Self-Piercing Nut Element for High-Strength Sheet Metal
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Solution Overview
Problem
Existing self-piercing fastener elements struggle to effectively attach to sheet metal parts with higher strengths or thicknesses greater than 3.5 mm, as they often require heat treatment, which is costly and inefficient, and fail to provide secure rotation and press-out resistance in high-strength materials.
Innovation Solution
A self-piercing nut element with a peripheral extending groove and piercing edge, where the piercing edge is spaced from the groove by a surface with an axial height of at least 30% of the sheet metal thickness, allowing the nut element to punch holes in sheet metals with strengths up to 1600 MPa and thicknesses over 3.5 mm, and ensuring secure attachment through deformation of the sheet metal material into the groove for rotation and press-out resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If self-piercing fastener elements are used with sheet metal parts of higher strength or greater thickness, then attachment capability is improved, but heat treatment is required which increases manufacturing cost and complexity
Solution Approach 1:
The fastener element features a piercing section with specifically optimized local geometry including a peripheral extending groove and piercing edge spaced at least 30% of sheet metal thickness away from the groove boundary. This localized geometric modification enables the element to pierce high-strength sheet metal without requiring heat treatment of the entire fastener element, thus improving attachment capability while avoiding increased manufacturing complexity
Solution Approach 2:
The invention changes the geometric parameters of the piercing section, specifically the distance between the piercing edge and the groove boundary (at least 30% of sheet metal thickness), and the radial wall thickness (1.2 to 1.8 times sheet metal thickness). These parameter modifications allow cold-formed fastener elements to effectively attach to sheet metal parts with strength up to 1600 MPa and thickness over 3.5 mm without heat treatment
2Strength
If existing self-piercing elements are used on high-strength sheet metal, then attachment is attempted, but rotation and press-out resistance are insufficient
Solution Approach 1:
The peripheral extending groove in the piercing section creates localized material deformation that forms a mechanical interlock with the sheet metal. This local geometric feature provides enhanced rotation and press-out resistance by creating friction and mechanical engagement between the fastener element and the sheet metal, ensuring reliable attachment for high-strength applications
Solution Approach 2:
The groove and piercing edge geometry creates curved deformation zones in the sheet metal material, forming a rivet-like bead that provides superior resistance against rotation and press-out forces. The curved deformation pattern distributes stresses more effectively than straight-cut holes, enhancing overall attachment reliability
3Strength
If heat treatment is applied to increase fastener element strength, then higher strength is achieved, but manufacturing time and cost increase
Solution Approach 1:
The invention achieves sufficient piercing capability by optimizing the geometric parameters of the piercing section (groove depth, piercing edge distance, radial wall thickness) rather than increasing material strength through heat treatment. This allows cold-formed fastener elements with standard material strength to effectively attach to high-strength sheet metal, maintaining manufacturing efficiency and productivity
Solution Approach 2:
The invention uses cold-formed fastener elements made from standard-strength material that are optimized geometrically for high-strength sheet metal attachment. This approach avoids the cost and time of heat treatment while achieving the necessary performance, effectively replacing expensive heat-treated elements with simpler, more economical cold-formed alternatives
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 secure attachment and rotation resistance in high-strength sheet metals by deforming the sheet metal material into a groove, reducing the need for heat treatment and allowing the use of thinner materials, while maintaining structural integrity and preventing fatigue cracks.
Implementation Method 1
the material of the sheet metal part at the side of the sheet metal part remote from the sheet metal contact surface has a recess adjacent to the piercing section and surrounding the piercing section and in that the material of the hole rim is displaced into the groove as a result of the formation of the recess
Data Source
AI summary
A piercing nut element having a strength in the range between 700 and 900 MPa which is designed to be pressed into the sheet metal part. The nut element is characterized in that the self-piercing attachment of the nut element into a sheet metal part of higher strength, or into a sheet metal part with a thickness greater than 3.5 mm, the nut element is designed in such a way that the piercing section has a peripheral extending groove below the sheet metal contact surface and in that the piercing section has a piercing edge at its free end face with the piercing edge being spaced from the boundary of the groove adjacent to the piercing section by a peripheral surface having an axial height which corresponds to at least 30% and preferably to at least 50% of the sheet metal thickness, wherein the radial wall thickness of the piercing section in the region of its free end face from the outer side of the piercing section up to the nominal diameter of the thread corresponds to a thickness between 1.2 to 1.8 and preferably 1.5 times the intended sheet metal thickness.