Burring Structural Member Geometry for Bend Crack Resistance
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Solution Overview
Problem
Conventional burring structural members tend to fracture when subjected to external forces such as bending or compression, due to cracks at the inside bend of the burring wall part.
Innovation Solution
The burring structural member is designed with specific characteristics, including a sheet-shaped part with a thickness of 2.0 mm or more, a Charpy impact value of 50 J/cm2 or more, and a BCI value of 2.5 or more, along with a curvature radius of the inside bend that is larger than R1, calculated by a specific formula.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the burring wall part is made thinner to reduce weight, then weight reduction is achieved, but fracture resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by establishing specific quantitative relationships between thickness T, curvature radius R, and Charpy impact value vE(0) through formulas (1) and (2). These formulas define minimum values for R and vE(0) based on T, ensuring fracture resistance is maintained while allowing thickness optimization. This resolves the contradiction by providing a systematic method to adjust parameters together rather than independently.
Solution Approach 2:
The patent employs composite material strategies by specifying both mechanical properties (Charpy impact value) and geometric properties (curvature radius) in combination with thickness. The requirement for high Charpy impact value indicates use of toughened steel materials, while the curvature radius specification optimizes the geometric composition. This multi-parameter composite approach ensures fracture resistance even when thickness is reduced.
2Strength
If the curvature radius of the inside bend is increased to reduce stress concentration, then fracture resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent uses parameter changes by establishing a minimum curvature radius R based on thickness T through formula (2). This provides a clear design guideline that balances stress reduction benefits with manufacturing feasibility. The formula R ≥ T × {0.065 × exp[1.85 - (vE(0)/50)²] + 0.005} ensures the curvature radius is sufficiently large to reduce stress concentration while remaining practical for manufacturing.
3Strength
If the Charpy impact value is increased to improve toughness, then fracture resistance is enhanced, but material cost increases
Solution Approach 1:
The patent applies parameter changes by establishing a minimum Charpy impact value vE(0) based on thickness T through formula (1). This provides a quantitative guideline for material selection that ensures sufficient toughness while avoiding excessive material quality requirements. The formula vE(0) ≥ 50 × exp{0.065 × [ln(T/0.5) - 1.85]² - 0.005} allows optimization of material toughness requirements based on the specific thickness application.
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 design significantly enhances the fracture resistance of the burring structural member, allowing it to withstand bending or compression without fracturing.
Implementation Method 1
A Charpy impact value vE(0) of the sheet-shaped part at 0° C. is 50 J/cm2 or more
Data Source
AI summary
A burring structural member resistant to fracture even if the burring structural part is bent back is provided. In the burring structural member of the present disclosure, a thickness T of the sheet-shaped part is 2.0 mm or more, a Charpy impact value vE(0) of the sheet-shaped part at 0° C. is 50 J/cm2 or more, a BCI value calculated by BCI=vE(0)/Lc based on the Charpy impact value vE(0) (J/cm2) and a maximum length Lc (μm) of a crack at the inside bend of the bent wall part of the burring structural parts is 2.5 or more, and a curvature radius R (mm) of the inside bend of the bent wall part is larger than R1 calculated by R1=25/BCI−1.5.