Interference Fit Bushing for Lightning Strike Protection in Titanium Aircraft Structures
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Solution Overview
Problem
Aircraft structural components, particularly those made of titanium, are vulnerable to damage from electro-magnetic effects like lightning strikes, which induce pitting and reduce fatigue resistance, and current assembly processes using interference fit fasteners are difficult to implement due to space constraints and require complex realignment of fasteners during assembly.
Innovation Solution
The method involves forming an initial channel in a metal component, inserting a bushing with an interference fit, and expanding the bushing to create a final channel suitable for fasteners, where the bushing acts as a sacrificial material to prevent damage from electro-magnetic effects, allowing for 'One-Up Assembly' without disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If interference fit fasteners are used to reduce electro-magnetic effects, then protection against lightning strike damage is improved, but assembly difficulty increases due to space constraints and complex realignment requirements
Solution Approach 1:
A bushing is introduced as an intermediary component between the fastener and the titanium structural component. The bushing serves as a sacrificial element that absorbs electro-magnetic effects from lightning strikes, preventing direct damage to the titanium. This intermediary solution maintains the protective function while enabling easier assembly through standard fastener installation procedures without requiring complex interference fit operations in constrained spaces
Solution Approach 2:
The bushing is designed as a disposable sacrificial component that is less expensive than the titanium structural component. When electro-magnetic damage occurs, the bushing is replaced rather than the expensive titanium structure. This approach provides economical protection while simplifying assembly, as the bushing can be pre-installed with standard fasteners without requiring complex realignment procedures
2Strength
If traditional assembly processes are used with multiple fasteners, then structural integrity is maintained, but time consumption increases due to the need for disassembly and realignment to remove defects
Solution Approach 1:
The bushing is pre-installed into the structural component before the final assembly operation. This preliminary action creates a prepared receptacle that guides subsequent fastener installation, eliminating the need for time-consuming disassembly and realignment operations. The bushing is positioned in advance to ensure proper alignment, allowing workers to complete assembly in a single operation without requiring parts to be taken apart and re-aligned
Solution Approach 2:
The fastening system is segmented into distinct functional components: the bushing that provides alignment and protection, and the fastener that provides structural connection. This segmentation allows each component to be optimized independently and simplifies the assembly process, as defects can be addressed by replacing individual components rather than disassembling the entire assembly with multiple fasteners
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 approach effectively prevents damage to titanium components by redirecting electro-magnetic effects to the bushing, reducing fatigue penalties and simplifying the assembly process by eliminating the need for disassembly and burr removal, thus enhancing the structural integrity and assembly efficiency of aircraft components.
Implementation Method 1
An interference fit is created between the outer surface of the bushing and the inner surface of the initial channel through the metal component
Data Source
AI summary
A method and apparatus for preventing damage to a metal component that is susceptible to damage by electro-magnetic effects or reduce manufacturing assembly steps. An initial channel is formed through the metal component and is defined by an inner surface. A bushing is placed into the initial channel. An interference fit is created between the outer surface of the bushing and the inner surface of the initial channel through the metal component. A final channel is formed through the bushing. A fastener is placed into the final channel to attach the metal component to a second component, wherein electrical magnetic effects occur between the fastener and the bushing.