Page 8 - Research and innovation In advanced materials with application to the railway sector

ACOUSTICS AND VIBRATIONS

In the field of dynamics, acoustics and vibrations, in order to improve the perception of well-
being inside a train, it is necessary to play with variables that are often in conflict, such as
optimal sound absorption at low frequency and in small volumes; or elevated acoustic
insulation with less weight. Combining these variables and reaching optimal balances often
requires developments that go beyond the component scale and require work at a material
level.

In this line of work, metamaterials, which arise from a structured geometric configuration,
and not from the physical properties of the materials that compose them, are especially
interesting. Some examples are the arrays of microresonators, with or without cavity,
acoustic labyrinths that cause the passive cancellation of waves in the propagation path, etc.
Or also the Acoustic Black Holes, which behave as energy sinks and are capable of
concentrating and damping the vibrations of the bending waves from a cut-off frequency, in
contrast to classic viscoelastic materials.

Also, in the field of viscoelastic and elastomeric materials, a high degree of innovation is
maintained in the search for new formulations that improve their performance.

III. PLATFORM AND TRACK

The Spanish commitment to high speed, despite the macroeconomic upheavals of recent
years, remains a fundamental pillar of future mobility, sustainability, and decarbonisation.
New lines continue to be built and the infrastructure already in service being improved, to
adapt it to the demands in terms of efficiency, costs, maintenance, and environmental
impact. In this path of continuous improvement, innovations related to the development
and use of new materials and materials with improved properties play a fundamental role.

MAINTENANCE

The maintenance chapter is key from the point of view of passenger comfort, planning,
safety and operation. All the developments, also in materials, that improve predictive
maintenance techniques represent an improvement in all these aspects.

In this sense, the use of fibre optic sensors embedded in structures is very relevant to
anticipate the appearance of cracks and deformations, to measure temperature and stress,
also of the rail, in what has come to be called the "Internet of Steel ". In this way, it would be
possible to monitor in real time, beyond the periodic auscultation by means of rolling stock
dedicated to this task. In parallel, the knowledge on materials is essential to make
projections about what will be the future evolution of their behaviour depending on the
traffic, speed, atmospheric conditions and the load of the vehicles that circulate on the
tracks. In this line of work, the study of the tribological behaviour of railway steels is very
relevant, through tribological tests, such as twin disc tests, to evaluate the problem of rolling
fatigue wear (RCF) in high-speed lines; and pin-on-disc tests or large-scale tests, to measure
wear and tear on the service. These results makes it possible to correlate the data obtained
in the laboratory with the real data on wear in service, with which to estimate the lifetime
due to wear on the railway track and guide the development of new materials with
improved behaviour.

__________________________________________________________________________________________________________________
Position paper: Research and innovation in advanced materials with application to the railway sector
6