Self-Piercing Rivet Clearance Hole for Hard Material Joining
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Solution Overview
Problem
Self-piercing riveting technologies face challenges with hard materials, leading to rivet fracture or buckling, substrate damage, and corrosion concerns due to galvanic potential, compromising joint integrity, especially in mixed metal and composite materials.
Innovation Solution
Forming a clearance hole in one or more layers before riveting to avoid deformation and damage, allowing the rivet to interlock without piercing the substrate, thus maintaining joint integrity and reducing corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If self-piercing riveting is used with hard materials, then joining capability is achieved, but rivet fracture or buckling occurs
Solution Approach 1:
A clearance hole is formed in the substrate material before the riveting process. This preliminary action removes the hardest-to-pierce portion of the substrate, allowing the rivet to be inserted without excessive force that would cause fracture or buckling, while still enabling the rivet to pierce and interlock with the remaining layers.
2Strength
If self-piercing riveting is used to join layers, then joint formation is achieved, but substrate damage occurs
Solution Approach 1:
The clearance hole is formed in advance in the substrate layer that is most susceptible to damage. This allows the rivet to pass through this layer without the high-stress piercing action that would cause deformation or damage, while the rivet still performs its interlocking function with the other layers.
3Adaptability or versatility
If self-piercing riveting is used in mixed metal applications, then joining of different materials is achieved, but corrosion concerns arise due to galvanic potential
Solution Approach 1:
The clearance hole removes the substrate material at the piercing location, creating a gap between the rivet and the substrate. This extraction of material prevents direct contact between dissimilar metals, thereby eliminating or reducing the galvanic cell formation and associated corrosion risks in mixed metal applications.
4Reliability
If clearance hole is formed in substrate, then rivet fracture is prevented, but additional manufacturing step is required
Solution Approach 1:
The clearance hole formation operation is combined with the existing riveting process by using the same punch and die setup. The punch that forms the rivet tail also forms the clearance hole, merging two functions into one operation and minimizing the increase in process complexity.
Data Source
AI summary
A system for attaching layers of material together comprised of a self-piercing rivet, a layer having a clearance hole through which the self-piercing rivet passes on assembly, and a layer free of a clearance hole and into which the self-piercing rivet is at least partially inserted. The system may include a third layer free of a clearance hole. The system may also include three layers wherein the clearance hole is formed in the middle layer. If the clearance hole is formed in the middle layer, the width of the hole may be greater than the diameter of the self-piercing rivet to avoid contact between the rivet and the middle layer. The layer having the clearance hole may be a hard material such as steel. One or more of the layers may be material that is difficult to pierce or can be damaged if pierced.