the ridge lines at short direction ends of the top plate, and vertical walls facing each other in a state extending from the respective ridge lines and at least one of the vertical walls configuring a curved wall curving as viewed from an upper side of the top plate, such that a step projecting toward an opposite side to a side on which the vertical walls face each other is formed to the curved wall so as to run along a length direction of the top plate. The manufacturing method further includes a second process of performing at least one out of pressing the intermediate formed component so as to narrow a projection width of the step, or pressing the intermediate formed component so as to move a portion of the curved wall on an opposite side of the step to a portion of the curved wall on the top plate side of the step toward the opposite side to the side on which the vertical walls face each other.