STP927

    Fatigue Life Enhancement and High Interference Bushing Installation Using the ForceMate Bushing Installation Technique

    Published: Jan 1986


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    Abstract

    The patented ForceMate bushing installation process, originally developed by McDonnell Aircraft, involves expansion of a hole and simultaneous installation of an interference fitted bushing. The process provides a significant improvement in the fatigue life of bushed holes in metallic structures and offers reduced bushing installation costs. Fatigue life improvement is attributed both to the creation of residual compressive stresses in the metal surrounding the hole and to the reduction in applied cyclic stress range caused by the interference fitted bushing. Installation is accomplished without loss of corrosion protection because of the initial clearance fit of the bushing in the hole. Installation costs are reduced by the elimination of liquid nitrogen needed for shrinkage of bushings, as well as the significant reduction in installation time and manpower.

    This paper describes the ForceMate process in detail. Fatigue lives of simulated aluminum lug geometries with bushings installed using the ForceMate process were compared with lives of lugs with bushings installed using conventional shrink fit methods. Constant amplitude and flight-by-flight spectrum loading were used for cyclic testing. Life improvement factors of greater than 3:1 were shown. Bushing-to-hole interferences were significantly greater than those achievable with traditional shrink-fit installation techniques. The process was demonstrated effectively with bushings manufactured from beryllium-copper, aluminum-nickel-bronze, and steel alloys.

    Keywords:

    fatigue (materials), fatigue enhancement, bushings, aluminum alloys, lugs, cold working, cold expansion, interference fit, residual stress


    Author Information:

    Champoux, RL
    Vice president/generalmanager and engineering manager, Fatigue Technology, Inc., Seattle, WA

    Landy, MA
    Vice president/generalmanager and engineering manager, Fatigue Technology, Inc., Seattle, WA


    Paper ID: STP29053S

    Committee/Subcommittee: E08.04

    DOI: 10.1520/STP29053S


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