Sheared End Surface Evaluation for Delayed Fracture in High-Tensile Steel
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Solution Overview
Problem
Existing methods do not adequately evaluate the delayed fracture characteristics of sheared end surfaces in high-tensile steel sheets, particularly after post-trimming, due to variations in shearing conditions caused by non-uniform shape restraints and poor contact between the sheet presser and lower die, which are critical factors in the production of automobile components.
Innovation Solution
A method to evaluate delayed fracture characteristics by simulating and quantifying shearing conditions through the use of spacers to reproduce poor contact states between the sheet presser and lower die, applying external stress to test pieces under hydrogen charging environments, and analyzing the correlation between shearing conditions and delayed fracture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If post-trimming is performed on a pressed component with shape variations, then the component can be manufactured with complex geometry, but the delayed fracture resistance of the sheared end surface deteriorates due to poor contact between the sheet presser and lower die
Solution Approach 1:
The invention applies preliminary action by performing pre-trimming on the metal sheet before press forming to remove potential defect zones that could lead to delayed fracture. This preliminary removal of problematic material prevents future fracture issues while still allowing the component to achieve its complex final geometry through subsequent press forming and post-trimming operations.
Solution Approach 2:
The invention applies local quality by selectively removing material only from specific regions prone to delayed fracture (the pre-trimmed portion) while preserving the rest of the component structure. This localized intervention addresses the reliability issue without compromising the overall complex geometry or requiring changes to the entire manufacturing process.
2Device complexity
If conventional delayed fracture evaluation methods are used, then the evaluation process is simple, but the evaluation accuracy for post-trimmed portions deteriorates due to insufficient consideration of shearing conditions
Solution Approach 1:
The invention applies segmentation by dividing the sheared end surface into two distinct evaluation zones: a pre-trimmed portion and a post-trimmed portion. Each zone is evaluated with appropriate consideration of its specific shearing conditions. The pre-trimmed portion is assessed for delayed fracture risk based on its shearing characteristics, while the post-trimmed portion is evaluated considering the restraint conditions during shearing, enabling accurate assessment of each region's fracture resistance.
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
Enables the evaluation and prediction of delayed fracture resistance in sheared end surfaces, allowing for the production of press-formed articles with improved resistance to delayed fracture, particularly in high-tensile steel components used in automobiles.
Implementation Method 1
leaving the test piece under a hydrogen charging environment with a load stress being applied to the sheared end surface of the test piece thus prepared
Data Source
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AI summary
Provided is a technology to evaluate the influence of a shearing condition for shearing to form a sheared end surface, on the delayed fracture characteristic of the sheared end surface. A delayed fracture characteristic evaluation method for evaluating a delayed fracture characteristic of a sheared end surface of a metal sheet (10) made of a high-tensile steel sheet includes: preparing a test piece having the sheared end surface from the metal sheet (10) by performing shearing on the metal sheet (10); after the preparing of the test piece, leaving the test piece under a hydrogen charging environment with a load stress being applied to the sheared end surface of the test piece; and evaluating the delayed fracture characteristic of the sheared end surface relative to a shearing condition in the shearing.