Punch Rivet Collar Swaging for Lower-Force High-Strength Joining
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Solution Overview
Problem
Existing punch rivet methods require high axial forces for joining workpieces, especially in locations with limited accessibility, and have limited strength against head tensile loads, which is dependent on the material of the workpieces.
Innovation Solution
A punch rivet arrangement comprising a rivet with radial recesses and a collar that supports the workpiece during punching and is modified by a higher modification force to allow radial swaging, enabling material flow into the rivet recesses without pre-drilling holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a retaining ring is configured to deform only at force above the punching force, then the punching process can be performed, but the punch rivet tools must be configured for providing comparatively high forces which limits accessibility
Solution Approach 1:
The collar is divided into a first collar portion and a second collar portion that can be separated from each other. The first collar portion remains on the rivet shaft while the second collar portion is detached and inserted into the radial recess. This segmentation allows the tool to apply force only during the punching phase, then release for the insertion phase, eliminating the need for continuously high force and improving accessibility.
Solution Approach 2:
The collar transitions from a static, rigid structure to a dynamic system where the second collar portion can be detached and repositioned. This dynamic behavior allows the system to adapt its force requirements - high force during punching, then zero force during the insertion of the second collar portion into the radial recess, thereby solving the accessibility limitation.
2Strength
If classic head-less punch rivets without retaining ring are used, then the joining process is simpler, but the strength against head tensile loads is comparatively low and strongly dependent on workpiece material
Solution Approach 1:
The second collar portion is inserted into the radial recess of the rivet shaft, creating a nested structure. This nesting provides a mechanical interlock that significantly enhances the strength against head tensile loads. The collar portions wrap around and secure the rivet shaft, preventing pull-out while maintaining a relatively simple overall joining system.
Solution Approach 2:
The joining system combines the rivet shaft (first collar portion) with the detached second collar portion to create a composite structural assembly. This composite structure leverages the geometric interlocking between the collar portions and the radial recess to achieve high tensile strength that exceeds simple head-less rivets, while the modular nature keeps the system complexity manageable.
3Reliability
If the collar is modified by applying a modification force higher than the punch force, then material of the collar flows into the radial recess of the rivet, but the tool must be configured for high forces
Solution Approach 1:
The punching operation is performed first as a preliminary action, creating the radial recess and positioning the first collar portion on the rivet shaft. Only after this preliminary punching is complete does the system proceed to detach the second collar portion and insert it into the recess. This sequencing eliminates the need to apply high modification force simultaneously with punching, as the recess is already formed and ready to receive the second collar portion.
Solution Approach 2:
By segmenting the collar into two separable portions, the system eliminates the need for high modification force. The first collar portion is punched through the workpieces in the conventional manner, then the second collar portion is detached and manually or automatically inserted into the pre-formed radial recess without requiring additional high-force modification, thereby maintaining joining reliability while reducing force requirements.
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 method provides increased strength and safety compared to classical punch rivet methods, reduces the necessary joining force, and eliminates the need for pre-drilling, making it suitable for various workpiece materials and locations.
Implementation Method 1
punching the rivet with a punch force through the workpiece arrangement
Implementation Method 2
modifying the collar by applying a modification force to the collar, wherein the modification force is higher than the punch force
Implementation Method 3
the modification of the collar allows a second engagement surface of the die to apply a radial swaging force onto the collar so that material of the collar flows into the at least one radial recess of the rivet
Data Source
Figure 1
Figure 2~5
Figure 6~7
AI summary
A method for joining at least two workpieces (181, 182) using a punch rivet arrangement (20), the punch rivet arrangement (20) comprising a rivet (22) and a collar (40), wherein the rivet (22) has at least one radial recess (28), comprising the steps of (i) placing the rivet (22) on a first side (161) of the workpieces which form a stacked workpiece arrangement (16); (ii) placing the collar (40) on a die (14) arranged on a second side (162) of the workpiece arrangement (16), (iii) punching the rivet (22) with a punch force (FP) through the workpiece arrangement (16) in an axial direction (L), wherein the workpiece arrangement (16) is supported by a support surface (46) of the collar (40), and wherein the collar (40) is supported by a first engagement surface (56) the die (14); and (iv) modifying the collar (40) by applying a modification force (FM) to the collar (40), wherein the modification force (FM) is higher than the punch force (FP), and wherein the modification of the collar (40) allows a second engagement surface (58) of the die (14) to apply a radial swaging force (FSr) onto the collar (40) so that material of the collar (40) flows into the at least one radial recess (28) of the rivet (22).