Fatigue Technology, Inc.

United States

FTI's Split Sleeve Cold Expansion system is a cost effective solution to problems associated with fatigue cracks in holes in metal structures. Split Sleeve Cold Expansion is accomplished by pulling a tapered mandrel, pre-fitted with a lubricated split sleeve, through a hole in aluminum, steel or titanium. The function of the disposable split sleeve is to reduce mandrel pull force, ensure correct radial expansion of the hole, preclude damage to the hole, and allow one-sided processing. The process works by imparting beneficial compressive residual stress around the hole. The action of drawing the mandrel through the starting hole causes a radial plastic flow of material and results in an annular zone of residual compressive stresses that extend up to one diameter beyond the edge of the hole as shown below. The sleeve allows for one-sided processing and shields the hole from frictional forces generated by the high interference of the expansion mandrel. The residual stresses created by cold expansion significantly increase fatigue life by reducing the stress intensity factor and crack growth life by reducing the applied stress ratio at the hole. The magnitude of the peak residual compressive circumferential stress is about equal to the compressive yield stress for the material. The compressive stress zone spans one radius to one diameter from the edge of the hole, for diameters up to 12 inch for most materials. A balancing zone of tensile stresses lies beyond the circumferential compressive stress zone.Benefits of Split Sleeve Cold ExpansionIn most cases, at least 3:1 fatigue life improvementArrests small crack growthCost effective alternative to redesignAdds no weight to structureSimple, one-sided operationWorks on all common aerospace materialsApplicable in both production and reworkCan be automated

ForceTec is a unique method of installing an innovative and cost effective rivetless nut plate. Unlike conventional riveted or swaged-in nut plates, the ForceTec system radially expands a retainer into a hole. The retainer is designed to be permanent, and only the nut itself requires replacement. ForceTec rivetless nut plate system is widely used as an alternative to traditional riveted nut plates. ForceTecs simple installation makes it a cost effective option, significantly reducing labor and maintenance costs over the life of the aircraft. ForceTec eliminates the need for satellite holes and rivets, which are required for most nut plate installations. Instead, ForceTec is fastened to the structure by radially expanding the ForceTec nut plate barrel into the hole. The expansion creates high interference between the barrel and the structure that allows the nut plate to resist torque and pushout. ForceTec installations exceed the requirements of MIL-N-25027 for torque and pushout. In addition, cold expansion of the retainers into the hole imparts compressive residual stresses into the surrounding material, increasing the fatigue performance of the hole.Benefits of Forcetec Rivetless NutplatesEliminates nut plate rivet holes Reduces production and manufacturing time Improves fatigue life of structure Exceeds MIL-N-25027 requirements for torque and pushout. Simple, quick installation.

One of the most time consuming and complex processes of aircraft manufacturing and repair is bushing installations. Installing a shrink-fit bushing, using dangerous cryogenics, had technicians pounding a frozen bushing into place before it expanded back to its original size. FTI has taken the proven science of cold expansion to make bushing installations a breeze. Using our technology, aircraft manufacturers and maintenance crews are reducing their bushing installation flow-time and costs while also installing a bushing that is superior in performance than the old shrink-fit or press-fit methods. The ForceMate System provides an alternative to shrink or press fit bushing installation methods. Use of the system results in consistent high interference bushing installation and enhanced fatigue performance (whether needed or not), at reduced installation cost. Benefits of ForceMate BushingsReduced Installation Cost:Eliminates the need for cryogenic liquids and significantly reduces installation flow-time while decreasing the safety risk for the technician. High Resistance to Rotation and Pushout:The high interference fit provides for greater resistance to rotation or pushout than other bushing installation techniques. Increased Resistance to Corrosion:Initial clearance fit insures that corrosion protection coatings (e.g. cadmium plating) remain intact. Since no cryogenic materials are required, the risk of moisture becoming trapped between the bore of the hole and the bushing is eliminated, reducing the risk of corrosion. Significant Life Improvement:Beneficial residual compressive stresses are created around the hole and the bushing is installed with a high interference fit. The bushing is initially placed in the hole as clearance fit, and then using an oversized tapered mandrel, the lubricated ForceMate bushing is cold expanded into the hole. The resulting interference fit of the bushing, coupled with simultaneous cold working of the metal surrounding the hole, produces a fatigue life improvement of, typically, 3:1 or better.

