Composite Rivet Joint With Deformable Washer to Prevent Abrasion
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Solution Overview
Problem
Traditional mechanical joining systems, such as rivet joints, are unsuitable for composite materials as they cause abrasion and fatigue, leading to unacceptable joints in industrial applications like motor-vehicle production.
Innovation Solution
A rivet connection system featuring a rivet with a sculptured stem and a washer that undergoes axial deformation to increase contact area and distribute axial compression, minimizing material abrasion and failure risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a traditional mechanical rivet joint is used to join layers of composite material, then the structural strength of the joint is achieved, but the material suffers from abrasion and fatigue damage during rivet introduction and closing operation
Solution Approach 1:
The patent introduces a specialized rivet system with a sculptured stem surface that acts as an intermediary between the rivet head and the composite material layers. The sculpturing (knurling or ridges) on the stem creates a mechanical interface that distributes stress and reduces direct abrasion on the composite material during the riveting process, while still achieving the required joint strength through controlled deformation and locking mechanisms.
Solution Approach 2:
The patent modifies the physical parameters of the rivet stem by adding surface sculpturing (knurling or circular ridges) along its length. This changes the surface topology and friction characteristics of the rivet, allowing it to grip the material layers more effectively during installation while distributing forces to minimize abrasion damage to the composite material during both introduction and closing operations.
2Ease of manufacture
If the rivet stem has a smooth surface for easy insertion, then the introduction process is simplified, but the closing operation causes surface abrasion and fatigue on the material layers
Solution Approach 1:
The patent applies different surface qualities to different parts of the rivet stem. The sculpturing (knurling or ridges) is applied locally along the stem surface rather than uniformly, creating zones of increased friction and mechanical interlocking that engage the material layers during closing while the overall insertion process remains facilitated by the rivet's geometry and material properties.
3Reliability
If the rivet stem is made longer to ensure complete penetration and secure connection, then the connection reliability is improved, but the risk of material damage during insertion and closing increases
Solution Approach 1:
The patent incorporates preliminary action by designing the rivet stem with pre-formed sculpturing (knurling or ridges) that is already present before insertion. This pre-configured surface geometry is intended to engage the material layers from the moment of insertion, distributing forces evenly throughout the stem length and preventing concentrated stress points that could cause material damage during both insertion and closing operations.
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 system effectively prevents material damage and ensures structural strength by distributing axial forces over a larger area, reducing the risk of joint failure and abrasion.
Implementation Method 1
bringing about axial deformation of the washer (4) from an undeformed condition in which it fits on the stem (8) with play, to a deformed condition in which it fits on the stem (8) in a condition of interference
Implementation Method 2
The stem (8) has an outer surface (10) provided with a surface sculpturing, preferably throughout its extension, and in any way along an axial extension that covers at least 80% of the length starting from the free end of the stem opposite to the head (6)
Data Source
Figure 1~2A
Figure 3~4A
AI summary
Described herein is a connection system (1) for connection of two or more overlapping layers (L1, L2) of material, the system comprising: - a rivet (2) including a head (6) and a stem (8), the head (6) of the rivet (2) being configured, in use, to bear upon a surface of a first layer (L1) of said two or more layers of material, the stem (8) having an outer surface that comprises a surface sculpturing and being configured, in use, for passing through said two or more layers of material (L1, L1) and projecting beyond them; and - a washer (4) configured to fit (11) on said stem (8) and configured to bear, in use, upon a surface of a last layer (L2) of said two or more overlapping layers (L1, L2) of material, said washer (4) being deformable by axial compression from an undeformed condition where it fits on said stem (8) with play, to a deformed condition where it fits on said stem (8) in a condition of interference with said outer surface of the stem (8). Moreover described is a corresponding method for joining two or more overlapping layers (L1, L2) of material using the aforesaid connection system (1).