Burring Wall Geometry for Fatigue-Resistant High-Strength Steel
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High strength steel parts used in fatigue-prone applications tend to experience crack growth and reduced fatigue resistance due to the susceptibility of high strength steel to crack formation during burring processing.
Innovation Solution
A burring processed member with specific structural features, including a sheet-shaped part and a burring processed part with a burring hole and wall part, where the burring wall part has a vertical and curved section, and the structure satisfies specific relations regarding arithmetic mean roughness, height, and tensile strength to minimize stress concentration and fatigue crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If high strength steel is used to reduce part weight, then weight reduction is achieved, but fatigue resistance deteriorates due to crack susceptibility
Solution Approach 1:
The patent applies local quality by creating a burring wall part with specific geometric characteristics (curved wall section, controlled roughness Ra=3-100μm, height h≥3.0mm) at the critical hole region. This localized structural modification with specific surface properties reduces stress concentration at the hole edge, thereby improving fatigue resistance in the critical area without changing the overall part weight or material properties.
Solution Approach 2:
The patent employs parameter changes by precisely controlling geometric parameters of the burring processed part: radius of curvature r≥2.0mm of the curved wall part, height h≥3.0mm, and surface roughness Ra=3-100μm of the burring end face. These parameter optimizations minimize stress concentration factors, enabling high strength steel to achieve both weight reduction and improved fatigue resistance.
2Strength
If burring processing is applied to high strength steel parts, then structural integrity is improved, but fatigue crack formation increases due to stress concentration
Solution Approach 1:
The patent applies spheroidality by introducing a curved wall part with radius of curvature r≥2.0mm in the burring wall structure. This curved geometry replaces sharp corners and transitions, distributing stress more evenly around the hole perimeter. The curved profile reduces stress concentration peaks that would otherwise initiate fatigue cracks, while maintaining the structural integrity provided by the burring process.
Solution Approach 2:
The patent creates a localized burring wall part with specific geometric and surface properties around the hole region. The controlled surface roughness (Ra=3-100μm) and curved profile (r≥2.0mm) in this local area reduce stress concentration without affecting the overall structural integrity. This localized modification prevents fatigue crack initiation at the critical hole edge while preserving the strength benefits of burring processing.
Data Source
AI summary
As a burring processed member able to suppress the formation of fatigue cracks in a burring part, one having a structure satisfying the following relations (1) to (3) is disclosed: 3≤Ra≤100 . . . (1), 3.0<h . . . (2), 24+r−[TS/(40+0.28×Ra)]<h . . . (3), where, “Ra” is an arithmetic mean roughness (μm) of the burring end face, “h” is a height (mm) from the first surface to the burring end face, “r” is a radius of curvature (mm) of the curved wall part, and “TS” is the tensile strength (MPa) of the sheet-shaped part.