Hat-Section Press Forming Using Twisted Sidewall Preforming

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Solution Overview

Problem

Existing press forming methods for automotive parts with hat-shaped cross sections face challenges in preventing fractures and wrinkles, particularly in high-strength steel sheets, due to limitations in applicability, versatility, and surface accuracy requirements.

Innovation Solution

A two-stage press forming method that includes a first process to preform a twisted side wall portion with a specific torsion amount, generating in-plane shear deformation to reduce line length differences between web and flange portions, and a second process to form the final product, ensuring the web and flange portions are convexly curved in the height direction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If high-strength steel sheets are used to reduce weight, then weight reduction is achieved, but fractures and wrinkles occur during press forming

Engineering Contradiction:

Improveautomotive body weightVSAvoidpress forming quality

Core Design Contradiction:

Weight of moving objectVSManufacturing precision

Solution Approach 1:

The press forming process is divided into two distinct stages: preforming and final forming. The preforming stage creates an intermediate shape with optimized material distribution, while the final forming stage achieves the target shape. This segmentation allows high-strength steel sheets to be formed without fractures or wrinkles by controlling material flow in each stage separately.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The preforming stage performs preliminary shaping of the high-strength steel sheet before final forming. By creating an intermediate preformed part with controlled material distribution and reduced line length differences, the preliminary action prevents excessive stretching and compressive forces that would cause fractures and wrinkles during final forming.

Inventive Principle:

Principle #10Preliminary action

2Ease of manufacture

If conventional press forming is used for curved parts, then manufacturing simplicity is maintained, but fractures and wrinkles occur in flange and web portions

Engineering Contradiction:

Improvepress forming process simplicityVSAvoidsurface accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The forming process is segmented into preforming and final forming stages. The preforming stage specifically addresses material distribution issues in curved parts by creating an intermediate shape that reduces line length differences between web and flange portions, while the final forming stage achieves the precise target shape with high surface accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the geometric parameters of the intermediate preformed part, specifically controlling the side wall angle and line length differences. By optimizing these parameters in the preforming stage, the material flow is controlled to prevent fractures and wrinkles, enabling successful final forming of curved parts with high surface accuracy.

Inventive Principle:

Principle #35Parameter changes

3Shape

If material is stretched to form convex curved shapes, then desired shape is achieved, but line length differences cause fractures and wrinkles

Engineering Contradiction:

Improveconvex curved shapeVSAvoiduniformity of deformation

Core Design Contradiction:

ShapeVSManufacturing precision

Solution Approach 1:

The preforming stage performs preliminary shaping that specifically addresses line length differences between web and flange portions. By creating an intermediate preformed part with reduced line length differences, the preliminary action ensures more uniform material distribution before final forming, preventing excessive stretching that causes fractures and wrinkles in convex curved shapes.

Inventive Principle:

Principle #10Preliminary action

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 suppresses fractures and wrinkles in press-formed products, allowing for the formation of automotive parts with high surface accuracy and reduced deformation issues.

Implementation Method 1

generating in-plane shear deformation to reduce line length differences between web and flange portions

Methodology Applied

Scientific EffectShear deformation: Shear Stress

Implementation Method 2

preform a twisted side wall portion with a specific torsion amount

Methodology Applied

Scientific EffectTorsion: Torsion Spring

Data Source

PatentUS12109600B2Press forming method

Publication Date: 2024.10.08 JFE STEEL CORP

AI summary

A press forming method forms a press-formed product having a hat-shaped cross section and includes: a first forming process of press-forming a preformed part in which a portion corresponding to web corresponding to a web portion, and a portion corresponding to side wall corresponding to a side wall portion and including a twisted side wall portion of a twisted shape along the longitudinal direction, are formed, the preformed part including a portion corresponding to convex curve corresponding to a convex curved portion; and a second forming process of press-forming the preformed part into the press-formed product. The twisted side wall portion at the first forming process is twisted such that an angle between the twisted side wall portion and the portion corresponding to web is larger on an end portion side than at a center of the portion corresponding to convex curve in the longitudinal direction.