will be made giving the freedom of the important variable density.
Researching the Feasibility
Materials research is focused on fundamental research to achieve last- ing strategic land power dominance through structural materials, ballistic materials, and manufacturing science, processing and sustainment. Structural materials focus on ballistic materials to enhance the performance and effi - ciency of army weapons and protection systems including lightweight, extreme performance materials, and energy absorbing materials. Manufacturing science, processing and sustainment is focused on discovery, innovation, and maturation of manufacturing inno- vations and understanding material properties and degradation mecha- nisms to improve durability of army systems in extreme environments. Porous metals made of aluminum and titanium are becoming increas- ingly popular as stiff but lightweight materials for use in structural com- ponents of automobiles and aircraft. However, engineering applications require stronger and more economi- cal materials than an aluminum or titanium foam can provide. Tradi- tional structural steel has proven valuable as an engineering material, but the properties of structural steel have remained invariant for the past century. Research conducted over approxi- mately the last 10-15 years has shown
This steel piston was machined from the cast steel foam billet.
that it is possible to fabricate steel foams at the laboratory scale and these foams can be made to have poten- tially desirable mechanical properties. Despite these substantial advances in the materials science of steel foams, a commercially available product re- mains elusive, and therefore structural designers have not begun to explore the potential benefi ts of using steel foam in civil structural applications
POTENTIAL STRUCTURAL APPLICATIONS
Steel foam material has many potential applications. For military vehicle components, it could be used for energy ab- sorbing bumpers, door side impact bars, front crash rails, fl ywheel containment rings, or blast containment components in military trucks and personnel carriers. Railcar applications could include crash protec- tion components and structural panels. Lightweight pallets and cargo containers, aircraft landing decks, elevator decks, deck rams and hatch covers, fi re doors, partitions and fl oors, docks, and cargo loading decks all could be naval applications. Other applications could include steel foam bars and rods, parking
fl oor slabs, factory enclosures, light walls and impact absorption for guard rails, auditorium walls and ceilings for sound absorption, blast protection for vehicles and buildings, and impact absorption for cars.
44 | METAL CASTING DESIGN & PURCHASING | Jan/Feb 2017
Perhaps because of the lack of
commercial availability of steel foam, no applications have been developed or widely implemented. In the past few years, interest in metal foams, especially in steel foams, has increased remarkably. T e reason for this is the wide range of applicability such as lightweight panels, crash energy absorption, exhaust muffl ers, vibration and noise control in the automotive industry, fi lters, heat exchangers, high strength wall panels for sound insula- tion and bio-medical implants. Steel foams exhibit excellent stiff ness-to- weight ratios when loaded in fl exure. In particular, steel foam panels have higher bending stiff ness than solid steel sheets of the same weight. T e basic objective of the develop-
ment process of metallic foams is the combination of physical and mechan- ical properties expected from metal- lic foams such as high stiff ness, low specifi c weight, high gas permeability, low thermal conductivity, unusual acoustic properties, high impact ab- sorption capacity and good electrical insulating properties.
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