Self-Piercing Fastener Edge Geometry for Lower Punching Force
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Solution Overview
Problem
Self-punching functional elements face challenges in attaching to workpieces with higher strength, requiring increased punching forces and inefficient force distribution during the attachment process.
Innovation Solution
A self-punching functional element with a fastening section featuring a punched edge that varies in distance from the head part in the circumferential direction, allowing focused force application and gradual deformation, reducing maximum loads and stresses through optimized geometry and transition sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the punching edge is designed with constant distance from the head part in the circumferential direction, then the structure is simple, but the punching force required increases when attaching to high-strength workpieces
Solution Approach 1:
The punching edge is segmented into multiple sections with different axial positions, creating a non-uniform geometry that distributes the punching action sequentially rather than simultaneously, reducing the peak force required
Solution Approach 2:
The punching edge geometry is extended into the axial dimension with varying distances from the head part, transforming a two-dimensional circular edge into a three-dimensional non-uniform structure that controls the sequence of material penetration
2Area of stationary object
If the punching edge contacts the entire workpiece surface simultaneously, then the contact area is maximized, but the force concentration is insufficient for high-strength materials
Solution Approach 1:
Different sections of the punching edge are given different axial positions, creating local variations in contact timing and force application, with some sections contacting the workpiece before others to achieve progressive force concentration
Solution Approach 2:
Sections of the punching edge that are axially further from the head part make contact with the workpiece first, initiating the punching action in a controlled sequence before the entire circumference engages
3Reliability
If higher punching forces are applied to attach functional elements to high-strength workpieces, then the attachment reliability improves, but the maximum loads and stresses on the functional element increase
Solution Approach 1:
The punching process occurs in periodic stages as different sections of the non-uniform punching edge sequentially contact and penetrate the workpiece, distributing the loading over time rather than applying it all at once
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
Enables easy and reliable attachment to stronger workpieces without excessive punching forces, by concentrating forces on specific areas and distributing loads spatially and temporally, enhancing the efficiency and reliability of the fastening process.
Implementation Method 1
The fastening section can, for example, be a rivet section which is plastically deformed during the fastening process
Data Source
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AI summary
The present invention relates to a self-punching 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, bears against the workpiece, a fastening section extending axially from the head part 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 punching edge on a side facing away from the head part, wherein the distance of the punching edge from the head part in the circumferential direction is not constant and/or wherein the punching edge, viewed in the circumferential direction, does not lie completely in a plane that is arranged perpendicular to a longitudinal axis or punching direction of the functional element.