Aircraft Fuselage Frame Stringer Reinforcement via Friction Stir Welding
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Solution Overview
Problem
Existing methods for reinforcing stringer openings in aircraft fuselage frame members, such as riveting and bonding, compromise the structural integrity and strength of the frame members, as they require drilling or use reinforcement pieces with lower material strength.
Innovation Solution
The use of reinforcement members made of the same metal as the frame members, lap joined to the frame members via a friction stir weld region, providing structural reinforcement without the need for riveting or bonding, and employing various shapes like L-shaped, curved, or reverse S-shaped structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If reinforcement members are riveted to frame members, then structural strength at stringer openings is improved, but the frame member's structural integrity deteriorates due to drilling
Solution Approach 1:
The patent replaces the mechanical riveting system with a friction stir welding system. Instead of using rivets that require drilling holes through the frame member, the invention uses a friction stir welder to create a friction stir weld between the reinforcement member and the frame member surface. This substitution eliminates the harmful drilling operation while maintaining strong structural connection, thereby preserving the frame member's structural integrity while still providing the necessary strength reinforcement at the stringer openings.
2Strength
If reinforcement pieces are bonded to frame members, then structural strength at stringer openings is improved, but the material strength equivalence deteriorates
Solution Approach 1:
The patent applies homogeneity by using reinforcement members made of the same material as the frame members (both aluminum alloy). The friction stir welding process creates a metallurgical bond that is as strong as or stronger than the base material itself. This eliminates the weakness inherent in bonded reinforcements where the adhesive or bonding material never achieves the same strength as the metal frame members, ensuring that the reinforced area has uniform and equivalent material strength throughout.
3Ease of operation
If mouse holes are formed in frame members, then stringer installation is enabled, but the frame member strength deteriorates
Solution Approach 1:
The patent applies local quality by providing reinforcement members only at the specific locations where stringer openings are made in the frame members. The reinforcement members are positioned locally at these critical areas to restore the strength that was compromised by the openings. This localized reinforcement approach allows the frame members to maintain their overall strength while enabling necessary stringer installation, rather than requiring the entire frame member to be redesigned or over-reinforced.
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 solution effectively restores the original design strength of the frame members by creating a strong, rigid lap joint that maintains the material integrity and strength of the frame members, enhancing the structural integrity of the aircraft fuselage.
Implementation Method 1
the reinforcement members are joined rigidly to the corresponding surfaces of the frame members by a friction stir weld region
Data Source
AI summary
Aircraft fuselage structures have reinforcement members in the vicinity of the stringer openings formed in frame members and are rigidly lap joined to a surface region of the frame members by a friction stir weld region. Such aircraft fuselage structural components may thus be provided with plural longitudinally spaced-apart frame members defining a transversal cross-section of an aircraft fuselage section, the frame members having a plurality of stringer holes therethrough, and plural longitudinally oriented stringers each being positioned within a respective one of the stringer holes of the frame member. The reinforcement members are lap joined to corresponding surfaces of frame members in the vicinity of the stringer holes such that the reinforcement members are joined rigidly to the corresponding surfaces of the frame members by a friction stir weld region.