Non-Circular Press-Fit Joint for High-Strength Sheet Fastening
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Solution Overview
Problem
High-strength metal components in the automotive industry pose challenges for press-fit connections due to their high strength, making it difficult to achieve sufficient resistance to axial extraction and twist without inducing tangential tensile stresses, which can lead to cracks and corrosion, and requiring complex geometries or deformation processes.
Innovation Solution
A press-fit connection is established using a pre-shaped hole with a non-circular cross-section and a press-fit element with a collar that undergoes solid forging, providing resistance to extraction and twist without tangential stresses, and ensuring a planar component underside by pressing the collar against the hole rim without embracing the component's underside.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If deformation of the metal sheet is used to achieve resistance to extraction and twist, then sufficient resistance to axial extraction and twist is achieved, but deformation is impossible or difficult when component strength is greater than press-fit element strength
Solution Approach 1:
Instead of deforming the metal sheet (component) to achieve resistance, the invention inverts the approach by deforming the press-fit element's collar against the hole rim. The collar is radially widened during press-fitting to create interference fit and resistance to extraction and twist, while the component itself remains undeformed or minimally deformed.
Solution Approach 2:
The invention changes the parameters of the press-fit element's collar by radially widening it during the press-fit operation. This parameter change (increasing collar diameter) creates the interference fit necessary for resistance to extraction and twist, solving the problem without requiring deformation of the high-strength component.
2Strength
If non-circular cross sectional geometry is used to provide resistance to twist, then resistance to twist is achieved, but the collar may shear off during press-fit operation when there are large strength differences
Solution Approach 1:
The invention changes the cross-sectional geometry parameter of the collar from circular to non-circular (oval, rectangular, or polygonal) to provide resistance to twist. The non-circular shape creates mechanical interlocking with the non-circular hole, preventing rotation while the controlled press-fit process prevents collar failure.
3Strength
If a bead is set around the forming collar to provide resistance to axial extraction, then resistance to axial extraction is achieved, but high tangential tensile stresses arise that may result in cracks and corrosion
Solution Approach 1:
The invention converts the potentially harmful tangential tensile stresses into beneficial compressive interference fit stresses. By radially widening the collar to create interference fit with the hole rim, the design generates compressive contact pressures that provide resistance to axial extraction without the harmful tangential tensile stresses that would cause cracks and corrosion.
4Strength
If the collar embraces the underside of the component to provide resistance to extraction, then resistance to axial extraction is achieved, but the press-fit element projects beyond the component underside
Solution Approach 1:
The invention applies partial action by creating interference fit only at the hole rim region where the collar is radially widened. This localized deformation provides sufficient resistance to axial extraction without requiring the collar to embrace or extend beyond the component underside, maintaining a planar surface for additional components.
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
This solution achieves reliable resistance to axial extraction and twist while avoiding cracks and corrosion, allowing for simple and cost-effective manufacturing without complex geometries or deformation processes, ensuring the collar does not project beyond the component's underside.
Implementation Method 1
for the purpose of providing resistance to extraction that is effective in the longitudinal direction, the collar is pressed by an upset process against a hole rim of the pre-shaped hole
Data Source
AI summary
A press-fit connection between a high-strength component and a press-fit element is characterized by a non-circular previously made hole into which the press-fit element having a collar is inserted. Here, the collar is merely upset and pressed against a hole rim without embracing an underside of the component. Preferably, the hole rim is widened in a longitudinal direction such that a form-locking connection acting in opposition to the longitudinal direction is formed. The non-circular hole geometry is produced with the aid of a punch of circular cross sectional geometry, in that a cutter of the punch has leading and recessed cutting regions, with the result that disrupted partial regions are formed.