Pressed Roof Rail Forming to Suppress Spring-Back Twisting
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Solution Overview
Problem
The manufacturing of automotive structural components with complex elongated profiles, such as roof rails, faces challenges with shape fixability due to spring-back and residual stress issues when using high tensile sheet steel, leading to bending and twisting problems during the cold pressing process.
Innovation Solution
A two-stage pressing method is employed, where an intermediate formed component is first created with a preliminary flange, and then the flange is deformed to progressively change the angle between its corner and the sharp curve portion along the length direction, reducing residual stress and bending by adjusting the flange's angle and length during the second pressing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high tensile sheet steel is cold pressed to manufacture curved configuration elements, then strength is improved and vehicle body weight is reduced, but spring-back occurs during press mold removal leading to twisting in the top plate and poor shape fixability
Solution Approach 1:
The patent divides the forming process into two distinct stages: a first pressing process that forms the basic configuration element shape, and a second pressing process that specifically addresses the curved portions. This segmentation allows each process to be optimized for its specific function, with the second process specifically targeting the reduction of spring-back in curved sections through controlled deformation and stress relief.
Solution Approach 2:
The first pressing process performs preliminary forming of the configuration element, creating the basic shape including the top plate, vertical walls, and flanges. This preliminary action prepares the workpiece for the second pressing process by establishing the initial geometry and stress distribution, making the subsequent curved portion forming more effective in controlling spring-back.
2Device complexity
If a single pressing process is used to form curved configuration elements, then manufacturing complexity is reduced, but bending occurs in curved walls due to spring-back after mold removal, preventing desired shape formation
Solution Approach 1:
The forming operation is segmented into two distinct pressing processes with different objectives. The first process forms the basic shape, while the second process specifically targets the curved portions. This segmentation, while increasing process steps, allows each process to be simpler and more specialized, with the second process using a specifically designed press mold with curved surface portions that match the target geometry to ensure accurate shape formation.
Solution Approach 2:
The first pressed component serves as an intermediary workpiece between the initial blank and the final configuration element. It contains the basic geometry and preliminary stress distribution, which the second pressing process then modifies by applying controlled deformation to the curved portions. This intermediary stage enables the final process to focus specifically on achieving the desired curved shape with minimal spring-back.
3Weight of moving object
If high tensile sheet steel is used for thickness reduction to improve fuel consumption, then weight is reduced and fuel efficiency is improved, but residual stress arises in the flange and vertical walls leading to bending after mold removal
Solution Approach 1:
The patent converts the harmful residual stress and spring-back effects into beneficial outcomes through the second pressing process. By intentionally applying controlled deformation to the curved portions in the second process, the method creates complementary stress distributions that counterbalance the residual stresses from the first process. This transforms the problematic spring-back into a mechanism that, when properly controlled, achieves the desired final shape with reduced net residual stress.
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 bending and twisting in the final pressed component, ensuring better shape fixability and reducing residual stress, thereby improving the manufacturing process for automotive structural components.
Implementation Method 1
a first pressing to form an intermediate formed component... a second pressing to deform the preliminary flange
Implementation Method 2
high tensile sheet steel... cold pressed... deform the preliminary flange
Implementation Method 3
spring-back occurs during press mold removal... bending occurs in curved walls as a result of spring-back after removal from the mold
Data Source
AI summary
A method for manufacturing a pressed component including an elongated top plate, a wall having one end connected to a short direction end portion of the top plate, that curves with a convex shape bowing toward an opposite side to the top plate as viewed from an upper side of the top plate, and that includes a sharp curve portion, and a flange that is connected to another end of the wall, and that extends in a plate thickness direction of the wall toward the opposite side to the top plate side. The manufacturing method includes pressing to form an intermediate formed component including a preliminary flange and pressing to deform the preliminary flange to form the preliminary flange into the flange.