Page 4 - Research and innovation un materials applied to railways

II. ROLLING STOCK

The presence of faster and lighter trains is leading to greater commercial competitiveness,
as well as reducing the contaminating emissions linked to railway transport. These factors,
together with improvements in quality, are especially relevant within the context of
passenger transport liberalization. At the same time, the standards of comfort demanded
by passengers continue to increase.

Greater comfort and passenger space, less weight and cost are somewhat contradictory
criteria that demand the development of new materials for structural applications,
aerodynamic related aspects and interiors.

On the other hand, the introduction of new materials to rolling stock should take into
account those characteristics specific to railways, such as compatibility with the
environment, maintenance, reparability and the life cycle of the rolling stock itself. In the
same way, solutions that have been successfully tried within other sectors should be
reevaluated to verify their suitability for use in rail.

Aluminum has played a key role in railway developments since the 1980s, giving a
competitive advantage over steel in terms of lightness, durability and performance in the
face of corrosion. In 1996 the TGV Duplex Train provided an increased capacity of 40%
with a reduction of 12% in weight .
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The success of introducing aluminum was possible thanks to innovations in the
manufacturing process, such as the development of extruded, large dimensions, hollow
sections, the incorporation of new alloys adopted for the aeronautic sector and
developments in soldering processes, in which there is still room for innovation, for
example, FSW welding (Friction Stir Welding).

Currently there are lines of research open which seek to widen the use of aluminum alloys,
not only in structural applications, but also in solid components. This is achieved through
semisolid state based technologies which aim to obtain aluminum components with high
structural integration, opening the possibility of substituting components currently forged
in iron alloys.

Metal matrix composites (MMC) are considered to be one of the greatest developments in
materials science in recent years, especially in their application to automotion and
aeronautics. Its potential is based on the improved adaptability of its mechanical
properties, especially in terms of rigidity, mechanic resistance and resistance to abrasion,
as well as the capacity to comply with the strict fire and smoke regulation (EN-144555)
enforced in the sector. These types of materials are manufactured using molding or
mechanical alloying, a process through which ceramic particles, mainly SiC and Al2O3 of
micrometric or nanometric size are added to reinforce.

The latter allow improved properties with a very small percentage of reinforcement. A
1% reinforcement Si3N4P (50nm) achieves a tensile strength comparable to a
reinforcement of 15% of SiCp (3.5µm).

Together with metal matrix composites, metal foams present interesting properties,
principally due to their lightness and capacity to absorb impact energy and for damping

Position Paper: Research and innovation in materials applied to railways 3