Self-Piercing Rivet Element With Curved Fastening Section
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Solution Overview
Problem
Functional elements, such as rivet elements, face challenges in attaching to workpieces efficiently without compromising the reliability of the connection, often requiring significant deformation and force application, which can lead to material weakening and increased costs due to pre-punching requirements.
Innovation Solution
A functional element with a fastening section featuring concave and convex curved sections in the circumferential direction, allowing for optimized force distribution during the fastening process, enabling efficient attachment with reduced material deformation and increased stability, and allowing self-piercing capabilities without the need for pre-punched holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rivet section is deformed significantly to create a rivet flange for reliable connection, then the connection strength is improved, but the material is weakened due to deformation stresses
Solution Approach 1:
The rivet section incorporates curved sections (convex and concave) instead of straight geometry. These curved sections guide the deformation process during setting, distributing stresses more evenly and preventing stress concentration that would weaken the material. The curvature allows controlled material flow during forming while maintaining structural integrity.
2Reliability
If the rivet section is made thicker to accommodate deformation stresses, then the material reliability is improved, but the device complexity and material usage increase
Solution Approach 1:
The curved sections in the rivet section enable more efficient stress distribution during deformation, allowing thinner wall thickness while maintaining the same load-bearing capacity. The geometry optimizes material utilization, reducing the amount of material needed compared to straight-walled designs.
3Strength
If substantial setting forces are applied to deform the rivet section reliably, then the connection strength is improved, but the ease of operation deteriorates due to equipment requirements
Solution Approach 1:
The curved sections guide the deformation process through controlled material flow, reducing the peak forces required during setting. The geometry allows progressive deformation rather than sudden stress concentration, enabling reliable connection with lower setting forces and simpler equipment.
4Productivity
If the rivet section is designed for self-punching to eliminate pre-drilling, then the productivity is improved, but the stability requirements increase during insertion
Solution Approach 1:
The curved sections provide structural reinforcement during the self-punching process. The convex portions act as stress concentrators that initiate controlled material separation, while concave portions provide structural support. This geometry enables self-punching capability while maintaining sufficient stability during insertion and slug removal.
Data Source
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AI summary
The present invention relates to a functional element for attachment to a workpiece, in particular to a sheet metal part, comprising a head part with a contact surface which, in a fixed state of the functional element, rests against the workpiece, a fastening section extending axially from the head part, in particular a rivet section, for fastening the functional element to the workpiece, wherein the fastening section comprises a wall defining a cavity in the circumferential direction, which has a free edge on a side facing away from the head part, wherein the edge and/or the wall comprises concave and convex curved sections in the circumferential direction.