Rivet Vents for Dissimilar Material Welding
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Solution Overview
Problem
Current methods for joining dissimilar materials like aluminum and steel, such as resistance spot welding, face challenges in achieving strong and reliable joints, particularly in terms of weld quality and consistency, especially when dealing with varying material thicknesses and tolerances.
Innovation Solution
The method involves using a rivet with a head and pin that expands radially during welding, creating a cavity to capture extruded material, and employing an adhesive to enhance joint integrity, while vents on the rivet head manage pressure and prevent porosity, allowing for both piloted and non-piloted joining processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If resistance spot welding is used to join dissimilar materials, then joining capability is achieved, but weld quality and consistency deteriorate due to varying material thicknesses and tolerances
Solution Approach 1:
The welding system dynamically adjusts process parameters including current magnitude, pulse duration, and electrode force based on real-time feedback from sensors monitoring weld characteristics. This adaptive parameter adjustment compensates for variations in material thickness and tolerance, maintaining consistent weld quality across dissimilar materials
Solution Approach 2:
The system incorporates sensors that monitor weld parameters such as electrical resistance, current flow, and displacement during the welding process. This feedback is used to detect weld quality in real-time and adjust subsequent welding parameters to maintain consistency, ensuring reliable joints despite material variations
2Device complexity
If traditional resistance spot welding is used, then joining process is simple, but joint strength and reliability deteriorate
Solution Approach 1:
The welding system employs a composite approach combining resistance spot welding with adhesive bonding. The adhesive is applied to the interface between materials and cured during or after welding, creating a hybrid joint that leverages both mechanical welding strength and chemical adhesive bonding, resulting in superior joint strength and reliability
Solution Approach 2:
The system applies adhesive to the joint interface before performing the resistance spot welding operation. This preliminary action ensures that the adhesive is in position to bond the materials together, and the subsequent welding process provides both mechanical strength and activates adhesive curing, creating a stronger combined joint
3Stress or pressure
If material extrusion is allowed during welding, then pressure relief is achieved, but porosity and weld defects increase
Solution Approach 1:
The system incorporates controlled venting channels that allow material extrusion to occur in a controlled manner during welding. These vents relieve built-up pressure that would otherwise cause defects, while the controlled design prevents uncontrolled extrusion that could create porosity. The vents are strategically positioned and sized to convert the potentially harmful pressure buildup into a beneficial pressure relief mechanism
Solution Approach 2:
The welding system incorporates porous or permeable structures in the form of vent channels within the weld zone or adjacent areas. These porous pathways allow gases and molten material to escape during welding, preventing porosity formation in the main weld zone while maintaining weld integrity through controlled pressure relief
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 results in strong, consistent joints with improved mechanical and corrosion resistance, capable of handling a wide range of material thicknesses and tolerances, and allows for efficient joining of dissimilar materials in a single welding cell, reducing fabrication costs and cycle time.
Implementation Method 1
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 2
the pin of the rivet expands radially within the pilot hole during the step of urging, the step of urging being conducted in a continuous manner
Implementation Method 3
infusing an adhesive in the pilot hole
Data Source
AI summary
An apparatus and method for method for joining materials includes a rivet that may extend through a first sheet to be resistance welded to a second sheet. The head of the rivet has a cavity and vents allowing adhesive extruded from a pilot hole to be received in the cavity and vented in a direction parallel to the first sheet. The rivet is deformed to an hourglass shape that fills the pilot hole and displaces the first sheet into the cavity. Rivet dimension allow for holding with a robotic gripper that can be withdrawn before welding. Methods of monitoring joint quality include comparing welding parameter profiles and images of good and discrepant joints.