Hat-Section Press Forming With Wavy Preform for Crack and Wrinkle Control
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Solution Overview
Problem
Existing press forming technologies face challenges in producing vehicle frame components with hat-shaped cross-sectional shapes, as they often result in cracks, wrinkles, and reduced dimensional accuracy due to material excess or shortage, and significant spring-back caused by the increased tensile strength of high-strength steel sheets.
Innovation Solution
A two-step press forming method involving initial stretch forming to create a wavy shape in the metal sheet, followed by bending to form ridge lines, ensuring a line length difference between the vertical wall and flange portions is minimized, thereby reducing material stress and preventing defects like cracks and wrinkles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high strength steel sheet is used to achieve vehicle lightweighting and collision safety, then material strength increases, but ductility decreases causing large spring-back and forming defects
Solution Approach 1:
The patent applies preliminary stretch forming before the final press forming step. In the first forming step, the metal sheet is stretched to create an intermediate formed product with a wavy shape, which pre-distributes the material and reduces spring-back in the subsequent bending step. This preliminary action prepares the material in advance to compensate for the elastic recovery that occurs during final forming.
2Ease of manufacture
If simple press forming is applied to hat-shaped components with curved portions, then production is straightforward, but material excess causes wrinkles and material shortage causes cracks
Solution Approach 1:
The patent divides the forming process into two distinct steps: (1) stretch forming to create an intermediate formed product with a wavy shape that redistributes material, and (2) bending to achieve the final hat-shaped component. This segmentation allows each step to address specific material distribution challenges, preventing both wrinkles and cracks in the final product.
Solution Approach 2:
The first forming step performs preliminary stretch forming to create a wavy shape in the intermediate formed product. This preliminary action pre-distributes the material along the longitudinal direction, ensuring adequate material supply to curved portions and preventing both material excess (wrinkles) and material shortage (cracks) in the final bending step.
3Productivity
If conventional press forming is used without intermediate steps, then production time is short, but spring-back causes poor dimensional accuracy
Solution Approach 1:
The forming process is segmented into two steps: stretch forming followed by bending. While this adds a step, each step is optimized to be efficient. The stretch forming creates a pre-distributed material state, and the bending step completes the shaping with minimal spring-back, maintaining overall productivity while improving dimensional accuracy.
Solution Approach 2:
The stretch forming step performs preliminary material distribution to create an intermediate formed product with a wavy shape. This preliminary action reduces the magnitude of spring-back in the subsequent bending step, improving dimensional accuracy without significantly extending the total forming cycle time.
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 reduces forming defects such as cracks, wrinkles, and dimensional inaccuracies, while suppressing spring-back, ensuring precise hat-shaped cross-sectional components are produced with improved material distribution and reduced stress differences.
Implementation Method 1
press forming a metal sheet into an intermediate formed product in which a wavy shape is formed
Implementation Method 2
problems may occur such as lowered dimensional accuracy due to elastic recovery in formed product after release
Data Source
AI summary
A press forming technology capable of reducing forming defects in a formed component having a hat-shaped cross-sectional shape and including a shape curved to protrude toward a flange portion in a side view. The technology includes a first forming step of press forming a metal sheet into an intermediate formed product that includes a wavy shape including uneven shapes continuous along a longitudinal direction in vertical wall portion and flange portion forming positions, an amplitude of the uneven shapes in a sheet thickness direction increasing toward a position corresponding to a boundary between the portions, and a second forming step of performing bending on the intermediate formed product. A longitudinal line length at the position corresponding to the boundary between the portions in the intermediate formed product is set to coincide with or approach a longitudinal line length at the boundary between the portions in the press-formed component shape.