Two-Step Press Forming of Curved Flanges to Suppress Spring-Back
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for producing press-formed vehicle frame components with curved shapes suffer from defects like cracks, wrinkles, and reduced dimensional accuracy due to material shortages and excesses, as well as spring-back issues caused by high tensile strength steel sheets.
Innovation Solution
A two-step press forming method involving stretch forming in the first step to create an intermediate product with a projection shape, followed by bending in the second step to form ridge lines, where the angle and projection height are carefully controlled to minimize material differences and stress differences between the top sheet and flange portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thin high strength steel sheet is used for press forming, then vehicle lightweighting and collision safety are achieved, but ductility decreases and large spring-back occurs causing cracks, wrinkles, and poor dimensional accuracy
Solution Approach 1:
The patent applies preliminary action by performing a first forming step before the final forming step. In this first step, an intermediate formed product is created with a top sheet portion having a smaller curvature radius that projects in excess, and flange portions with increased line length. This preliminary deformation prepares the material distribution and stress state to prevent cracks, wrinkles, and excessive spring-back in the final high-strength steel component.
Solution Approach 2:
The patent changes geometric parameters during the two-step forming process. The first forming step creates an intermediate shape with specific curvature radius and projection height parameters, which are then adjusted in the second step to achieve the final component shape. This parameter transformation allows control over material flow and stress distribution throughout the forming process.
2Manufacturing precision
If drawing is performed while pinching the top sheet portion to eliminate material shortage, then cracks on the top sheet portion are prevented, but shear wrinkles occur on vertical wall portions and bonding becomes difficult
Solution Approach 1:
The first forming step performs preliminary deformation that creates an intermediate formed product with adjusted material distribution. This preliminary action eliminates material shortage on the top sheet portion without applying excessive shear deformation to vertical wall portions, thereby preventing both cracks and shear wrinkles while maintaining bonding capability.
3Quantity of substance
If the top sheet portion is made to project in excess in the first forming step, then material shortage is eliminated, but excessive tensile deformation is applied to the top sheet portion
Solution Approach 1:
The patent carefully controls the projection height parameter in the first forming step. By optimizing this parameter, the top sheet portion projects sufficiently to eliminate material shortage and prevent cracks, while avoiding excessive projection that would cause harmful tensile deformation. The second forming step then adjusts this projection to achieve the final desired shape.
4Manufacturing precision
If compressive stress is generated in the longitudinal direction to reduce spring-back, then dimensional accuracy improves, but the component shape must be changed to include recessed shapes
Solution Approach 1:
The patent controls the curvature radius and projection height parameters in the first forming step to inherently reduce spring-back. By optimizing these geometric parameters, the need for additional recessed shapes to generate compressive stress is minimized or eliminated, maintaining both dimensional accuracy and the desired component shape.
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 reduces forming defects such as cracks, wrinkles, and dimensional inaccuracies, effectively suppressing spring-back by ensuring precise material distribution and stress management in the final component.
Implementation Method 1
press forming a metal sheet into an intermediate formed product... press forming, a crack or a wrinkle may be formed... ductility of the metal sheet decreases, so that a large spring-back occurs
Implementation Method 2
problems may occur such as lowered dimensional accuracy due to elastic recovery in a formed product after release... a large spring-back occurs in a press-formed product
Data Source
AI summary
A method includes press forming a metal sheet into an intermediate formed product bent out of a plane and forming into a desired press-formed component shape. In a region to be a flange portion, an angle to be bent out of the plane is equal to or less than an angle formed by the flange portion at the curved portion in the press-formed component shape. The projection portion has a largest projection height at the center portion in the longitudinal direction of the region to be the curved portion as seen in the side view, and a longitudinal length of a region to be the top sheet portion is set to coincide with or approach a longitudinal length of the top sheet portion in the press-formed component shape.