Concave Blank Press Forming to Suppress Stretch Flange Cracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Press-forming methods for high-strength metal plates with low ductility, such as those with concave curved portions, often result in stretch flange cracking due to concentrated tensile strain, leading to forming defects and reduced productivity.
Innovation Solution
A three-step press-forming method involving blank forming, intermediate shape forming, and target shape forming, where a concave shape is formed in the blank with a cutout portion at the central curve, reducing tensile stress and dispersing it to both ends, thereby suppressing stretch flange cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional press-forming is applied to high-strength metal plates with low ductility, then manufacturing efficiency is maintained, but stretch flange cracking occurs due to concentrated tensile strain
Solution Approach 1:
The invention applies preliminary action by forming a pre-formed product with modified geometry (different curvature radius) before final press-forming. This pre-forming step redistributes material flow and reduces concentrated tensile strain in the concave curved portion, preventing stretch flange cracking while maintaining manufacturing efficiency
Solution Approach 2:
The invention changes geometric parameters by using a pre-formed product where the curvature radius of the concave curved portion is different from the final target shape. This parameter modification alters material flow patterns during press-forming, reducing tensile strain concentration and preventing cracking in high-strength metal plates
2Shape
If the curvature radius of the concave curved portion is small, then the target shape is achieved, but tensile strain concentrates at the end portion of the vertical wall portion causing cracking
Solution Approach 1:
The pre-forming step creates an intermediate geometry with different curvature characteristics, preparing the material distribution before final forming. This preliminary action ensures that when the small curvature radius is achieved in the target shape, tensile strain is not concentrated at the vertical wall portion end
Solution Approach 2:
The invention addresses the two-dimensional strain concentration problem by introducing a forming sequence dimension. The multi-step process transforms the material flow in time, allowing the final small curvature radius to be achieved without the harmful strain concentration that would occur in single-step forming
3Reliability
If a pre-formed product with short flange portion line length is used, then some cracking is prevented, but the vertical wall portion still experiences insufficient strain reduction
Solution Approach 1:
The invention optimizes geometric parameters by carefully designing the curvature radius of the pre-formed product's concave curved portion. This parameter adjustment ensures adequate material flow and strain distribution during final press-forming, achieving both crack suppression and uniform strain distribution in the vertical wall portion
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 stretch flange cracking, enhances productivity, and maintains dimensional accuracy by reducing tensile stress and improving yield in the press-forming process.
Implementation Method 1
press-forming a blank that is a metal plate
Implementation Method 2
cracking is likely to occur due to tensile deformation in a direction along a curve of the blank
Data Source
AI summary
A press-forming method includes: forming a blank having a concave shape corresponding to a curve of a concave curved portion of a target shape; press-forming the formed blank into a press-formed product having an intermediate shape having a top portion, a vertical wall portion continuous from the top portion, a flange portion continuous from the vertical wall portion, a concave curved portion curved in a concave shape in a top view, and a cutout portion located at a part of the flange portion and the vertical wall portion or at a part of the flange portion, the vertical wall portion, and the top portion in a central portion of the curve of the concave curved portion; and press-forming the press-formed product having the intermediate shape into the target shape. The press-forming is performed such that a part of the concave shape provided in the blank becomes the cutout portion.