Split Sleeve Cold Expansion (SsCx) System
Split Sleeve Cold Expansion is a fatigue life enhancement process for fastener holes in metal structures. It was pioneered by Fatigue Technology Inc. (FTI, now part of Precision Castparts) and is used widely in aerospace manufacturing, repair, and maintenance. A tapered mandrel fitted with a lubricated split sleeve is pulled through a hole expanding the surrounding material and leaving a zone of compressive residual stress that resists the start and growth of fatigue cracks. It works in aluminum, steel, and titanium and is used on new builds and to extend the life of holes in aging structures.
Key Features Split Sleeve Cold Expansion
- Proven fatigue life improvement: FTI states at least a 3:1 fatigue life improvement in most cases
- How it works: the compressive residual stress around the hole lowers the stress intensity factor and the applied stress ratio at the hole which slows crack growth
- Works across materials: aluminum, steel, and titanium structures
- Cold Expansion to Size: a variation of the process that removes the final reaming step with the final hole size predicted from the material response and well suited to automated drilling and fastener insertion systems
- Countersink Cold Expansion: applicable to holes that need a countersink in both production and rework
- Disposable, internally lubricated split sleeves: protect the hole surface and allow the sleeve to be removed after expansion
- Complete tooling system: puller units and a hydraulic PowerPak with mandrels, split sleeves, nosecaps, and backup blocks selected for each hole size and application
- Automated option: Automated Cold Expansion (AtCx) pullers convert rotary motion to linear pull for use in automated work cells
- Production and repair use: applied to new structure to improve fatigue performance and to rework holes in aging aircraft
- Potential weight savings: by improving fatigue performance designs can run at higher stress levels with less material
Typical Applications
- Aircraft structural fastener holes in wings, fuselage, and landing gear parts
- Aircraft wheels and other rotating or high cycle components
- Rework and life extension of aging aircraft structure
- Holes in aluminum, steel, and titanium parts in other fatigue critical applications
- Automated drilling and fastening cells
Why Choose It
Fastener holes are a common starting point for fatigue cracks. Split sleeve cold expansion provides a cost effective well established way to improve the fatigue life of those holes and is specified by airframe manufacturers for critical structure.
