Resistance Welding Fastener for Aluminum-Steel Laminate Joints
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for joining aluminum to other materials, such as steel, face challenges including poor mechanical performance, high cycle times, and the need for precise alignment, especially when using high-strength materials, due to issues like intermetallic compound formation and galvanic corrosion.
Innovation Solution
A method using electrical resistance welding with a conductive fastener having a cap and shaft, where the fastener is placed between electrodes and an electrical potential is applied to induce resistive heating, allowing the fastener to weld to the second material while capturing the first material between the cap and the second material, enabling efficient joining of dissimilar metals with reduced cycle times and improved corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional through-hole riveting or self-pierce riveting is used to join aluminum to steel, then mechanical fastening is achieved, but the aluminum can crack during the riveting process and high magnitude forces are required
Solution Approach 1:
The patent replaces the mechanical riveting system with an electrical resistance welding system. Instead of using mechanical force to drive a rivet through aluminum and steel, the invention uses electrical current to generate resistive heating that welds the fastener to the steel substrate, eliminating the need for high magnitude mechanical forces that cause aluminum cracking
Solution Approach 2:
The patent changes the physical state and properties of materials during the joining process by applying electrical energy. The resistive heating raises the temperature of the fastener and steel interface to welding temperature, transforming the joining mechanism from cold mechanical deformation to thermal metallurgical bonding, which prevents aluminum cracking
2Strength
If friction stir spot welding is used to join aluminum to steel, then welding is achieved, but the process requires very precise alignment and fitup and cycle times increase dramatically for thicker joints
Solution Approach 1:
The patent replaces the mechanical friction stir welding system with an electrical resistance welding system. Instead of using rotating tools that require precise alignment and generate heat through friction, the invention uses electrical current passed through the fastener to generate resistive heating, eliminating the need for precise alignment and reducing cycle times
Solution Approach 2:
The patent employs a rapid cyclic process where electrical current is applied in controlled pulses to generate heat and complete the weld quickly. The process involves placing the fastener, applying electrical potential, inducing current flow, and completing the weld in a sequence that totals 2-3 seconds, significantly faster than friction stir welding for thick joints
3Strength
If direct welding is used between aluminum and steel, then joining is achieved, but intermetallic compounds are generated which negatively affect mechanical strength and corrosion resistance
Solution Approach 1:
The patent introduces a conductive fastener as an intermediary between aluminum and steel. The fastener is welded to the steel substrate, and the aluminum is captured between the fastener cap and the steel, preventing direct welding between dissimilar metals and thus eliminating intermetallic compound formation while maintaining joint strength
Solution Approach 2:
The patent segments the joining process into separate operations: the fastener is welded to steel, and the aluminum is mechanically captured by the fastener cap. This segmentation prevents direct contact and welding between aluminum and steel, avoiding intermetallic compound formation while achieving the desired joint strength
4Strength
If high strength steels are used, then mechanical strength is improved, but the materials are difficult to pierce requiring large heavy riveting guns
Solution Approach 1:
The patent replaces the heavy mechanical riveting gun system with a lighter electrical resistance welding system. Instead of using large heavy equipment to pierce and drive rivets through high strength steels, the invention uses electrical current to generate heat that facilitates joining, significantly reducing the size and weight of the required equipment
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 method effectively joins aluminum to steel with improved mechanical strength and reduced cycle times, minimizing intermetallic compound formation and galvanic corrosion, while allowing for the use of high-strength materials and varying thicknesses, and is compatible with conventional resistance spot welding equipment.
Implementation Method 1
applying an electrical potential across the stack, inducing a current to flow through the fastener and the stack and causing resistive heating
Data Source
AI summary
An apparatus and method for fastening dissimilar materials like steel, plastic and aluminum. A resistance welding fastener having multiple layers may be used with or without a sealant. The fastener may be used to form an aluminum covered steel laminate via a hemming pattern of attachment. The fastener may have a solid shaft or have an extended reach and have features for interacting with the welding electrode. A variety of electrode tips may be employed to cooperate with the fastener.