Self-Integrating Insert Sleeve for Fatigue Life Repair
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Solution Overview
Problem
In high-performance structures like aircraft and aerospace vehicles, achieving precise and flawless fastener holes is challenging due to manufacturing errors and the need for oversized fasteners, which affects structural fatigue life and is economically burdensome.
Innovation Solution
A self-integrating insert sleeve assembly comprising an expander pin and insert sleeve that radially expands upon installation, securing the sleeve to the work piece and inducing compressive residual stresses, allowing for the installation of standard fasteners in oversized or reconditioned apertures, and enhancing structural fatigue life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a standard size hole is drilled to accommodate oversized fasteners due to manufacturing errors or damage, then the fastener can be installed, but the structural fatigue life is reduced and economic costs increase
Solution Approach 1:
An insert sleeve is introduced as an intermediary component between the oversized hole and the standard fastener. The sleeve has an inner diameter matching the standard fastener and an outer diameter that fits within the oversized hole. This mediator restores the proper fit and induces compressive residual stresses in the surrounding structure, thereby preserving fatigue life while enabling fastener installation.
Solution Approach 2:
The insert sleeve changes the effective dimensional parameters of the hole by providing a precise inner diameter interface for the standard fastener. This parameter transformation allows the use of standard fasteners in oversized holes while maintaining the geometric compatibility required for proper fastener function and fatigue performance.
2Ease of repair
If a thin wall cylindrical insert is attached with bonding agent to repair damaged holes, then the hole can be reused, but dimensioning and manufacturing tolerances cause relative movement between components
Solution Approach 1:
The insert sleeve with integrated expander pin performs self-alignment and self-securing during installation. The expander pin, when actuated, causes the sleeve to radially expand and press against the hole walls, creating friction-based mechanical retention without requiring bonding agents. This self-service mechanism eliminates the need for precise pre-dimensioning and bonding processes, reducing sensitivity to manufacturing tolerances.
Solution Approach 2:
The insert sleeve transitions from a loose fit during insertion to a tightly secured position through radial expansion actuated by the expander pin. This dynamic adjustment allows the sleeve to adapt to variations in hole dimensions and tolerances, ensuring proper component alignment and eliminating relative movement between the sleeve, fastener, and surrounding structure.
3Strength
If bonding agents are used to attach insert sleeves to structure, then the insert can be secured, but the bonding process adds complexity and potential failure points
Solution Approach 1:
The chemical bonding mechanism is replaced with a purely mechanical retention system. The expander pin, when actuated, causes the insert sleeve to radially expand and press against the hole walls, creating friction-based mechanical retention. This substitution eliminates the bonding agent and associated curing processes, reducing installation complexity and potential failure points while maintaining strong retention.
4Ease of operation
If oversized fasteners are used to accommodate damaged or reconditioned apertures, then the fastener can be installed, but expensive specialized fasteners are required
Solution Approach 1:
The insert sleeve serves as a mediator that interfaces between the oversized aperture and the standard-sized fastener. The sleeve's inner diameter is precision-matched to standard fasteners, while its outer diameter accommodates the oversized hole. This allows the use of inexpensive standard fasteners instead of expensive oversized specialized fasteners, significantly reducing material costs.
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 solution effectively repairs damaged holes, ensures proper fastener fit, and enhances structural fatigue life by inducing compressive residual stresses, reducing the need for expensive oversized fasteners and addressing issues of hole quality and component alignment.
Implementation Method 1
the insert sleeve component is radially expanded by interaction with the pin, and secured to the aperture of the work piece, such that the resulting aperture of the installed insert sleeve has a predetermined diameter, and the resulting structure now contains compressive residual stresses
Data Source
AI summary
A self-integrating insert sleeve assembly, comprising an insert sleeve and an expander pin, for insertion into an aperture of a work piece is provided. Upon installation, the insert sleeve component is incrementally expanded by interaction with the pin, and secured to the aperture of the work piece, such that the resulting aperture of the installed insert sleeve has a predetermined diameter, and the resulting structure now contains compressive residual stresses. Thus, the installed insert sleeve may be employed as a hole repair solution, allowing for the installation of an original size fastener per structural design within a damaged and reconditioned aperture, or simply for enhanced structural fatigue life. The installation of this insert sleeve may be done through various manners, including pull type, push type, and blind type installation processes.