Friction Weld Fastener Sealing for Corrosion-Resistant Joints
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Solution Overview
Problem
Friction welding methods for automotive body parts face corrosion issues due to exposure of the interface between the fastener and the joined structures to environmental substances, which existing fasteners like EJOWELD® friction welding methods fail to adequately address.
Innovation Solution
A welded structural assembly with a fastener and a sealing member, where the sealing member is placed under the head portion of the fastener and extends beyond its outer periphery to inhibit corrosion, using materials such as thermoplastic polymer, lead, foam, or paper, and can be in the form of a coating or washer, and is deformed to fill recesses or extend at specific angles during installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If friction welding method is used to join automotive body parts, then joining efficiency and productivity are improved, but corrosion resistance at the fastener interface deteriorates due to exposure to environmental substances
Solution Approach 1:
A sealing member is introduced as an intermediary component between the fastener head and the upper substrate. This sealing member (which can be a coating, tape, or washer) physically blocks environmental substances from reaching the fastener interface, thereby preventing corrosion while maintaining the efficiency of the friction welding process
Solution Approach 2:
The sealing member is applied to the fastener or substrate before the friction welding operation. This preliminary application ensures that the sealing is in place before the joining process begins, protecting the interface from corrosion during and after welding without interfering with the welding efficiency
2Reliability
If a sealing member is added to protect the fastener interface from corrosion, then corrosion resistance is improved, but device complexity increases due to additional components
Solution Approach 1:
The sealing function is merged with existing components in the assembly process. The sealing member can be integrated with the fastener (as a coating) or the substrate (as a pre-applied tape or washer), combining the sealing function with components that are already part of the friction welding system, thereby minimizing additional complexity
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 sealing member effectively prevents corrosion at the interface between the substrates and the fastener, enhancing the durability and longevity of the welded assembly by creating a barrier against environmental penetration.
Implementation Method 1
the sealing member provides a seal to inhibit corrosion at or near the interface between the substrates and the fastener
Implementation Method 2
heat is generated by rotation of a friction element (i.e., fastener) under application of an axial force
Implementation Method 3
the materials of the upper and lower pieces 2/3 harden, or recrystallize, thus forming a mechanical connection
Data Source
AI summary
A welded structural assembly and method, in one form, includes an upper substrate, a lower substrate adjacent the upper substrate, a fastener, and a sealing member. The fastener includes a shank portion, a first head portion, and a second head portion. The shank portion extends through the upper substrate and into the lower substrate. The shank is welded to the lower substrate. The first head portion has an outer periphery and an underside. The second head portion is frangibly coupled to the first head portion. The sealing member is disposed under the first head portion between the upper substrate and the first head portion. The sealing member contacts the underside and extends beyond the outer periphery such that the sealing member extends radially outward beyond all points of the first head portion.