Self-Piercing Rivet Geometry for Brittle Multi-Layer Joining
Find Innovative SolutionsGenerate Solutions
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 issues with 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 ratio of shank outer surface diameter to bore depth between 0.50 and 0.67, which reduces the rivet and die volume, allowing for lower insertion forces and improved joining quality in brittle materials like aluminum alloys and stacks of three components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rivet shank diameter is increased to provide sufficient axial stability for punching through high-strength top layers, then the rivet volume and weight increase, but the insertion force and die volume requirements increase proportionally
Solution Approach 1:
The patent applies parameter changes by optimizing the ratio between shank outer diameter and bore depth to a specific range (0.50-0.67). This parameter optimization allows the rivet to achieve sufficient axial stability for punching through high-strength materials while minimizing rivet volume and weight, thereby reducing insertion force and die volume requirements compared to conventional rivet designs
Solution Approach 2:
The patent implements local quality by providing a conical transition zone at the rivet base with a specific angle range (30-60 degrees). This localized geometric feature concentrates stress during the punching operation, enabling the rivet to penetrate high-strength top layers effectively without requiring increased overall rivet diameter, thus maintaining optimal volume and weight
2Manufacturing precision
If the rivet geometry is optimized for penetrating high-strength top layers with sharp geometry, then joining quality improves, but material deformation increases in softer underlying layers
Solution Approach 1:
The patent applies parameter changes by defining a specific ratio range (0.50-0.67) between shank outer diameter and bore depth. This optimized parameter ensures the rivet has sufficient sharpness at the piercing end to penetrate high-strength top layers with minimal deformation, while the controlled bore depth prevents excessive deformation in softer underlying material layers
Solution Approach 2:
The patent implements curvature principles through the conical transition zone at the rivet base with angles of 30-60 degrees. This curved transition geometry distributes stress more evenly during penetration, reducing sharp geometric concentration that would cause excessive material deformation in softer layers while maintaining effective piercing capability
3Force
If the die volume is reduced to lower insertion forces, then energy consumption decreases, but the rivet geometry constraints increase
Solution Approach 1:
The patent applies parameter changes by establishing an optimized ratio range (0.50-0.67) between shank outer diameter and bore depth. This parameter optimization enables the use of smaller die volumes that require lower insertion forces, while the rivet geometry remains within manufacturable constraints through the defined parameter relationships
Solution Approach 2:
The patent implements local quality through the conical transition zone with specific angle ranges (30-60 degrees) at the rivet base. This localized geometric feature allows the rivet to maintain effective piercing capability with reduced overall dimensions, enabling compatibility with smaller die volumes and lower insertion forces without excessive geometric constraints
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 optimized geometry of the self-piercing rivet enables better joining quality, reduces the weight and volume of the rivet, and lowers the required insertion force, while preventing material deformation and ensuring a flat joint appearance, suitable for use in car production.
Implementation Method 1
the shank deforms outwardly to interlock with the material
Implementation Method 2
The sheets of material are caused to deform around the shank, creating an annulus that encapsulates the shank
Data Source
AI summary
Self-piercing rivet joint and self-piercing rivet for producing a joining connection between at least two components comprising a rivet head and a rivet shank having a central shank bore comprising a base, the rivet shank comprises a cylindrical shank outer surface and a shank inner surface limiting the central shank bore, the rivet shank comprises an annular piercing end facing away from the rivet head, the shank outer surface has a first diameter (Ds), the central shank bore comprises a bore depth (T) between the base of the central shank bore and the annular piercing end, wherein a ratio of the first diameter (Ds) to the bore depth (T) is in the range of 0.50≤Ds/T≤0.67.