3313. Engineering Guidelines for Tungsten Heavy Alloy Counterweights

Paper

Abstract

For both fixed and rotary wing aircraft, there are needs for concentrated mass to either balance gravitational forces or provide inertial damping of specific mechanisms. Several high-density materials have been used historically in such applications, but the continued use of some now falls into question on the basis of associated environmental and/or occupational safety issues.
Tungsten heavy alloys (WHAs) offer a unique combination of high density, good mechanical properties, easy machinability, and low life cycle cost in addition to low toxicity. As a consequence, they are the ideal materials for counterbalance weight applications. While composed of common metals, WHAs are a unique family of engineering alloys for which material properties and design information are generally difficult to locate, as they are listed in few reference texts. This presentation provides basic design and metallurgical considerations for the use of this family of materials in a variety of aerospace applications. Important engineering aspects such as elevated temperature implications, mechanical strength requirements, joining considerations, and corrosion protection are addressed. Additionally, as WHA components are fabricated by the powder metallurgy process of liquid phase sintering, special design guidelines should be followed for obtaining optimal performance of these metal matrix composite materials. Examples are also presented that illustrate how larger assemblies can be constructed and yet circumvent the size and shape limitations of the liquid phase sintering process for individual components.
These data are presented to assist the mass properties designer with information specific to WHAs for better utilization of material properties and weight integration options for aircraft systems. WHAs allow the design of space efficient, environmentally friendly aviation counterweights for both new vehicles and the retrofit of existing craft to comply with increased regulatory constraints for toxic metals.