Two-Stage Sheet Forming for L-Shaped Hat Cross Sections
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Solution Overview
Problem
Existing methods for sheet forming L-shaped parts, particularly those with a hat-shaped cross section, struggle to prevent wrinkles and cracks when using high-strength steel sheets with low ductility, as they cannot effectively form the entire length of the L-shaped part.
Innovation Solution
A two-stage sheet forming process using a first sheet forming tool with a pad to hold the top portion and a second tool to stretch the side wall and top portions, increasing the area ratio by 0.3% to 1.2% to prevent wrinkles and cracks, while maintaining the L-shape and hat cross section.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional sheet forming methods are used to form L-shaped parts, then the process is simple, but an L-shaped part having a hat-shaped cross section extending over the entire length cannot be formed
Solution Approach 1:
The patent segments the complex forming operation into two distinct processes: the first process forms the L-shaped bent portion, and the second process forms the hat-shaped cross section. This segmentation enables the formation of the complete hat-shaped cross section over the entire length of the L-shaped part, which cannot be achieved by conventional single-step methods.
Solution Approach 2:
The first sheet forming process performs the preliminary action of creating the L-shaped bent portion with the metal sheet, preparing it for the second process that will form the hat-shaped cross section. This preliminary forming enables the subsequent process to achieve the final precise hat-shaped geometry over the entire part length.
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 allows for the precise and stable formation of L-shaped parts with a hat cross section over the entire length, preventing wrinkles and cracks in high-strength steel sheets, ensuring the quality of the sheet-formed parts.
Implementation Method 1
a part of the top portion is held by the pad
Implementation Method 2
the punch and the die are brought closer to each other in a state that the whole periphery of the metal sheet is held by the die and the blank holder to apply drawing to the metal sheet
Data Source
Figure 1A~1D
Figure 2
Figure 3
AI summary
A method of sheet forming according to the present invention includes a first sheet forming process that sheet-forms a metal sheet 11 into a first sheet-formed part 27 having an intermediate shape with a first sheet forming tool 1 and a second sheet forming process that sheet-forms the first sheet-formed part 27 into a second sheet-formed part having a product shape. The first sheet-formed part 27 has a side-wall stretching portion 29 formed on a side wall portion 23 on an outer side including an L-shaped bent portion and a top-portion stretching portion 31 formed on the outside of a top portion 21 of the L-shaped bent portion. A curvature radius of the side-wall stretching portion 29 is larger than the curvature radius of the L-shaped bent portion of a sheet-formed part 19, and the curvature radius of a shoulder portion contiguously formed with the top-portion stretching portion 31 is larger than the curvature radius of a shoulder portion contiguously formed with the outside of the top portion 21 of the L-shaped bent portion of the sheet-formed part 19.