Localized Reinforcement of Navy Helicopter Transmission Housings

A magnesium alloy is used for many Navy helicopter gearbox and main transmission housings. There are two durability related concerns for these components: 1) housing service life is currently limited due to fretting fatigue and corrosion problems; and 2)several heavily loaded points in the housing (e.g., linkage/actuator attachment) will experience even more severe damage.Foster-Miller's approach to resolve this problem is to selectively reinforce the highly loaded regions of the magnesium casting with a unique metal matrix composite (MMC) insert. Foster-Miller has already demonstrated the use of high strength MMC insertsas localized reinforcement of large aluminum gravity castings. The mechanical performance and environmental resistance of potential MMC insert materials will be studied. The selective reinforcement concept will be demonstrated at a specimen level duringthe Phase I Base Effort. The Phase II program will involve sub-scale components fabrication and testing. Foster-Miller will work closely with a major military helicopter prime contractor and its foundry suppliers in order to develop a technology withnear-term implementation potential. (P-030173) The project will incrementally demonstrate full-scale, production capable technology toproduce high durability magnesium alloy castings selectively reinforced with MMCinserts. A clear path to implementation of the technology on Navy helicopters has already been established.The proposed technology has broader applications in replacing certain cast iron, steel, or titanium castings with less expensive and lightweight aluminum/magnesium castings through use of strategically placed MMC inserts. Thus, the technology addressesthe overall metal casting industry which is a $29 billion per year industry.Foster-Miller MMC materials could be an attractive alternative for a broad structural (as a light weigh replacement for steels and inexpensive replacement for exotic materials) applications and for specific application where MMCs complex of mechanical,themophysical, and service properties would enable implementation of the materials with unique properties, low cost and versatile fabrication technology.