Vented Resistance Welding Rivet for Dissimilar Material Joints
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Solution Overview
Problem
Existing methods for joining dissimilar materials, such as aluminum and steel, face challenges in achieving consistent weld quality and efficiency, particularly due to issues like joint porosity, expulsion, and sensitivity to robotic placement tolerances.
Innovation Solution
The use of a rivet-like fastener with channels, grooves, or holes in the head and/or shaft to vent gases and adhesives during the joining process, combined with monitoring of dynamic welding parameters, and the design of a rivet that accommodates both piloted and non-piloted applications, allowing for flexible rivet placement and reduced sensitivity to robotic tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If resistance spot welding is used to join dissimilar materials, then welding speed and productivity are improved, but weld quality consistency and reliability deteriorate due to varying material thicknesses and tolerances
Solution Approach 1:
The patent applies parameter changes by using a rivet design with a pin diameter (DR) that is 0.8 to 1.2 times the pilot hole diameter (DP), creating a ratio relationship that accommodates tolerance variations. The rivet pin is designed to radially expand during welding, dynamically adjusting to fit within the pilot hole despite thickness variations, thereby maintaining weld quality consistency while preserving high welding speed
Solution Approach 2:
The patent employs preliminary action by pre-forming a pilot hole in the first material before welding. This pilot hole serves as a predetermined guide that ensures the rivet pin is properly positioned and constrained during the welding process, eliminating misalignment issues and ensuring consistent weld quality across varying material thicknesses and tolerances
2Strength
If a rivet with radial expansion capability is used, then mechanical interlock strength is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by concentrating the complexity only in the rivet pin region, which is designed with specific dimensional relationships (diameter DR = 0.8 to 1.2 times pilot hole diameter DP) and radial expansion capability. The rest of the rivet structure remains simple and conventional, minimizing overall device complexity while achieving superior mechanical interlock strength through the localized sophisticated pin design
3Reliability
If adhesive is used in the pilot hole, then joint integrity and corrosion resistance are improved, but pressure buildup during welding increases
Solution Approach 1:
The patent applies the taking out principle by extracting or removing excess adhesive from the joint through the vent hole provided in the rivet head. This allows the adhesive to be initially present for improving joint integrity and corrosion resistance, while the vent hole continuously removes excess adhesive and pressure buildup during welding, preventing harmful pressure accumulation
4Reliability
If a vent hole is provided in the rivet head, then pressure management and adhesive expulsion control are improved, but rivet design complexity increases
Solution Approach 1:
The patent applies the porous materials principle by incorporating a vent hole (creating a porous or permeable structure) in the rivet head. This simple opening allows pressure equalization and controlled adhesive expulsion during welding, managing pressure effectively without requiring complex mechanical components. The vent hole is a minimal structural addition that provides sophisticated pressure management functionality
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 approach enhances weld consistency, reduces joint porosity, and improves cycle time while maintaining mechanical strength and corrosion resistance, enabling efficient joining of dissimilar materials with reduced sensitivity to robotic placement errors.
Implementation Method 1
the pin expands radially within the pilot hole during the step of urging
Implementation Method 2
applying an electrical potential across the rivet and the second material, inducing a current to flow through the rivet and the second material; and urging the rivet towards the second material, the step of applying causing resistive heating of the rivet, the current causing the rivet to weld to the second material
Implementation Method 3
infusing an adhesive in the pilot hole
Implementation Method 4
the rivet having at least one vent in the head; venting material from under the head through the at least one vent during the step of applying
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An apparatus and method for method for joining materials includes a rivet (10) that may extend through a first sheet (26) to be resistance welded to a second sheet (24). The head (14) of the rivet (10) has a cavity (18) and vents (240) allowing adhesive (236) extruded from a pilot hole (28) to be received in the cavity (18) and vented in a direction parallel to the first sheet (26). The rivet (10) is deformed to an hourglass shape that fills the pilot hole (28) and displaces the first sheet (26) into the cavity (18). Rivet (10) dimensions allow for holding with a robotic gripper (1316) that can be withdrawn before welding. Methods of monitoring joint quality include comparing welding parameter profiles and images of good and discrepant joints.