Self-Piercing Rivet Geometry for Brittle Multi-Layer Joining
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Solution Overview
Problem
Existing self-piercing rivets face challenges in achieving high joining quality, particularly with brittle materials and stacks of more than two components, due to limitations in material deformation and the need for reduced insertion force and die volume.
Innovation Solution
A self-piercing rivet with a specific geometry, characterized by a shank outer surface diameter to bore depth ratio of 0.50 to 0.67, allowing for lower insertion force and reduced die volume, which is advantageous for joining brittle materials and stacks of three components, while maintaining robustness and visual appeal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rivet shank diameter is increased to provide sufficient undercut for fixation, then the joining strength is improved, but the insertion force and die volume increase
Solution Approach 1:
The patent applies parameter changes by optimizing the ratio between the outer diameter of the rivet shank and the depth of the central bore. By setting this ratio within a specific range (0.5-0.67), the invention achieves sufficient undercut for fixation and joining strength while maintaining lower insertion forces and reduced die volume compared to conventional rivet designs.
2Strength
If the rivet shank diameter is increased to provide sufficient undercut for fixation, then the joining strength is improved, but the die volume increases
Solution Approach 1:
The patent applies parameter changes by optimizing the ratio between the outer diameter of the rivet shank and the depth of the central bore. By setting this ratio within a specific range (0.5-0.67), the invention achieves sufficient undercut for fixation and joining strength while maintaining lower insertion forces and reduced die volume compared to conventional rivet designs.
3Speed
If the rivet geometry is optimized for sharp penetration, then the ability to pierce high-strength top layer is improved, but the stability during punching decreases
Solution Approach 1:
The patent applies local quality by creating different geometric characteristics at different locations of the rivet shank. The rivet features a central bore with specific depth and diameter ratios that provide sharp penetration capability at the leading edge, while the overall shank geometry provides sufficient axial stability during the punching process. This localized optimization of geometry allows the rivet to simultaneously achieve both penetration efficiency and structural stability.
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
The described geometry enhances joining quality by reducing the rivet and die volume, enabling effective connection of brittle materials with lower insertion forces and minimizing the risk of material deformation and visual defects.
Implementation Method 1
the shank deforms outwardly to interlock with the material
Data Source
Figure 1~2
Figure 3~4B
AI summary
Self-piercing rivet joint and self-piercing rivet (10) for producing a joining connection between at least two components (C1, C2, C3) comprising a rivet head (12) and a rivet shank (14) having a central shank bore comprising a base, the rivet shank (14) comprises a cylindrical shank outer surface and a shank inner surface limiting the central shank bore, the rivet shank (14) comprises an annular piercing end (22) facing away from the rivet head (12), the shank outer surface has a first diameter (Ds), the central shank bore comprises a bore depth (T) between the base (17) of the central shank bore and the annular piercing end (22), wherein a ratio of the first diameter (Ds) to the bore depth (T) is in the range of 0.50≦Ds/T≦0.67.