Waveform Bumper Stay for Crack-Free Flange Expansion
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Solution Overview
Problem
Conventional electromagnetic molding methods for producing energy-absorbing members like bumper stays face limitations in achieving sufficient flange width without cracking or reducing thickness, especially when molding materials with small diameters, and struggle to form rectangular or polygon cross-sections with small corner radii, leading to instability and reduced energy absorption performance.
Innovation Solution
The method involves using a tubular material with a circumferential wall that undulates in a waveform pattern, allowing for increased flange width and reduced thickness by expanding the entire circumference of the material's ends using a helically wound electromagnetic molding coil, which minimizes the gap between the material and the coil, and forms irregular regions with excessive line lengths to accommodate complex cross-sectional shapes without local thickness reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the tube expansion rate is increased to form a wider flange, then the flange width is improved, but cracks occur on the outer circumference and thickness decreases
Solution Approach 1:
The patent applies preliminary action by pre-forming convex curved regions and irregular regions with excessive line lengths in the tubular material before electromagnetic molding. These pre-formed features prepare the material to accommodate expansion without cracking, allowing the flange to achieve greater width while maintaining structural integrity. The excessive line lengths in irregular regions provide material reserve that prevents thinning and cracking during the expansion process.
Solution Approach 2:
The patent applies local quality by creating non-uniform distribution of material properties through the convex curved regions and irregular regions. The convex curved regions concentrate material in areas prone to cracking, while irregular regions with excessive line lengths provide local material reserve. This localized variation in material distribution allows different parts of the flange to have different thickness characteristics, preventing uniform thinning and crack propagation across the entire flange circumference.
2Area of moving object
If the tube expansion rate is increased to form a wider flange, then the flange width is improved, but the thickness of the flange decreases
Solution Approach 1:
The patent applies preliminary action by pre-forming irregular regions with excessive line lengths in the tubular material before electromagnetic molding. These pre-formed irregular regions contain additional material reserve that compensates for thickness reduction during expansion. When the flange is expanded to greater width, the excessive line lengths in irregular regions provide local material that prevents excessive thinning, maintaining manufacturing precision of the flange thickness even at higher expansion rates.
Solution Approach 2:
The patent applies local quality by creating localized material concentration through irregular regions with excessive line lengths. These irregular regions are strategically positioned to provide local material reserve in areas where thickness maintenance is critical. This non-uniform material distribution allows the flange to achieve greater overall width while maintaining adequate thickness in specific critical regions, resolving the contradiction between flange width and thickness precision.
3Shape
If electromagnetic molding is used to form rectangular or polygon cross-sections, then the shape complexity is improved, but the corner radius cannot be made small leading to instability
Solution Approach 1:
The patent applies preliminary action by pre-forming convex curved regions and irregular regions in the tubular material before electromagnetic molding. These pre-formed features prepare the material to accommodate the formation of sharp corners in rectangular or polygon cross-sections. The excessive line lengths in irregular regions provide material reserve that prevents excessive thinning at corners during molding, enabling the formation of small corner radii while maintaining manufacturing precision and structural stability.
Solution Approach 2:
The patent applies local quality by creating non-uniform material distribution through convex curved regions and irregular regions. The irregular regions with excessive line lengths are positioned to provide local material reserve at corner areas, while convex curved regions concentrate material in areas prone to stress concentration. This localized variation in material properties allows the formation of sharp corners with small radii in rectangular or polygon cross-sections while preventing excessive thinning and maintaining manufacturing precision.
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 approach enables the formation of energy-absorbing members with increased flange width, improved load transmission, and enhanced energy absorption capabilities, while preventing cracking and maintaining structural stability during collisions.
Implementation Method 1
passing a large current through the electromagnetic molding coil in this state, inducing an induction current in the metal tubular material by electromagnetic inductive phenomenon, thereby causing an electromagnetic force according to Fleming's left-hand rule to expand the metal tubular material into a cross-sectional shape
Implementation Method 2
causing an electromagnetic force according to Fleming's left-hand rule to expand the metal tubular material
Data Source
AI summary
An end of a stay material made of a tubular aluminum alloy extruded material is expanded by electromagnetic molding to form a flange for producing a bumper stay. The flange width is increased without cracking and a decrease in the thickness. A stay material having a circumferential wall undulating in a waveform pattern is used. A circumferential length L (one round length along waveform pattern) of the outer periphery wall along the circumferential direction of the stay material is longer than a circumferential length L0 of a simple cylindrical circumferential wall having the same outer diameter (circumscribed circle) (L>L0). L−L0 is an excessive line length. Since the circumferential wall has the excessive line length, when the end of the circumferential wall is expanded to form the flange, the flange having a large diameter can be formed.