Frangible Fastener Retention to Restrict Airflow After Shear
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Solution Overview
Problem
In turbine engines, fasteners can break or shear off during rotation, leading to unsecured components and unrestricted airflow through apertures, which can exacerbate fires and cause damage.
Innovation Solution
A fastener design with a narrower, preferentially frangible portion that fails before other parts, ensuring the shoulder or washer remains in contact with the surface, restricting airflow and maintaining securement even after shearing, and allowing for adjustable installation in various aperture sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional fastener is used to secure two bodies, then the bodies are securely fastened, but the fastener may break off or shear under stress, causing the bodies to become unsecured and allowing unrestricted fluid flow
Solution Approach 1:
The fastener is segmented into a head portion and a shaft portion with a frangible section. The shaft portion is divided into a first portion (proximal to head), a frangible section (intermediate), and a second portion (distal). This segmentation allows the frangible section to fail preferentially under stress while retaining portions of the fastener that can still restrict fluid flow through the aperture.
Solution Approach 2:
The invention converts the harmful effect of fastener failure into a beneficial outcome by designing the frangible section to fail in a controlled manner. When the fastener breaks, the remaining portions (head and selected shaft portions) are retained within the aperture, transforming the complete failure scenario into a partial retention scenario that still provides fluid flow restriction and prevents complete unsecuring of the bodies.
2Strength
If a fastener is designed to be strong and durable, then it can withstand stress, but it cannot be easily adjusted to fit various aperture sizes
Solution Approach 1:
The fastener design incorporates a frangible section with controlled mechanical properties that differ from the rest of the fastener body. This parameter change allows the frangible section to have lower strength and different failure characteristics, enabling it to break at a predetermined stress level while the rest of the fastener maintains high strength. This creates a multi-parameter fastener that can adapt to different aperture sizes and stress conditions.
Data Source
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AI summary
According to one aspect, an apparatus includes a first member that has a first aperture and a second member adjacent to the first member and having a second aperture extending between opposed first and second faces of the second member and aligned with the first aperture to define a combined aperture that has a longitudinal extent. The second aperture is defined by a surface that has a portion having an extent transverse to the longitudinal extent. The apparatus further includes at least a portion of a fastener disposed in the combined aperture. The fastener has a first end proximal the first member and a second end proximal the second member and includes a first retaining member in contact with the first member, a second retaining member in interfering relationship with the portion, and a third retaining member in contact with the second face. A corresponding method for securing a first member to a second member is also provided.