Press-Formed Outward Flange Without Cutouts in High-Strength Steel
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Solution Overview
Problem
Conventional press-forming methods struggle to form floor cross members from high-tensile strength steel sheets without cutouts, leading to issues like stretch flange fractures and wrinkling, which compromise the rigidity and joint strength of the press-formed articles.
Innovation Solution
A press-formed article and method that involve shearing deformation to form a stepped portion with an outward flange without cutouts, using a first and second punch and die to restrict parts of the workpiece, allowing the flange to be formed continuously from the top sheet to the flange via convex and concaved ridge line portions, with specific thickness and angle constraints to enhance rigidity and joint strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional press-forming methods (drawing or bending) are used to form floor cross members from high-tensile strength steel sheets, then the material can be formed, but stretch flange fractures and wrinkling occur, compromising the rigidity and joint strength
Solution Approach 1:
The press-forming process is divided into two distinct stages: first forming the main body of the floor cross member, then separately forming the outward flange at the end portion. This segmentation allows each stage to be optimized independently, preventing the simultaneous occurrence of fractures and wrinkles that plague conventional single-stage forming methods.
Solution Approach 2:
The main body of the floor cross member is formed first, creating a preliminary structure with controlled material flow. Subsequently, the outward flange is formed in a second step, allowing the material to be progressively deformed without exceeding the formability limits of high-tensile strength steel sheets, thereby preventing fractures and wrinkling.
2Reliability
If cutouts are provided in the outward flange to prevent forming failures, then the joint strength is reduced, but the forming process becomes more reliable
Solution Approach 1:
By segmenting the forming process into two stages, the patent eliminates the need for cutouts in the outward flange. The controlled sequential deformation allows the flange to be formed continuously without material failure, maintaining both forming reliability and joint strength simultaneously.
3Weight of moving object
If high-tensile strength steel sheets are used to reduce vehicle weight, then the weight is reduced, but the formability decreases, making it difficult to form complex shapes without fractures
Solution Approach 1:
The two-stage press-forming process segments the complex deformation into manageable steps, each within the formability limits of high-tensile strength steel sheets. This enables the use of lightweight high-strength materials while successfully forming the complex shape of the floor cross member with outward flanges.
Solution Approach 2:
The preliminary formation of the main body creates a favorable stress state and material distribution that facilitates the subsequent formation of the outward flange. This preliminary action reduces the forming difficulty and prevents fractures when using high-tensile strength steel sheets.
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 solution enables the formation of press-formed articles with enhanced rigidity and joint strength, improving bending and twisting rigidity, steering stability, and noise reduction in automotive applications without the need for cutouts, thus overcoming the limitations of conventional methods.
Implementation Method 1
a shearing step that shears and deforms a workpiece in which a cross section perpendicular to a predetermined direction has a top sheet portion, a sidewall continuing to the top sheet portion via a convex ridge line portion, and a flange continuing to the sidewall via a concaved ridge line portion
Data Source
Figure 1~2A
Figure 2B~2D
Figure 2E~3
AI summary
This press-formed article includes: a top sheet portion; a sidewall continuing to the top sheet portion via a convex ridge line portion; a flange continuing to the sidewall via a concaved ridge line portion; and an outward flange continuing from an edge portion of the top sheet portion to an edge portion of the flange, via an edge portion of the convex ridge line portion, an edge portion of the sidewall, and an edge portion of the concaved ridge line portion, wherein in the same unit, an average thickness TAve, a minimum thickness TMin, and a maximum thickness TMax of the outward flange satisfy Equation 1 and Equation 2. 0.8×TAve≤TMin<TAve TAve<TMax≤1.2×TAve