Castellated Substrate Joint for SPR Air Void Elimination
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Solution Overview
Problem
Mechanical joining of substrates using self-piercing rivets often results in air voids within the adhesive, which weaken the joint and create environmental corrosion and water leak paths due to air intake during the installation process.
Innovation Solution
A castellated upper substrate with alternating troughs and ridges is used, where the angled walls and ridge heights are designed in relation to the adhesive thickness, allowing for plastic deformation that reduces air intake by creating a hinged joint and ensuring the adhesive flows to fill the area, thereby preventing air from entering the joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If self-piercing rivets are used to mechanically join substrates, then the primary structural joint strength is achieved, but air voids are introduced into the adhesive which weaken the joint and create corrosion paths
Solution Approach 1:
The adhesive is applied to the lower substrate before the substrates are brought together and before the self-piercing rivet installation begins. This preliminary application ensures the adhesive is in position to fill voids as they are created during the joining process, rather than attempting to add adhesive after air voids have already formed.
Solution Approach 2:
The plastic deformation of substrates during SPR installation, which initially creates air voids, is converted into a beneficial process by allowing the adhesive to flow into and fill these voids as they are created. The harmful air intake is transformed into an opportunity for adhesive redistribution and void elimination.
2Manufacturing precision
If the gun nose and die are forced together to compress the adhesive to less than 0.2 mm thickness, then the adhesive joint is formed, but air is drawn into the joint creating air voids
Solution Approach 1:
The adhesive is pre-applied to the lower substrate before the substrates are compressed together. This ensures the adhesive is already in position to be drawn into and fill any air voids that may form during the compression and fastener installation process, rather than relying on subsequent adhesive application.
Solution Approach 2:
The compression process that initially creates air voids by forcing the gun nose and die together is converted into a beneficial process by allowing the pre-applied adhesive to flow into and fill these voids as they are created, transforming the harmful air intake into an opportunity for void elimination.
3Ease of operation
If multiple self-piercing rivets are installed, then the substrates are securely fastened, but air voids accumulate in the adhesive joint
Solution Approach 1:
The adhesive is applied to the lower substrate before any fasteners are installed. This preliminary application ensures a continuous supply of adhesive is available to fill air voids as they are created by each subsequent fastener installation, preventing void accumulation during the fastening process.
Solution Approach 2:
The repeated fastener installation process that creates multiple air voids is converted into a beneficial process by allowing the adhesive to flow into and fill each void as it is created, transforming the harmful void accumulation into an opportunity for continuous void elimination throughout the fastening sequence.
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 castellated substrate design effectively minimizes air voids within the adhesive joint, enhancing the structural integrity and preventing environmental corrosion by ensuring a continuous adhesive layer during the installation of self-piercing rivets.
Implementation Method 1
the substrates 11/12 are plastically deformed
Implementation Method 2
ensuring the adhesive flows to fill the area
Data Source
AI summary
An assembly is provided that includes a castellated upper substrate defining a plurality of alternating troughs and ridges. A lower substrate is disposed adjacent the upper castellated substrate, and an adhesive material is disposed between the castellated upper substrate and the lower substrate. A fastener extends through a trough of the castellated upper substrate, through the adhesive material, and into the lower substrate. A method of assembling the upper and lower substrates is also provided, which includes plastically deforming the castellated upper substrate to reduce an intake of air between the substrates.