Burring Mold Geometry to Prevent In-Bend Cracks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Burring processing methods often result in tensile residual stress and minute cracks (in-bend cracks) in the curved portion of vehicle undercarriage components like lower arms and trailing arms, leading to deformation and shape changes.
Innovation Solution
A burring processing method that increases the diameter of a prepared hole and bends a part of the metal component to form a buffing processed portion with specific cross-sectional shapes, including a curved portion with a length perpendicular to the axis that is at least 1.2 times the height parallel to the axis, and uses a mold with corresponding die and punch configurations to inhibit crack generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional burring processing is performed on metal components for vehicle undercarriage, then the prepared hole diameter is increased and the burring processed portion is formed, but tensile residual stress occurs inside the curved portion and minute cracks (in-bend cracks) are generated
Solution Approach 1:
The patent applies parameter changes by modifying the cross-sectional shape parameters of the curved portion. Specifically, it sets the length in the radial direction to be at least 1.2 times the height in the axial direction, and configures the cross-sectional shape to consist of a curve rather than straight lines. These parameter changes optimize the geometry to reduce stress concentration and prevent crack formation during burring processing, thereby improving fatigue characteristics while maintaining manufacturability.
2Reliability
If the radius of curvature of the curved portion is increased to prevent cracks, then crack generation is reduced, but the shape of the burring processed portion must be changed
Solution Approach 1:
The patent resolves this contradiction by precisely defining optimal parameter ranges for the curved portion geometry. It specifies that the length in the radial direction should be at least 1.2 times the height in the axial direction, and the cross-sectional shape should consist of a curve. These parameter changes achieve crack resistance while maintaining a controlled and predictable shape, allowing the design requirements to be met without arbitrary shape changes.
3Productivity
If conventional burring processing is performed, then the burring processed portion is formed efficiently, but tensile residual stress causes deformation when fatigue load is applied
Solution Approach 1:
The patent maintains processing efficiency while improving dimensional accuracy by optimizing the cross-sectional shape parameters of the curved portion. The specific configuration where the radial length is at least 1.2 times the axial height, combined with a curved cross-sectional profile, reduces tensile residual stress concentration. This allows the component to maintain its shape and dimensional accuracy under fatigue loads without sacrificing the efficiency of the burring processing operation.
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
Inhibits the generation of cracks in the curved portion of the burring processed portion, enhancing fatigue characteristics and dimensional accuracy.
Implementation Method 1
the punch is inserted into the die hole along an axis of the die hole to increase a diameter of the prepared hole and to bend a part of the metal component
Implementation Method 2
bending a part of the metal component to form a buffing processed portion including an upright portion and a curved portion
Data Source
AI summary
A burring processing method including increasing a diameter of a prepared hole provided in a metal component and bending a part of the metal component to form a burring processed portion (110) including an upright portion (120) and a curved portion (130), wherein in a cross-section that passes through an axis (cb) of the burring processed portion (110) and is parallel to the axis (cb) of the buffing processed portion (110), a cross-sectional shape of the curved portion (130) on an inner surface of the curved portion consists of a curve, and a length of the curved portion (130) in a direction perpendicular to the axis (cb) of the burring processed portion (110) is at least 1.2 times a height of the curved portion in a direction parallel to the axis (cb) of the burring processed portion (110).