Semi-Hollow Self-Piercing Rivet Structure for High-Strength Joining
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Solution Overview
Problem
Existing semi-hollow self-piercing rivets struggle to effectively join high-strength and ultra-high-strength materials without collapsing, applying excessive forces, or resulting in crack-free joints.
Innovation Solution
A semi-tubular self-piercing rivet with a shaft featuring a blind cavity and longitudinal projections radially extending from its outer face, which allows the rivet to radially widen when punched into the workpiece, reducing the slug hole area and enhancing joint stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the outer diameter of the SPR is reduced to decrease the hole slug area, then the system forces and cracking tendency are reduced, but the stability of the rivet is significantly lost
Solution Approach 1:
The rivet shaft is segmented into a cylindrical base portion and a projection portion with longitudinal projections. This segmentation allows the projection portion to provide enhanced stability during the joining process while the overall reduced diameter minimizes the hole slug area. The longitudinal projections create additional contact points with the workpiece material, distributing forces and preventing rivet instability despite the reduced outer diameter.
Solution Approach 2:
The rivet features local quality enhancement through the projection portion with longitudinal projections that extend along the cylindrical shaft. These projections are strategically positioned to provide localized stability and grip in the projection portion, while the cylindrical base portion maintains the reduced diameter for minimizing hole slug area. This local quality differentiation allows the rivet to simultaneously achieve reduced harmful effects and maintained stability.
2Strength
If the rivet is designed to join high-strength and ultra-high-strength materials, then the joint strength is improved, but the rivet may collapse or excessive forces may be required
Solution Approach 1:
The rivet is segmented into a cylindrical base portion for strength and a projection portion for controlled deformation. The longitudinal projections in the projection portion are designed to engage with the workpiece material at specific points, distributing the joining forces and preventing rivet collapse when joining high-strength materials. This segmentation allows the rivet to achieve both high joint strength and reliability.
Solution Approach 2:
The rivet design changes the geometric parameters by introducing longitudinal projections with specific heights and spacing. These parameter changes create optimal engagement characteristics with high-strength and ultra-high-strength materials, allowing the rivet to join these materials without collapsing or requiring excessive forces. The projection height and spacing are optimized to match the material properties being joined.
3Productivity
If the shaft is radially widened during punching, then the joining effectiveness is improved, but the device complexity increases
Solution Approach 1:
The shaft is segmented into a cylindrical base portion and a projection portion with longitudinal projections. This segmentation enables the projection portion to radially widen during punching, improving joining effectiveness through enhanced material engagement. The longitudinal projections provide controlled radial expansion that increases the mechanical interlock with the workpiece, while the segmented structure manages the complexity by providing predictable deformation behavior.
Solution Approach 2:
The rivet shaft transitions from a static cylindrical form to a dynamic structure during the punching process. The projection portion with longitudinal projections is designed to radially widen under the punching force, creating a dynamic joining action that improves effectiveness. This controlled dynamic deformation allows the shaft to adapt to the workpiece material during installation, enhancing joining effectiveness while the predefined projection geometry keeps the overall device complexity manageable.
Data Source
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AI summary
A semi-tubular self-piercing rivet (10) comprising a head (12), and a shaft (14), wherein the shaft (14) comprises a shaft axial end face (16) opposite to the head (12), wherein the shaft (14) has a shaft blind cavity (18), wherein the shaft (14) comprises a shaft radial outer face (28) and a plurality of longitudinal projections (22) projecting from the shaft radial outer face (28), wherein the radial shaft outer face (28) defines a first shaft outer diameter (DA1), wherein the longitudinal projections (22) each have a radial height (HV) relative to the shaft radial outer face (28), and wherein the shaft (14) is configured to be radially widened when being punched into a workpiece arrangement. A ratio of the radial height (HV) of the longitudinal projections (22) to the first shaft outer diameter (DA1) defined by the radial shaft outer face (28) is in a range from 0.03 to 0.2.