Self-Piercing Rivet Geometry for Symmetrical Steel Joint Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing self-piercing riveted joints for high-strength and super-high-strength steels face issues with asymmetrical expansion, shank compression, twisting, and potential fracturing, as well as difficulties in piercing the workpieces due to inadequate deformation behavior of the rivet shank.
Innovation Solution
A self-piercing rivet design with a reduced axial recess depth ratio to shank diameter, a flat surface section at the foot end, and a recess shape that minimizes expansion focus, allowing for an upsetting operation driven by counter pressure from high-strength steels, enhancing stability and connection strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the axial depth of the shank cavity is increased to achieve sufficient expansion after piercing, then the expansion behavior improves, but the rivet shank becomes more prone to asymmetrical expansion, compression, and twisting
Solution Approach 1:
The patent optimizes the ratio of axial depth of the shank cavity to outside diameter of the rivet foot to be between 0.3 and 0.7, and the head diameter to be between 1.05 and 1.3 times the shank diameter. These parameter changes ensure sufficient expansion while maintaining symmetrical deformation and preventing shank compression and twisting.
2Reliability
If the rivet foot is designed with truncated shape to reduce expansion endeavor, then the deformation behavior improves, but the piercing capability into high-strength steel decreases
Solution Approach 1:
The patent specifies that the outside diameter of the rivet foot should be between 0.8 and 0.95 times the shank diameter, and the axial depth of the shank cavity should create a ratio between 0.3 and 0.7. These parameter changes balance the truncated rivet foot design for controlled deformation while maintaining sufficient piercing capability into high-strength steel workpieces.
3Strength
If the head diameter is increased to distribute setting forces, then the connection strength improves, but the rivet geometry becomes less suitable for high-strength steel joining
Solution Approach 1:
The patent defines the head diameter to be between 1.05 and 1.3 times the shank diameter. This parameter change optimizes the head size to distribute setting forces effectively for strong connections while maintaining geometric suitability for joining high-strength and super-high-strength steel workpieces.
4Strength
If the rivet shank is designed to expand significantly after piercing, then the joint strength improves, but the rivet becomes prone to fracturing during the piercing process
Solution Approach 1:
The patent optimizes the axial depth of the shank cavity to create a ratio between 0.3 and 0.7 relative to the outside diameter of the rivet foot. This parameter change ensures that the rivet shank expands sufficiently to create strong joints while maintaining resistance to fracturing during the piercing process through controlled deformation behavior.
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 design achieves symmetrical deformation, increased stability, and sufficient connection strength for high-strength steels, enabling successful piercing and forming strong joints with reduced undercut, even in high-strength materials like Usibor®, while maintaining low setting forces.
Implementation Method 1
a self-piercing rivet design with a reduced axial recess depth ratio to shank diameter, a flat surface section at the foot end, and a recess shape that minimizes expansion focus, allowing for an upsetting operation driven by counter pressure from high-strength steels, enhancing stability and connection strength
Implementation Method 2
Existing self-piercing riveted joints for high-strength and super-high-strength steels face issues with asymmetrical expansion, shank compression, twisting, and potential fracturing
Implementation Method 3
allowing for an upsetting operation driven by counter pressure from high-strength steels
Data Source
AI summary
A riveted joint comprising: an upper workpiece and a lower workpiece, and a self-piercing rivet. The rivet in an undeformed state, before the creation of the riveted joint, included: a head defining a head diameter (DH); a shank defining a shank diameter (DS); and a foot end opposite the head. Radially outward at the foot end is a flat surface facing away from the head; and an axial recess located radially inward of the flat surface, partly defined in the foot end, open axially away from the head, and frustoconical in longitudinal cross section. The axial recess defining an axial depth (LB). The ratio of recess axial depth (LB) to shank diameter (DS) is less than 0.3. And in a deformed state, after the creation of the riveted joint, the rivet extends through the first workpiece and penetrates the second workpiece; and the head bears against the upper surface.