TukLoc, the first mechanically attached blind fastening system for use in primary and secondary structures, utilizes a blind nut that is installed into the aircraft structure using FTI's state of the art cold expansion process. TukLoc is installed in the structure by radially expanding the fastener into the hole. This expansion creates an interference fit that is resistant to torque and pushout that also meets or exceeds the NASM25027 specification. The expansion process locks the fastener into the structure and then common aerospace screws are installed to finish the fastened joint. The unique tooling utilized by this fastening system provides the first blind fastener that incorporates the benefits of Fatigue Technology's proprietary cold expansion systems to provide resistance to fatigue cracking. TukLoc is available in two versions: non-sealed or sealed applications (such as fuel tanks). The mechanical expansion provides a secure, permanent sealing in applications where sealing is required. TukLoc is currently available in elliptical head configuration. Benefits of TukLocProcess consistency and repeatabilityNo additional sealants required when wet installed with primerRapid installationCan be easily automated

FTI's FleXmate Advanced Aerospace Fitting process is a new system for installing hardware that is beneficial to your aircraft structure in multiple aspects - from design and manufacturing, to operation and maintenance. This system supports current manufacturing practices and is flexible in its uses from fuel and gases fittings to hydraulics, electrical and drain fittings. Legacy Fittings are usually large and heavily flanged requiring a thick or large diameter pad up. The assembly is often complex with multiple penetrations that require satellite fasteners around the fitting. This adds weight to the structure and limits the design of the aircraft. The FleXmate system offers a better way of installing these fittings. Using our advance knowledge of the cold expansion process, we can provide a fitting that gives you design flexibility, offers structural durability, saves weight, and reduces production and maintenance costs. Weight reductionSmaller footprint and simplified assemblySimple one-piece designsElectrically conductiveFast and consistent interference fit installationTypically 2:1 life improvement of the structureElimination of satellite holes (saving manufacturing time and eliminating areas of future crack growth)Excellent sealing characteristics

FTI's patented GromEx system is a cost-effective method for reinforcing fastener holes in composite materials using a thin interference fit metal sleeve or grommet. GromEx is based on FTI's proven cold expansion technology and is designed specifically for use in composites. The amount of radial expansion of the grommet in the hole is carefully tailored to ensure adequate grommet retention and at the same time prevent localized damage to the composite. The GromEx system is easier to install, more reliable, and has improved performance over adhesive bonded or swaged grommets. FTI expanded products achieve excellent bonding and grounding (or earthing) performance because each product is radially expanded from a clearance fit starting hole to produce a final interference fit in the structure or component. Our highly repeatable process produces uniform contact with the hole surface without gaps or insulating sealant. GromEx panel liners are used to protect composite panels from lightning strike damage and hole wear. They are suitable for use with any class or fit fastener and can be used to facilitate the installation of net fit fastners in load transfer applications. GromEx is available in common fastener configurations including "t-shape" and 100 degree countersunk configurations.

The RailTec System was developed for the rail industry and is based on FTI's Split Sleeve Cold Expansion System. The flexibility of the system enables it to be easily applied to all main line or branch line track as part of routine maintenance. Rail with small fatigue cracks can be reworked and safely returned to service. Additionally, the system can be used during the manufacture of rails, frogs, and switches. The cold expansion process increases the life of a bolt hole by producing a zone of residual compressive stresses around the hole. This is achieved by drawing an oversized, tapered mandrel through an internally pre-lubricated split sleeve in the hole. When the mandrel passes through the hole, the combined major diameter of the mandrel and thickness of the sleeve enlarge the hole, yielding the material directly around the hole and creating the protective zone of residual stress. This zone protects the hole from the stresses applied to the rail end and significantly decreases the probability of fatigue cracks. The cold expansion process, when applied to typical rail stock, increases the life of the bolt hole by at least 3:1. BENEFITS OF THE RAILTEC SYSTEMImproves the fatigue life of the hole by at least 3:1 Arrests the growth or small cracks Cost-effective alternative to new track Reduces maintenance and inspection costs Increases the overall structural integrity and safety of the line