Press Forming Fracture Judgment Using Bending-Aware Forming Limits
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Solution Overview
Problem
Existing methods for predicting press forming fracture in high-strength metal sheets, such as those with tensile strengths over 980 MPa, fail to accurately consider bending deformation, leading to deviations between predicted and actual fracture generation in press formed parts.
Innovation Solution
A method and device that judge the forming limit of metal sheets by considering bending deformation, using a relationship between bending deformation degree, maximum principal strain, and minimum principal strain to determine fracture likelihood, and adjust press forming conditions to prevent fractures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the strength of metal sheet is enhanced to achieve weight reduction of automotive body, then the weight reduction and strength enhancement are improved, but the ductility decreases and fracture is likely to be generated in press forming
Solution Approach 1:
The invention changes the parameters used for fracture prediction from conventional forming limit diagrams (based only on major and minor strains) to a three-parameter system that includes bending deformation degree. This parameter change allows accurate prediction of fracture in high-strength sheets by accounting for the influence of bending deformation that occurs during press forming, thereby resolving the contradiction between using high-strength materials and maintaining formability.
2Device complexity
If conventional forming limit diagram is used for fracture prediction without considering bending deformation, then the prediction method is simple, but the prediction accuracy deviates from actual fracture generation
Solution Approach 1:
The invention transitions from a two-dimensional forming limit diagram (major strain vs. minor strain) to a three-dimensional prediction framework by adding bending deformation degree as a third parameter. This dimensional expansion allows the prediction model to account for the influence of bending deformation, significantly improving fracture prediction accuracy while maintaining practical applicability through systematic measurement methods.
3Loss of time
If the forming limit is determined without considering bending deformation, then the determination process is simple, but the determination cannot accurately reflect the actual forming limit in press forming
Solution Approach 1:
The invention performs preliminary determination of the relationship between bending deformation degree and forming limit through separate experiments before actual press forming. This preliminary action creates a reference database that can be used for quick and accurate fracture prediction during production, avoiding the need for complex real-time measurements while ensuring high determination accuracy.
Data Source
AI summary
A press forming fracture judgment method includes: a forming limit acquisition process including forming a metal sheet at various bending deformation degrees, and acquiring a forming limit of the metal sheet which limit is expressed by a relationship between a bending deformation degree of the formed metal sheet and a maximum principal strain and a minimum principal strain of the metal sheet formed at the bending deformation degree; and a press formed part fracture judgment process including acquiring, as fracture judgment parameters in the press formed part, a maximum principal strain and a minimum principal strain in the press formed part and a curvature in a maximum principal strain direction as a bending deformation degree in the press formed part, and judging presence or absence of fracture generation in the press formed part based on the acquired fracture judgment parameters and the acquired forming limit.