Self-Piercing Rivet Recess Ratio for Thin Aluminum Joints
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Solution Overview
Problem
Current self-piercing rivets face challenges in achieving high joining quality and cost-effective manufacturing for thin aluminum panels, particularly in vehicle door applications, where they compete with other methods like resistance spot welding.
Innovation Solution
A self-piercing rivet with a specific geometry featuring an axial recess and annular piercing end, where the ratio of recess volume to shank and head volume is between 0.01 and 0.06, allowing for straight upsetting and spreading through internal geometry, and made of materials like steel or aluminum alloys, with a sharp-edged outer edge for improved cutting and cold-forming without heat or surface treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a self-piercing rivet with traditional geometry is used, then the manufacturing process is simple, but the joining quality is insufficient for thin aluminum panels
Solution Approach 1:
The patent applies local quality by creating a specific axial recess geometry at a particular location (foot end) of the rivet shank. This localized structural modification concentrates the deformation control function in a specific region, enabling improved joining quality for thin panels without requiring complex overall rivet design or additional manufacturing steps.
Solution Approach 2:
The patent utilizes parameter changes by optimizing the ratio of recess volume to shank and head volume within the specific range of 0.01 to 0.06. This quantitative parameter optimization controls the spreading and upsetting behavior during riveting, achieving reliable joining of thin aluminum panels while maintaining simple cold-forming manufacturing processes.
2Reliability
If the recess volume ratio is too high, then the spreading and upsetting process is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The patent applies partial action by implementing a moderate recess volume ratio (0.01 to 0.06) rather than extreme values. This partial modification of the shank geometry provides sufficient deformation control for reliable joining while avoiding excessive geometric complexity that would complicate cold-forming manufacturing. The recess is just enough to achieve the desired effect without over-engineering.
3Ease of manufacture
If cold-forming without heat treatment is used, then manufacturing cost is reduced, but achieving sufficient strength is difficult
Solution Approach 1:
The patent applies preliminary action by pre-shaping the shank with an axial recess during cold-forming manufacturing. This preliminary geometric preparation enables the rivet to achieve proper spreading and upsetting behavior during installation, obtaining sufficient joining strength through the controlled deformation process without requiring subsequent heat treatment operations.
Solution Approach 2:
The patent utilizes parameter changes by optimizing the recess geometry parameters (volume ratio, axial depth, diameter) to control the material flow and deformation characteristics during cold-forming. These optimized parameters enable the rivet to develop adequate strength through cold-forming alone, eliminating the need for heat treatment and reducing manufacturing costs.
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 rivet achieves good joining quality and low-cost manufacturing by enhancing the spreading and upsetting process, competing effectively with other joining methods, and obtaining strength through cold forming without additional treatments.
Implementation Method 1
the shank deforms outwardly to interlock with the material
Implementation Method 2
pierces the upper surface thereof
Data Source
Figure 1~2
AI summary
Self-piercing riveted joint and self-piercing rivet (10) with a head and a shank which has a shank diameter (Ds), wherein, at a foot end opposite the head, the shank has an axial recess which has an axial depth (LB) and the shank (14) further comprises an annular piercing end (20), characterized in that the recess has a recess volume, wherein a ratio of recess volume to volume of the shank and the head is between 0.01 and 0.06.